Explore topic-wise InterviewSolutions in Current Affairs.

StreamMessage carries a stream of Java primitive types as it's payload. It contains some conveient methods for reading the data stored in the payload. However, StreamMessage prevents reading a long value as SHORT, something that is allowed in case of BytesMessage. This is so because the StreamMessage also writes the TYPE information along with the value of the primitive type and ENFORCES a set of strict CONVERSION rules which ACTUALLY prevents reading of one primitive type as another.

StreamMessage carries a stream of Java primitive types as it's payload. It contains some conveient methods for reading the data stored in the payload. However, StreamMessage prevents reading a long value as short, something that is allowed in case of BytesMessage. This is so because the StreamMessage also writes the type information along with the value of the primitive type and enforces a set of strict conversion rules which actually prevents reading of one primitive type as another.

BytesMessage contains an array of primitive bytes in it's PAYLOAD. Thus it can be used for transfer of data between two applications in their native FORMAT which may not be compatible with other Message types. It is also useful where JMS is used purely as a transport between two systems and the message payload is opaque to the JMS client. Whenever you store any primitive type, it is converted into it's byte representation and then stored in the payload. There is no boundary LINE between the different data types stored. Thus you can even READ a long as short. This would result in ERRONEOUS data and hence it is advisable that the payload be read in the same order and using the same type in which it was created by the sender.

BytesMessage contains an array of primitive bytes in it's payload. Thus it can be used for transfer of data between two applications in their native format which may not be compatible with other Message types. It is also useful where JMS is used purely as a transport between two systems and the message payload is opaque to the JMS client. Whenever you store any primitive type, it is converted into it's byte representation and then stored in the payload. There is no boundary line between the different data types stored. Thus you can even read a long as short. This would result in erroneous data and hence it is advisable that the payload be read in the same order and using the same type in which it was created by the sender.

Publish SUBSCRIBE model is typically used in one-to-many SITUATION. It is UNRELIABLE but very fast. P2P model is used in one-to-one situation. It is highly RELIABLE.

Publish Subscribe model is typically used in one-to-many situation. It is unreliable but very fast. P2P model is used in one-to-one situation. It is highly reliable.

Message is a light WEIGHT message having only header and properties and no payload. THUS if the receivers are to be NOTIFIED about an event, and no DATA needs to be exchanged then using Message can be very EFFICIENT.

Message is a light weight message having only header and properties and no payload. Thus if the receivers are to be notified about an event, and no data needs to be exchanged then using Message can be very efficient.

JMS is typically used in the following scenarios
1. Enterprise Application Integration: - Where a legacy application is integrated with a new application via messaging.
2. B2B or Business to Business: - Businesses can interact with each other via messaging because JMS allows organizations to COOPERATE without tightly COUPLING their business systems.
3. Geographically dispersed units: - JMS can ensure SAFE exchange of data amongst the geographically dispersed units of an organization.
4. One to many applications: - The applications that NEED to push data in packet to huge number of clients in a one-to-many fashion are good candidates for the use JMS. Typical such applications are Auction Sites, Stock Quote Services etc.

JMS is typically used in the following scenarios
1. Enterprise Application Integration: - Where a legacy application is integrated with a new application via messaging.
2. B2B or Business to Business: - Businesses can interact with each other via messaging because JMS allows organizations to cooperate without tightly coupling their business systems.
3. Geographically dispersed units: - JMS can ensure safe exchange of data amongst the geographically dispersed units of an organization.
4. One to many applications: - The applications that need to push data in packet to huge number of clients in a one-to-many fashion are good candidates for the use JMS. Typical such applications are Auction Sites, Stock Quote Services etc.

A topic is typically USED for one to MANY messaging i.e. it supports PUBLISH SUBSCRIBE model of messaging. While queue is used for one-to-one messaging i.e. it supports Point to Point Messaging.

A topic is typically used for one to many messaging i.e. it supports publish subscribe model of messaging. While queue is used for one-to-one messaging i.e. it supports Point to Point Messaging.

