Java JDBC web MySql communication

Question

I am new in java with database and even java. I know how to code in java. I am trying to connect with the web database. I am successful at localhost and everything is fine.

But in the time of my web server i am having problem.

String url = "jdbc:mysql://localhost:3306/cdcol";
    String user = "root";
    String pass = "";

    try {
        con = (Connection) DriverManager.getConnection(url, user, pass);
        st = (Statement) con.createStatement();
        rs = st.executeQuery("SELECT*from cds");
        if(rs.next()) {
            System.out.println(rs.getString(1)+" "+rs.getString(2));
        }
    }

I just changed the 'localhost' keyword into my web database location. Now it shows some error.

Mar 22, 2014 3:53:26 PM showcolors.databaseTest main
SEVERE: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has      
not received any packets from the server.
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has    
not received any packets from the server.




at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1117)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:355)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2461)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2498)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2283)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:822)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:404)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:317)
    at java.sql.DriverManager.getConnection(DriverManager.java:571)
    at java.sql.DriverManager.getConnection(DriverManager.java:215)
    at showcolors.databaseTest.main(databaseTest.java:45)
    at showcolors.ShowColors.actionPerformed(ShowColors.java:70)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:694)
    at java.awt.EventQueue$3.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:708)
    at java.awt.EventQueue$4.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:579)
    at java.net.Socket.connect(Socket.java:528)
    at java.net.Socket.<init>(Socket.java:425)
    at java.net.Socket.<init>(Socket.java:241)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:259)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:305)
    ... 52 more

I look for the solution but i was failed. Please help me with the solution.

refer http://stackoverflow.com/questions/6865538/solving-a-communications-link-failure-with-jdbc-and-mysql?rq=1 — swapnil7, Mar 22 '14 at 11:13

score 1 · Answer 1 · answered Mar 22 '14 at 11:03

You are connecting to remote server as root , when you install mysql ,in the installation process it asks for

allow remote access as root?

at that time if you selected no , this may cause exceptions.

To check whether above possibility causes exception,please follow following steps

1) Make new user on the web server,set password ,set select privileges true for new user. 2) Try to connect and retrieve data with new user.

If new user is able to access the data , then it will be clear that your root remote access is false.

score 1 · Answer 2 · answered Mar 22 '14 at 11:28

You have to use the following statements for the sql connectionn in java-----

String url = "jdbc:mysql://localhost:3306/cdcol";
String user = "root";
String pass = "";

Class.forName("com.mysql.jdbc.Driver");//for adding sql class

Connection con = DriverManager.getConnection(url,user,pass);

Statement st = con.createStatement();

Then Execute the query & get the data:----

ResultSet rs = st.executeQuery("SELECT * from cds");

if(rs.next())
 {
        System.out.println(rs.getString(1)+" "+rs.getString(2));
 }

I Hope it will help you....

My code works on my pc. But i want to get data from the web server. Each time it triggers error report like the above. — Bipul Chandra Dev Nath, Mar 23 '14 at 04:11

score 0 · Answer 3 · answered Mar 22 '14 at 10:45

0

I think you are not loading driver class as eg.

Class.forName("com.mysql.jdbc.Driver");

answered Mar 22 '14 at 10:45

Shekhar Khairnar

2,643
3
26
44

score 0 · Answer 4 · answered Mar 23 '14 at 12:49

0

You should use the DriverManager.registerDriver or class.forName for load the thin driver from the correspondent API. Once you would be completed with the drivers you can retrieve the data from the remote server too.

answered Mar 23 '14 at 12:49

Ajay Sharma

46
2

Java JDBC web MySql communication

4 Answers4