JDBC connection problem

[Arvind Purohit]

Arvind Purohit wrote:Hi All
I am trying to connect a data base. below i have given the code. I am able to connect to data base but unable to connect 2nd time if difference between 1st time and 2nd time is greater then "wait time out" of mysql data base.
I am using mysql data base. I am getting "Communications link failure" problem
wait_timeout is 10 sec (for convenience) it is 8 hour for my DB
I am giving you code

public class DatabaseManager {
	private static Connection jConn;
	private static DatabaseManager manager;

public Boolean getUser(){
		Statement jStmt = null;
		ResultSet rs = null;
		try {

			String query = "SELECT * FROM  USER  ";
			 System.out.println(query);
			jStmt = jConn.createStatement();
			rs = jStmt.executeQuery(query);
			while (rs.next()) {
			
			}
		}catch (Exception e) {
			e.printStackTrace();
			return false;
		}
		return true;
	}

    public static synchronized DatabaseManager getInstance() {
		if (manager == null) {
			try {
				manager = initialize();
			} catch (DatabaseInitializationException e) {
				// e.printStackTrace();
				// throw new RuntimeException("Database Initialization
				// Exception");
			}
		}
		return manager;
	}
        private static DatabaseManager initialize()
			throws DatabaseInitializationException {

		try {
			Class.forName(serverSrv.readPropertyValue("Srver_Path",
					"DBdriver"));
		} catch (ClassNotFoundException e) {
			throw new DatabaseInitializationException(e.getMessage());
		}
		try {
			jConn = DriverManager.getConnection("DB_URL","user","password");
			System.out.println("Excecuted initialize() for Database ");
		} catch (SQLException e) {
			throw new DatabaseInitializationException(e.getMessage());
		}
		return new DatabaseManager();
	}
}

AND I am testing like

	
	

	public static void main(String[] args) {
		long st = System.currentTimeMillis();
		long end ;
		DatabaseManager dm = DatabaseManager.getInstance();
		
		if( dm.getUser() )
			System.out.println("success");
		else
			System.out.println("failed..");
		
		do{
			end = System.currentTimeMillis();
		}while( (end-st)<12*1000 );
		
		if( dm.getUser() )
			System.out.println("success");
		else
			System.out.println("failed..");
	}

and it is giving exception like

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Last packet sent to the server was 0 ms ago.
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2873)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2763)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3299)
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1837)
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1961)
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2537)
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2466)
	at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1383)
	at mypackage.db.DatabaseManager.getUser(DatabaseManager.java:127)
	at mypackage.test.Test.main(Test.java:23)
Caused by: java.net.SocketException: Software caused connection abort: recv failed
	at java.net.SocketInputStream.socketRead0(Native Method)
	at java.net.SocketInputStream.read(Unknown Source)
	at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)
	at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
	at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)
	at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2329)
	at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2774)

[Tom Reilly]

I don't know if this is your problem but you are not closing your connection, statement or result set. I see you are also eating the DatabaseInitializationException in getInstance().

[Arvind Purohit]

Tom Reilly wrote:I don't know if this is your problem but you are not closing your connection, statement or result set. I see you are also eating the DatabaseInitializationException in getInstance().

Thanks for your reply...
I am not getting what do you want to say. how do i solve this problem

Thanks

[Tom Reilly]

You need to tell JDBC that you are done using its resources. Examples:

Statement.close()
ResultSet.close()
Connection.close()

Take a look at one of the JDBC tutorials out there. I haven't looked at one in years so cannot recommend a good one. Perhaps someone else can.