Weblogic Interview questions -4

                                               Weblogic Interview questions -4

Why do I get the following exception when viewing the JNDI tree?

java.io.PrintWriter at

The Weblogic Server JNDI implementation requires objects to be serializable, not referencable. A PrintWriter cannot be serialized and therefore should be declared transient.

When deploying a resource adapter (.rar) to WebLogic Server, are its classes placed in the WebLogic classpath?

For instance, I am deploying an EJB and a resource adapter (.rar), the EJB has no dependencies on the .rar because the EJB is writing to the common client interface (CCI). The EJB client application has sends/marshals as parameter classes that are defined in the .rar. For some reason the EJB's class loader hierarchy cannot find the definition of this .rar-specific class, even though the .rar is deploying successfully. I receive the following error on the EJB client:
java.rmi.UnmarshalException: error unmarshalling arguments; nested

When you pass an instance of com.myclientcompany.server.eai.InteractionSpecImpl as an argument to your EJB, the appServer needs to de-serialize (unmarshal) the object under the EJB context, and it needs the required class for unmarshalling, inside the ejb-jar(raTester.jar). So if you include the interactionspecimpl class in your ejb-jar file, then you do not need to include those classes in your server's classpath.

How is security handled in the WebLogic J2EE Connector Architecture?

Due to the fact that the current configuration and packaging requirements for resource adapters in WebLogic Server require the hand-editing of the weblogic-ra.xml file, any new passwords specified in the security-principal-map entries are done in clear-text.

BEA understands the importance of protecting security passwords. Hence, we provide a Converter Tool that allows for the encryption of all passwords present in the weblogic-ra.xml file. The Converter Tool is shipped in the standard weblogic.jar file.

Can I enable requests to a JDBC connection pool for a database connection to wait until a connection is available?

No, there's no way to allow a request to wait for a pool connection, and from the system point of view there should not be. Each requests that waits for a connection ties up one of the fixed number of execute threads in the server, which could otherwise be running another server task. Too many waiting requests could tie up all of the execute threads and freeze the server.

How do I use multibyte character sets with WebLogic jDriver for Informix?

Currently, multibyte character sets are not supported for the WebLogic jDriver for Informix driver.

How do I connect to an SQL Server instance that is running on a machine with multiple instances of SQL Server 2000?

Each instance of MS SQL Server must be listening on a different port. So, you can use the port number in the properties that you pass to the getConnection() method or, in case of connection pools, you can specify the port property in the following properties:


To find the port number where each MS SQL Server instance is running, run the server network utility (in the Microsoft SQL Server program group), select the server instance, select TCP/IP, and click the properties button.

How do I limit the number of Oracle database connections generated by WebLogic Server?

You can use connection pools to limit the number of Oracle database connections generated by WebLogic Server in response to client requests. Connection pools allow T3 applications to share a fixed number of database connections. For information on how to set up connection pools,

How do I call Oracle stored procedures that take no parameters?

Here is what we use that works:
CallableStatement cstmt = conn.prepareCall("Begin procName;

where procName is the name of an Oracle stored procedure. This is standard Oracle SQL syntax that works with any Oracle DBMS. You might also use the following syntax:

CallableStatement cstmt = conn.prepareCall("{call procName};");

This code, which conforms to the Java Extended SQL spec, will work with any DBMS, not just Oracle.

Why do I get unexpected characters from 8-bit character sets in WebLogic jDriver for Oracle?

If you are using an Oracle database with an 8-bit character set on Solaris, make sure you set NLS_LANG to the proper value on the client. If NLS_LANG is unset, it defaults to a 7-bit ASCII character set, and tries to map characters greater than ASCII 128 to a reasonable approximation (for example, á, à, â would all map to a). Other characters are mapped to a question mark (?).

How many deployment descriptor files does a CMP entity bean deployed on the WebLogic Server have?

a. One J2EE specific deployment descriptor and two WebLogic specific deployment descriptors
b. One J2EE specific deployment descriptor and one WebLogic specific deployment descriptors
c. One J2EE specific deployment descriptor only
d. One WebLogic specific deployment descriptor only

Choice A is correct. Deployment descriptors are text documents formatted with XML tags. The J2EE specifications define standard, portable deployment descriptors for J2EE components and applications. BEA defines additional WebLogic-specific deployment descriptors required to deploy a component or application in the WebLogic Server environment.

When packaging an enterprise bean, we need to create an ejb-jar.xml deployment descriptor in the META-INF subdirectory and add entries for the bean. We also need to create a weblogic-ejb-jar.xml deployment descriptor in the META-INF subdirectory and add entries for the bean. If the bean is an entity bean with container-managed persistence, first we create a weblogic-rdbms-cmp-jar-bean_name.xml deployment descriptor in the META-INF directory with entries for the bean. Then we map the bean to this CMP deployment descriptor with a attribute in the weblogic-ejb-jar.xml file.

Why do I get an error while trying to retrieve the text for ORA-12705?

This error occurs when you have not set the ORACLE_home environment variable properly — a common mistake. In order to use WebLogic jDriver for Oracle, the Oracle client software needs to be installed and ORACLE_home must be set.

You may also see this error message if you try to use WebLogic jDriver for Oracle's internationalization capabilities with a language/codeset combination that is not installed on your system. If you get the ORA-12705 error with the correct error text, then either you have set NLS_LANG improperly, or you do not have the right codesets installed on your system.

Why do I run out of resources during updates with Oracle's database link?

When you use Oracle's database link to update your database, you may get error "maximum number of temporary table locks exceeded" even if you close your result sets and statements when you finish.

The database link is an object in the local database that allows you to access tables, views, and such in a remote database. The database link is controlled by the Oracle server, so the driver has no control over its use of resources.

The link appears to perform the commit (since other processes could see the records that were
being created), but it doesn't free any resources until the connection is closed. The solution is to remove the database link and use the JDBC driver to do your selects, inserts, and updates.

Why am I getting an "ORA-01000: maximum open cursors exceeded" error, even though I closed all ResultSet, Statement, and Connection objects?

This is an Oracle issue. According to Oracle's documentation, dynamic cursors can remain open from run to run in a session and are not closeable when a procedure closes. To work around this issue, you can increase the number of open cursors allowed in the database or you can reset the connection pool (close and reopen database connections in the connection pool).

To reset the connection pool, you can untarget and retarget the connection pool using the Administration Console. You can also use the reset() method through the JMX API or the RESET_POOL command on the WebLogic Server command line interface.

0 Response to "Weblogic Interview questions -4"

Post a Comment

Powered by Blogger