BEA WebLogic Interview Questions and Answers
ANS: BEA WebLogic is a J2EE application server.BEA WebLogic Server is part of the BEA WebLogic Platform.
2. JNDI Usage for weblogic?
ANS: Java Naming and Directory Interface it is a API.
The Weblogic Server Uses This For storing te Different
objects(Like Connection factories, Datasourc….). These
Objects Retrived from JNDI tree when they are want to be
3. What are the Components of JNDI?
ANS: Naming Interface- The naming interface organizes information hierarchically and maps human-friendly names to addresses or objects that are machine-friendly. It allows access to named objects through multiple namespaces.
Directory Interface – JNDI includes a directory service interface that provides access to directory objects, which can contain attributes, thereby providing attribute-based searching and schema support.
Service Provider Interface – JNDI comes with the SPI, which supports the protocols provided by third parties.
4. What happens when a failure occurs and the stub cannot connect to a WebLogic Server instance?
ANS: When the failure occurs, the stub removes the failed server instance from its list. If there are no servers left in its list, the stub uses DNS again to find a running server and obtain a current list of running instances. Also, the stub periodically refreshes its list of available server instances in the cluster; this allows the stub to take advantage of new servers as they are added to the cluster.
5. Why is there no polymorphic-type response from a create() or find() method?
ANS: The EJB Specification prohibits this behavior, and the weblogic.ejbc compiler checks for this behavior and prohibits any polymorphic type of response from a create () or find () method. The reason the create () and find () methods are not polymorphic is similar to the reason constructors are not polymorphic in Java. The derived classes generally do not know or cannot initialize the base class properly.
6. Which types of JDBC databases does WebLogic JMS support?
ANS: The JMS database can be any database that is accessible through a JDBC driver. WebLogic supports and provides JDBC drivers for the following databases:
* Microsoft SQL (MSSQL) Server (Versions 6.5 and 7)
* Oracle (Version 8.1.6)
* Sybase (Version 12)
7. Does WebLogic JMS support clustering?
ANS: WebLogic JMS supports cluster-wide, transparent access to destinations from any server in the cluster. A system administrator can establish cluster-wide, transparent access to destinations from any server in the cluster by configuring multiple connection factories and using targets to assign them to WebLogic Servers. Each connection factory can be deployed on multiple WebLogic Servers.
You can configure multiple JMS servers on the various nodes in the cluster as long as you give them different names. You can assign destinations to the various JMS servers.
8. Can WebLogic Server start with a UNIX boot?
You can add a startup script to your UNIX rc scripts to run WebLogic Server at UNIX boot time.
9. How does WebLogic support CORBA and client communication via IIOP?
ANS: “CORBA” support means many things to many people. It often means simply IIOP /ORB support and not much on CORBA services. WebLogic supports CORBA in multiple ways.
First, Java clients can tunnel through a CORBA environment to WebLogic Server. We call this “IIOP tunneling,” and it is intended for use with applets coming through an IIOP firewall, such as the IONA Wonder wall product. This is a Java-to-Java model riding over an IIOP communications framework.
WebLogic RMI over IIOP provides RMI services for many clients (including CORBA clients) over IIOP.
WebLogic Enterprise Connectivity enables you to create IIOP connection pools to a BEA WebLogic Enterprise System, allowing you to execute WebLogic Enterprise CORBA objects from WebLogic Server servlets and Enterprise JavaBeans.
10. How do I configure WebLogic to use a SOCKS proxy?
ANS: You can configure a java.net socket to use SOCKS by setting a Java system property.
11. How to increase WebLogic Server memory?
ANS: Increase the allocation of Java heap memory for WebLogic Server. (Set the minimum and the maximum to the same size.) Start WebLogic Server with the -ms32m option to increase the allocation, as in this example:
Java … -ms32m -mx32m…
This allocates 32 megabytes of Java heap memory to WebLogic Server, which improves performance and allows WebLogic Server to handle more simultaneous connections. You can increase this value if necessary.
12. How to set up CLASSPATH?
ANS: Setting up CLASSPATH depends on most common tasks are described below:
• Starting WebLogic Server. See Setting the Class path Option in the Starting and Stopping WebLogic Servers section of the Administration Guide. In addition, your WebLogic distribution includes shell scripts that you can use to start the server.
• These scripts, which are located in the domain directories under the config directory of your WebLogic Server distribution, automatically set up the CLASSPATH variable in the shell before starting the server.
13. How does a file store compare with a JDBC store?
ANS: The following are some similarities and differences between file stores and JDBC stores:
* Both have the same transaction semantics, including rolling back transactions (e.g., received messages are put back on the queue).
* Both have the same application interface (no difference in application code).
* The file store should be much faster.
* JDBC may make it easier to handle failure recovery since the JDBC interface can access the database from any client machine; with the file store, the disk must be shared or migrated.
* File store reliability is limited to reliability of disk and O/S; run it on Veritas or a RAID 5 system. Database reliability may be higher.
* File stores will require more memory, but perhaps not significantly more; it depends on how fragmented the file store gets, if the application works roughly.
* FIFO it shouldn’t get very fragmented at all.
* File stores generate no additional network traffic, database stores do if the database server is on a different JVM or machine.
14. What type of object is returned by Result Set.getObject ()?
ANS: WebLogic jDriver for Oracle always returns a Java object that preserves the precision of the data retrieved. WebLogic jDriver for Oracle returns the following from the get Object () method:
* For columns of types NUMBER (n) and NUMBER (m,n): a Double is returned if the defined precision of the column can be represented by a Double; otherwise Big Decimal is returned.
* For columns of type NUMBER: Because there is no explicit precision, the Java type to return is determined based on the actual value in each row, and this may vary from row to row. An Integer is returned if the value has a zero-valued fractional component and the value can be represented by an integer.