import java.sql.*;
/*
 *the environment
C:\Temp>java -version
java version "1.4.2_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_01-b06)
Java HotSpot(TM) Client VM (build 1.4.2_01-b06, mixed mode)

>mysql --version
>mysql  Ver 14.3 Distrib 4.1.1-alpha, for pc-linux (i686)

 * the command lines to compile and test it
 *
	@echo off
	javac -classpath c:\mystocks\mysql-connector-java-3.1-nightly-20040524-bin.jar TestQuery.java
	java -classpath c:\mystocks\mysql-connector-java-3.1-nightly-20040524-bin.jar;. TestQuery %1
 * the TestQuery takes option argument "true" . If "true" is passed
 * as an argument, compression will be used 
 * run the following script to create and test the database
 * mysql --batch --force < input_script 
 *

-- start of sql script ---
drop database if exists test_sql_compress;
create database test_sql_compress;
create table test_sql_compress.present (first VARCHAR(30), last VARCHAR(30));
insert ignore into test_sql_compress.present Values('MySQL', 'Connector');
insert ignore into test_sql_compress.present Values('Testing', 'UseCompress');
-- dont create another table here -- but try to select from absent table --

select * from test_sql_compress.absent;
select * from test_sql_compress.present;
-- end of sql script ---

The problem : run this command without "true" and you the program runs
fine. Run it with "true" as argument and the connection to the server
drops/hangs. UseCompression=true doesn't work.

SQLException: Server connection failure during transaction. Due to underlying ex
ception: 'java.sql.SQLException: Communication link failure message from server:
 "Unknown command"'.

** BEGIN NESTED EXCEPTION **

java.sql.SQLException
MESSAGE: Communication link failure message from server: "Unknown command"

STACKTRACE:

java.sql.SQLException: Communication link failure message from server: "Unknown
command"
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2441)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1396)
        at com.mysql.jdbc.Connection.ping(Connection.java:3207)
        at com.mysql.jdbc.Connection.createNewIO(Connection.java:1799)
        at com.mysql.jdbc.Connection.execSQL(Connection.java:2248)
        at com.mysql.jdbc.Connection.execSQL(Connection.java:2199)
        at com.mysql.jdbc.Statement.executeQuery(Statement.java:1182)
        at TestQuery.do_select(TestQuery.java:16)
        at TestQuery.send_queries(TestQuery.java:82)
        at TestQuery.<init>(TestQuery.java:60)
        at TestQuery.main(TestQuery.java:32)


** END NESTED EXCEPTION **


Attempted reconnect 3 times. Giving up.

*/

public class TestQuery {
	Connection con;
	Statement stmt;
	// replace these next 3 statements with your username, passwd
	// and your server address
	static String username = "USERNAME";
	static String passwd = "PASSWRORD";
        static String url="jdbc:mysql://your.server.addr.here:3306/?autoReconnect=true&useCompression=";


    private void do_select(String query) throws Exception
    {
	    try {
            stmt = con.createStatement();
	    System.out.println("statement = " + query);
            ResultSet result = stmt.executeQuery(query);
	    System.out.println("=======  Result query = " + query + " ===== ");
            while (result.next()) {
                String name = result.getString(1) + " " + result.getString(2);
                System.out.println(name);
            }
            stmt.close();
	    System.out.println("======End of query =======");
	    } catch (Exception e) {
		    	throw e;
	    }

    }

    public static void main(String args[]) {

	    TestQuery tq = new TestQuery(args);

	}
    public TestQuery (String args[]) {

        String query;
	String newurl;

        try {
            Class.forName("com.mysql.jdbc.Driver");
        }
        catch (java.lang.ClassNotFoundException e) {
            System.err.print("ClassNotFoundException: ");
            System.err.println(e.getMessage());
        }

        try {
	    if (args.length == 1 && args[0].equals("true"))
	    {
		    newurl = url + "true";
	    } else {
		    newurl = url + "false";
	    }
	    System.out.println("URL = " + newurl);
            System.out.print("Trying to connect ... ");
            con = DriverManager.getConnection (newurl, username, passwd);
            System.out.println("connected!");

            send_queries();

            con.close();
        }
        catch(SQLException ex) {
            System.err.print("SQLException: ");
            System.err.println(ex.getMessage());
        }
     }

     private void send_queries()
     {
	String queries[] = new String[2];

	queries[0] = new String("SELECT * FROM test_sql_compress.absent");
	queries[1] = new String("SELECT * FROM test_sql_compress.present");

	for (int i = 0; i < queries.length; i++)
	{
		try {

		if (queries[i] != null)
		    do_select(queries[i]);
		} catch (SQLException ex) {
		    System.err.print("SQLException: ");
		    System.err.println(ex.getMessage());
		} catch (Exception e) {
		    System.err.println(e.getMessage());
		}
	}
    }
}