Looking for a job managing Java applications at the enterprise level? Be ready to impress your interviewer by mastering WebLogic Server, a widely used Java application server. With its ability to handle large applications, WebLogic has become a go-to choice for many enterprises. To help you prepare for your interview, we've put together an expert guide featuring common WebLogic Interview Questions and tips for answering them. Whether you're a seasoned WebLogic pro or new to the field, this guide can help you stand out from the competition and secure your dream job.
In this article, we will cover the following:
Ans: Weblogic server is basically a software application working on the middle tier, integrating the back-end database, related applications and browser-based clients. A Weblogic server is an instance of a Java process and executes in a JVM. It supports all major JDBC-compliant databases like Microsoft SQL Server, Oracle etc. There can be two types of Weblogic servers:
Ans: A WebLogic server primarily comprises the following:
Ans: Deployment descriptors are XML documents that are used in describing the contents of a jar file or a directory. These can be found in most of the modules and applications. The standard and deployment descriptors are defined by the J2EE applications and modules.
Ans: Admin server in WebLogic serves as the central point of control that allows you to gain access to the configuration, monitoring and management of all resources. It is one of the instances of the WebLogic server that allows and maintains the data configuration of a given domain. It is a singleton service and every domain has at least 1 admin server.
Ans: Web.xml is an XML document that finds its applicability in the listing out of J2EE components and is primarily used for application purposes. It also helps in the configuration of applications in the J2EE module format.
Ans: A logically related group of WebLogic server resources like Oracle and collectively managed as a single unit is called a domain. These can be used to logically separate organizational divisions, tests, production and development applications. Domains serve as a single administration point.
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Ans: Stage deployment refers to the process wherein the admin receives a physical copy that has been distributed among other instances.
Ans: A managed server is another instance of your WebLogic server that runs on the JVM and has a self-managed specific configuration. A managed server is used to deploy the components of Java-like EJB applications, Web applications, JMS applications and other related web services. A domain may or may not have a managed server and the count can go up to N number of managed servers. Until and unless the servers are in a cluster, a managed server always operates independently.
Ans: The basic point of relation between the admin server and the managed server is that the admin server acts as a master manager for all the other servers including a managed server. To initiate the managed server start-up configuration, the admin server must be running. This is only a one-time process. Every managed server has a local copy of the configuration stored in it. Whenever there is an unavailability of the admin server, the managed server uses its local copy to boot. However, the managed server needs an admin server to synchronize its configurations over subsequent reboots.
Ans: BSU stands for BEA Smart update which is a java based application used to apply patches on Weblogic servers. This utility allows you to work both online and offline.
Ans: Any physical computer that is present or hosts instances in the WebLogic environment is called a machine. It is logically represented in a WebLogic server.
Ans: In case of the absence of an admin server, the managed server can start up by fetching the configuration files and other related files. However, the managed server is bound to work on the retrieved information and no alterations are possible. Alterations can only be done as and when the admin server is actually available. The managed server can carry out its operation in the independent mode until the availability of the admin server.
Ans: SSL stands for Secure Sockets Layer which is a security protocol enabling secure transfer of data and information in an encrypted format. Standard certificate authorities provide SSL certification to ensure the authentication of the secure transfer of the data at the transport level.
Ans: Yes, there are multiple ways to start and stop a WebLogic server.
Following are the ways to start and stop the admin server:
Following are the ways to start and stop a managed server:
Ans: The T3 protocol in a WebLogic server is used to establish a connection between the internal and external servers. It is also used in the implementation of RMI in a WebLogic server.
HTTP is a protocol that is used for establishing communication between the web server and the browser. It is authenticated by the World Wide Web Consortium, W3C.
Ans: This can be dealt with by using Java WebLogic.Admin PING and see if there is a normal response. Several thread dumps need to be checked with a kill-3 pid on Unix and CTRL Break on Windows. This step needs to be analyzed deeply to narrow down the root cause.
Ans: A node manager is a controlling program that is used to manage and control the WebLogic server instances. It allows you to control all server instances that may be running on single or multiple physical machines. To be able to communicate with a node manager, every machine must be configured with your node manager.
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Ans: There are three different application layers in a WebLogic server:
Ans: Multicasting refers to establishing a peer to peer communication to initiate the process of messaging communications between different IP sockets.
