∟Closing InputStream Too Early on setBinaryStream()
This section describes an error condition where executeUpdate() gives an exception if the InputStream 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 binary data from the InputStream is done at the time
of executeUpdate() call, not before. Here is a test program:
/**
* MySqlBlobSetBinaryStreamError.java
* Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
*/
import java.io.*;
import java.sql.*;
public class MySqlBlobSetBinaryStreamError {
public static void main(String [] args) {
Connection con = null;
try {
com.mysql.jdbc.jdbc2.optional.MysqlDataSource ds
= new com.mysql.jdbc.jdbc2.optional.MysqlDataSource();
ds.setServerName("localhost");
ds.setPortNumber(3306);
ds.setDatabaseName("HerongDB");
ds.setUser("Herong");
ds.setPassword("TopSecret");
con = ds.getConnection();
// Deleting the record for re-testing
String subject = "Test of setBinaryStream() method error";
Statement sta = con.createStatement();
sta.executeUpdate("DELETE FROM Image WHERE Subject = '"
+subject+"'");
// Inserting CLOB value with PreparedStatement.setBinaryStream()
PreparedStatement ps = con.prepareStatement(
"INSERT INTO Image (Subject, Body) VALUES (?,?)");
ps.setString(1, subject);
InputStream bodyIn =
new FileInputStream("MySqlBlobSetBinaryStream.class");
File fileIn = new File("MySqlBlobSetBinaryStream.class");
ps.setBinaryStream(2, bodyIn, (int) fileIn.length());
// Error - Closing the InputStream too early.
bodyIn.close();
int count = ps.executeUpdate();
ps.close();
// Retrieving BLOB value with getBytes()
sta = con.createStatement();
ResultSet res = sta.executeQuery("SELECT * FROM Image"
+" WHERE Subject = '"+subject+"'");
res.next();
System.out.println("The inserted record: ");
System.out.println(" Subject = "+res.getString("Subject"));
System.out.println(" Body = "
+new String(res.getBytes("Body"),0,32));
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 InputStream is closed.
C:\>java -cp .;\local\lib\mysql-connector-java-5.0.7-bin.jar
MySqlBlobSetBinaryStreamError
Exception: Error reading from InputStream java.io.IOException
java.sql.SQLException:
Error reading from InputStream java.io.IOException
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:910)
at com.mysql.jdbc.PreparedStatement.readblock(...)
at com.mysql.jdbc.PreparedStatement.streamToBytes(...)
at com.mysql.jdbc.PreparedStatement.fillSendPacket(...)
at com.mysql.jdbc.PreparedStatement.executeUpdate(...)
at MySqlBlobSetBinaryStreamError.main(MySqlBlobSetBinar...java:38)