PUBLISH and SUBSCRIBE i.e. pub/suc and POINT to Point i.e. P2P.

Publish and Subscribe i.e. pub/suc and Point to Point i.e. p2p.

Message, TextMessage, BYTESMESSAGE, STREAMMESSAGE, ObjectMessage, MapMessage are the DIFFERENT messages AVAILABLE in the JMS API.

Message, TextMessage, BytesMessage, StreamMessage, ObjectMessage, MapMessage are the different messages available in the JMS API.

IBM's MQ Series is one of the most popular PRODUCT used as Message Oriented Middleware. Some of the other products are SonicMQ, iBus etc.All the J2EE compliant APPLICATION servers come built with thier own implementation of JMS.

IBM's MQ Series is one of the most popular product used as Message Oriented Middleware. Some of the other products are SonicMQ, iBus etc.All the J2EE compliant application servers come built with thier own implementation of JMS.

JMS is asynchronous in nature. Thus not all the pieces NEED to be up all the TIME for the application to function as a whole. Even if the receiver is down the MOM will store the messages on it's behalf and will send them once it COMES BACK up. Thus at least a part of application can still function as there is no blocking.

JMS is asynchronous in nature. Thus not all the pieces need to be up all the time for the application to function as a whole. Even if the receiver is down the MOM will store the messages on it's behalf and will send them once it comes back up. Thus at least a part of application can still function as there is no blocking.

In RPC the method invoker WAITS for the method to finish execution and return the control back to the invoker. Thus it is completely synchronous in nature. While in JMS the message SENDER just SENDS the message to the destination and continues it's own processing. The sender does not wait for the receiver to respond. This is asynchronous BEHAVIOR.

In RPC the method invoker waits for the method to finish execution and return the control back to the invoker. Thus it is completely synchronous in nature. While in JMS the message sender just sends the message to the destination and continues it's own processing. The sender does not wait for the receiver to respond. This is asynchronous behavior.

JMS is an ACRONYM used for Java Messaging Service. It is Java's answer to creating software using asynchronous messaging. It is ONE of the OFFICIAL SPECIFICATIONS of the J2EE TECHNOLOGIES and is a key technology.

JMS is an acronym used for Java Messaging Service. It is Java's answer to creating software using asynchronous messaging. It is one of the official specifications of the J2EE technologies and is a key technology.

setSecurityManager() METHOD is USED for SETTING SECURITY in APPLETS.

setSecurityManager() method is used for setting security in applets.

The AWT event dispatcher thread is not a DAEMON thread. You must explicitly call System.exit to TERMINATE the JVM.

The AWT event dispatcher thread is not a daemon thread. You must explicitly call System.exit to terminate the JVM.

The only thread-safe METHODS are REPAINT(), revalidate(), and INVALIDATE()

The only thread-safe methods are repaint(), revalidate(), and invalidate()

A callback IMPLEMENTATION like ActionListener.actionPerformed or MouseListener.mouseClicked is TAKING a LONG TIME to execute thereby blocking the event dispatch thread from PROCESSING other UI events.

A callback implementation like ActionListener.actionPerformed or MouseListener.mouseClicked is taking a long time to execute thereby blocking the event dispatch thread from processing other UI events.

I WANT to update a SWING component but I’m not in a callback. If I want the update to happen immediately (perhaps for a progress BAR component) then I’d use INVOKEANDWAIT. If I don’t care when the update occurs, I’d use INVOKELATER.

I want to update a Swing component but I’m not in a callback. If I want the update to happen immediately (perhaps for a progress bar component) then I’d use invokeAndWait. If I don’t care when the update occurs, I’d use invokeLater.

SWING components should be updated directly only in the context of callback methods invoked from the EVENT dispatch THREAD. Any other context is not thread safe.

Swing components should be updated directly only in the context of callback methods invoked from the event dispatch thread. Any other context is not thread safe.

Because callbacks are invoked by the EVENT DISPATCH thread which will be blocked processing other EVENTS for as long as your method takes to EXECUTE.

