解决 ‘The last packet successfully received from the server was xxx milliseconds ago‘ 问题

springboot + druid + mysql 在查询某些比较耗时的sql会报错

com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

The last packet successfully received from the server was 10,010 milliseconds ago. The last packet sent successfully to the server was 10,010 milliseconds ago.
	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.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953)
	at com.mysql.cj.jdbc.ClientPreparedStatement.execute(ClientPreparedStatement.java:371)
	at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3446)
	at com.alibaba.druid.filter.FilterEventAdapter.preparedStatement_execute(FilterEventAdapter.java:434)
	at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3444)
	at com.alibaba.druid.filter.FilterEventAdapter.preparedStatement_execute(FilterEventAdapter.java:434)
	at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3444)
	at com.alibaba.druid.proxy.jdbc.PreparedStatementProxyImpl.execute(PreparedStatementProxyImpl.java:152)
	at com.alibaba.druid.pool.DruidPooledPreparedStatement.execute(DruidPooledPreparedStatement.java:483)
	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.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:59)
	at com.sun.proxy.$Proxy160.execute(Unknown Source)
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64)
	... ...
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查阅了一下，网上一般的做法有以下几种：

1. 修改mysql的wait_timeout，修改spring数据源配置，增加maxWait（要比数据库wait_timeout小）、testOnBorrow=true、queryTimeout等配置，在datasource.url后面增加autoReconnect=true配置。

2. 更新mysql-connector版本，我用的是8.0.28

3. 更新jdk版本，如jdk1.7升级到jdk1.8

尝试过上面的几个方法都没办法解决。

从报错信息来看，这里设置的超时是10000毫秒，然后把mysql-connector源码下载下来debug了一下，发现有socketTimeout参数的值正好是10000，然后尝试在spring数据源配置上增加次配置依旧不行。

最后在datasource.url后面socketTimeout参数配置，重启测试发现能被正确识别，到此问题解决。

下面是druid和datasource的配置，仅供参考

druid:
  initial-size: 5
  min-idle: 2
  maxActive: 10
  maxWait: 60000
  timeBetweenEvictionRunsMillis: 60000
  minEvictableIdleTimeMillis: 300000
  validationQuery: SELECT 1 FROM DUAL
  testWhileIdle: true
  testOnBorrow: false
  testOnReturn: false
  poolPreparedStatements: true
  maxPoolPreparedStatementPerConnectionSize: 20
  filters: stat,slf4j
  connectionProperties: druid.stat.mergeSql\=true;druid.stat.slowSqlMillis\=5000
  
datasource:
  driver-class-name: com.mysql.cj.jdbc.Driver
  url: jdbc:mysql://localhost:3306/test?useUnicode=true&useSSL=false&allowLoadLocalInfile=false&autoReconnect=true&failOverReadOnly=false&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&serverTimezone=GMT%2B8&connectTimeout=1000&socketTimeout=30000
  username: root
  password: 123456
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