Question

- 代码更新 -

我正在尝试使用JDBC连接MySQL数据库，但我无法使连接正常工作。我不确定我构建连接字符串的方式是否正确。这是代码和错误：

代码：

    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);
    }

错误：

    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

我确实尝试过将mysql与java连接起来。我是这样做的。

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用于更新，插入和删除表。希望有所帮助..

哦，JDBC驱动程序也必须在程序路径中。

使用Java连接Mysql数据库

1 个答案: