Communications link failure ？为啥这个错误

Communications link failure ？为啥这个错误

"C:\Program Files\Java\jdk1.8.0_251\bin\java.exe" -ea -Didea.test.cyclic.buffer.size=1048576 -javaagent:D:\IntelliJ-IDEA-2022.1.1\lib\idea_rt.jar=61427:D:\IntelliJ-IDEA-2022.1.1\bin -Dfile.encoding=UTF-8 -classpath "D:\IntelliJ-IDEA-2022.1.1\lib\idea_rt.jar;D:\IntelliJ-IDEA-2022.1.1\plugins\junit\lib\junit5-rt.jar;D:\IntelliJ-IDEA-2022.1.1\plugins\junit\lib\junit-rt.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_251\jre\lib\rt.jar;D:\java_code\redisIm\target\test-classes;D:\java_code\redisIm\target\classes;C:\Users\DELL\.m2\repository\redis\clients\jedis\4.4.0\jedis-4.4.0.jar;C:\Users\DELL\.m2\repository\org\slf4j\slf4j-api\1.7.36\slf4j-api-1.7.36.jar;C:\Users\DELL\.m2\repository\org\apache\commons\commons-pool2\2.11.1\commons-pool2-2.11.1.jar;C:\Users\DELL\.m2\repository\org\json\json\20230227\json-20230227.jar;C:\Users\DELL\.m2\repository\com\google\code\gson\gson\2.10.1\gson-2.10.1.jar;C:\Users\DELL\.m2\repository\com\alibaba\fastjson\1.2.54\fastjson-1.2.54.jar;C:\Users\DELL\.m2\repository\org\mybatis\mybatis\3.5.1\mybatis-3.5.1.jar;C:\Users\DELL\.m2\repository\mysql\mysql-connector-java\8.0.29\mysql-connector-java-8.0.29.jar;C:\Users\DELL\.m2\repository\com\google\protobuf\protobuf-java\3.19.4\protobuf-java-3.19.4.jar;C:\Users\DELL\.m2\repository\junit\junit\4.12\junit-4.12.jar;C:\Users\DELL\.m2\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar" com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit4 Mybatis.MybatisTestor,testSqlsessionFactory
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
ok
org.apache.ibatis.exceptions.PersistenceException: 
### Error getting a new connection.  Cause: com.mysql.cj.jdbc.exceptions.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.
### Cause: com.mysql.cj.jdbc.exceptions.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 org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.getConnection(DefaultSqlSession.java:299)
	at Mybatis.MybatisTestor.testSqlsessionFactory(MybatisTestor.java:24)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: com.mysql.cj.jdbc.exceptions.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 com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:828)
	at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:448)
	at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:241)
	at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198)
	at java.sql.DriverManager.getConnection(DriverManager.java:664)
	at java.sql.DriverManager.getConnection(DriverManager.java:208)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:201)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:196)
	at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:93)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:403)
	at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:89)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:138)
	at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:60)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.getConnection(DefaultSqlSession.java:297)
	... 25 more
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: 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:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
	at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
	at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:89)
	at com.mysql.cj.NativeSession.connect(NativeSession.java:120)
	at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:948)
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:818)
	... 38 more
Caused by: java.net.ConnectException: Connection refused: connect
	at java.net.DualStackPlainSocketImpl.connect0(Native Method)
	at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
	at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	at java.net.Socket.connect(Socket.java:606)
	at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:153)
	at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:63)
	... 41 more

Process finished with exit code 0



<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>redisIm</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
<!--    <repositories>-->
<!--        <repository>-->
<!--            <id>aliyun</id>-->
<!--            <name>aliyun</name>-->
<!--            <url>https://maven.aliyun.com/repository/pubilc</url>-->
<!--        </repository>-->
<!--    </repositories>-->
    <dependencies>
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>4.4.0</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.54</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.29</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>



package Mybatis;


import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.Reader;
import java.sql.Connection;
import java.util.*;

public class MybatisTestor {
    @Test
    public void testSqlsessionFactory() throws IOException {
        Reader reader=Resources.getResourceAsReader("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(reader);
        System.out.println("ok");
        SqlSession session=null;
        try {
            session=sqlSessionFactory.openSession();
            Connection connection=session.getConnection();
            System.out.println(connection);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (session != null){
                session.close();
            }
        }

    }
}



<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="dev">
        <environment id="dev">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/babytun?useUnicode=true&amp;characterEncodeing=UTF-8&amp;useSSL=false&amp;serverTimezone=GMT"/>
                <property name="username" value="root"/>
                <property name="password" value="qwQW123456789@"/>
            </dataSource>
        </environment>
    </environments>
</configuration>
热爱编程学习 2023-06-11
源自：MyBatis入门   3-3 SqlSessionFactory
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好帮手慕小蓝 2023-06-12 10:11:15

同学你好，从报错信息“Communications link failure”和“Connection refused: connect”推测，是因为MySql的服务没有开启导致的。

建议同学在本地操作系统的服务中，找到MySql的服务，将其手动开启之后再尝试一下。

祝学习愉快~


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