Ans: There are 7 different networking protocols deployed in a WebLogic server. These are:
Ans: A WebLogic Server can be installed in three different modes:
1. Silent mode: uses configuration files, there is no manual intervention during the installation
2. Graphical mode: GUI interaction with the user during installation
3. Console mode: Command-based interactive mode of installation
Ans: JVM tuning refers to the enhancement and improvisation in the performance of a JVM execution engine in the WebLogic server. This is done by changing, adding or removing a few parameters in the WebLogic server like garbage collection or heap size, etc.
Ans: The various capabilities of a WebLogic server are:
Ans: Yes, we can change the default JVM in Weblogic servers. It can be done as follows:
Ans: A classpath in Windows can be set using the following script WL_HOMEserverbinsetWLSEnv.cmd
Ans: A pooling in the Tomcat server can be created by:
Ans: Yes, it is different. When a server crash happens, the Java process does not exist whereas in server hang the Java process stops responding.
Ans: A server hang generally happens due to a memory leak, deadlock, longer than anticipated return time in a database query
Ans: A memory leak is a condition in which the objects are retained in the heap even after they are no longer required.
Ans: MSI mode can be enabled or disabled by ensuring that the managed server’s root directory has the configuration subdirectory available. The following command can be used: Environment > Servers > Server_Name > Tuning > Advanced > Managed Server Independence Enabled checkbox
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Ans: The default port for configuring the WebLogic server is port 7001.
Ans: DB or JDBC connection pools can be configured when the WebLogic server is started. The application you are running ideally borrows a connection from the existing database pool and returns it back to the pool by closing it.
Ans: The basic difference between WebLogic and WebSphere lies in the standards used in their functionality. While a WebLogic server focuses primarily on the ease of use of J2EE and emerging standards governing them, the WebSphere is more focused on connectivity, web services, and integration.
Websphere is better in terms of transaction management and integration and strictly follows J2EE architecture.
Ans: The WebLogic server failure can be dealt with in the following ways:
Ans: The switch from development mode to production mode can be done as follows:
Go to the $root_domain/bin folder and edit the setDomainEnv.cmd.
Set PRODUCTION_MODE = false; save and exit to restart in production mode.
Ans: A WebSphere supports:
Ans: The following syntax can be used to call such procedures:
CallableStatement cstmt = conn.prepare all(“Begin to proclaim;
END;”);
cstmt.execute();
Ans: Go to WebLogic console >> left navigation tree >> Environment >> servers >> click of any server >> click monitoring tab >> note the WebLogic version field.
Q39) What is meant by OS tuning?
Ans: OS tuning refers to the process of tuning your operating system with a WebLogic server by setting up TCP/IP parameters.
Ans: Multicast is essentially a broadcast UDP option that allows sending of packets or announcements over a specific multicast address to a given group listening to the announcement. The announcements are similar to getting broadcast updates on most social media platforms like Twitter.
Unicast is more personalized and refers to one to one option for sending a packet or message to a particular member and not the whole group. It can be compared with personal messaging apps.
Ans: The port number of a WebLogic server can be checked by using netstat-na|grep connected
Ans: No, there can be any number of WebLogic servers held inside a multi-processor machine.
Ans: The boot.properties file stores your credentials like user id and password
Q44) What are vertical and horizontal clustering?
Ans: There are 2 ways in which clustering can be done WebLogic server:
1. Vertical clustering: under this type, multiple Java applications are run on a single physical machine.
2. Horizontal clustering: under this type, multiple Java application servers are run over two or more than two physical machines. It accounts for higher reliability.
Ans: Every WebLogic server instance in a WebLogic domain sends regular heartbeats via multicast broadcasting to all other servers in the cluster which is indicative of its presence. If three consecutive heartbeats go missing, the other server instances drop the particular server instance whose heartbeat goes missing.
Ans: A broadcast message regarding the addition of a new server instance is sent to all existing users in case there is an addition. A server instance list is also maintained and regularly updated by the cluster-aware stubs.
Ans: The auto-deployment feature is a monitoring utility that checks the application folder in every 3 seconds to look for any potential changes in the existing applications and/or the addition of any new applications. If there is any such change, it auto-deploys these changes in the existing application dynamically. The same can be done by monitoring socket errors.
Ans: Managed servers communicate through the T3 protocol.
Ans: ANT is a task that helps you carry out a smooth configuration of other tasks and applications in a developed environment.
Ans: MSI stands for Managed Server Independence. Managed servers have the ability to launch and operate even in the absence of the admin server.
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