JBOSS Interview Questions and Answers
Q1. What is JBOSS?
Ans: JBoss is a popular open supply application server primarily based on JEE generation. Being JEE primarily based, the JBoss supports go-platform java packages. It become 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).
Q2. What is JBoss JBPM?
Ans: JBoss JBPM is a workflow and BPM engine. Enabling the creation of enterprise techniques that coordinates among humans, programs and services is the capability of BPM engine. The combination of workflow packages improvement with process design is a characteristic of JBoss jBPM. The business system is graphically represented to facilitate a strong link between the enterprise analyst and technical developer. This characteristic is provided by way of the JBoss jBPM manner fashion designer.
Q3. What's the distinction between Standalone mode and Domain mode?
Ans: When configured in Standalone mode every distribution begins a single JVM manner with its personal configuration, control gadgets and deployments. When configured in Domain mode, a couple of servers are managed from a centralized factor known as Domain Controller which keep the configuration and provisions programs for deployment at the unmarried nodes which can be part of the Domain
Q4. What do you want to set-up a cluster with JBoss?
Ans: Basically starting JBoss with the “all” configuration carries the whole thing wished for clustering:
It has all the libraries for clustering:
Clustered beans (cluster-service.Xml)
HTTP session replications (tc5-cluster-provider.Xml)
Q5. How do you display JBoss and discover the bottleneck of an application?
Ans: Different components of the utility are to be measured. This step is to find where the degradation is, whether or not it is external or internal and in which is the appliciation spending all the time. Using Joss JMX retailers and tracking the deployed components to the software server includes in the first step.
After locating the most of the time spent by means of unique components or libraries or maximum of the resources, you'll use Jprobe a specialized device for inspecting the single item or the objects loaded within the memory.
Q6. Is it viable to position a JBoss server instance into more than one cluster at the same time?
Ans: It is technically possible to put a JBoss server instance into more than one clusters at the same time, this exercise is usually now not recommended, as it increases the control complexity.
Q7. Does Seam run on different utility servers except JBoss?
Ans: Seam runs beautifully on other application servers - just like everything else the Hibernate group does, this is not a JBoss-most effective component.
Q8. What's jBoss cache in short?
Ans: JBossCache enables easy distribution of datasets throughout your computing environments. It is primarily based on JGroups and permits clustering and excessive availability of that statistics. You may additionally pick to distribute the information with JBoss Messaging to move it where it's miles wished for computation or occasion-based programming.
Q9. Which Hibernate item wraps the JDBC Connection?
Ans: The Session interface wraps a JDBC Connection. This interface is a unmarried threaded item which represents a unmarried unit of labor with application and continual database. It's retrieved via the SessionFactory's openSession() technique.
Q10. How can you start a JTA transaction from a Servlet deployed on JBoss?
Ans: JBoss registers within the JNDI tree a JTA UserTransaction Object which can be user to control a allotted transaction.
Q11. What optimization may want to I use if the EJB field is the simplest factor of write get admission to to the database?
Ans: You may want to activate the "Commit Option A" that is the field caches entity bean kingdom among transactions. This choice assumesthat the field has distinct get right of entry to to the persistentstore and consequently it doesnâ€™t want to synchronizethe in-reminiscence bean nation from the chronic keep at the start of every transaction.
Q12.Which aspect handles cluster verbal exchange in JBoss?
Ans: The JGroups framework provides offerings to allow peer-to-peer communications between nodes in a cluster. It is built on pinnacle a stack of community communication protocols that provide delivery, discovery, reliability and failure detection, and cluster club management offerings.
Q13. Is it feasible to position a JBoss server example into multiple cluster on the same time?
Ans: It is technically viable to place a JBoss server instance into a couple of clusters on the equal time, this exercise is generally no longer advocated, because it increases the management complexity.
Q14. What do you already know about Seam?
Ans: Built at the requirements JavaServer Faces and EJB three.Zero, JBoss Seam unifies component and programming models and supplies a consistent and effective framework for speedy advent of internet programs with Java EE five.Zero. Seam simplifies internet utility development and enables new capability that became tough to put into effect via hand before, consisting of stateful conversations, multi-window operation, and dealing with concurrent satisfactory-grained AJAX requests. Seam also unifies and integrates famous open supply technology like Facelets, Hibernate, iText, and Lucene.
Q15. How do you screen JBoss and locate the bottleneck of an application?
Ans: The first step is to measure the unique components of your app to peer where the degradation is. Is it an external aid (database, message server, and so on.)? Is it internal? Where is the app spending all its time?
So step one can be to to apply JBoss JMX sellers and display the components deployed to the software server. Once it's clean which component or library takes most of the time or maximum of aid you can use a extra specialised device like JProbe and study the single technique or the unmarried gadgets loaded in memory.
Q16. How are you able to begin a JTA transaction from a Servlet deployed on JBoss?
Ans: JBoss registers in the JNDI tree a JTA UserTransaction Object which can be user to manipulate a distributed transaction.
Q17. What is the difference among validate-on-in shape and historical past-validation? Can you operate both of them?
Ans: When the validate-on-fit option is about to real, the database connection is verified on every occasion it's far checked out from the connection pool using the validation mechanism specified in the subsequent step.
On the alternative hand, historical past-validation fires a history validation as dictated via the history-validation-millis.
You can not observe both of them, they may be at the same time distinctive.
Q18. Porting one application from Standalone mode to Domain mode: is it guaranteed that you may not run in any trouble?
Ans: One center distinction among Standalone mode and Domain mode is that Standalone mode lets in manual deployment of packages via copying records into the deployment folder. On the other hand, in Domain mode packages are managed and copied via the CLI or the Admin Console into the information folder of the unmarried nodes. That being said, some packages may require to recognize the bodily route where the application has been deployed: one suitable example is LifeRay portal which calls for a few workarounds to run in Domain mode. So continually test the packages requirement before committing to a change from Standalone mode to Domain mode.
Q19. Why must I prefer mod_cluster over mod_jk?
Ans: In terms of configuration: The httpd facet does not need to realize cluster topology earlier, so the configuration is dynamic and not static and thus you need very little configuration on the httpd facet
In phrases of load balancing: You have an progressed load balancing as predominant calculations are done on the backend servers, wherein extra statistics is available and for that reason a high-quality grained net software lifecycle manipulate
Q20. What is the distinction among JAX--WS and JAX-RPC?
Ans: Java API for XML-Based RPC (JAX-RPC) is a Legacy Web Services Java API, it uses SOAP and HTTP to do RPCs over the community and enables constructing of Web offerings and Web programs based on the SOAP 1.1 specification, Java SE 1.4 or lower.JAX-WS 2.Zero is the successor to JAX-RPC 1.1. JAX-WS nevertheless supports SOAP 1.1 over HTTP 1.1, so interoperability will now not be affected. However there are lots of variations:
JAX-WS maps to Java five.0 and is predicated on a few of the capabilities new in Java five.0 like Web Service annotations.
JAX-RPC has its own statistics mapping version, JAX-WS's facts mapping model is JAXB. JAXB guarantees mappings for all XML schemas.
JAX-WS introduces message-oriented capability, dynamic asynchronous functionality which might be lacking in JAX-RPC.
JAX-WS also add assist, thru JAXB, for MTOM, the brand new attachment specification.