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

刚刚经历过。

必须做到: (这可以放在静态块初始化器中)

static{ // would have to be surrounded by try catch
    Class.forName("com.mysql.jdbc.Driver");   // this will load the class Driver
}

也可以通过以下方式获得连接:

conn = DriverManager.getConnection(DBURL,<username>,<password>);

而不是指定登录参数

  Connection conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/projects?user=user1&password=123");

的问候。

2013-05-12 06:59:18

其他回答

就我而言，在连接字符串中添加查询参数解决了这个问题。 &useSSL = false

jdbc:mysql://${jdbc_url}:${jdbc_port}/${database_name}?serverTimezone=UTC&autoReconnect=true&useSSL=false&failOverReadOnly=false&maxReconnects=10

2022-07-28 12:55:49

我也遇到过同样的问题，我是这样解决的:

中的.jsp调用了尚未定义的属性 servlet。我有两个列名，我通过ResultSet (getString("columnName"))传递到一个对象，这与我的数据库中的列名不匹配。

我不太确定哪一个解决了这个问题，但它确实有效。另外，请确保为每个表查询创建了一个新的Statement和ResultSet。

2014-03-17 05:34:49

下载MySQL-JDBC-Type-4-Treiber (i.g。Mysql -connector-java-5.1.11-bin.jar从Mysql -connector-java-5.1.11.zip)

在编译和运行时期间，您需要在类路径中包含驱动程序jar。

Class.forName( "com.mysql.jdbc.Driver" ); // do this in init
// edit the jdbc url 
Connection conn = DriverManager.getConnection( "jdbc:mysql://MyDbComputerNameOrIP:3306/myDatabaseName", username, password );
Statement st = conn.createStatement();
ResultSet rs = st.executeQuery( "select * from table" );

2010-06-06 06:50:38

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

在我的例子中，我遇到了这个问题。当我试图通过IntelliJ Idea数据源连接到AWS RDS MySQL时，CommunicationsException:通信链路故障)。

这个视频帮助了我: https://www.youtube.com/watch?v=v3jH1YxJqaY

2022-11-08 08:59:51

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

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