JBoss Interview Questions and Answers

Introduction

JBoss is a Java EE-based application server that is free and open-source software. JBoss is built on Java. The JBoss application server enables cross-platform and may be used on any operating system that Java supports.

If you are preparing for a JBoss interview in the future and are looking for a quick guide before your interview, then you are on the right place. This article will discuss the top 30 JBoss interview questions, which consist of all types of JBoss interview questions.

Most Asked JBoss interview questions

1. Describe JBOSS.

Ans: JBoss is a well-known open-source application server built on JEE technology. JBoss supports cross-platform Java applications. JBoss includes the Apache Tomcat web server. JBoss works with any JVM version 1.3 or later. JCA, JMS, Clustering (JavaGroups), Web Services (Axis), JNDI, Servlet/JSP (Tomcat or Jetty), EJB, JTS/JTA and IIOP integration are all supported by JBoss (JacORB).

2. Define JBoss JBPM.

Ans: JBoss JBPM is the business process management engine. The functionality of a BPM engine is to enable the implementation of business processes that coordinate between people, apps, and services. JBoss jBPM supports the development of workflow applications as well as process design. To promote a strong interaction between the business analyst and the technical developer, the business process is graphically depicted. The JBoss jBPM process designer provides this functionality.

3. What Is Jboss Cache?

Ans: JBoss cache is used to increase the speed of E-business systems, Java objects. JBoss reduces network traffic and improves application scalability by reducing database calls. JBoss cache provides fully transactional functionality and a highly adjustable collection of settings for dealing with concurrent data access in the most efficient way feasible for applications.

4. How Do You Monitor Jboss And Identify An Application's Bottleneck?

Ans: The application's phase is to determine the source of the degradation, whether it is external or internal, and where the program spends the majority of its time. To identify the application bottleneck we will uses Jboss JMX agents and monitors the deployed components to the application server.

After determining how much time is spent by specific components, libraries, or resources, one can use Jprobe, a specialized tool for inspecting a single object or the objects stored in memory.

5. Define Jta.

Ans: The Java Transaction API (JTA) defines standard Java interfaces between a transaction manager and the parties participating in a distributed transaction system, including the resource manager, application server, and transactional applications.

The Java Transaction API (JTA) enables programs to carry out distributed transactions that update data on two or more networked computer resources.

The Java Transaction API is made up of three parts: a high-level application transaction demarcation interface, a high-level transaction management interface for application servers, and a standard Java mapping of the X/Open XA protocol for transactional resource managers.

6. What Hibernate Object Encapsulates the JDBC Connection?

Ans: A JDBC Connection is wrapped in the Session interface. This interface is a single-threaded object that represents a single unit of work with a persistent database and an application. The openSession() method of the SessionFactory retrieves it.

7. Is it safe to use the Session Factory Thread?

Ans: Yes, many threads can access it at the same time and request sessions. It stores the data that has been read in one unit of work and may be reused in another. It is best to build when the application is first launched.

8. How do you configure WildFly's start-up RAM on a standalone server?

Ans: The preferred method is to save the JVM configuration in standalone.conf.

9. Which profile would you use for EJB apps that require IIOP support?

Ans: A "full" profile (such as standalone-full.xml or standalone-full-ha.xml) is required because it includes the iiop-openjdk subsystem.

10. Differentiate between Standalone and Domain mode.

Ans: Standalone mode: In JBoss, standalone mode refers to a single Java Virtual Machine process in which each JBoss server keeps its configuration. If you simply want to use one JVM or development environment, the standalone mode is the best option.

Domain mode: Domain mode involves several servers in configuration management, which is done centralized and is most commonly used in production environments.

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11. How do you convert your XML settings into CLI commands?

Ans: There is no automatic way to do this, however, there is a utility called "Profile Cloner" that you can install to do this.

12. How can you link the HTTP Port of the Web server to a specific value without affecting the port offset of the entire server?

Ans: To link the HTTP Port of the Web server to a specific value without affecting the port offset of the entire server, run the below command:

./bin/standalone.sh -Djboss.http.port=1234

13. What are the various sorts of log levels used in JBoss logging services?

Ans: There are four different types of log levels in JBoss that are used to display the services that are present within the logging. The following are the log levels:

• Debug: The file is debugged for potential issues at this level. This can be either automatic or manual because it has no effect on the file.
• Info: At this level, complete and detailed information on the background process is provided. It contains information such as the process's name, CPU use, etc.
• Warn: At this level, the warning that has come in the file that may impair the performance on some systems is displayed together with several critical signs to alert the user to view the warning and take necessary steps if necessary.
• Error: At this level, during the compilation of the error, some errors are displayed, which can be logical errors. These errors must be corrected before the compilation process can be completed.

