[报错解决]Communications link failure

报错

主机IDEA项目连接虚拟机的数据库报错。

主要报错信息有：

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.

.........

先排查基本问题。端口开启且没被占用、防火墙关闭了、数据库开启了，IDEA导出的Jar包在虚拟机中也没问题，所以只能是主机IDEA这边的项目代码或者是IDEA本身的问题。

整段报错信息有14万字。

只帖取部分具体报错信息。

具体报错：

2024-05-05 14:24:04.558 ERROR 4900 --- $main$ com.alibaba.druid.pool.DruidDataSource : init datasource error, url: jdbc:mysql://localhost:3306/student?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC

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) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:148) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.filter.FilterAdapter.connection_connect(FilterAdapter.java:785) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.filter.FilterEventAdapter.connection_connect(FilterEventAdapter.java:38) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:142) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.filter.FilterAdapter.connection_connect(FilterAdapter.java:785) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:142) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:211) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:142) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1454) ~ $druid-1.0.28.jar:1.0.28$

at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1516) ~ $druid-1.0.28.jar:1.0.28$

具体报错：

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

at jdk.internal.reflect.GeneratedConstructorAccessor42.newInstance(Unknown Source) ~ $na:na$

at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~ $na:na$

at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499) ~ $na:na$

at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480) ~ $na:na$

at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.NativeSession.connect(NativeSession.java:152) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:955) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

... 14 common frames omitted

Caused by: java.net.ConnectException: Connection refused: connect

at java.base/sun.nio.ch.Net.connect0(Native Method) ~ $na:na$

at java.base/sun.nio.ch.Net.connect(Net.java:579) ~ $na:na$

at java.base/sun.nio.ch.Net.connect(Net.java:568) ~ $na:na$

at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588) ~ $na:na$

at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:327) ~ $na:na$

at java.base/java.net.Socket.connect(Socket.java:633) ~ $na:na$

at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65) ~ $mysql-connector-java-8.0.16.jar:8.0.16$

... 17 common frames omitted

进程已结束,退出代码1

解决

1.找到项目的application-dev.yml配置文件，找到url

复制代码

url: jdbc:mysql://localhost:3306/student?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC

把其中的localhost修改为MySQL所在服务器的ip地址

修改完毕后如下图：

2.同样是application-dev.yml配置文件，找到username和password

复制代码

username: root
password:

把数据库密码填入password

修改完毕后如下图：