JBoss下CLOB.createTemporary抛出ClassCast的异常

JBoss下CLOB.createTemporary抛出ClassCast的异常

错误用法：CLOB.createTemporary(conn,....);
正确用法：CLOB.createTemporary(((WrappedConnection) con).getUnderlyingConnection() ,.....);
原理：
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if you are using jboss or any other AS that perform jdbc connection pooling , the classcast exception is caused by the "conn" object. (I had this problem using jboss4.0.1/oracle9.2).
In jboss4 the Connection object retrieved by ConnectionFactory.makeconnection() is an instance of org.jboss.resource.adapter.jdbc.WrappedConnection class (or a DelegatingConnection in tomcat or products that use DBCP)
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include jboss-common-jdbc-wrapper.jar with WrappedConnection class

=============================《2008-9-10》=======================
最近看了看人家Spring，老早处理了这种情况了，具体见NativeJdbcExtractor接口

public   interface  NativeJdbcExtractor {    
    boolean  isNativeConnectionNecessaryForNativeStatements();

     boolean  isNativeConnectionNecessaryForNativePreparedStatements();

     boolean  isNativeConnectionNecessaryForNativeCallableStatements();

    // 呵呵，就是这个方法
    Connection getNativeConnection(Connection con)  throws  SQLException;

    Connection getNativeConnectionFromStatement(Statement stmt)  throws  SQLException;

    Statement getNativeStatement(Statement stmt)  throws  SQLException;

    PreparedStatement getNativePreparedStatement(PreparedStatement ps)  throws  SQLException;

    CallableStatement getNativeCallableStatement(CallableStatement cs)  throws  SQLException;

    ResultSet getNativeResultSet(ResultSet rs)  throws  SQLException;

}

来看看，Jboss的特定实现：

public   class  JBossNativeJdbcExtractor  extends  NativeJdbcExtractorAdapter {

     private   static   final  String WRAPPED_CONNECTION_NAME  =   " org.jboss.resource.adapter.jdbc.WrappedConnection " ;

     private   static   final  String WRAPPED_STATEMENT_NAME  =   " org.jboss.resource.adapter.jdbc.WrappedStatement " ;

     private   static   final  String WRAPPED_RESULT_SET_NAME  =   " org.jboss.resource.adapter.jdbc.WrappedResultSet " ;


     private  Class wrappedConnectionClass;

     private  Class wrappedStatementClass;

     private  Method getUnderlyingConnectionMethod;

     private  Method getUnderlyingStatementMethod;


     /**
     * This constructor retrieves JBoss JDBC wrapper classes,
     * so we can get the underlying vendor connection using reflection.
      */
     public  JBossNativeJdbcExtractor() {
         try  {
             this .wrappedConnectionClass  =  getClass().getClassLoader().loadClass(WRAPPED_CONNECTION_NAME);
             this .wrappedStatementClass  =  getClass().getClassLoader().loadClass(WRAPPED_STATEMENT_NAME);
             this .getUnderlyingConnectionMethod  =
                 this .wrappedConnectionClass.getMethod( " getUnderlyingConnection " , (Class[])  null );
             this .getUnderlyingStatementMethod  =
                 this .wrappedStatementClass.getMethod( " getUnderlyingStatement " , (Class[])  null );
        }
         catch  (Exception ex) {
             throw   new  DASEntityRuntimeException(ExceptionConstant.DAS_14101034,
                             " Could not initialize JBossNativeJdbcExtractor because JBoss API classes are not available " ,
                            ex);
        }
    }


     /**
     * Retrieve the Connection via JBoss' <code>getUnderlyingConnection</code> method.
      */
     protected  Connection doGetNativeConnection(Connection con)  throws  SQLException {
         if  ( this .wrappedConnectionClass.isAssignableFrom(con.getClass())) {
             try  {
                 return  (Connection)  this .getUnderlyingConnectionMethod.invoke(con, (Object[])  null );
            }
             catch  (InvocationTargetException ex) {
                 throw   new  DASEntityRuntimeException(ExceptionConstant.DAS_14101034,
                         " JBoss' getUnderlyingConnection method failed " , ex
                                .getTargetException());
            }
             catch  (Exception ex) {
                 throw   new  DASEntityRuntimeException(ExceptionConstant.DAS_14101034,
                                 " Could not access JBoss' getUnderlyingConnection method " ,
                                ex);
            }
        }
         return  con;
    }

     /**
     * Retrieve the Connection via JBoss' <code>getUnderlyingStatement</code> method.
      */
     public  Statement getNativeStatement(Statement stmt)  throws  SQLException {
         if  ( this .wrappedStatementClass.isAssignableFrom(stmt.getClass())) {
             try  {
                 return  (Statement)  this .getUnderlyingStatementMethod.invoke(stmt, (Object[])  null );
            }
             catch  (InvocationTargetException ex) {
                 throw   new  DASEntityRuntimeException(ExceptionConstant.DAS_14101034,
                         " JBoss' getUnderlyingStatement method failed " , ex
                                .getTargetException());
            }
             catch  (Exception ex) {
                 throw   new  DASEntityRuntimeException(ExceptionConstant.DAS_14101034,
                                 " Could not access JBoss' getUnderlyingStatement method " ,
                                ex);
            }
        }
         return  stmt;
    }

     /**
     * Retrieve the Connection via JBoss' <code>getUnderlyingStatement</code> method.
      */
     public  PreparedStatement getNativePreparedStatement(PreparedStatement ps)  throws  SQLException {
         return  (PreparedStatement) getNativeStatement(ps);
    }

     /**
     * Retrieve the Connection via JBoss' <code>getUnderlyingStatement</code> method.
      */
     public  CallableStatement getNativeCallableStatement(CallableStatement cs)  throws  SQLException {
         return  (CallableStatement) getNativeStatement(cs);
    }

     /**
     * Retrieve the Connection via JBoss' <code>getUnderlyingResultSet</code> method.
     * <p>We access WrappedResultSet via direct reflection, since this class only
     * appeared in JBoss 3.2.4 and we want to stay compatible with at least 3.2.2+.
      */
     public  ResultSet getNativeResultSet(ResultSet rs)  throws  SQLException {
         if  (rs.getClass().getName().equals(WRAPPED_RESULT_SET_NAME)) {
             try  {
                Method getUnderlyingResultSetMethod  =  rs.getClass().getMethod( " getUnderlyingResultSet " , (Class[])  null );
                 return  (ResultSet) getUnderlyingResultSetMethod.invoke(rs, (Object[])  null );
            }
             catch  (InvocationTargetException ex) {
                 throw   new  DASEntityRuntimeException(ExceptionConstant.DAS_14101034,
                         " JBoss' getUnderlyingResultSet method failed " , ex
                                .getTargetException());
            }
             catch  (Exception ex) {
                 throw   new  DASEntityRuntimeException(ExceptionConstant.DAS_14101034,
                                 " Could not access JBoss' getUnderlyingResultSet method " ,
                                ex);
            }
        }
         return  rs;
    }

}

看来Spring中还是有不少经验总结的