Because callbacks are invoked by the event dispatch thread which will be blocked processing other events for as long as your method takes to execute.

This is a TRICK. most people would SAY ‘add a KeyListener to the JComboBox’ - but the RIGHT answer is ‘add a KeyListener to the JComboBox’s EDITOR component.’

This is a trick. most people would say ‘add a KeyListener to the JComboBox’ - but the right answer is ‘add a KeyListener to the JComboBox’s editor component.’

USE a JEditorPane or JTextPane and SET it with an HTMLEditorKit, then LOAD the TEXT into the PANE.

Use a JEditorPane or JTextPane and set it with an HTMLEditorKit, then load the text into the pane.

The java.AWT.AWTEvent CLASS is the highest-level class in the AWT event-class HIERARCHY..

The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy..

The FONT Class is used to render ‘glyphs’ - the characters you see on the screen. FontMetrics encapsulates INFORMATION about a SPECIFIC font on a specific Graphics OBJECT. (width of the characters, ASCENT, descent)

The Font Class is used to render ‘glyphs’ - the characters you see on the screen. FontMetrics encapsulates information about a specific font on a specific Graphics object. (width of the characters, ascent, descent)

In the UIDefaults table, OVERRIDE the entry for TABBED pane and PUT in the SOLARISUI delegate. (I don’t KNOW it offhand, but I think it’s "com.sun.ui.motiflookandfeel.MotifTabbedPaneUI" - anything simiar is a good answer.)

In the UIDefaults table, override the entry for tabbed pane and put in the SolarisUI delegate. (I don’t know it offhand, but I think it’s "com.sun.ui.motiflookandfeel.MotifTabbedPaneUI" - anything simiar is a good answer.)

There’s 2 ways. The first thing is to know that a JButton’s EDGES are drawn by a Border. so you can override the Button’s PAINTCOMPONENT(Graphics) METHOD and draw a circle or rounded rectangle (whatever), and TURN off the border. Or you can create a custom border that draws a circle or rounded rectangle around any COMPONENT and set the button’s border to it.

There’s 2 ways. The first thing is to know that a JButton’s edges are drawn by a Border. so you can override the Button’s paintComponent(Graphics) method and draw a circle or rounded rectangle (whatever), and turn off the border. Or you can create a custom border that draws a circle or rounded rectangle around any component and set the button’s border to it.

Because JComponent is a SUBCLASS of CONTAINER, and can CONTAIN other COMPONENTS and jcomponents.

Because JComponent is a subclass of Container, and can contain other components and jcomponents.

Sure. an example could be a CLASS that extends Jbutton and IMPLEMENTS ActionListener. In the actionPerformed METHOD, put the CODE to PERFORM when the button is pressed.

Sure. an example could be a class that extends Jbutton and implements ActionListener. In the actionPerformed method, put the code to perform when the button is pressed.

There is no such guarantee. The server (or servers) can INSTANTIATE as many instances of the same underlying ENTITY Bean (with the same PK) as it wants. However, each instance is GUARANTEED to have up-to-date data values, and be transactionally consistent, so uniqueness is not required. This allows the server to scale the SYSTEM to support multiple threads, multiple concurrent requests, and multiple hosts.

There is no such guarantee. The server (or servers) can instantiate as many instances of the same underlying Entity Bean (with the same PK) as it wants. However, each instance is guaranteed to have up-to-date data values, and be transactionally consistent, so uniqueness is not required. This allows the server to scale the system to support multiple threads, multiple concurrent requests, and multiple hosts.

Asynchronous notification is a known hole in the first versions of the EJB spec. The recommended solution to this is to use JMS, which is becoming AVAILABLE in J2EE-compliant servers. The other OPTION, of COURSE, is to use client-side THREADS and POLLING. This is not an ideal solution, but it’s workable for many scenarios.

Asynchronous notification is a known hole in the first versions of the EJB spec. The recommended solution to this is to use JMS, which is becoming available in J2EE-compliant servers. The other option, of course, is to use client-side threads and polling. This is not an ideal solution, but it’s workable for many scenarios.

