Top most important J2EE interview questions and answers by Experts:

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1.What is J2EE?
J2EE is an environment for developing and deploying enterprise applications. The J2EE platform consists of a set of services, application programming interfaces (APIs), and protocols that provide the functionality for developing multitier, web-based applications.

2.What is the J2EE module? 
A J2EE module consists of one or more J2EE components for the same container type and one component deployment descriptor of that type.

3.What are the components of J2EE application? 
A J2EE component is a self-contained functional software unit that is assembled into a J2EE application with its related classes and files and communicates with other components. The J2EE specification defines the following J2EE components: 
   Application clients and applets are client components. 
   Java Servlet and JavaServer PagesTM (JSPTM) technology components are web components.
   Enterprise JavaBeansTM (EJBTM) components (enterprise beans) are business components.
   Resource adapter components provided by EIS and tool vendors.

4.What are the four types of J2EE modules? 
1. Application client module
2. Web module 
3. Enterprise JavaBeans module 
4. Resource adapter module

5.What does application client module contain? 
The application client module contains:
–class files, 
–an application client deployment descriptor.
Application client modules are packaged as JAR files with a .jar extension.

6.What does web module contain? 
The web module contains:
–JSP files,
–class files for servlets,
–GIF and HTML files, and 
–a Web deployment descriptor. 
Web modules are packaged as JAR files with a .war (Web ARchive) extension.

7.What are the differences between Ear, Jar and War files? Under what circumstances should we use each one?

There are no structural differences between the files; they are all archived using zip-jar compression. However, they are intended for different purposes.
–Jar files (files with a .jar extension) are intended to hold generic libraries of Java classes, resources, auxiliary files, etc.
–War files (files with a .war extension) are intended to contain complete Web applications. In this context, a Web application is defined as a single group of files, classes, resources, .jar files that can be packaged and accessed as one servlet context. 
–Ear files (files with a .ear extension) are intended to contain complete enterprise applications. In this context, an enterprise application is defined as a collection of .jar files, resources, classes, and multiple Web applications. 
Each type of file (.jar, .war, .ear) is processed uniquely by application servers, servlet containers, EJB containers, etc.

8.What is the difference between Session bean and Entity bean ? 
The Session bean and Entity bean are two main parts of EJB container. 
Session Bean
–represents a workflow on behalf of a client
–one-to-one logical mapping to a client.
–created and destroyed by a client 
–not permanent objects
–lives its EJB container(generally) does not survive system shut down
–two types: stateless and stateful beans
Entity Bean
–represents persistent data and behavior of this data
–can be shared among multiple clients 
–persists across multiple invocations 
–findable permanent objects
–outlives its EJB container, survives system shutdown 
–two types: container managed persistence(CMP) and bean managed persistence(BMP)

9.What is “applet”  ?
A J2EE component that typically executes in a Web browser but can execute in a variety of other applications or devices that support the applet programming model.

10.What is “applet container”  ?
A container that includes support for the applet programming model.

11.What is “application assembler” ?
A person who combines J2EE components and modules into deployable application units.

12.What is “application client” ?
A first-tier J2EE client component that executes in its own Java virtual machine. Application clients have access to some J2EE platform APIs.

13.What is “application client container” ?
A container that supports application client components.

14.What is “application client module” ?
A software unit that consists of one or more classes and an application client deployment descriptor.

15.What is “application component provider” ?
A vendor that provides the Java classes that implement components’ methods, JSP page definitions, and any required deployment descriptors.

16.What is “application configuration resource file” ?
An XML file used to configure resources for a Java Server Faces application, to define navigation rules for the application, and to register converters, Validator, listeners, renders, and components with the application.

17.What is “archiving” ?
The process of saving the state of an object and restoring it.

18.What is “asant” ?
A Java-based build tool that can be extended using Java classes. The configuration files are XML-based, calling out a target tree where various tasks get executed.

19.What is “attribute”?
A qualifier on an XML tag that provides additional information.

20.What is authentication ? 
The process that verifies the identity of a user, device, or other entity in a computer system, usually as a prerequisite to allowing access to resources in a system. The Java servlet specification requires three types of authentication-basic, form-based, and mutual-and supports digest authentication.

21.What is authorization ? 
The process by which access to a method or resource is determined. Authorization depends on the determination of whether the principal associated with a request through authentication is in a given security role. A security role is a logical grouping of users defined by the person who assembles the application. A deployer maps security roles to security identities. Security identities may be principals or groups in the operational environment.

22.What is authorization constraint ?
An authorization rule that determines who is permitted to access a Web resource collection.

23.What is B2B ?
B2B stands for Business-to-business.

24.What is backing bean ?
A JavaBeans component that corresponds to a JSP page that includes JavaServer Faces components. The backing bean defines properties for the components on the page and methods that perform processing for the component. This processing includes event handling, validation, and processing associated with navigation.

25.What is basic authentication ?
An authentication mechanism in which a Web server authenticates an entity via a user name and password obtained using the Web application’s built-in authentication mechanism.

26.What is bean-managed persistence ?
The mechanism whereby data transfer between an entity bean’s variables and a resource manager is managed by the entity bean.

27.What is bean-managed transaction ?
A transaction whose boundaries are defined by an enterprise bean.

28.What is binding (XML) ?
Generating the code needed to process a well-defined portion of XML data.

29.What is binding (JavaServer Faces technology) ?
Wiring UI components to back-end data sources such as backing bean properties.

30.What is build file ?
The XML file that contains one or more asant targets. A target is a set of tasks you want to be executed. When starting asant, you can select which targets you want to have executed. When no target is given, the project’s default target is executed.

31.What is business logic ?
The code that implements the functionality of an application. In the Enterprise JavaBeans architecture, this logic is implemented by the methods of an enterprise bean.

32.What is business method ?
A method of an enterprise bean that implements the business logic or rules of an application.

33.What is callback methods ?
Component methods called by the container to notify the component of important events in its life cycle.

34.What is caller ?
Same as caller principal.

35.What is caller principal ?
The principal that identifies the invoker of the enterprise bean method.

36.What is cascade delete ?
A deletion that triggers another deletion. A cascade delete can be specified for an entity bean that has container-managed persistence.

37.What is CDATA ?
A predefined XML tag for character data that means “don’t interpret these characters,” as opposed to parsed character data (PCDATA), in which the normal rules of XML syntax apply. CDATA sections are typically used to show examples of XML syntax.

38.What is certificate authority ?
A trusted organization that issues public key certificates and provides identification to the bearer.

39.What is client-certificate authentication ?
An authentication mechanism that uses HTTP over SSL, in which the server and, optionally, the client authenticate each other with a public key certificate that conforms to a standard that is defined by X.509 Public Key Infrastructure.

40.What is comment ?
In an XML document, text that is ignored unless the parser is specifically told to recognize it.

41.What is commit ?
The point in a transaction when all updates to any resources involved in the transaction are made permanent.

