Workaround for using Oracle JDBC extension with WLS pooling

Question

Reading the newsgroup I saw that many of us encountered the problems
with ClassCastException when tried to use Oracle JDBC extension
with WLS pooling. I also had.
In this case BEA recommends to use dangerous
method getVendorConnection() which exposes
the physical connection object to your code.
Yes it's really dangerous because of unsafe usage may breaks
WLS pooled connection(s).
Moreover, this practice will make your JDBC code
unportable (your JDBC code in addition to Oracle dependence
became Weblogic dependent):
void doSmth() {
Connection con = ...;
Connection vCon = ((WLConnection)con).getVendorConnection();
// + mess of usage con in one places and vCon in others
// (where Oracle extensions are needed)
// !Don't forget to don't close vCon!
Sux.
I found the workaround.
Introduction
============
Yes the real cause of ClassCastException is that
in depth of Oracle driver the casting
to class oracle.jdbc.driver.OracleConnection
(not to interface oracle.jdbc.OracleConnection)
is performed.
Someone can say that this is bug or pure desing.
Weblogic pooled connection provide dynamic
implementation for all public interfaces
which real physical (wrapped) connection object implements.
Great feature!
But I guess that all interface methods implemented
by simple call-delegation to physical (wrapped) connection object.
In case of oracle.jdbc.OracleConnection interface
this approach doesn't work for at least one its method:
public OracleConnection unwrap()
WLS pooled connection shoudn't implement this method by
delegation to physical connection object BUT should
return physical connection object itself!
// Wrong implementation of unwrap()
// delegation is used
public OracleConnection unwrap() {
return physicalConnection.unwrap();
// Right implementation of unwrap()
// physical connection returned
public OracleConnection unwrap() {
return physicalConnection;
Workaround
==========
1. Develop your own OracleConnection wrapper class:
import oracle.jdbc.OracleConnection;
import weblogic.jdbc.extensions.WLConnection;
public class MyOracleConnectionImpl implements OracleConnection {
private OracleConnection con;
public MyOracleConnectionImpl(OracleConnection connection)
throws SQLException
this.con = connection;
public OracleConnection unwrap() {
return (OracleConnection)
((WLConnection)con).getVendorConnection();
/* Implement all other methods by delegation to con object */
2. Don't get Connections directly from DataSource --
develop your own simple (may be static) utility
class which retrives Connections from dataSource
and returns them wrapped into your MyOracleConnectionImpl
to your code from some method:
puclic abstract class MyConnectionSource {
public static Connection getConnection() {
Connection con = // get it from DataSource
return new MyOracleConnectionImpl((OracleConnection)con);
3. Add attribute RemoveInfectedConnectionsEnabled="false"
to definition of your JDBCConnectionPool within config.xml
You may do it because of you `safely` use vendorConnection --
you don't expose it to application code.
4. Enjoy the Oracle JDBC extensions in your code!
Example:
Connection con = MyConnectionSource.getConnection;
ArrayDescriptor add =
ArrayDescriptor.createDescriptor("your_type", con);
Hope it helps to someone.
Best regards,
Eugene Voytitsky

Answer 1

Hello Eugene Voytitsky,
Thanks Eugene Voytitsky for your idea
I have tried the solution suggested by You, but it did not work.
It still throws ClassCastException.
I am sorry for posting the whole code of two classes below.
I did this to give you more clarity.
I am also indicating the place where the exception was thrown..
Please let me know if I am doing something wrong.