It’s certainly possible. In fact, there’s an EXAMPLE that ships with the Inprise Application SERVER of an Account INTERFACE with SEPARATE implementations for CheckingAccount and SavingsAccount, one of which was CMP and one of which was BMP.

It’s certainly possible. In fact, there’s an example that ships with the Inprise Application Server of an Account interface with separate implementations for CheckingAccount and SavingsAccount, one of which was CMP and one of which was BMP.

No. To ACHIEVE this you have to deploy your EJB MULTIPLE times each specifying a different JNDI NAME.

No. To achieve this you have to deploy your EJB multiple times each specifying a different JNDI name.

ENTERPRISE beans MAKE use of the services provided by the EJB CONTAINER, such as life-cycle management. To avoid conflicts with these services, enterprise beans are restricted from performing certain operations: Managing or synchronizing threads.

Enterprise beans make use of the services provided by the EJB container, such as life-cycle management. To avoid conflicts with these services, enterprise beans are restricted from performing certain operations: Managing or synchronizing threads.

The FOLLOWING code snippet SHOWS how a SERVLET instantiates a bean and initializes it with FORM data posted by a browser. The bean is then placed into the request, and the call is then forwarded to the JSP page, Bean1.jsp, by means of a request dispatcher for downstream processing.

The following code snippet shows how a servlet instantiates a bean and initializes it with FORM data posted by a browser. The bean is then placed into the request, and the call is then forwarded to the JSP page, Bean1.jsp, by means of a request dispatcher for downstream processing.

A select method can return a persistent field (or a collection thereof) of a related ENTITY bean. A finder method can return only a local or remote interface (or a collection of INTERFACES).

Because it is not exposed in any of the local or remote interfaces, a select method cannot be INVOKED by a client. It can be invoked only by the methods implemented WITHIN the entity bean class. A select method is USUALLY invoked by either a business or a home method.

A select method is defined in the entity bean class. For bean-managed persistence, a finder method is defined in the entity bean class, but for container-managed persistence it is not.

A select method can return a persistent field (or a collection thereof) of a related entity bean. A finder method can return only a local or remote interface (or a collection of interfaces).

Because it is not exposed in any of the local or remote interfaces, a select method cannot be invoked by a client. It can be invoked only by the methods implemented within the entity bean class. A select method is usually invoked by either a business or a home method.

A select method is defined in the entity bean class. For bean-managed persistence, a finder method is defined in the entity bean class, but for container-managed persistence it is not.

Abstract SCHEMA is part of an ENTITY bean’s deployment descriptor which defines the bean’s PERSISTENT fields and their relationship. Abstract schema is specified for entity beans with container managed persistence. We specify the name of the Abstract schema name in the deployment descriptor. The queries written in EJB QL for the finder methods references this name. The INFORMATION provided in this Abstract Schema is used by the container for persistence management and relationship management.

Abstract schema is part of an entity bean’s deployment descriptor which defines the bean’s persistent fields and their relationship. Abstract schema is specified for entity beans with container managed persistence. We specify the name of the Abstract schema name in the deployment descriptor. The queries written in EJB QL for the finder methods references this name. The information provided in this Abstract Schema is used by the container for persistence management and relationship management.

An EJB can use local client view only if it is really guaranteed that other enterprise beans or clients will only address the bean within a single JVM. With local client view, you can do pass-by-reference, which MEANS your bean, as well as the client, will work directly with one COPY of the data. Any changes made by the bean will be seen by the client and vice versa. Pass-by-reference ELIMINATES time/system expenses for copying data variables, which PROVIDES a PERFORMANCE advantage.

An EJB can use local client view only if it is really guaranteed that other enterprise beans or clients will only address the bean within a single JVM. With local client view, you can do pass-by-reference, which means your bean, as well as the client, will work directly with one copy of the data. Any changes made by the bean will be seen by the client and vice versa. Pass-by-reference eliminates time/system expenses for copying data variables, which provides a performance advantage.