42.What is component contract ?
The contract between a J2EE component and its container. The contract includes life-cycle management of the component, a context interface that the instance uses to obtain various information and services from its container, and a list of services that every container must provide for its components.

43.What is component-managed sign-on ?
A mechanism whereby security information needed for signing on to a resource is provided by an application component.

44.What is connector ?
A standard extension mechanism for containers that provides connectivity to enterprise information systems. A connector is specific to an enterprise information system and consists of a resource adapter and application development tools for enterprise information system connectivity. The resource adapter is plugged in to a container through its support for system-level contracts defined in the Connector architecture.

45.What is container-managed persistence ?
The mechanism whereby data transfer between an entity bean’s variables and a resource manager is managed by the entity bean’s container.

46.What is container-managed sign-on ?
The mechanism whereby security information needed for signing on to a resource is supplied by the container.

47.What is container-managed transaction ?
A transaction whose boundaries are defined by an EJB container. An entity bean must use container-managed transactions.

48.What is content ?
In an XML document, the part that occurs after the prolog, including the root element and everything it contains.

49.What is context attribute ?
An object bound into the context associated with a servlet.

50.What is context root ?
A name that gets mapped to the document root of a Web application.

51.What is conversational state ?
The field values of a session bean plus the transitive closure of the objects reachable from the bean’s fields. The transitive closure of a bean is defined in terms of the serialization protocol for the Java programming language, that is, the fields that would be stored by serializing the bean instance.

52.What is CORBA ?
Common Object Request Broker Architecture. A language-independent distributed object model specified by the OMG.

53.What is create method ?
A method defined in the Interview Questions – Home interface and invoked by a client to create an enterprise bean.

54.What is credentials ?
The information describing the security attributes of a principal.

55.What is CSS ?
Cascading style sheet. A stylesheet used with HTML and XML documents to add a style to all elements marked with a particular tag, for the direction of browsers or other presentation mechanisms.

56.What is CTS ?
Compatibility test suite. A suite of compatibility tests for verifying that a J2EE product complies with the J2EE platform specification.

57.What is data ?
The contents of an element in an XML stream, generally used when the element does not contain any subelements. When it does, the term content is generally used. When the only text in an XML structure is contained in simple elements and when elements that have subelements have little or no data mixed in, then that structure is often thought of as XML data, as opposed to an XML document.

58.What is DDP ?
Document-driven programming. The use of XML to define applications.

59.What is declaration ?
The very first thing in an XML document, which declares it as XML. The minimal declaration is . The declaration is part of the document prolog.

60.What is declarative security ?
Mechanisms used in an application that are expressed in a declarative syntax in a deployment descriptor.

61.What is delegation ?
An act whereby one principal authorizes another principal to use its identity or privileges with some restrictions.

62.What is deployer ?
A person who installs J2EE modules and applications into an operational environment.

63.What is deployment ?
The process whereby software is installed into an operational environment.

64.What is deployment descriptor ?
An XML file provided with each module and J2EE application that describes how they should be deployed. The deployment descriptor directs a deployment tool to deploy a module or application with specific container options and describes specific configuration requirements that a deployer must resolve.

65.What is destination ?
A JMS administered object that encapsulates the identity of a JMS queue or topic. See point-to-point messaging system, publish/subscribe messaging system.

66.What is digest authentication ?
An authentication mechanism in which a Web application authenticates itself to a Web server by sending the server a message digest along with its HTTP request message. The digest is computed by employing a one-way hash algorithm to a concatenation of the HTTP request message and the client’s password. The digest is typically much smaller than the HTTP request and doesn’t contain the password. 

67.What is distributed application ?
An application made up of distinct components running in separate runtime environments, usually on different platforms connected via a network. Typical distributed applications are two-tier (client-server), three-tier (client-middleware-server), and multitier (client-multiple middleware-multiple servers).

68.What is document ?
In general, an XML structure in which one or more elements contains text intermixed with subelements.

69.What is Document Object Model ?
An API for accessing and manipulating XML documents as tree structures. DOM provides platform-neutral, language-neutral interfaces that enables programs and scripts to dynamically access and modify content and structure in XML documents. 

70.What is document root ?
The top-level directory of a WAR. The document root is where JSP pages, client-side classes and archives, and static Web resources are stored.

71.What is DTD ?
Document type definition. An optional part of the XML document prolog, as specified by the XML standard. The DTD specifies constraints on the valid tags and tag sequences that can be in the document. The DTD has a number of shortcomings, however, and this has led to various schema proposals. For example, the DTD entry says that the XML element called username contains parsed character data-that is, text alone, with no other structural elements under it. The DTD includes both the local subset, defined in the current file, and the external subset, which consists of the definitions contained in external DTD files that are referenced in the local subset using a parameter entity.

72.What is durable subscription ?
In a JMS publish/subscribe messaging system, a subscription that continues to exist whether or not there is a current active subscriber object. If there is no active subscriber, the JMS provider retains the subscription’s messages until they are received by the subscription or until they expire.

73.What is EAR file ?
Enterprise Archive file. A JAR archive that contains a J2EE application.

74.What is ebXML ?
Electronic Business XML. A group of specifications designed to enable enterprises to conduct business through the exchange of XML-based messages. It is sponsored by OASIS and the United Nations Centre for the Facilitation of Procedures and Practices in Administration, Commerce and Transport (U.N./CEFACT).

75. What is EJB ?
Enterprise JavaBeans.

76.What is EJB container ?
A container that implements the EJB component contract of the J2EE architecture. This contract specifies a runtime environment for enterprise beans that includes security, concurrency, life-cycle management, transactions, deployment, naming, and other services. An EJB container is provided by an EJB or J2EE server.

77.What is EJB container provider ?
A vendor that supplies an EJB container.

78.What is EJB context ?
A vendor that supplies an EJB container. An object that allows an enterprise bean to invoke services provided by the container and to obtain the information about the caller of a client-invoked method

79.What is EJB Home object ?
An object that provides the life-cycle operations (create, remove, find) for an enterprise bean. The class for the EJB Home object is generated by the container’s deployment tools. The EJB Home object implements the enterprise bean’s Home interface. The client references an EJB Home object to perform life-cycle operations on an EJB object. The client uses JNDI to locate an EJB Home object.

80.What is EJB JAR file ?
A JAR archive that contains an EJB module.

81.What is EJB module ?
A deployable unit that consists of one or more enterprise beans and an EJB deployment descriptor.

82.What is EJB object ?
An object whose class implements the enterprise bean’s remote interface. A client never references an enterprise bean instance directly; a client always references an EJB object. The class of an EJB object is generated by a container’s deployment tools.

83.What is EJB server ?
Software that provides services to an EJB container. For example, an EJB container typically relies on a transaction manager that is part of the EJB server to perform the two-phase commit across all the participating resource managers. The J2EE architecture assumes that an EJB container is hosted by an EJB server from the same vendor, so it does not specify the contract between these two entities. An EJB server can host one or more EJB containers.

84.What is EJB server provider ?
A vendor that supplies an EJB server.