OracleConnection Wrapper class
package ejbTesting;
// sql imports
import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.Statement;
// util imports
import java.util.Map;
import java.util.Properties;
// imports from Oracle Driver Classes
import oracle.jdbc.OracleConnection;
import oracle.jdbc.OracleOCIFailover;
import oracle.jdbc.OracleSavepoint;
// import from Weblogic extensions
import weblogic.jdbc.extensions.WLConnection;
public class WeblogicConnectionWrapper implements OracleConnection
     // oracle connection object
     private OracleConnection connection;
     public WeblogicConnectionWrapper (OracleConnection orclConnection)
          try
               this.connection = orclConnection;
          catch(Exception unexpected )
               unexpected.printStackTrace();
     public OracleConnection unwrap()
          try
          // The datasource returns a weblogic.jdbc.pool.Connection
          // This needs to be type casted to weblogic.jdbc.extensions.WLConnection
          // Only this weblogic.jdbc.extensions.WLConnection CAN BE type casted
          // to OracleConnection
     return (OracleConnection) ((WLConnection) connection).getVendorConnection();
     catch(Exception sqlException )
          sqlException.printStackTrace ();
          return null;
     /* Implement all other methods by delegation to connection object */      
public Connection _getPC()
return connection._getPC();
public void archive(int i, int j, String s)
throws SQLException
connection.archive(i, j, s);
public void assertComplete()
throws SQLException
connection.assertComplete();
public void clearWarnings()
throws SQLException
connection.clearWarnings();
public void close()
throws SQLException
connection.close();
public void commit()
throws SQLException
connection.commit();
public Statement createStatement()
throws SQLException
return connection.createStatement();
public Statement createStatement(int i, int j)
throws SQLException
return connection.createStatement(i, j);
public boolean getAutoClose()
throws SQLException
return connection.getAutoClose();
public boolean getAutoCommit()
throws SQLException
return connection.getAutoCommit();
public CallableStatement getCallWithKey(String s)
throws SQLException
return connection.getCallWithKey(s);
public String getCatalog()
throws SQLException
return connection.getCatalog();
public boolean getCreateStatementAsRefCursor()
return connection.getCreateStatementAsRefCursor();
public int getDefaultExecuteBatch()
return connection.getDefaultExecuteBatch();
public int getDefaultRowPrefetch()
return connection.getDefaultRowPrefetch();
public Object getDescriptor(String s)
return connection.getDescriptor(s);
public boolean getExplicitCachingEnabled()
throws SQLException
return connection.getExplicitCachingEnabled();
public boolean getImplicitCachingEnabled()
throws SQLException
return connection.getImplicitCachingEnabled();
public boolean getIncludeSynonyms()
return connection.getIncludeSynonyms();
public Object getJavaObject(String s)
throws SQLException
return connection.getJavaObject(s);
public DatabaseMetaData getMetaData()
throws SQLException
return connection.getMetaData();
public Properties getProperties()
return connection.getProperties();
public boolean getRemarksReporting()
return connection.getRemarksReporting();
public boolean getRestrictGetTables()
return connection.getRestrictGetTables();
public String getSQLType(Object obj)
throws SQLException
return connection.getSQLType(obj);
public String getSessionTimeZone()
return connection.getSessionTimeZone();
public int getStatementCacheSize()
throws SQLException
return connection.getStatementCacheSize();
public PreparedStatement getStatementWithKey(String s)
throws SQLException
return connection.getStatementWithKey(s);
public int getStmtCacheSize()
return connection.getStmtCacheSize();
public short getStructAttrCsId()
throws SQLException
return connection.getStructAttrCsId();
public boolean getSynchronousMode()
return connection.getSynchronousMode();
public int getTransactionIsolation()
throws SQLException
return connection.getTransactionIsolation();
public Map getTypeMap()
throws SQLException
return connection.getTypeMap();
public String getUserName()
throws SQLException
return connection.getUserName();
public boolean getUsingXAFlag()
return connection.getUsingXAFlag();
public SQLWarning getWarnings()
throws SQLException
return connection.getWarnings();
public boolean getXAErrorFlag()
return connection.getXAErrorFlag();
public boolean isClosed()
throws SQLException
return connection.isClosed();
public boolean isLogicalConnection()
return connection.isLogicalConnection();
public boolean isReadOnly()
throws SQLException
return connection.isReadOnly();
public String nativeSQL(String s)
throws SQLException
return connection.nativeSQL(s);
public Object openJoltConnection(String s, short word0, short word1)
return connection.openJoltConnection(s, word0, word1);
public void oracleReleaseSavepoint(OracleSavepoint oraclesavepoint)
throws SQLException
connection.oracleReleaseSavepoint(oraclesavepoint);
public void oracleRollback(OracleSavepoint oraclesavepoint)
throws SQLException
connection.oracleRollback(oraclesavepoint);
public OracleSavepoint oracleSetSavepoint()
throws SQLException
return connection.oracleSetSavepoint();
public OracleSavepoint oracleSetSavepoint(String s)
throws SQLException
return connection.oracleSetSavepoint(s);
public int pingDatabase(int i)
throws SQLException
return connection.pingDatabase(i);
public CallableStatement prepareCall(String s)
throws SQLException
