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JBoss Interview Questions

Q. What is JBOSS?
JBoss is a popular open source application server based on JEE technology. Being JEE based, the JBoss supports cross-platform java applications. It was embedded with Apache Tomcat web server. It runs under any JVM of 1.3 or later versions. JBoss supports JNDI, Servlet/JSP (Tomcat or Jetty), EJB, JTS/JTA, JCA, JMS, Clustering (JavaGroups), Web Services (Axis), and IIOP integration (JacORB).

Q. What is JBoss JBPM?
JBoss JBPM is a workflow and BPM engine. Enabling the creation of business processes that coordinates between people, applications and services is the functionality of BPM engine. The combination of workflow applications development with process design is a feature of JBoss jBPM. The business process is graphically represented to facilitate a strong link between the business analyst and technical developer. This feature is provided by the JBoss jBPM process designer.

Q. What’s the difference between Standalone mode and Domain mode?
When configured in Standalone mode each distribution starts a single JVM process with its own configuration, management instruments and deployments. When configured in Domain mode, multiple servers are managed from a centralized point called Domain Controller which maintain the configuration and provisions applications for deployment on the single nodes which are part of the Domain

Q. What do you need to set-up a cluster with JBoss?
Basically starting JBoss with the “all” configuration contains everything needed for clustering:

  • It has all the libraries for clustering:
  • JGroups.jar, jboss-cache.jar
  • Clustered beans (cluster-service.xml)
  • HA-JNDI
  • HTTP session replications (tc5-cluster-service.xml)
  • Farming
  • HA-JMS

Q. How do you monitor JBoss and detect the bottleneck of an application?
Different components of the application are to be measured. This step is to find where the degradation is, whether it is external or internal and where is the appliciation spending all the time. Using Joss JMX agents and monitoring the deployed components to the application server involves in the first step.
After finding the most of the time spent by specific components or libraries or most of the resources, one can use Jprobe a specialized tool for examining the single object or the objects loaded in the memory.

Q. Is it possible to put a JBoss server instance into multiple cluster at the same time?
It is technically possible to put a JBoss server instance into multiple clusters at the same time, this practice is generally not recommended, as it increases the management complexity.

Q. Does Seam run on other application servers besides JBoss?
Seam runs beautifully on other application servers – just like everything else the Hibernate team does, this is not a JBoss-only thing.

Q. What’s jBoss cache in short?
JBossCache enables easy distribution of datasets across your computing environments. It is based on JGroups and enables clustering and high availability of that data. You may choose to distribute the data with JBoss Messaging to move it where it is needed for computation or event-based programming.

Q. Which Hibernate object wraps the JDBC Connection?
The Session interface wraps a JDBC Connection. This interface is a single threaded object which represents a single unit of work with application and persistent database. It’s retrieved by the SessionFactory’s openSession() method.

Q. How can you start a JTA transaction from a Servlet deployed on JBoss?
JBoss registers in the JNDI tree a JTA UserTransaction Object which can be user to manage a distributed transaction.

Q. How would you convince my IT department to adopt SOA?

In my opinion one of the biggest obstacle in the movement towards SOA adoption is the organization’s own IT department.Too many people in the IT organization conceive SOA as a technology concept only, and as such think of SOA as just a set of technologies and infrastructure for exposing, securing, running, and managing Services. Put it this way, SOA is nothing more than Web Services and standardized middleware. The critical flaw in thinking is confusing the technology that sits beneath the Services level of abstraction and the mechanism by which Services are accessed with the architectural approach that aims to decouple the implementation from the consumption and focus on sustainable architecture that allows for continuous change.

Successful SOA adoption requires a cultural shift in the way IT is done. The Service-oriented movement to agility and loose coupling demands a shift from traditional, waterfall styles of development (design-build-test-deploy-manage) to iterative approaches to continuous Service modeling

Q. Which JDK is needed to run Seam?

Seam only works on JDK 5.0 and above. It uses annotations and other JDK 5.0 features.