85.What is element ?
A unit of XML data, delimited by tags. An XML element can enclose other elements.

86.What is empty tag ?
A tag that does not enclose any content.

87.What is enterprise bean ?
A J2EE component that implements a business task or business entity and is hosted by an EJB container; either an entity bean, a session bean, or a message-driven bean.

88.What is enterprise bean provider ?
An application developer who produces enterprise bean classes, remote and Interview Questions – Home interfaces, and deployment descriptor files, and packages them in an EJB JAR file.

89.What is enterprise information system ?
The applications that constitute an enterprise’s existing system for handling companywide information. These applications provide an information infrastructure for an enterprise. An enterprise information system offers a well-defined set of services to its clients. These services are exposed to clients as local or remote interfaces or both. Examples of enterprise information systems include enterprise resource planning systems, mainframe transaction processing systems, and legacy database systems.

90.What is enterprise information system resource ?
An entity that provides enterprise information system-specific functionality to its clients. Examples are a record or set of records in a database system, a business object in an enterprise resource planning system, and a transaction program in a transaction processing system.

91.What is Enterprise JavaBeans (EJB) ?
A component architecture for the development and deployment of object-oriented, distributed, enterprise-level applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and secure.

92.What is Enterprise JavaBeans Query Language (EJB QL) ?
Defines the queries for the finder and select methods of an entity bean having container-managed persistence. A subset of SQL92, EJB QL has extensions that allow navigation over the relationships defined in an entity bean’s abstract schema.

93.What is an entity ?
A distinct, individual item that can be included in an XML document by referencing it. Such an entity reference can name an entity as small as a character (for example, <, which references the less-than symbol or left angle bracket, <). An entity reference can also reference an entire document, an external entity, or a collection of DTD definitions.

94.What is entity bean ?
An enterprise bean that represents persistent data maintained in a database. An entity bean can manage its own persistence or can delegate this function to its container. An entity bean is identified by a primary key. If the container in which an entity bean is hosted crashes, the entity bean, its primary key, and any remote references survive the crash.

95.What is entity reference ?
A reference to an entity that is substituted for the reference when the XML document is parsed. It can reference a predefined entity such as < or reference one that is defined in the DTD. In the XML data, the reference could be to an entity that is defined in the local subset of the DTD or to an external XML file (an external entity). The DTD can also carve out a segment of DTD specifications and give it a name so that it can be reused (included) at multiple points in the DTD by defining a parameter entity.

96.What is error ?
A SAX parsing error is generally a validation error; in other words, it occurs when an XML document is not valid, although it can also occur if the declaration specifies an XML version that the parser cannot handle. See also fatal error, warning. 

97.What is Extensible Markup Language ?
XML.

98.What is external entity ?
An entity that exists as an external XML file, which is included in the XML document using an entity reference.

99.What is external subset ?
That part of a DTD that is defined by references to external DTD files.

100.What is fatal error ?
A fatal error occurs in the SAX parser when a document is not well formed or otherwise cannot be processed. See also error, warning.

101.What is filter ?
An object that can transform the header or content (or both) of a request or response. Filters differ from Web components in that they usually do not themselves create responses but rather modify or adapt the requests for a resource, and modify or adapt responses from a resource. A filter should not have any dependencies on a Web resource for which it is acting as a filter so that it can be composable with more than one type of Web resource.

102.What is filter chain ?
A concatenation of XSLT transformations in which the output of one transformation becomes the input of the next.

103.What is finder method ?
A method defined in the Interview Questions – Home interface and invoked by a client to locate an entity bean.

104.What is form-based authentication ?
An authentication mechanism in which a Web container provides an application-specific form for logging in. This form of authentication uses Base64 encoding and can expose user names and passwords

105.What is general entity ?
An entity that is referenced as part of an XML document’s content, as distinct from a parameter entity, which is referenced in the DTD. A general entity can be a parsed entity or an unparsed entity.

106.What is group ?
An authenticated set of users classified by common traits such as job title or customer profile. Groups are also associated with a set of roles, and every user that is a member of a group inherits all the roles assigned to that group.

107.What is handle ?
An object that identifies an enterprise bean. A client can serialize the handle and then later deserialize it to obtain a reference to the enterprise bean.

108.What is Interview Questions – Home handle ?
An object that can be used to obtain a reference to the Interview Questions – Home interface. A Interview Questions – Home handle can be serialized and written to stable storage and de-serialized to obtain the reference.

109.What is Interview Questions – Home interface ?
One of two interfaces for an enterprise bean. The Interview Questions – Home interface defines zero or more methods for managing an enterprise bean. The Interview Questions – Home interface of a session bean defines create and remove methods, whereas the Interview Questions – Home interface of an entity bean defines create, finder, and remove methods.

110.What is HTML ?
Hypertext Markup Language. A markup language for hypertext documents on the Internet. HTML enables the embedding of images, sounds, video streams, form fields, references to other objects with URLs, and basic text formatting.

111.What is HTTP ?
Hypertext Transfer Protocol. The Internet protocol used to retrieve hypertext objects from remote hosts. HTTP messages consist of requests from client to server and responses from server to client.

112.What is HTTPS ?
HTTP layered over the SSL protocol.

113.What is IDL ?
Interface Definition Language. A language used to define interfaces to remote CORBA objects. The interfaces are independent of operating systems and programming languages.

114.What is IIOP ?
Internet Inter-ORB Protocol. A protocol used for communication between CORBA object request brokers.

115.What is impersonation ?
An act whereby one entity assumes the identity and privileges of another entity without restrictions and without any indication visible to the recipients of the impersonator’s calls that delegation has taken place. Impersonation is a case of simple delegation.

116.What is initialization parameter ?
A parameter that initializes the context associated with a servlet.

117.What is ISO 3166 ?
The international standard for country codes maintained by the International Organization for Standardization (ISO).

118.What is ISV ?
Independent software vendor.

119.What is J2EE ?
Java 2 Platform, Enterprise Edition.

120.What is J2EE application ?
Any deployable unit of J2EE functionality. This can be a single J2EE module or a group of modules packaged into an EAR file along with a J2EE application deployment descriptor. J2EE applications are typically engineered to be distributed across multiple computing tiers.

121.What is J2EE component ?
A self-contained functional software unit supported by a container and configurable at deployment time. The J2EE specification defines the following J2EE components: Application clients and applets are components that run on the client. Java servlet and JavaServer Pages (JSP) technology components are Web components that run on the server. Enterprise JavaBeans (EJB) components (enterprise beans) are business components that run on the server. J2EE components are written in the Java programming language and are compiled in the same way as any program in the language. The difference between J2EE components and “standard” Java classes is that J2EE components are assembled into a J2EE application, verified to be well formed and in compliance with the J2EE specification, and deployed to production, where they are run and managed by the J2EE server or client container.

122.What is J2EE module ?
A software unit that consists of one or more J2EE components of the same container type and one deployment descriptor of that type. There are four types of modules: EJB, Web, application client, and resource adapter. Modules can be deployed as stand-alone units or can be assembled into a J2EE application.

