Using OraclePreparedStatement with DBCP Connection

Question

I'm trying to make a connection pool with the dbcp framework for my oracle server. I used this tutorial for the connection. The problem is to create a OraclePreparedStatement with this connection:

Connection oracleCon;
OraclePreparedStatement o_stmt;
String sql = "INSERT INTO T002_metadata (T002_datacitexml,T002_version, T002_active)       VALUES (?,?,?) RETURNING T002_id INTO ?";


oracleCon = ConnectionManager.ds.getConnection();

o_stmt = ((OraclePreparedStatement) oracleCon.prepareStatement(sql));

After executing this, an exception is thrown.

org.apache.commons.dbcp.DelegatingPreparedStatement cannot be cast to oracle.jdbc.OraclePreparedStatement

Is there any possibility to cast the statement?

Answer 1

I had the same problem today and solved it by changing Tomcat configuration as suggestedhere . I changed the context.xml file by changing the type and factory properties like this:

....
<Resource name="jdbc/dsName"
       auth="Container"
          type="oracle.jdbc.pool.OracleDataSource"
          factory="oracle.jdbc.pool.OracleDataSourceFactory"
       user="username"
       password="password"
       driverClassName="oracle.jdbc.driver.OracleDriver"
       url="jdbcurl"/>
....

also resource definition in web.xml file had to be changed

....
 <resource-ref>
    <description>Oracle datasource</description>
    <res-ref-name>jdbc/test</res-ref-name>
    <!-- <res-type>javax.sql.DataSource</res-type>-->
    <res-type>oracle.jdbc.pool.OracleDataSource</res-type>
    <res-auth>Container</res-auth>
  </resource-ref>
....

no changes have been needed in my code.

Answer 2

Not to an Oracle class, no. That's what JDBC is for. It's an API. Use java.sql.PreparedStatement only. By attempting to downcast, you violate polymorphism and break things like this, where a library is wrapping the real connection and statement to provide some additional services for you.

Answer 3

I f you're using Oracle, you can cast your connection to OracleConnection, and then cast your prepared statement to OraclePreparedStatement. What jdbc does is upcast the Oracle objects to standard sql objects, but they are still Oracle sql objects.

Answer 4

I use an utility method

public static OraclePreparedStatement getOraclePreparedStatement(PreparedStatement stmt) {
        if (stmt instanceof OraclePreparedStatement) {
            return (OraclePreparedStatement) stmt;
        }
        if (stmt instanceof DelegatingPreparedStatement) {
            DelegatingPreparedStatement stmt1 = (DelegatingPreparedStatement) stmt;

            return (OraclePreparedStatement) stmt1.getInnermostDelegate();
        }
        System.out.println(stmt);
        throw new RuntimeException("unknown statement");
    }

Essentially it allows using the same code standalone (eg in tests) or in tomcat. I use it instead of casting, so the code does not get longer.

try (OraclePreparedStatement stmt = getOraclePreparedStatement(con.prepareStatement(SQL_INSERT_TREATMENT))) {
    ...
    }