1. setEntityContext().
2. EJBCREATE().
3. EJBPOSTCREATE().
4. EJBACTIVATE(). 
5. ejbPassivate().
6. EJBREMOVE().

DEPLOYMENT descriptor is a XML FILE. which is used to locate the web application by container.it includes the details of respective bean.

Deployment descriptor is a XML file. which is used to locate the web application by container.it includes the details of respective bean.

For a SESSION bean - ONE EJB OBJECT for one bean instance.
For entity bean - it depends , if 2 users are accessing one row at time then one EJB object is used for both the beans other wise for each bean one EJB object.

For a Session bean - one EJB object for one bean instance.
For entity bean - it depends , if 2 users are accessing one row at time then one EJB object is used for both the beans other wise for each bean one EJB object.

If we define the entity bean as being reentrant, multiple clients can connect to the Entity bean & execute methods within the entity bean CONCURRENTLY. CONTAINER takes care of synchronization. If we define the entity bean as non-reentrant and MANY clients connect to it concurrently to execute a method, EXCEPTION is THROWN .

If we define the entity bean as being reentrant, multiple clients can connect to the Entity bean & execute methods within the entity bean concurrently. Container takes care of synchronization. If we define the entity bean as non-reentrant and many clients connect to it concurrently to execute a method, exception is thrown .

J2EE defines three types of archives:
1. Java Archives (JAR) A JAR file encapsulates ONE or more Java classes, a manifest, and a descriptor. JAR files are the lowest level of archive. JAR files are used in J2EE for packaging EJBs and client-side Java APPLICATIONS.
2. Web Archives (WAR) WAR files are similar to JAR files, except that they are specifically for web applications made from Servlets, JSPs, and supporting classes.
3. Enterprise Archives (EAR) ”An EAR file contains all of the components that make up a particular J2EE application.

J2EE defines three types of archives:
1. Java Archives (JAR) A JAR file encapsulates one or more Java classes, a manifest, and a descriptor. JAR files are the lowest level of archive. JAR files are used in J2EE for packaging EJBs and client-side Java Applications.
2. Web Archives (WAR) WAR files are similar to JAR files, except that they are specifically for web applications made from Servlets, JSPs, and supporting classes.
3. Enterprise Archives (EAR) ”An EAR file contains all of the components that make up a particular J2EE application.

No. Decorator design pattern, is the ONE which exhibits very low LEVEL runtime polymorphism, for the specific and single object (INSTANCE of the class), but not for atleast for a class. It is the stuff to add specific functionality to a single & pointed object and leaves others like it unmodified. It is having close similarities like aspectJ stuff, but not with EJB stuff.

No. Decorator design pattern, is the one which exhibits very low level runtime polymorphism, for the specific and single object (Instance of the class), but not for atleast for a class. It is the stuff to add specific functionality to a single & pointed object and leaves others like it unmodified. It is having close similarities like aspectJ stuff, but not with EJB stuff.

No, you cannot map more than one table to a SINGLE CMP Entity Bean. CMP has been, in FACT, DESIGNED to map a single table.

No, you cannot map more than one table to a single CMP Entity Bean. CMP has been, in fact, designed to map a single table.

The purpose of ejbPostCreate() is to perform clean-up database operations after SQL INSERTs (which OCCUR when EJBCREATE() is called) when working with CMP ENTITY beans. ejbCreate() is called before database INSERT operations. You NEED to USE ejbPostCreate() to define operations, like set a flag, after INSERT completes successfully.

The purpose of ejbPostCreate() is to perform clean-up database operations after SQL INSERTs (which occur when ejbCreate() is called) when working with CMP entity beans. ejbCreate() is called before database INSERT operations. You need to use ejbPostCreate() to define operations, like set a flag, after INSERT completes successfully.

The bulk of the changes in EJB 2.0 are found in the DEFINITION of a new CMP component model. It’s radically DIFFERENT from the old CMP model because it introduces an ENTIRELY new participant, the PERSISTENCE manager, and a completely new way of defining container-managed fields, as well as relationships with other beans and dependent OBJECTS.