123.What is J2EE product ?
An implementation that conforms to the J2EE platform specification.

124.What is J2EE product provider ?
A vendor that supplies a J2EE product.

125.What is J2EE server ?
The runtime portion of a J2EE product. A J2EE server provides EJB or Web containers or both.

126.What is J2ME ?
Abbreviate of Java 2 Platform, Micro Edition.

127.What is J2SE ?
Abbreviate of Java 2 Platform, Standard Edition.

128.What is JAR ?
Java archive. A platform-independent file format that permits many files to be aggregated into one file.

129.What is Java 2 Platform, Enterprise Edition (J2EE) ?
An environment for developing and deploying enterprise applications. The J2EE platform consists of a set of services, application programming interfaces (APIs), and protocols that provide the functionality for developing multitiered, Web-based applications.

130.What is Java 2 Platform, Micro Edition (J2ME) ?
A highly optimized Java runtime environment targeting a wide range of consumer products, including pagers, cellular phones, screen phones, digital set-top boxes, and car navigation systems.

131.What is Java 2 Platform, Standard Edition (J2SE) ?
The core Java technology platform.

132.What is Java API for XML Processing (JAXP) ?
An API for processing XML documents. JAXP leverages the parser standards SAX and DOM so that you can choose to parse your data as a stream of events or to build a tree-structured representation of it. JAXP supports the XSLT standard, giving you control over the presentation of the data and enabling you to convert the data to other XML documents or to other formats, such as HTML. JAXP provides namespace support, allowing you to work with schema that might otherwise have naming conflicts.

133.What is Java API for XML Registries (JAXR) ?
An API for accessing various kinds of XML registries.

134.What is Java API for XML-based RPC (JAX-RPC) ?
An API for building Web services and clients that use remote procedure calls and XML.  

135.What is Java IDL ?
A technology that provides CORBA interoperability and connectivity capabilities for the J2EE platform. These capabilities enable J2EE applications to invoke operations on remote network services using the Object Management Group IDL and IIOP.

136.What is Java Message Service (JMS) ?
An API for invoking operations on enterprise messaging systems.

137.What is Java Naming and Directory Interface (JNDI) ?
An API that provides naming and directory functionality.

138.What is Java Secure Socket Extension (JSSE) ?
A set of packages that enable secure Internet communications.

139.What is Java Transaction API (JTA) ?
An API that allows applications and J2EE servers to access transactions.

140.What is Java Transaction Service (JTS) ?
Specifies the implementation of a transaction manager that supports JTA and implements the Java mapping of the Object Management Group Object Transaction Service 1.1 specification at the level below the API.

141.What is JavaBeans component ?
A Java class that can be manipulated by tools and composed into applications. A JavaBeans component must adhere to certain property and event interface conventions. 

142.What is JavaMail ?
An API for sending and receiving email.

143.What is JavaServer Faces Technology ?
A framework for building server-side user interfaces for Web applications written in the Java programming language.

144.What is JavaServer Faces conversion model ?
A mechanism for converting between string-based markup generated by JavaServer Faces UI components and server-side Java objects.

145.What is JavaServer Faces event and listener model ?
A mechanism for determining how events emitted by JavaServer Faces UI components are handled. This model is based on the JavaBeans component event and listener model.

146.What is JavaServer Faces expression language ?
A simple expression language used by a JavaServer Faces UI component tag attributes to bind the associated component to a bean property or to bind the associated component’s value to a method or an external data source, such as a bean property. Unlike JSP EL expressions, JavaServer Faces EL expressions are evaluated by the JavaServer Faces implementation rather than by the Web container.

147.What is JavaServer Faces navigation model ?
A mechanism for defining the sequence in which pages in a JavaServer Faces application are displayed.

148.What is JavaServer Faces UI component ?
A user interface control that outputs data to a client or allows a user to input data to a JavaServer Faces application.

149.What is JavaServer Faces UI component class ?
A JavaServer Faces class that defines the behavior and properties of a JavaServer Faces UI component.

150.What is JavaServer Faces validation model ?
A mechanism for validating the data a user inputs to a JavaServer Faces UI component.

151.What is JavaServer Pages (JSP) ?
An extensible Web technology that uses static data, JSP elements, and server-side Java objects to generate dynamic content for a client. Typically the static data is HTML or XML elements, and in many cases the client is a Web browser.

152.What is JavaServer Pages Standard Tag Library (JSTL) ?
A tag library that encapsulates core functionality common to many JSP applications. JSTL has support for common, structural tasks such as iteration and conditionals, tags for manipulating XML documents, internationalization and locale-specific formatting tags, SQL tags, and functions.

153.What is JAXR client ?
A client program that uses the JAXR API to access a business registry via a JAXR provider.

154.What is JAXR provider ?
An implementation of the JAXR API that provides access to a specific registry provider or to a class of registry providers that are based on a common specification.

155.What is JDBC ?
An JDBC for database-independent connectivity between the J2EE platform and a wide range of data sources.

156.What is JMS ?
Java Message Service.

157.What is JMS administered object ?
A preconfigured JMS object (a resource manager connection factory or a destination) created by an administrator for the use of JMS clients and placed in a JNDI namespace.

158.What is JMS application ?
One or more JMS clients that exchange messages.

159.What is JMS client ?
A Java language program that sends or receives messages.

160.What is JMS provider ?
A messaging system that implements the Java Message Service as well as other administrative and control functionality needed in a full-featured messaging product.

161.What is JMS session ?
A single-threaded context for sending and receiving JMS messages. A JMS session can be nontransacted, locally transacted, or participating in a distributed transaction.

162.What is JNDI ?
Abbreviate of Java Naming and Directory Interface.

163.What is JSP ?
Abbreviate of JavaServer Pages.

164.What is JSP action ?
A JSP element that can act on implicit objects and other server-side objects or can define new scripting variables. Actions follow the XML syntax for elements, with a start tag, a body, and an end tag; if the body is empty it can also use the empty tag syntax. The tag must use a prefix. There are standard and custom actions.

165.What is JSP container ?
A container that provides the same services as a servlet container and an engine that interprets and processes JSP pages into a servlet.

166.What is JSP container, distributed ?
A JSP container that can run a Web application that is tagged as distributable and is spread across multiple Java virtual machines that might be running on different hosts.

167.What is JSP custom action ?
A user-defined action described in a portable manner by a tag library descriptor and imported into a JSP page by a taglib directive. Custom actions are used to encapsulate recurring tasks in writing JSP pages.

168.What is JSP custom tag ?
A tag that references a JSP custom action.

169.What is JSP declaration ?
A JSP scripting element that declares methods, variables, or both in a JSP page.

170.What is JSP directive ?
A JSP element that gives an instruction to the JSP container and is interpreted at translation time.

171.What is JSP document ?
A JSP page written in XML syntax and subject to the constraints of XML documents. 

172.What is JSP element ?
A portion of a JSP page that is recognized by a JSP translator. An element can be a directive, an action, or a scripting element.

