Connection to MYSQL Database Using JDBC

Question

I am trying to connect to a new database using JDBC for a project I am working on which will allow me to output a whole load of statistics on sports game. But I am running into some trouble whilst trying to connect to the database. I receive the following error below.

com.mysql.jdbc.CommunicationsException: Communications link failure due      to underlying exception: 

** BEGIN NESTED EXCEPTION ** 

java.net.ConnectException
MESSAGE: Connection refused

STACKTRACE:

java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at java.net.Socket.<init>(Socket.java:434)
at java.net.Socket.<init>(Socket.java:244)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at JDBC.main(JDBC.java:22)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)


** END NESTED EXCEPTION **



Last packet sent to the server was 0 ms ago.
    at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847)
    at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at JDBC.main(JDBC.java:22)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

This error is produced from my code which is as followed:

//STEP 1. Import required packages
import java.sql.*;

public class JDBC {
    // JDBC driver name and database URL
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost/";

    //  Database credentials
    static final String USER = "username";
    static final String PASS = "password";

    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try{
            //STEP 2: Register JDBC driver
            Class.forName("com.mysql.jdbc.Driver");

            //STEP 3: Open a connection
            System.out.println("Connecting to database...");
            conn = DriverManager.getConnection(DB_URL, USER, PASS);

            //STEP 4: Execute a query
            System.out.println("Creating database...");
            stmt = conn.createStatement();

            String sql = "CREATE DATABASE PREDICTOR";
            stmt.executeUpdate(sql);
            System.out.println("Database created successfully...");
        }catch(SQLException se){
            //Handle errors for JDBC
            se.printStackTrace();
        }catch(Exception e){
            //Handle errors for Class.forName
            e.printStackTrace();
        }finally{
            //finally block used to close resources
            try{
                if(stmt!=null)
                    stmt.close();
            }catch(SQLException se2){
            }// nothing we can do
            try{
                if(conn!=null)
                    conn.close();
            }catch(SQLException se){
                se.printStackTrace();
            }//end finally try
        }//end try
        System.out.println("Goodbye!");
    }//end main
}

I have disabled my firewall and looked on previous posts on stack overflow trying to amend my problem but alas connection is being refused. Any help appreciated.

Connection refused is pretty self explanatory. The server isn't running or it isn't listening on that host:port — e4c5, Dec 21 '16 at 00:37
Possible duplicate of [Connect Java to a MySQL database](http://stackoverflow.com/questions/2839321/connect-java-to-a-mysql-database) — , Dec 21 '16 at 00:42

score 0 · Answer 1 · edited Dec 21 '16 at 03:30

Connection refused

This means that the TCP communication to the server was actively rejected - this was done at the TCP layer, the connection never made it to your service - your code is irrelevant at this point.

This can be caused by a few different issues:

The SQL server is not actually running
There is a firewall in place blocking the connections
You are connecting to a different port than the server is listening to.

score 0 · Answer 2 · answered Dec 21 '16 at 00:53

0

I think your SQL server is not running . Please check the server status. or You should reinstall the server. It may solve your problem.

answered Dec 21 '16 at 00:53

nag

19
1

score 0 · Answer 3 · answered Dec 21 '16 at 14:49

Your DB_URL is incorrect. It should

DB_URL = "jdbc:mysql://localhost/databaseName";

or you can also use port number in your url if the database server is not using the default port

DB_URL = "jdbc:mysql://localhost:portNumber/databaseName";

For detail information please visit this site

Connection to MYSQL Database Using JDBC

3 Answers3