A very surprise problem about JDBC and connection pool

Question

I occur a very problem about JDBC and connection pool on Weblogic Platform
8.1.
There is a table in Oracle
Table
Name: t1
id varchar2(5);
content clob;
id is primary key.
If I use a connection pool to connect to Oracle,like following program:
InitialContext ic = new InitialContext();
DataSource ds = (DataSource) ic.lookup("cgOracleDataSource");
con = ds.getConnection();
then following program will throw a ClassCastException
String sql = "select content from t1 where id = ?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1,"001");
oracle.sql.CLOB clob = (oralce.sql.CLOB)rs.getClob("content") //this
statement will throw ClassCastException
but if I use JNDI to connect to Oracle,like following program, then those
program above is ok
private String dbdriver="oracle.jdbc.driver.OracleDriver";
private String dburl="jdbc:oracle:thin:@192.168.7.148:1521:ep";
private String username="ep";
private String password="epuser";
Class.forName(dbdriver);
conn = DriverManager.getConnection(dburl, username, password);
conn.setAutoCommit(false);
On the contrary, if I use JNDI to connect to Oracle, following program will
throw ClassCastException
weblogic.jdbc.vendor.oracle.OracleThinClob clob =
(weblogic.jdbc.vendor.oracle.OracleThinClob)rs.getClob("content");
but it is fine if I use connection pool to connect to Oracle.
I am confused this problem, who can tell me why?
Daniel

Answer 1

When you are getting connection using datasource lookup from weblogic
connection pool, this connection is internally wrapped and hence you have to
cast it to weblogic.jdbc.vendor.oracle.OracleThinClob which you do and so it
works.
But when you get connection by loading driver straight, you are getting naked
oracle connection. In this case when you cast it to oracle.sql.Clob it works,
as you have seen in your test case.
I hope this explains what is going on with your code.
Thanks,
Mitesh
Daniel wrote:
I occur a very problem about JDBC and connection pool on Weblogic Platform
8.1.
There is a table in Oracle
Table
Name: t1
id varchar2(5);
content clob;
id is primary key.
If I use a connection pool to connect to Oracle,like following program:
InitialContext ic = new InitialContext();
DataSource ds = (DataSource) ic.lookup("cgOracleDataSource");
con = ds.getConnection();
then following program will throw a ClassCastException
String sql = "select content from t1 where id = ?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1,"001");
oracle.sql.CLOB clob = (oralce.sql.CLOB)rs.getClob("content") //this
statement will throw ClassCastException
but if I use JNDI to connect to Oracle,like following program, then those
program above is ok
private String dbdriver="oracle.jdbc.driver.OracleDriver";
private String dburl="jdbc:oracle:thin:@192.168.7.148:1521:ep";
private String username="ep";
private String password="epuser";
Class.forName(dbdriver);
conn = DriverManager.getConnection(dburl, username, password);
conn.setAutoCommit(false);
On the contrary, if I use JNDI to connect to Oracle, following program will
throw ClassCastException
weblogic.jdbc.vendor.oracle.OracleThinClob clob =
(weblogic.jdbc.vendor.oracle.OracleThinClob)rs.getClob("content");
but it is fine if I use connection pool to connect to Oracle.
I am confused this problem, who can tell me why?
Daniel