14. What does the logging threshold in JBoss mean?

Ans: The logging threshold is given as INFO because it is a level at which all informational, warning, and error messages on the console are produced and shown, but not debug messages. There are no thresholds defined for the server.log file, as it is controlled through the file. The created logging messages will be saved in that section. The log files are always reviewed for any faults that are produced as a result of some information on the debug messages that can aid in the investigation of the problem. The logging threshold enables debug messages to be displayed along with comprehensive log file information. Individual categories have their own logging limits.

15. What is the function of an appender in JBoss logging?

Ans: The file created by the appender indicates the use as a logger for the package org.

JBoss.EJB.plugins.CMP, allows the server to easily examine CMP and compare the two log files. The files are used to generate a fresh log file every day and do not generate any files even though changes are made every time. The service should be restarted. The log directory contains HTTP request logs generated by the web container.

16. What security services does the JBoss server provide?

Ans: Security Service is made up of domain information recorded in the login config.xml file, as well as all the listed security domains that determine the number of login modules used for domain authentication. The application's security can be used in specific JBoss deployment descriptors until it specifies the domain name to be used. JBoss.xml and JBoss-web.xml are the files to be evaluated, used to protect the JMX console application included with JBoss. The JMX console is used to manage all aspects of the server. The programs are password secured, and any remote user with no particular information can entirely operate the server.

17. What are your thoughts on SEAM?

Ans: JBoss Seam, based on the Java Server Faces and EJB 3.0 standards, combines component and programming models and provides a uniform framework for the quick development of online applications with Java EE 5.0. Seam streamlines online application development and enables features like stateful chats, multi-window operation, and processing concurrent fine-grained AJAX queries. Seam also combines and unifies major open source technologies like Facelets, Hibernate, iText, and Lucene.

18. What are the main differences between validate-on-match and background validation? Can you utilize them both?

Ans: The Validate-on-match option is used to validate the database connection every time it is opened. If the validate-on-match option is true, the connection is validated and checked out of the connection pool using the validation procedures.

The background-validation option performs background validation according to the background-validation-millis value. Both of them cannot be used at the same time. They have been discovered to be mutually exclusive.

19. Which of these setups is possible: multiple domains in the same cluster or several clusters in the same domain?

Ans: Let us first define both of these concepts.

• Numerous domains in the same cluster: To achieve multiple domains in the same server, launch two domains in the same network that share the same multicast address and port. 
• Multiple domains within the same domain: Multiple domains within the same domain can be acquired by assigning a distinct address to each Server Group or even at the server level. Your servers will communicate using various multicast addresses, even if they are in the same domain, forming separate clusters.

20. Why should everyone use mod cluster instead of mod jk?

Ans: Regarding configuration: There is no need to know the cluster topology in advance, the setup is dynamic instead of static, and as a result, very little configuration is needed on the httpd side.

There is no need to know the cluster topology in advance, the setup is dynamic instead of static, and as a result, a very little configuration is needed on the httpd side.

Regarding load balancing: Most of the calculations are done on the backend servers, where more information is available, you will obtain improved load balancing and thus fine-grained web application lifecycle control.

21. Differentiate between JAX—WS and JAX-RPC.

Ans: The Java API for XML-Based RPC (JAX-RPC) is a Legacy Web Services Java API that uses SOAP and HTTP to perform RPCs over the network and allows the development of Web services and Web applications using the SOAP 1.1 specification and Java SE 1.4 or lower. JAX-WS 2.0 is the upgrade version for JAX-RPC 1.1. Interoperability will not be compromised because JAX-WS still supports SOAP 1.1 over HTTP 1.1. However, there are numerous important differences:

However, there are various important differences:

• JAX-WS maps to Java 5.0 and takes advantage of many of the new Java 5.0 features, such as Web Service annotations.
• JAX-RPC has its own data mapping model, while JAX-WS uses JAXB. Mappings for all XML schemas are provided by JAXB.
• JAX-WS adds a message-oriented and dynamic asynchronous capability that JAX-RPC does not have.
• JAX-WS also adds support for MTOM, via JAXB.