173.What is JSP expression ?
A scripting element that contains a valid scripting language expression that is evaluated, converted to a String, and placed into the implicit out object.

174.What is JSP expression language ?
A language used to write expressions that access the properties of JavaBeans components. EL expressions can be used in static text and in any standard or custom tag attribute that can accept an expression.

175.What is JSP page ?
A text-based document containing static text and JSP elements that describes how to process a request to create a response. A JSP page is translated into and handles requests as a servlet.

176.What is JSP scripting element ?
A JSP declaration, scriptlet, or expression whose syntax is defined by the JSP specification and whose content is written according to the scripting language used in the JSP page. The JSP specification describes the syntax and semantics for the case where the language page attribute is “java”.

177.What is JSP scriptlet ?
A JSP scripting element containing any code fragment that is valid in the scripting language used in the JSP page. The JSP specification describes what is a valid scriptlet for the case where the language page attribute is “java”.

178.What is JSP standard action ?
An action that is defined in the JSP specification and is always available to a JSP page.

179.What is JSP tag file ?
A source file containing a reusable fragment of JSP code that is translated into a tag handler when a JSP page is translated into a servlet.

180.What is JSP tag handler ?
A Java programming language object that implements the behavior of a custom tag.

181.What is JSP tag library ?
A collection of custom tags described via a tag library descriptor and Java classes. 

182.What is JSTL ?
Abbreviate of JavaServer Pages Standard Tag Library.

183.What is JTA ?
Abbreviate of Java Transaction API.

184.What is JTS ?
Abbreviate of Java Transaction Service.

185.What is keystore ?
A file containing the keys and certificates used for authentication

186.What is life cycle (J2EE component) ?
The framework events of a J2EE component’s existence. Each type of component has defining events that mark its transition into states in which it has varying availability for use. For example, a servlet is created and has its init method called by its container before invocation of its service method by clients or other servlets that require its functionality. After the call of its init method, it has the data and readiness for its intended use. The servlet’s destroy method is called by its container before the ending of its existence so that processing associated with winding up can be done and resources can be released. The init and destroy methods in this example are callback methods. Similar considerations apply to the life cycle of all J2EE component types: enterprise beans, Web components (servlets or JSP pages), applets, and application clients.

187.What is life cycle (JavaServer Faces) ?
A set of phases during which a request for a page is received, a UI component tree representing the page is processed, and a response is produced. During the phases of the life cycle: The local data of the components is updated with the values contained in the request parameters. Events generated by the components are processed. Validators and converters registered on the components are processed. The components’ local data is updated to back-end objects. The response is rendered to the client while the component state of the response is saved on the server for future requests.

188.What is local subset ?
That part of the DTD that is defined within the current XML file.

189.What is managed bean creation facility ?
A mechanism for defining the characteristics of JavaBeans components used in a JavaServer Faces application.

190.What is message ?
In the Java Message Service, an asynchronous request, report, or event that is created, sent, and consumed by an enterprise application and not by a human. It contains vital information needed to coordinate enterprise applications, in the form of precisely formatted data that describes specific business actions.

191.What is message consumer ?
An object created by a JMS session that is used for receiving messages sent to a destination.

192.What is message-driven bean ?
An enterprise bean that is an asynchronous message consumer. A message-driven bean has no state for a specific client, but its instance variables can contain state across the handling of client messages, including an open database connection and an object reference to an EJB object. A client accesses a message-driven bean by sending messages to the destination for which the bean is a message listener.

193.What is message producer ?
An object created by a JMS session that is used for sending messages to a destination.

194.What is mixed-content model ?
A DTD specification that defines an element as containing a mixture of text and one more other elements. The specification must start with #PCDATA, followed by diverse elements, and must end with the “zero-or-more” asterisk symbol (*).

195.What is method-binding expression ?
A Java Server Faces EL expression that refers to a method of a backing bean. This method performs either event handling, validation, or navigation processing for the UI component whose tag uses the method-binding expression.

196.What is method permission ?
An authorization rule that determines who is permitted to execute one or more enterprise bean methods.

197.What is mutual authentication ?
An authentication mechanism employed by two parties for the purpose of proving each other’s identity to one another.

198.What is namespace ?
A standard that lets you specify a unique label for the set of element names defined by a DTD. A document using that DTD can be included in any other document without having a conflict between element names. The elements defined in your DTD are then uniquely identified so that, for example, the parser can tell when an element should be interpreted according to your DTD rather than using the definition for an element in a different DTD.

199.What is naming context ?
A set of associations between unique, atomic, people-friendly identifiers and objects.

200.What is naming environment ?
A mechanism that allows a component to be customized without the need to access or change the component’s source code. A container implements the component’s naming environment and provides it to the component as a JNDI naming context. Each component names and accesses its environment entries using the java:comp/env JNDI context. The environment entries are declaratively specified in the component’s deployment descriptor.

201.What is normalization ?
The process of removing redundancy by modularizing, as with subroutines, and of removing superfluous differences by reducing them to a common denominator. For example, line endings from different systems are normalized by reducing them to a single new line, and multiple whitespace characters are normalized to one space.

202.What is North American Industry Classification System (NAICS) ?
A system for classifying business establishments based on the processes they use to produce goods or services.

203.What is notation ?
A mechanism for defining a data format for a non-XML document referenced as an unparsed entity. This is a holdover from SGML. A newer standard is to use MIME data types and namespaces to prevent naming conflicts.

204.What is OASIS ?
Organization for the Advancement of Structured Information Standards. A consortium that drives the development, convergence, and adoption of e-business standards.

205.What is OMG ?
Object Management Group. A consortium that produces and maintains computer industry specifications for interoperable enterprise applications.

206.What is one-way messaging ?
A method of transmitting messages without having to block until a response is received.

207.What is ORB ?
Object request broker. A library that enables CORBA objects to locate and communicate with one another.

208.What is OS principal ?
A principal native to the operating system on which the J2EE platform is executing.

209.What is OTS ?
Object Transaction Service. A definition of the interfaces that permit CORBA objects to participate in transactions

210.What is parameter entity ?
An entity that consists of DTD specifications, as distinct from a general entity. A parameter entity defined in the DTD can then be referenced at other points, thereby eliminating the need to recode the definition at each location it is used.

211.What is parsed entity ?
A general entity that contains XML and therefore is parsed when inserted into the XML document, as opposed to an unparsed entity.

212.What is parser ?
A module that reads in XML data from an input source and breaks it into chunks so that your program knows when it is working with a tag, an attribute, or element data. A nonvalidating parser ensures that the XML data is well formed but does not verify that it is valid. See also validating parser.

213.What is passivation ?
The process of transferring an enterprise bean from memory to secondary storage. See activation.

214.What is persistence ?
The protocol for transferring the state of an entity bean between its instance variables and an underlying database.

215.What is persistent field ?
A virtual field of an entity bean that has container-managed persistence; it is stored in a database.

216.What is POA ?
Portable Object Adapter. A CORBA standard for building server-side applications that are portable across heterogeneous ORBs.

