CommunicationsException: Communications link failure； 项目启动遇到数据库报错

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1、 问题

今天启动项目突然报此错误

2、 原因之一

MySQL服务没有启动

3、 解决办法

启动MySQL服务，本地的启动方法（查看方法），打开任务管理器（ctrl+shift+esc)，选择顶部的服务列，查看MySQL服务启动了吗（可以输入M快速定位到服务名附近（这个M表示服务名首字母））。
如果没有启动，就右键启动。

4、 报错信息

2022-05-02 07:30:07,374 ERROR com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread 2840 run - create connection SQLException, url: jdbc:mysql://localhost:3308/tmalldemodb?characterEncoding=utf-8&useSSL=false&allowPublicKeyRetrieval=true, errorCode 0, state 08S01 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-8.0.27.jar:8.0.27]
	at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:828) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:448) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:241) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1657) ~[druid-1.2.8.jar:1.2.8]
	at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1723) ~[druid-1.2.8.jar:1.2.8]
	at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2838) [druid-1.2.8.jar:1.2.8]
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) ~[?:1.8.0_41]
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:1.8.0_41]
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_41]
	at java.lang.reflect.Constructor.newInstance(Constructor.java:422) ~[?:1.8.0_41]
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:89) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.NativeSession.connect(NativeSession.java:120) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:948) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:818) ~[mysql-connector-java-8.0.27.jar:8.0.27]
	... 6 more
Caused by: java.net.ConnectException: Connection refused: connect
	at java.net.DualStackPlainSocketImpl.connect0(Native Method) ~[?:1.8.0_41]
	at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79) ~[?:1.8.0_41]

本文标签： 报错数据库项目CommunicationsCommunicationsException