com.mysql.jdbc.exceptions.jdbc4。CommunicationsException:通信链路故障

我正在努力让我的数据库与我的Java程序对话。

有人能给我一个使用JDBC的快速而简单的示例程序吗?

我得到了一个相当大的错误

Exception in thread "main" 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:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2260)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:787)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:49)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:357)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
    at java.sql.DriverManager.getConnection(DriverManager.java:582)
    at java.sql.DriverManager.getConnection(DriverManager.java:207)
    at SqlTest.main(SqlTest.java:22)
Caused by: 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:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181)
    ... 12 more
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:432)
    at java.net.Socket.connect(Socket.java:529)
    at java.net.Socket.connect(Socket.java:478)
    at java.net.Socket.<init>(Socket.java:375)
    at java.net.Socket.<init>(Socket.java:218)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:293)
    ... 13 more

测试文件内容:

import com.mysql.jdbc.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class SqlTest {

    public static void main(String [] args) throws Exception {
        // Class.forName( "com.mysql.jdbc.Driver" ); // do this in init
        // // edit the jdbc url 
        Connection conn = DriverManager.getConnection( 
            "jdbc:mysql://localhost:3306/projects?user=user1&password=123");
        // Statement st = conn.createStatement();
        // ResultSet rs = st.executeQuery( "select * from table" );

        System.out.println("Connected?");
    }
}

当前回答

如果您更改了端口，则会得到这种错误"com.mysql.jdbc.exceptions.jdbc4 "。CommunicationsException:通信链路故障请检查你的端口号

2014-11-13 10:05:05

其他回答

我解决了两件事: 1. 使用以下connads创建非root的新用户:

CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON *.* TO 'newuser'@'localhost';
FLUSH PRIVILEGES;

2. 注释mysqld.conf中的IP地址行

然后用新的用户名和密码连接。它应该会起作用。

2017-08-16 08:06:43

打开文件/etc/mysql/my.cnf: 更改以下参数为

' bind-address = 127.0.0.1

Bind-address = 0.0.0.0 #允许所有系统连接

在mysql中针对特定的IP地址执行以下命令->

grant all privileges on dbname.* to dbusername@'192.168.0.3' IDENTIFIED BY 'dbpassword';

如果你想访问所有的IP地址，运行下面的命令:

grant all privileges on dbname.* to dbusername@'%' IDENTIFIED BY 'dbpassword';

2018-11-17 06:18:36

请更新/etc/mysql/my.cnf文件中的IP地址

bind-address  = 0.0.0.0

重新启动mysql daemon和mysql服务。

2014-04-12 19:07:58

添加这个 useSSL = false&allowPublicKeyRetrieval = true

jdbc: mysql: / / localhost: 3306 / cloudapp吗?useSSL = false&allowPublicKeyRetrieval = true

https://youtu.be/ray3YvnIohM

2022-03-12 07:27:22

在我的情况下，原来是mysql-connector-java的版本太旧了。

在我的演示中，我像这样使用mysql-connector-java:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.9</version>
</dependency>

但是在开发环境中，我使用这个:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.31</version>
</dependency>

我的MySQL版本是5.1.48(是的，它是旧的，只是为了模仿产品版本)。所以我遇到了同样的错误。

既然找到了原因，解决办法也就找到了。匹配版本!

2015-07-02 02:54:08

com.mysql.jdbc.exceptions.jdbc4。CommunicationsException:通信链路故障

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