217.What is point-to-point messaging system ?
A messaging system built on the concept of message queues. Each message is addressed to a specific queue; clients extract messages from the queues established to hold their messages.

218.What is primary key ?
An object that uniquely identifies an entity bean within a home.

219.What is principal ?
The identity assigned to a user as a result of authentication.

220.What is privilege ?
A security attribute that does not have the property of uniqueness and that can be shared by many principals.

221.What is processing instruction ?
Information contained in an XML structure that is intended to be interpreted by a specific application.

222.What is programmatic security ?
Security decisions that are made by security-aware applications. Programmatic security is useful when declarative security alone is not sufficient to express the security model of an application.

223.What is prolog ?
The part of an XML document that precedes the XML data. The prolog includes the declaration and an optional DTD.

224.What is public key certificate ?
Used in client-certificate authentication to enable the server, and optionally the client, to authenticate each other. The public key certificate is the digital equivalent of a passport. It is issued by a trusted organization, called a certificate authority, and provides identification for the bearer.

225.What is publish/subscribe messaging system ?
A messaging system in which clients address messages to a specific node in a content hierarchy, called a topic. Publishers and subscribers are generally anonymous and can dynamically publish or subscribe to the content hierarchy. The system takes care of distributing the messages arriving from a node’s multiple publishers to its multiple subscribers.

226.What is query string ?
A component of an HTTP request URL that contains a set of parameters and values that affect the handling of the request.

227.What is queue ?
A messaging system built on the concept of message queues. Each message is addressed to a specific queue; clients extract messages from the queues established to hold their messages.

228.What is RAR ?
Resource Adapter Archive. A JAR archive that contains a resource adapter module.

229.What is RDF ?
Resource Description Framework. A standard for defining the kind of data that an XML file contains. Such information can help ensure semantic integrity-for example-by helping to make sure that a date is treated as a date rather than simply as text.

230.What is RDF schema ?
A standard for specifying consistency rules that apply to the specifications contained in an RDF.

231.What is realm ?
See security policy domain. Also, a string, passed as part of an HTTP request during basic authentication, that defines a protection space. The protected resources on a server can be partitioned into a set of protection spaces, each with its own authentication scheme or authorization database or both. In the J2EE server authentication service, a realm is a complete database of roles, users, and groups that identify valid users of a Web application or a set of Web applications.

232.What is reentrant entity bean ?
An entity bean that can handle multiple simultaneous, interleaved, or nested invocations that will not interfere with each other.

233.What is reference ?
A reference to an entity that is substituted for the reference when the XML document is parsed. It can reference a predefined entity such as < or reference one that is defined in the DTD. In the XML data, the reference could be to an entity that is defined in the local subset of the DTD or to an external XML file (an external entity). The DTD can also carve out a segment of DTD specifications and give it a name so that it can be reused (included) at multiple points in the DTD by defining a parameter entity.

234.What is registry ?
An infrastructure that enables the building, deployment, and discovery of Web services. It is a neutral third party that facilitates dynamic and loosely coupled business-to-business (B2B) interactions.

235.What is registry provider ?
An implementation of a business registry that conforms to a specification for XML registries (for example, ebXML or UDDI).

236.What is relationship field ?
A virtual field of an entity bean having container-managed persistence; it identifies a related entity bean.

237.What is remote interface ?
One of two interfaces for an enterprise bean. The remote interface defines the business methods callable by a client.

238.What is remove method ?
Method defined in the Home interface and invoked by a client to destroy an enterprise bean.

239.What is render kit ?
A set of renderers that render output to a particular client. The JavaServer Faces implementation provides a standard HTML render kit, which is composed of renderers that can render HMTL markup.

240.What is renderer ?
A Java class that can render the output for a set of JavaServer Faces UI components.

241.What is resource adapter ?
A system-level software driver that is used by an EJB container or an application client to connect to an enterprise information system. A resource adapter typically is specific to an enterprise information system. It is available as a library and is used within the address space of the server or client using it. A resource adapter plugs in to a container. The application components deployed on the container then use the client API (exposed by the adapter) or tool-generated high-level abstractions to access the underlying enterprise information system. The resource adapter and EJB container collaborate to provide the underlying mechanisms-transactions, security, and connection pooling-for connectivity to the enterprise information system.

242.What is resource adapter module ?
A deployable unit that contains all Java interfaces, classes, and native libraries, implementing a resource adapter along with the resource adapter deployment descriptor.

243.What is resource manager ?
Provides access to a set of shared resources. A resource manager participates in transactions that are externally controlled and coordinated by a transaction manager. A resource manager typically is in a different address space or on a different machine from the clients that access it. Note: An enterprise information system is referred to as a resource manager when it is mentioned in the context of resource and transaction management.

244.What is resource manager connection ?
An object that represents a session with a resource manager.

245.What is resource manager connection factory ?
An object used for creating a resource manager connection.

246.What is RMI ?
Remote Method Invocation. A technology that allows an object running in one Java virtual machine to invoke methods on an object running in a different Java virtual machine.

247.What is RMI-IIOP ?
A version of RMI implemented to use the CORBA IIOP protocol. RMI over IIOP provides interoperability with CORBA objects implemented in any language if all the remote interfaces are originally defined as RMI interfaces.

248.What is role (development) ?
The function performed by a party in the development and deployment phases of an application developed using J2EE technology. The roles are application component provider, application assembler, deployer, J2EE product provider, EJB container provider, EJB server provider, Web container provider, Web server provider, tool provider, and system administrator.

249.What is role mapping ?
The process of associating the groups or principals (or both), recognized by the container with security roles specified in the deployment descriptor. Security roles must be mapped by the deployer before a component is installed in the server.

250.What is role (security) ?
An abstract logical grouping of users that is defined by the application assembler. When an application is deployed, the roles are mapped to security identities, such as principals or groups, in the operational environment. In the J2EE server authentication service, a role is an abstract name for permission to access a particular set of resources. A role can be compared to a key that can open a lock. Many people might have a copy of the key; the lock doesn’t care who you are, only that you have the right key.

251.What is rollback ?
The point in a transaction when all updates to any resources involved in the transaction are reversed.

252.What is root ?
The outermost element in an XML document. The element that contains all other elements.

253.What is SAX ?
Abbreviation of Simple API for XML.

254.What is Simple API for XML ?
An event-driven interface in which the parser invokes one of several methods supplied by the caller when a parsing event occurs. Events include recognizing an XML tag, finding an error, encountering a reference to an external entity, or processing a DTD specification.

255.What is schema ?
A database-inspired method for specifying constraints on XML documents using an XML-based language. Schemas address deficiencies in DTDs, such as the inability to put constraints on the kinds of data that can occur in a particular field. Because schemas are founded on XML, they are hierarchical. Thus it is easier to create an unambiguous specification, and it is possible to determine the scope over which a comment is meant to apply.

256.What is Secure Socket Layer (SSL) ?
A technology that allows Web browsers and Web servers to communicate over a secured connection.

