∟Closing InputStream Too Early on setCharacterStream()
This section describes an error condition where executeUpdate() gives an exception if the Reader is closed too early.
The program in the previous tutorial worked nicely. But if you make a mistake by placing the bodyIn.close() statement before ps.executeUpdate(),
you may get an IOException when ps.executeUpdate() is called. The reason is simple, reading of data from the Reader is done at the time
of executeUpdate() call, not before. Here is a test program:
/**
* OracleClobSetCharacterStreamError.java
* Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
*/
import java.io.*;
import java.sql.*;
public class OracleClobSetCharacterStreamError {
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 the record for re-testing
String subject = "Error test of setCharacterStream()";
Statement sta = con.createStatement();
sta.executeUpdate("DELETE FROM Article WHERE Subject = '"
+subject+"'");
// Inserting CLOB value with a PreparedStatement
PreparedStatement ps = con.prepareStatement(
"INSERT INTO Article (ID, Subject, Body) VALUES (4,?,?)");
ps.setString(1, subject);
Reader bodyIn =
new FileReader("OracleClobSetCharacterStreamError.java");
File fileIn = new File(
"OracleClobSetCharacterStreamError.java");
ps.setCharacterStream(2, bodyIn, (int) fileIn.length());
// Error - Closing the Reader too early.
bodyIn.close();
int count = ps.executeUpdate();
ps.close();
// Retrieving CLOB value with getString()
sta = con.createStatement();
ResultSet res = sta.executeQuery("SELECT * FROM Article"
+" WHERE Subject = '"+subject+"'");
res.next();
System.out.println("The inserted record: ");
System.out.println(" Subject = "+res.getString("Subject"));
System.out.println(" Body = "
+res.getString("Body").substring(0,256));
res.close();
sta.close();
con.close();
} catch (Exception e) {
System.err.println("Exception: "+e.getMessage());
e.printStackTrace();
}
}
}
Surprisingly, I did not get any I/O exceptions. May be the Oracle JDBC driver reads
data at the time of setCharacterStream() call. The program executed correctly:
C:\>java -cp .;\local\lib\ojdbc14.jar
OracleClobSetCharacterStreamError
The inserted record:
Subject = Error test of setCharacterStream()
Body = /**
* OracleClobSetCharacterStreamError.java
* Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
*/
import java.io.*;
import java.sql.*;
public class OracleClobSetCharacterStreamError {
public static void main(String [] args) {
Connectio
