用Java连接Mysql数据库

Question

--CODE UPDATED--

I'm trying to connect a MySQL database using JDBC but I'm not able to get the connection to work. I'm not sure if the way I've constructed the connection string is right. Here's the code and the error:

Code:

    Connection conn;
    String userName = "root";
    String serverName = "127.0.0.1";
    String portNumber = "3306";
    String password = "password";
    String dbName = "myDB";

    /**
     * Establishes connection with the sql database
     * @throws SQLException
     */
    public SQLConnector() throws SQLException {
        setConnection();
    }

    private void setConnection() throws SQLException {
        Properties connectionProps = new Properties();
        connectionProps.put("user", this.userName);
        connectionProps.put("password", this.password);
        String connectionString = "jdbc:mysql://" + this.serverName
                + ":" + this.portNumber + "/" + this.dbName;
        System.out.println(connectionString);
        this.conn = DriverManager.getConnection(connectionString, connectionProps);
    }

Error:

    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(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:377)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1036)
    at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:627)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1013)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2234)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2265)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2064)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:790)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
    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:377)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:395)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:325)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at com.source.database.SQLConnector.setConnection(SQLConnector.java:69)
    at com.source.database.SQLConnector.<init>(SQLConnector.java:25)
    at com.source.main.Start.main(Start.java:13)
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
    at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2914)
    at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:559)
    ... 18 more

Answer 1

I did tried connecting mysql with java sometime back. Here is how i did it.

private Connection getConnection() throws SQLException 
    {
        Connection conn = null;
        Properties connectionProps = new Properties();
        connectionProps.put("user", this.userName);
        connectionProps.put("password", this.password);

        conn = DriverManager.getConnection("jdbc:mysql://"
                + this.serverName + ":" + this.portNumber + "/" + this.dbName,
                connectionProps);

        return conn;
    }

public boolean executeUpdate(Connection connection, String command) throws SQLException
    {
        try
        {
          Statement st = connection.createStatement();

          st.executeUpdate(command);

          connection.close();
        }
        catch (Exception e)
        {
          System.err.println("Got an exception!");
          e.printStackTrace();
        }

        return false;
    }

executeUpdate was used to update, insert and delete from the tables. Hope that helped..

Oh, and also JDBC driver must be in the program path.