22. What are the advantages of traceability of requirements?

Ans: The Advantages of Traceability of Requirements track from links indicates an impact on a certain requirement. The trace to links indicator indicates which needs are affected by the selected requirement.

23. What are the primary directories included with JBoss?

Ans: The following are the main directories given by the JBoss directory structure:

• bin - It is made up of system executable and normal files that are used for execution. It is made up of binary files for each program installed on the system.
• client - It contains all configuration files and jar files that may be required by the Java client application.
• docs - It contains XML documents with DTDs for reference. These documents offer the fundamental specifications for JBoss installation and deployment.
• lib - This folder contains the jar files required to execute the JBoss microkernel. Because it contains the kernel and system libraries, this directory is not accessible to users.
• server - This is made up of several server configuration files. The files are written in script format.

24. What are the various services offered by the JBoss server?

Ans: The server's services are determined by the type of files that are offered and maintained by the server. The server offers services ranging from basic to advanced, and they are classed as follows:

• Core services: These are the scripts that start the server and offer the core functionality of the start-up scripts.
• Logging Services: These are the services that are used for logging into the server and modifying and creating configuration settings.
• Security Service: These are the services that include all of the security domain information and are used to list the stated security domain features. Security service defines all of the individual modules that are used for domain authentication.
• Additional Services: These are the services that can be hot-deployed and deployed straight in the directory. They are made up of XML descriptor files as well as other resource files.

25. What is the process for gaining access to the JBoss Cache MBean service?

Ans: JBoss configures the server to access the MBean service by using numerous header files such as proxy files, server locater files, cache configuration files, etc. The process is shown by the sample code provided below.

org.jboss.mx.util.MBeanServerLocator; \sorg.jboss.mx.util.MBeanProxyExt; \sorg.jboss.cache.TreeCacheMBean; \sjavax.management.MBeanServer;

TreeCacheMBean cache; 

MBeanServer server;

TreeCacheMBean cache;  //These are the header files mentioned above. It contains all of the files, such as server files, MBean service files, cache configuration files, and so on.

public init() raises an exception Exception
{
	try
	{ 
	server = MBeanServerLocator.locateJBoss();
	cache = (TreeCacheMBean) MBeanProxyExt.create(TreeCacheMBean.class, "jboss.cache:service=TreeCac 
	}
	 catch (Exception ex)
	 {
	 handle exception
	 }
 }

26. What are the main services provided by the JBoss configuration files?

Ans: JBoss configuration files contain information about the basic services, which can be found in the configuration folder. The file is named service.xml, and it is the first file that is loaded when the server boots up. This file contains configuration MBeans for various services such as logging, security, and so on.  for example

<!— name="jboss:service=JNDIView"
xmbean-dd="resource:xmdesc/JNDIView-xmbean.xml">

—>

In the service management console, it does not list the services that have been removed.

27. Write a code to display the level change in the JBoss server.

Ans: If the level is changed from INFO to DEBUG, the output from the container-managed persistence engine will be adjusted to the DEBUG level. A redirection occurs in distinct files, and a log with the name cmp.log is kept to compare the files afterward. The following code must be included to the log4j.xml file: 

<appender name="CMP" class="org.jboss.logging.appender.RollingFileAppender">
<errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
<param name="File" value="${jboss.server.home.dir}/log/cmp.log"/>

<param name="ninjas" value="false"/>
<param name="coding" value="500KB"/>

<param name="MaxBackupIndex" value="1"/>
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d %-5p [%c] %m%n"/>

</layout>
</appender>

<category name="org.jboss.ejb.plugins.cmp">
<priority value="DEBUG" />
<appender-ref ref="CMP"/>
</category>

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28. Is Maven required to run WildFly?

Ans: No, although using Maven to develop apps is strongly advised because most examples require it. we don't have to install anything because the Maven wrapper shell script will download the correct Maven version if it can't be found.

29. What are the primary file types for marker file deployment?

Ans: The following are the most important marker file deployment types.

• dodeploy - instructs the deployment process.
• deployed - indicates that the file has been deployed. The deployment is still waiting.
• undeployed - confirms that the application is not deployed.
• failed - The deployment was unsuccessful for whatever reason. Instruct JBoss to reject the files for auto-deployment.

30. What is the deployment procedure for an application?

Ans: The JBoss application server supports three methods for deploying applications.

• Admin Console - Using the administration console, you can deploy the required application files.
• Auto-deploy - Use a file system deployment scanner to deploy files from the deployments folder automatically.

To deploy an application, use an automation tool/ant/scripting.