257.What is security attributes ?
A set of properties associated with a principal. Security attributes can be associated with a principal by an authentication protocol or by a J2EE product provider or both. 

258.What is security constraint ?
A declarative way to annotate the intended protection of Web content. A security constraint consists of a Web resource collection, an authorization constraint, and a user data constraint.

259.What is security context ?
An object that encapsulates the shared state information regarding security between two entities.

260.What is security permission ?
A mechanism defined by J2SE, and used by the J2EE platform to express the programming restrictions imposed on application component developers.

261.What is security permission set ?
The minimum set of security permissions that a J2EE product provider must provide for the execution of each component type.

262.What is security policy domain ?
A scope over which security policies are defined and enforced by a security administrator. A security policy domain has a collection of users (or principals), uses a well-defined authentication protocol or protocols for authenticating users (or principals), and may have groups to simplify setting of security policies.

263.What is security role ?
An abstract logical grouping of users that is defined by the application assembler. When an application is deployed, the roles are mapped to security identities, such as principals or groups, in the operational environment. In the J2EE server authentication service, a role is an abstract name for permission to access a particular set of resources. A role can be compared to a key that can open a lock. Many people might have a copy of the key; the lock doesn’t care who you are, only that you have the right key.

264.What is security technology domain ?
A scope over which the same security mechanism is used to enforce a security policy. Multiple security policy domains can exist within a single technology domain.

265.What is security view ?
The set of security roles defined by the application assembler.

266.What is server certificate ?
Used with the HTTPS protocol to authenticate Web applications. The certificate can be self-signed or approved by a certificate authority (CA). The HTTPS service of the Sun Java System Application Server Platform Edition 8 will not run unless a server certificate has been installed.

267.What is server principal ?
The OS principal that the server is executing as.

268.What is service element ?
A representation of the combination of one or more Connector components that share a single engine component for processing incoming requests.

269.What is service endpoint interface ?
A Java interface that declares the methods that a client can invoke on a Web service.

270.What is servlet ?
A Java program that extends the functionality of a Web server, generating dynamic content and interacting with Web applications using a request-response paradigm.

271.What is servlet container ?
A container that provides the network services over which requests and responses are sent, decodes requests, and formats responses. All servlet containers must support HTTP as a protocol for requests and responses but can also support additional request-response protocols, such as HTTPS.

272.What is servlet container, distributed ?
A servlet container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.

273.What is servlet context ?
An object that contains a servlet’s view of the Web application within which the servlet is running. Using the context, a servlet can log events, obtain URL references to resources, and set and store attributes that other servlets in the context can use. 

274.What is servlet mapping ?
Defines an association between a URL pattern and a servlet. The mapping is used to map requests to servlets.

275.What is session ?
An object used by a servlet to track a user’s interaction with a Web application across multiple HTTP requests.

276.What is session bean ?
An enterprise bean that is created by a client and that usually exists only for the duration of a single client-server session. A session bean performs operations, such as calculations or database access, for the client. Although a session bean can be transactional, it is not recoverable should a system crash occur. Session bean objects either can be stateless or can maintain conversational state across methods and transactions. If a session bean maintains state, then the EJB container manages this state if the object must be removed from memory. However, the session bean object itself must manage its own persistent data.

277.What is SGML ?
Standard Generalized Markup Language. The parent of both HTML and XML. Although HTML shares SGML’s propensity for embedding presentation information in the markup, XML is a standard that allows information content to be totally separated from the mechanisms for rendering that content.

278.What is SOAP ?
Simple Object Access Protocol. A lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. It defines, using XML technologies, an extensible messaging framework containing a message construct that can be exchanged over a variety of underlying protocols.

279.What is SOAP with Attachments API for Java (SAAJ) ?
The basic package for SOAP messaging, SAAJ contains the API for creating and populating a SOAP message.

280.What is SQL ?
Structured Query Language. The standardized relational database language for defining database objects and manipulating data.

281.What is SQL/J ?
A set of standards that includes specifications for embedding SQL statements in methods in the Java programming language and specifications for calling Java static methods as SQL stored procedures and user-defined functions. An SQL checker can detect errors in static SQL statements at program development time, rather than at execution time as with a JDBC driver.

282.What is SSL ?
Secure Socket Layer. A security protocol that provides privacy over the Internet. The protocol allows client-server applications to communicate in a way that cannot be eavesdropped upon or tampered with. Servers are always authenticated, and clients are optionally authenticated.

283.What is stateful session bean ?
A session bean with a conversational state.

284.What is stateless session bean ?
A session bean with no conversational state. All instances of a stateless session bean are identical.

285.What is system administrator ?
The person responsible for configuring and administering the enterprise’s computers, networks, and software systems.

286.What is tag ?
In XML documents, a piece of text that describes a unit of data or an element. The tag is distinguishable as markup, as opposed to data, because it is surrounded by angle brackets (< and >). To treat such markup syntax as data, you use an entity reference or a CDATA section.

287.What is template ?
A set of formatting instructions that apply to the nodes selected by an XPath expression.

288.What is tool provider ?
An organization or software vendor that provides tools used for the development, packaging, and deployment of J2EE applications.

289.What is transaction attribute ?
A value specified in an enterprise bean’s deployment descriptor that is used by the EJB container to control the transaction scope when the enterprise bean’s methods are invoked. A transaction attribute can have the following values: Required, RequiresNew, Supports, NotSupported, Mandatory, or Never.

290.What is transaction ?
An atomic unit of work that modifies data. A transaction encloses one or more program statements, all of which either complete or roll back. Transactions enable multiple users to access the same data concurrently.

291.What is transaction isolation level ?
What is transaction isolation level The degree to which the intermediate state of the data being modified by a transaction is visible to other concurrent transactions and data being modified by other transactions is visible to it.

292.What is transaction manager ?
Provides the services and management functions required to support transaction demarcation, transactional resource management, synchronization, and transaction context propagation.

293.What is Unicode ?
A standard defined by the Unicode Consortium that uses a 16-bit code page that maps digits to characters in languages around the world. Because 16 bits covers 32,768 codes, Unicode is large enough to include all the world’s languages, with the exception of ideographic languages that have a different character for every concept, such as Chinese.

294.What is Universal Description, Discovery and Integration (UDDI) project ?
An industry initiative to create a platform-independent, open framework for describing services, discovering businesses, and integrating business services using the Internet, as well as a registry. It is being developed by a vendor consortium.

295.What is Universal Standard Products and Services Classification (UNSPSC) ?
A schema that classifies and identifies commodities. It is used in sell-side and buy-side catalogs and as a standardized account code in analyzing expenditure.

296.What is unparsed entity ?
A general entity that contains something other than XML. By its nature, an unparsed entity contains binary data.

297.What is URI ?
Uniform resource identifier. A globally unique identifier for an abstract or physical resource. A URL is a kind of URI that specifies the retrieval protocol (http or https for Web applications) and physical location of a resource (host name and host-relative path). A URN is another type of URI.