Q. Does Seam run on other application servers besides JBoss?

Seam runs beautifully on other application servers – just like everything else the Hibernate team does, this is not a JBoss-only thing.

Q. What do you know about Seam?

Built on the standards JavaServer Faces and EJB 3.0, JBoss Seam unifies component and programming models and delivers a consistent and powerful framework for rapid creation of web applications with Java EE 5.0. Seam simplifies web application development and enables new functionality that was difficult to implement by hand before, such as stateful conversations, multi-window operation, and handling concurrent fine-grained AJAX requests. Seam also unifies and integrates popular open source technologies like Facelets, Hibernate, iText, and Lucene.

Q. Is it possible to put a JBoss server instance into multiple cluster at the same time?

It is technically possible to put a JBoss server instance into multiple clusters at the same time, this practice is generally not recommended, as it increases the management complexity.

Q. Which component handles cluster communication in JBoss?

The JGroups framework provides services to enable peer-to-peer communications between nodes in a cluster. It is built on top a stack of network communication protocols that provide transport, discovery, reliability and failure detection, and cluster membership management services.

Q. What optimization could I use if the EJB container is the only point of write access to the database?

You could activate the “Commit Option A” that is the container caches entity bean state between transactions. This option assumesthat the container has exclusive access to the persistentstore and therefore it doesn’t need to synchronizethe in-memory bean state from the persistent store at the beginning of each transaction.

Q. What do you need to set-up a cluster with JBoss?

Basically starting JBoss with the “all” configuration contains everything needed for clustering:
It has all the libraries for clustering:

► JGroups.jar, jboss-cache.jar
► Clustered beans (cluster-service.xml)
► HA-JNDI
► HTTP session replications (tc5-cluster-service.xml)
► Farming
► HA-JMS

Q. What is the diffrence between a local-tx-datasource and a xa-datasource? can you use transactions in both?

A local-tx-datasource identifies a data source that uses transactions, even distributed trans actions within the local application server, but doesn’t use distributed transactions among multiple application servers. An xa-datasource on the other hand identifies a data source that uses distributed transaction among multi-ple application servers.

Q. Can I Run Seam Outside Of Jboss As?

Answer :Yes, you could run Seam packages in plain Tomcat 5.5+ or within the Sun GlassFish software server. To run Seam utility in Tomcat, you need some of additional library files and a few configuration files to bootstrap the JBoss EJB3 internal Tomcat.Question 26. Can I Run Seam In A J2ee Environment?Answer :Yes, as of Seam 1.1, you may use Seam in any J2EE software server, with one caveat: you’ll not be capable of use EJB three.0 session beans. However, you could use either Hibernate or JPA for persistence, and you can use Seam JavaBean components in preference to session beans.

Q. Can I Run Seam With Jdk 1.4 And Earlier?

No, Seam only works on JDK five.0 and above. It uses annotations and different JDK five.0 features.

Q. Where Can I Find Seam Examples And Documentation?

The supply code and build script of all Seam example programs are blanketed in the examples directory of the Seam distribution.

Q. Is It True That Seam Only Works With Jsf?

Seam simplest helps JSF as a view framework at this time. We plan to help other internet frameworks in the future. We like JSF as it is part-based totally UI framework, which fits truely well with Seam’s issue-primarily based technique to enterprise gadgets and patience gadgets. Seam made a major development to JSF by using removing almost all XML configuration for backing beans — you can now define again beans from POJOs or EJB3 additives the usage of simple annotations.We advise you operate Facelets, rather than JSP, with JSF. Facelets offer a powerful templating framework, higher appplication overall performance, and allows us to write down a lot easier JSF pages. Please see the Seam reserving instance utility for an instance on a way to use Facelets.

Q. Can I Use Ajax With Seam?

Yes, Seam presents tremendous help for AJAX. First, Seam supports the ICEfaces and Ajax4JSF Ajax element libraries for JSF. If you pick a extra “old fashioned” method, Seam offers a complete JavaScript remoting framework which helps you to call Seam additives and join JMS subjects directly from the purchaser.

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