This section describes how to insert CLOB values with the PreparedStatement.setClob() method.
If you want to insert a CLOB column with a character string that comes from a java.sql.Clob object,
you can directly set the value with PreparedStatement.setClob() method.
To test this, I wrote the following program to copy some records with CLOB values as new records back into the same table.
During the copy process, the CLOB values are also modified with some Clob object methods - The first 32 characters are converted to upper case
characters.
/**
* OracleClobSetClob.java
* Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
*/
import java.io.*;
import java.sql.*;
public class OracleClobSetClob {
public static void main(String [] args) {
Connection con = null;
try {
oracle.jdbc.pool.OracleDataSource ds
= new oracle.jdbc.pool.OracleDataSource();
ds.setDriverType("thin");
ds.setServerName("localhost");
ds.setPortNumber(1521);
ds.setDatabaseName("XE");
ds.setUser("Herong");
ds.setPassword("TopSecret");
con = ds.getConnection();
// Deleting records for re-testing
Statement sta = con.createStatement();
sta.executeUpdate(
"DELETE FROM Article WHERE Subject LIKE 'Copy of %'");
// Creating a PreparedStatement for inserting new records
PreparedStatement ps = con.prepareStatement(
"INSERT INTO Article (Subject, Body, ID) VALUES (?,?,?)");
// Looping though the first 3 records
ResultSet res = sta.executeQuery(
"SELECT * FROM Article ORDER BY ID");
int i = 0;
while (res.next() && i<3) {
i++;
System.out.println("Copying record ID: "+res.getInt("ID"));
String subject = res.getString("Subject");
Clob body = res.getClob("Body");
// Modifying the Clob object
String chuck = body.getSubString(1,32);
chuck = chuck.toUpperCase();
body.setString(1,chuck);
// Inserting a new record with setClob()
ps.setString(1, "Copy of "+subject);
ps.setClob(2,body);
ps.setInt(3,res.getInt("ID")+100);
ps.executeUpdate();
}
ps.close();
res.close();
// Checking the new records
res = sta.executeQuery(
"SELECT * FROM Article WHERE Subject LIKE 'Copy of %'");
while (res.next()) {
System.out.println("Record ID: "+res.getInt("ID"));
System.out.println(" Subject = "+res.getString("Subject"));
String body = res.getString("Body");
if (body.length() > 100) body = body.substring(0,100);
System.out.println(" Body = "+body+"...");
}
res.close();
sta.close();
con.close();
} catch (Exception e) {
System.err.println("Exception: "+e.getMessage());
e.printStackTrace();
}
}
}
Unfortunately, my program failed because Oracle JDBC driver requires
that the result set row must be locked:
C:\>java -cp .;\local\lib\ojdbc14.jar OracleClobSetClob
Copying record ID: 1
Exception: ORA-22920: row containing the LOB value is not locked
java.sql.SQLException: ORA-22920:
row containing the LOB value is not locked
at oracle.jdbc.driver.DatabaseError.throwSqlException(
DatabaseError.java:112)
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:331)
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:283)
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:278)
at oracle.jdbc.driver.T4C8TTILob.receiveReply(T4C8TTILob.java:930)
at oracle.jdbc.driver.T4C8TTIClob.write(T4C8TTIClob.java:435)
at oracle.jdbc.driver.T4CConnection.putChars(
T4CConnection.java:2678)
at oracle.sql.CLOB.putChars(CLOB.java:433)
at oracle.sql.CLOB.setString(CLOB.java:910)
at OracleClobSetClob.main(OracleClobSetClob.java:43)
The problem is caused by the Oracle JDBC driver implementation of ResultSet objects.
The Clob object returned by getClob() is still tied up to the ResultSet object.
When Clob object is updated, Oracle consider that the ResultSet is updated,
which requires locking the row in the database for automatic updates.
In another word, Oracle does not allow you to update result set.
If you do, Oracle will try to persist the changes back to the database.
