BEA WebLogic Interview Questions and Answers 3

How do I use OS Authentication with WebLogic jDriver for Oracle and Connection Pools?
Using OS authentication in connection pools essentially means that you are using the UserId of the user who started WebLogic Server. OS authentication is available on NT and UNIX, but not on Solaris. This means that database security will rely strictly on the security of WebLogic; that is, if you are allowed to make a client connection to the WebLogic Server and access the pool, then you can get to the database.

You can do this with WebLogic jDriver for Oracle because Oracle uses the process owner to determine who is attempting the connection. In the case of WebLogic JDBC, this is always the user that started the WebLogic Server.

To set up your Oracle instance to use this feature, your DBA needs to follow these basic steps. The full procedure is described in more detail in your Oracle documentation.

1. Add the following line to the INIT[sid].ORA file:
OS_AUTHENT_PREFIX = OPS$
Note that the string "OPS$" is arbitrary and up to the DBA.
2. Log in to the Oracle server as SYSTEM.
3. Create a user named OPS$userid, where userid is some operating system login ID. This user should be granted the standard privileges (for example, CONNECT and RESOURCE).
4. Once the userid is set up, you can connect with WebLogic jDriver for Oracle by specifying "/" as the username property and "" as the password property. Here is an example for testing this connection with the dbping utility:

$ java utils.dbping ORACLE "/" "" myserver

Here is a code example for WebLogic jDriver for Oracle:
Properties props = new Properties();
props.put("user", "/");
props.put("password", "");
props.put("server", "myserver");

Class.forName("weblogic.jdbc.oci.Driver").newInstance();
Connection conn = myDriver.connect("jdbc:weblogic:oracle",
props);

1. Use the Administration Console to set the attribute for your connection pool. The following code is an example of a JDBC connection pool configuration using the WebLogic jDriver for Oracle:

<JDBCConnectionPool
Name="myPool"
Targets="myserver,server1"
DriverName="weblogic.jdbc.oci.Driver"
InitialCapacity="1"

MaxCapacity="10"
CapacityIncrement="2"
Properties="databaseName=myOracleDB"

What type of object is returned by ResultSet.getObject()?
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 getObject() 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 BigDecimal 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.

For example, 1.0000 will be an integer. A long is returned for a value such as 123456789123.00000. If a value has a non-zero fractional component, a Double is returned if the precision of the value can be represented by a Double; otherwise a BigDecimal is returned.

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;
END;");
cstmt.execute();

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};");
cstmt.execute();

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 do I learn what codesets are available in Oracle?
To find out what codesets you currently have available in Oracle, execute the following SQL query from SQLPlus at the command line:

SQL> SELECT value FROM v$nls_valid_values WHERE parameter='CHARACTERSET';

The response lists of all codesets currently installed on your system. This listing will look something like the following shortened list:
VALUE
---------------
US7ASCII
WE8DEC
WE8HP
US8PC437
WE8EBCDIC37
WE8EBCDIC500
WE8EBCDIC285
...

If you want to constrain the value in the query to a specific codeset you are searching for, you might use a SQL query like the following:
SQL> SELECT value FROM v$nls_valid_values
WHERE parameter='CHARACTERSET' and VALUE='AL24UTFFSS';

This would produce the following response if the codeset is installed:

VALUE
-------------------
AL24UTFFSS

You can use Oracle's installation tools to install additional codesets. Contact Oracle for more information.

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.