The bulk of the changes in EJB 2.0 are found in the definition of a new CMP component model. It’s radically different from the old CMP model because it introduces an entirely new participant, the persistence manager, and a completely new way of defining container-managed fields, as well as relationships with other beans and dependent objects.

EJB was originally designed around remote invocation using the Java Remote Method Invocation (RMI) mechanism, and later EXTENDED to support to standard CORBA transport for these calls using RMI/IIOP. This design ALLOWED for maximum flexibility in developing applications without consideration for the deployment scenario, and was a strong feature in support of a goal of component reuse in J2EE. Many developers are using EJBs locally, that is, some or all of their EJB calls are between beans in a single container. With this feedback in mind, the EJB 2.0 expert group has created a local interface mechanism. The local interface may be defined for a bean during development, to allow streamlined calls to the bean if a caller is in the same container. This does not involve the overhead involved with RMI like marshalling etc. This facility will THUS improve the PERFORMANCE of applications in which co-location is planned. Local interfaces also provide the foundation for container-managed relationships among entity beans with container-managed persistence.

EJB was originally designed around remote invocation using the Java Remote Method Invocation (RMI) mechanism, and later extended to support to standard CORBA transport for these calls using RMI/IIOP. This design allowed for maximum flexibility in developing applications without consideration for the deployment scenario, and was a strong feature in support of a goal of component reuse in J2EE. Many developers are using EJBs locally, that is, some or all of their EJB calls are between beans in a single container. With this feedback in mind, the EJB 2.0 expert group has created a local interface mechanism. The local interface may be defined for a bean during development, to allow streamlined calls to the bean if a caller is in the same container. This does not involve the overhead involved with RMI like marshalling etc. This facility will thus improve the performance of applications in which co-location is planned. Local interfaces also provide the foundation for container-managed relationships among entity beans with container-managed persistence.

Although technically it is legal, static initializer blocks are USED to execute some piece of CODE before executing any constructor or method while instantiating a class. Static initializer blocks are also TYPICALLY used to initialize static fields - which may be illegal in EJB if they are read/write - In EJB this can be achieved by INCLUDING the code in either the ejbCreate(), setSessionContext() or setEntityContext() METHODS.

Although technically it is legal, static initializer blocks are used to execute some piece of code before executing any constructor or method while instantiating a class. Static initializer blocks are also typically used to initialize static fields - which may be illegal in EJB if they are read/write - In EJB this can be achieved by including the code in either the ejbCreate(), setSessionContext() or setEntityContext() methods.

An entity bean REPRESENTS PERSISTENT global DATA from the database; a session bean represents transient user-specific data that will die when the user DISCONNECTS (ENDS his session). Generally, the session beans implement business methods (e.g. Bank.transferFunds) that call entity beans (e.g. Account.deposit, Account.withdraw)

An entity bean represents persistent global data from the database; a session bean represents transient user-specific data that will die when the user disconnects (ends his session). Generally, the session beans implement business methods (e.g. Bank.transferFunds) that call entity beans (e.g. Account.deposit, Account.withdraw)

EJBDoclet is an open SOURCE JavaDoc doclet that generates a LOT of the EJB related source FILES from CUSTOM JavaDoc comments tags EMBEDDED in the EJB source file.

EJBDoclet is an open source JavaDoc doclet that generates a lot of the EJB related source files from custom JavaDoc comments tags embedded in the EJB source file.

Entity beans that have container-managed relationships with other entity beans, MUST be ACCESSED in the same local scope as those related beans, and therefore typically PROVIDE a local CLIENT VIEW. In order to be the target of a container-managed relationship, an entity bean with container-managed persistence must provide a local interface.

Entity beans that have container-managed relationships with other entity beans, must be accessed in the same local scope as those related beans, and therefore typically provide a local client view. In order to be the target of a container-managed relationship, an entity bean with container-managed persistence must provide a local interface.