298.What is URL ?
Uniform resource locator. A standard for writing a textual reference to an arbitrary piece of data in the World Wide Web. A URL looks like this: protocol://host/local info where protocol specifies a protocol for fetching the object (such as http or ftp), host specifies the Internet name of the targeted host, and local info is a string (often a file name) passed to the protocol handler on the remote host.

299.What is URL path ?
The part of a URL passed by an HTTP request to invoke a servlet. A URL path consists of the context path + servlet path + path info, where Context path is the path prefix associated with a servlet context of which the servlet is a part. If this context is the default context rooted at the base of the Web server’s URL namespace, the path prefix will be an empty string. Otherwise, the path prefix starts with a / character but does not end with a / character. Servlet path is the path section that directly corresponds to the mapping that activated this request. This path starts with a / character. Path info is the part of the request path that is not part of the context path or the servlet path

300.What is URN ?
Uniform resource name. A unique identifier that identifies an entity but doesn’t tell where it is located. A system can use a URN to look up an entity locally before trying to find it on the Web. It also allows the Web location to change, while still allowing the entity to be found.

301.What is user data constraint ?
Indicates how data between a client and a Web container should be protected. The protection can be the prevention of tampering with the data or prevention of eavesdropping on the data.

302.What is user (security) ?
An individual (or application program) identity that has been authenticated. A user can have a set of roles associated with that identity, which entitles the user to access all resources protected by those roles.

303.What is validating parser ?
A parser that ensures that an XML document is valid in addition to being well formed. See also parser.

304.What is value-binding expression ?
A JavaServer Faces EL expression that refers to a property of a backing bean. A component tag uses this expression to bind the associated component’s value or the component instance to the bean property. If the component tag refers to the property via its value attribute, then the component’s value is bound to the property. If the component tag refers to the property via its binding attribute then the component itself is bound to the property.

305.What is virtual host ?
Multiple hosts plus domain names mapped to a single IP address.

306.What is W3C ?
World Wide Web Consortium. The international body that governs Internet standards. Its Web site is http://www.w3.org/.

307.What is WAR file ?
Web application archive file. A JAR archive that contains a Web module.

308.What is warning ?
A SAX parser warning is generated when the document’s DTD contains duplicate definitions and in similar situations that are not necessarily an error but which the document author might like to know about, because they could be. See also fatal error, error.

309.What is Web application ?
An application written for the Internet, including those built with Java technologies such as JavaServer Pages and servlets, as well as those built with non-Java technologies such as CGI and Perl.

310.What is Web application, distributable ?
A Web application that uses J2EE technology written so that it can be deployed in a Web container distributed across multiple Java virtual machines running on the same host or different hosts. The deployment descriptor for such an application uses the distributable element.

311.What is Web component ?
A component that provides services in response to requests; either a servlet or a JSP page.

312.What is Web container ?
A container that implements the Web component contract of the J2EE architecture. This contract specifies a runtime environment for Web components that includes security, concurrency, life-cycle management, transaction, deployment, and other services. A Web container provides the same services as a JSP container as well as a federated view of the J2EE platform APIs. A Web container is provided by a Web or J2EE server.

313.What is Web container, distributed ?
A Web container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.

314.What is Web container provider ?
A vendor that supplies a Web container.

315.What is Web module ?
A deployable unit that consists of one or more Web components, other resources, and a Web application deployment descriptor contained in a hierarchy of directories and files in a standard Web application format.

316.What is Web resource ?
A static or dynamic object contained in a Web application that can be referenced by a URL. 

317.What is Web resource collection ?
A list of URL patterns and HTTP methods that describe a set of Web resources to be protected.

318.What is Web server ?
Software that provides services to access the Internet, an intranet, or an extranet. A Web server hosts Web sites, provides support for HTTP and other protocols, and executes server-side programs (such as CGI scripts or servlets) that perform certain functions. In the J2EE architecture, a Web server provides services to a Web container. For example, a Web container typically relies on a Web server to provide HTTP message handling. The J2EE architecture assumes that a Web container is hosted by a Web server from the same vendor, so it does not specify the contract between these two entities. A Web server can host one or more Web containers. 

319.What is Web server provider ?
A vendor that supplies a Web server.

320.What is Web service ?
An application that exists in a distributed environment, such as the Internet. A Web service accepts a request, performs its function based on the request, and returns a response. The request and the response can be part of the same operation, or they can occur separately, in which case the consumer does not need to wait for a response. Both the request and the response usually take the form of XML, a portable data-interchange format, and are delivered over a wire protocol, such as HTTP.

321.What is well-formed ?
An XML document that is syntactically correct. It does not have any angle brackets that are not part of tags, all tags have an ending tag or are themselves self-ending, and all tags are fully nested. Knowing that a document is well formed makes it possible to process it. However, a well-formed document may not be valid. To determine that, you need a validating parser and a DTD.

322.What is Xalan ?
An interpreting version of XSLT.

323.What is XHTML ?
An XML look-alike for HTML defined by one of several XHTML DTDs. To use XHTML for everything would of course defeat the purpose of XML, because the idea of XML is to identify information content, and not just to tell how to display it. You can reference it in a DTD, which allows you to say, for example, that the text in an element can contain < em > and < b > tags rather than being limited to plain text.

324.What is XLink ?
The part of the XLL specification that is concerned with specifying links between documents.

325.What is XLL ?
The XML Link Language specification, consisting of XLink and XPointer.

326.What is XML ?
Extensible Markup Language. A markup language that allows you to define the tags (markup) needed to identify the content, data, and text in XML documents. It differs from HTML, the markup language most often used to present information on the Internet. HTML has fixed tags that deal mainly with style or presentation. An XML document must undergo a transformation into a language with style tags under the control of a style sheet before it can be presented by a browser or other presentation mechanism. Two types of style sheets used with XML are CSS and XSL. Typically, XML is transformed into HTML for presentation. Although tags can be defined as needed in the generation of an XML document, a document type definition (DTD) can be used to define the elements allowed in a particular type of document. A document can be compared by using the rules in the DTD to determine its validity and to locate particular elements in the document. A Web services application’s J2EE deployment descriptors are expressed in XML with schemas defining allowed elements. Programs for processing XML documents use SAX or DOM APIs.

327.What is XML registry ?
An infrastructure that enables the building, deployment, and discovery of Web services. It is a neutral third party that facilitates dynamic and loosely coupled business-to-business (B2B) interactions.

328.What is XML Schema ?
The W3C specification for defining the structure, content, and semantics of XML documents.

329.What is XPath ?
An addressing mechanism for identifying the parts of an XML document.

330.What is XPointer ?
The part of the XLL specification that is concerned with identifying sections of documents so that they can be referenced in links or included in other documents.

331.What is XSL-FO ?
A subcomponent of XSL used for describing font sizes, page layouts, and how information flows from one page to another.

332.What is component (JavaServer Faces technology) ?
A user interface control that outputs data to a client or allows a user to input data to a JavaServer Faces application.