JMS Interview Questions And Answers

What is JMS?
A1:
Java Message Service: An interface implemented by most J2EE containers to provide point-to-point queueing and topic (publish/subscribe) behavior. JMS is frequently used by EJB's that need to start another process asynchronously.
For example, instead of sending an email directly from an Enterprise JavaBean, the bean may choose to put the message onto a JMS queue to be handled by a Message-Driven Bean (another type of EJB) or another system in the enterprise. This technique allows the EJB to return to handling requests immediately instead of waiting for a potentially lengthy process to complete.

A2:
The Java Message Service (JMS) defines the standard for reliable Enterprise Messaging. Enterprise messaging, often also referred to as Messaging Oriented Middleware (MOM), is universally recognized as an essential tool for building enterprise applications. By combining Java technology with enterprise messaging, the JMS API provides a powerful tool for solving enterprise computing problems.

A3:
JMS stands for Java Messaging Service which is developed by Sun Microsystems . JMS Provider allow applications which are running on different systems can communicate with each other asynchronously . Many EAI tools support JMS as their standard messaging service.

A4:
The Java Message Service is a Java API that allows applications to create, send, receive, and read messages. Designed by Sun and several partner companies, the JMS API defines a common set of interfaces and associated semantics that allow programs written in the Java programming language to communicate with other messaging implementations.

A5;
JMS stands for Java Message Service. It allows applications to communicate through reliable, scaleable, and asynchronous text messages and objects over the network.

A6;
Java Message Service (JMS) is the new standard for interclient communication. It allows J2EE application components to create, send, receive, and read messages. It enables distributed communication that is loosely coupled, reliable, and asynchronous.

A7;
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.

Must I place all my class files in the WEB-INF folder and all JSP's outside?
A1:
The class files should place into WEB-INF/classes folder and the JSP files should place within a separate folder.

A2:
Yes! Otherwise the web server/ application server cannot access the .jsp files and classes.
The java class files can be placed either in WEB-INF/lib or WEB-INF/classes. But it is recommended to put the class files in WEB-INF/classes. The server will load the files from the classpath so it just will not matter where the class is.

A3:
Yes, class files is private resources, so you must store class in WEB-INF/classes folder.
JSP and HTML files should be placed outside.

A4:
Class files inside web-inf cannot be access by browsers, while the JSP files are meant for accessible by browsers so, it may be strictly place outside the web-inf only.

A5:
Here is structure of web app.
web (this folder is Accessible from www)
Store all your JSP and HTML files here
WEB-INF (this folder is not Accessible )
classes (store your classes here, classes you are using in jsp
lib (store 3rd party jars)


A6:
1. Class files - Either they must be in WEB-INF\classes directory OR you can package them as JAR and put in WEB-INF\lib
2. JSP files - Depends how do you design your arch. If you have controller/delegator that can forward requests to JSPs, you can keep them under WEB-INF directory also. If not, you have to keep them outside WEB-INF.

A7:
The Java Message Service (JMS) API is a messaging standard that allows application components based on the Java 2 Platform, Enterprise Edition (J2EE) to create, send, receive, and read messages. It enables distributed communication that is loosely coupled, reliable, and asynchronous

What type messaging is provided by JMS?
Both synchronous and asynchronous.

How may messaging models do JMS provide for and what are they?
JMS provides for two messaging models, publish-and-subscribe and point-to-point queuing.

What is the point-to-point model in JMS?
A point-to-point model is based on the concept of a message queue: Senders send messages into the queue, and the receiver reads messages from this queue. In the point-to-point model, several receivers can exist, attached to the same queue. However, (Message Oriented Middleware)MOM will deliver the message only to one of them. To which depends on the MOM implementation.

What are the advantages of JMS?
One of the principal advantages of JMS messaging is that it's asynchronous. Thus not all the pieces need to be up all the time for the application to function as a whole.

What is the publish-and-subscribe model in JMS?
A publish-subscribe model is based on the message topic concept: Publishers send messages in a topic, and all subscribers of the given topic receive these messages.

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

What is publish/subscribe messaging?
With publish/subscribe message passing the sending application/client establishes a named topic in the JMS broker/server and publishes messages to this queue. The receiving clients register (specifically, subscribe) via the broker to messages by topic; every subscriber to a topic receives each message published to that topic. There is a one-to-many relationship between the publishing client and the subscribing clients