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From Ken Katsma <kenkat...@gmail.com>
Subject Custom Type Handler question
Date Sun, 15 May 2005 21:44:59 GMT
Hi,

My group is currently using stored procedures in Oracle for all our
database access. To get around the n+m problem we are considering
several alternatives. One we know will work is to do a user function
for each column that maps to a "m" table that gives us the data in
string format (name,value pairs).

Another approach, (which we would prefer) is to return the results for
each "m" column as a cursor. I can do this in java with code that looks
something like this:

class RefCursor
{

public static void main (String args [])
throws SQLException, ClassNotFoundException
{
String query = "begin "+
"open ? for "+
"'select dname, CURSOR(select ename "+
"from emp "+
"where
emp.deptno=dept.deptno) "+
"from dept'; "+
"end;";

DriverManager.registerDriver
(new oracle.jdbc.driver.OracleDrive r());

Connection conn=
DriverManager.getConnection
("jdbc:oracle:thin:@aria-dev:1521:ora817dev",
"scott", "tiger");

Statement trace = conn.createStatement();

CallableStatement cstmt = conn.prepareCall(query);

cstmt.registerOutParameter(1,OracleTypes.CURSOR);
cstmt.execute();

ResultSet rset= (ResultSet)cstmt.getObject(1);

for(int i = 0; rset.next(); i++ )
{
System.out.println( rset.getString(1) );
ResultSet rset2 = (ResultSet)rset.getObject(2);
for( int j = 0; rset2.next(); j++ )
System.out.println( " " + rset2.getString(1) );
rset2.close();

}

rset.close();
cstmt.close();
}
}

To get the same functionality in iBatis we tried writing a custom type
handler for the cursor column that looks like this:

import java.sql.Ref;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.ibatis.sqlmap.client.extensions.ParameterSetter;
import com.ibatis.sqlmap.client.extensions.ResultGetter;
import com.ibatis.sqlmap.client.extensions.TypeHandlerCallback;
import com.ibatis.sqlmap.engine.type.ResultGetterImpl;

/**
* @author S001027
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class RefTypeHandler implements TypeHandlerCallback {

/* (non-Javadoc)
* @see
com.ibatis.sqlmap.client.extensions.TypeHandlerCallback#setParameter(
com.ibatis.sqlmap.client.extensions.ParameterSetter,
java.lang.Object)
*/
public void setParameter(ParameterSetter arg0, Object arg1)
throws SQLException {
if (arg1 != null)
{
arg0.setObject(arg1);
}
}

/* (non-Javadoc)
* @see
com.ibatis.sqlmap.client.extensions.TypeHandlerCallback#getResult(
com.ibatis.sqlmap.client.extensions.ResultGetter)
*/
public Object getResult(ResultGetter arg0) throws SQLException {
System.out.println("Object: " +
arg0.getObject().getClass().getName());
ResultSet result = (ResultSet) arg0.getObject();
System.out.println("Iterating");
while(result.next())
System.out.println("test");
result.close();

return result;
}

/* (non-Javadoc)
* @see
com.ibatis.sqlmap.client.extensions.TypeHandlerCallback#valueOf(
java.lang.String)
*/
public Object valueOf(String arg0) {
// TODO Auto-generated method stub
return null;
}

Unfortunately, when the statement:

ResultSet result = (ResultSet) arg0.getObject();

executes, we get an error from oracle that says "FETCH OUT OF
SEQUENCE". Is there something with the cursor going on in iBatis that
prevents us from touching the nested cursor? I guess my next step is to
start stepping through the iBatis code in debug to see whats happening,
but I was hoping somebody may already have a solution or know the problem.

Thanks,

Ken

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