return connection.prepareCall(s);
public CallableStatement prepareCall(String s, int i, int j)
throws SQLException
return connection.prepareCall(s, i, j);
public CallableStatement prepareCallWithKey(String s)
throws SQLException
return connection.prepareCallWithKey(s);
public PreparedStatement prepareStatement(String s)
throws SQLException
return connection.prepareStatement(s);
public PreparedStatement prepareStatement(String s, int i, int j)
throws SQLException
return connection.prepareStatement(s, i, j);
public PreparedStatement prepareStatementWithKey(String s)
throws SQLException
return connection.prepareStatementWithKey(s);
public void purgeExplicitCache()
throws SQLException
connection.purgeExplicitCache();
public void purgeImplicitCache()
throws SQLException
connection.purgeImplicitCache();
public void putDescriptor(String s, Object obj)
throws SQLException
connection.putDescriptor(s, obj);
public void registerApiDescription(String s, short word0, short word1, String
s1)
connection.registerApiDescription(s, word0, word1, s1);
public void registerSQLType(String s, Class class1)
throws SQLException
connection.registerSQLType(s, class1);
public void registerSQLType(String s, String s1)
throws SQLException
connection.registerSQLType(s, s1);
public void registerTAFCallback(OracleOCIFailover oracleocifailover, Object
obj)
throws SQLException
connection.registerTAFCallback(oracleocifailover, obj);
public void rollback()
throws SQLException
connection.rollback();
public void setAutoClose(boolean flag)
throws SQLException
connection.setAutoClose(flag);
public void setAutoCommit(boolean flag)
throws SQLException
connection.setAutoCommit(flag);
public void setCatalog(String s)
throws SQLException
connection.setCatalog(s);
public void setCreateStatementAsRefCursor(boolean flag)
connection.setCreateStatementAsRefCursor(flag);
public void setDefaultExecuteBatch(int i)
throws SQLException
connection.setDefaultExecuteBatch(i);
public void setDefaultRowPrefetch(int i)
throws SQLException
connection.setDefaultRowPrefetch(i);
public void setExplicitCachingEnabled(boolean flag)
throws SQLException
connection.setExplicitCachingEnabled(flag);
public void setImplicitCachingEnabled(boolean flag)
throws SQLException
connection.setImplicitCachingEnabled(flag);
public void setIncludeSynonyms(boolean flag)
connection.setIncludeSynonyms(flag);
public void setReadOnly(boolean flag)
throws SQLException
connection.setReadOnly(flag);
public void setRemarksReporting(boolean flag)
connection.setRemarksReporting(flag);
public void setRestrictGetTables(boolean flag)
connection.setRestrictGetTables(flag);
public void setSessionTimeZone(String s)
throws SQLException
connection.setSessionTimeZone(s);
public void setStatementCacheSize(int i)
throws SQLException
connection.setStatementCacheSize(i);
public void setStmtCacheSize(int i)
throws SQLException
connection.setStmtCacheSize(i);
public void setStmtCacheSize(int i, boolean flag)
throws SQLException
connection.setStmtCacheSize(i, flag);
public void setSynchronousMode(boolean flag)
connection.setSynchronousMode(flag);
public void setTransactionIsolation(int i)
throws SQLException
connection.setTransactionIsolation(i);
public void setTypeMap(Map map)
throws SQLException
connection.setTypeMap(map);
public void setUsingXAFlag(boolean flag)
connection.setUsingXAFlag(flag);
public void setWrapper(OracleConnection oracleconnection)
connection.setWrapper(oracleconnection);
public void setXAErrorFlag(boolean flag)
connection.setXAErrorFlag(flag);
public void shutdown(int i)
throws SQLException
connection.shutdown(i);
public void startup(String s, int i)
throws SQLException
connection.startup(s, i);
Util class to get Wrapped Connections from
datasource
package ejbTesting;
// j2ee imports
import javax.naming.InitialContext;
import javax.sql.DataSource;
// sql imports
import java.sql.Connection;
// imports from Oracle Driver Classes
import oracle.jdbc.OracleConnection;
* Wrapper class for the DataSource Connection from Weblogic pool
public class DataSourceConnectionWrapper
     // datasource variable
     private static transient DataSource datasource = null;
     private static String dbName = "jdbc/workbench";
* Method that returns the database connection
     public static Connection getConnection()
          try
               // initialsing the datasource object
               initialiseDataSource ();
               // Getting a connection from the datasource
               Connection con = datasource.getConnection( );
               // wrapping it custom wrapper class and
               // returning the connection object
               return new WeblogicConnectionWrapper((OracleConnection)con);
          catch(Exception exception )
               exception.printStackTrace();
               return null;
     private static void initialiseDataSource( ) throws Exception
if ( datasource == null )
try
InitialContext ic = new InitialContext( );
datasource = (DataSource) ic.lookup( dbName );
catch (Exception ne )
throw new Exception( "NamingException while looking up DataSource with
JNDI name" +
dbName + ": \n" + ne.getMessage( ) );
Exception Stack Trace
The line 46 in DataSourceConnectionWrapper
corresponds to
return new WeblogicConnectionWrapper((OracleConnection)con);
Which I feel is logical as the connection which we get from Weblogic
datasource cannot be type casted to OracleConnection
java.lang.ClassCastException: weblogic.jdbc.pool.Connection
at ejbTesting.DataSourceConnectionWrapper.getConnection(DataSourceConnectionWrapper.java:46)