com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:通信链路故障
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:通信链路故障
提问于 2010-06-06 13:49:11
我正在努力让我的数据库与我的Java程序对话。
有没有人能给我一个使用JDBC的又快又脏的示例程序？
我收到了一个相当惊人的错误：
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测试文件的内容：
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?");
}
}回答 31
Stack Overflow用户
发布于 2014-03-12 18:32:07
在我的示例中，我需要将Localhost替换为实际的数据库服务器IP地址
而不是
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/DBname", "root", "root");我需要
Connection con = DriverManager.getConnection(
"jdbc:mysql://192.100.0.000:3306/DBname", "root", "root");Stack Overflow用户
发布于 2015-02-26 17:22:51
如果数据库连接长时间处于空闲状态，则会发生此com.mysql.jdbc.exceptions.jdbc4.CommunicationsException异常。
这个空闲连接在connection.isClosed();上返回true，但是如果我们尝试执行语句，那么它将触发这个异常，所以我建议使用数据库池。
Stack Overflow用户
发布于 2015-07-02 10:54:09
在我的例子中，结果是mysql-connector-java的版本太旧了。
在我的演示中，我以某种方式使用mysql-connector-java如下：
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.9</version>
</dependency>但在开发环境中，我使用的是：
<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，它很旧，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，解决方案也就找到了。匹配版本！
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/2983248
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