【MySQL8.0】com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

启动springboot后遇到错误：

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:172) ~[mysql-connector-java-8.0.11.jar:8.0.11]
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.11.jar:8.0.11]
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:862) ~[mysql-connector-java-8.0.11.jar:8.0.11]
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:444) ~[mysql-connector-java-8.0.11.jar:8.0.11]

....(手动省略)

Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

 

然后查找相关资料，发现各大网站千篇一律的都是数据库连接失败，新增两个配置，配置如下：

#下面这两个配置，可以在每次连接的时候判断一些连接是否有效
spring.datasource.druid.test-on-borrow=true
spring.datasource.druid.test-while-idle=true

以上两个配置 

test-on-borrow=true 表示当应用向连接池申请连接时，连接池会判断这条连接是否是可用的

test-while-idle=true 表示申请连接的时候检测，如果空闲时间大于timeBetweenEvictionRunsMillis，执行validationQuery检测连接是否有效。

于是我将其加入application.properties重启项目，错误依旧存在。

考虑到我使用的数据库是MySQL8，于是仔细检查了我的驱动

application中的驱动 
　　spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
pom.xml中的配置 
　　<dependency>
　　　　<groupId>mysql</groupId>
　　　　<artifactId>mysql-connector-java</artifactId>
　　　　<version>8.0.11</version>
　　</dependency>

咋一看好像没什么问题，驱动类加了 cj，版本也是用的MySQL8.0的版本。

我又检查了一下MySQL的版本 8.0.19，和8.0.11差了一点点，于是我抱着尝试的心态把version改成了8.0.19。果然报错的内容起了变化：

Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value '�й���׼ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the 'serverTimezone' configuration property) to use a more specifc time zone value if you want to utilize time zone support.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_172]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_172]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_172]
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_172]
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:85) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    at com.mysql.cj.util.TimeUtil.getCanonicalTimezone(TimeUtil.java:132) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    at com.mysql.cj.protocol.a.NativeProtocol.configureTimezone(NativeProtocol.java:2118) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    at com.mysql.cj.protocol.a.NativeProtocol.initServerSession(NativeProtocol.java:2142) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    at com.mysql.cj.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:1310) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:967) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:826) ~[mysql-connector-java-8.0.19.jar:8.0.19]
    ... 76 common frames omitted

出现了乱码的情况，这个比较好处理，经查找是因为时差的原因，于是在配置文件的url后面添加&serverTimezone=Asia/Shanghai

完整url如下

spring.datasource.url = jdbc:mysql://localhost:3306/mydevotion?characterEncoding=utf8&useSSL=true&serverTimezone=Asia/Shanghai

至此，springboot正常启动，问题解决。

在pom.xml中配置的mysql的版本号，一定要跟所连接的MySQL的数据库完全一致。