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)
... ...
查阅了一下，网上一般的做法有以下几种：
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。更新
mysql-connector版本，我用的是8.0.28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/xxx?useUnicode=true&useSSL=false&allowLoadLocalInfile=false&autoReconnect=true&failOverReadOnly=false&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&serverTimezone=GMT%2B8&connectTimeout=1000&socketTimeout=30000
username:
password:
