∟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 will 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:
/**
* SqlServerClobSetCharacterStreamError.java
* Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
*/
import java.io.*;
import java.sql.*;
public class SqlServerClobSetCharacterStreamError {
public static void main(String [] args) {
Connection con = null;
try {
com.microsoft.sqlserver.jdbc.SQLServerDataSource ds
= new com.microsoft.sqlserver.jdbc.SQLServerDataSource();
ds.setServerName("localhost");
ds.setPortNumber(1269);
ds.setDatabaseName("AdventureWorksLT");
ds.setUser("Herong");
ds.setPassword("TopSecret");
con = ds.getConnection();
// Deleting the record for re-testing
String subject = "Test of setCharacterStream() methods";
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 (Subject, Body) VALUES (?,?)");
ps.setString(1, subject);
Reader bodyIn =
new FileReader("SqlServerClobSetCharacterStream.java");
File fileIn = new File("SqlServerClobSetCharacterStream.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();
}
}
}
The IOException is shown below. It doesn't tell you that the Reader is closed.
C:\>java -cp .;\local\lib\sqljdbc.jar
SqlServerClobSetCharacterStreamError
Exception: Unexpected IOException processing character stream Reader.
com.microsoft.sqlserver.jdbc.SQLServerException:
Unexpected IOException processing character stream Reader.
at com.microsoft.sqlserver.jdbc.SQLServerException
.makeFromDriverError(...)
at com.microsoft.sqlserver.jdbc.IOBuffer
.bufferAppendRPCReader(...)
at com.microsoft.sqlserver.jdbc.DTV$SendByRPCOp.execute(...)
at com.microsoft.sqlserver.jdbc.DTV.executeOp(Unknown Source)
at com.microsoft.sqlserver.jdbc.DTV.sendByRPC(Unknown Source)
at com.microsoft.sqlserver.jdbc.Parameter.sendByRPC(...)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement
.sendParamsByRPC(...)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement
.doPrepExec(...)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement
.executeUpdate(...)
at SqlServerClobSetCharacterStreamError.main
(SqlServerClobSetCharacterStreamError.java:38)
