mysql报错Packet for query is too large (12238 > 1024). You can change this value

                1、先切换到：cd usr/local/tomcat5/logs

2、tail -f catalina.out

3、这样运行时就可以实时查看运行日志了

                rg.springframework.dao.TransientDataAccessResourceException:
### Error querying 
                database.  Cause: com.mysql.jdbc.PacketTooBigException: Packet for query is too large (1233>1024). You can change this value on the server by setting the max_allowed_packet‘ variable.
### The error may exist in cn/xm/exam/mapper/employee/out/custom/UnitCustomMapper.xml
### The error may involve cn.xm.exam.mapper.employee.out.custom.UnitCustomMapper.getHaulunitByCondition-Inline
### The error occurred while setting parameters
### SQL: SELECT   haulunit.unitId,   haulunit.unitBigId,   haulunit.bigId,   (select   group_concat(projectname) from project where projectid in (select projectId from   haulunitproject where bigId =haulunit.bigId and unitId=   haulunit.unitId)) as   projectNames,   haulunit.manager,   haulunit.managerPhone,   haulunit.secure,   haulunit.securePhone,   @b:=   (IFNULL((SELECT SUM(minusNum) FROM breakrules,   haulemployeeout WHERE   breakrules.BigEmployeeoutId =   haulemployeeout.BigEmployeeoutId    AND haulemployeeout.unitid =   haulunit.unitId           and breakTime LIKE CONCAT(Year(CurDate()),‘%‘)   ),0)) AS unitMinisMum,   haulinfo.bigName,   haulinfo.bigStatus,   haulinfo.bigCreateDate,   unit.name,   unit.address,   unit.contact,   unit.phone,   @a:= (SELECT   COUNT(BigEmployeeoutId)   FROM haulemployeeout   WHERE   haulemployeeout.bigId   = haulunit.bigId   AND haulemployeeout.unitId =   haulunit.unitId and trainstatus=‘2‘) AS   personNum,   TRUNCATE(IFNULL(@b/@a,0),3) AS jiaquan   FROM haulunit,   haulinfo,   unit    WHERE haulunit.bigId=haulinfo.bigId AND    haulunit.unitId=unit.unitId                      and haulunit.bigId = ?     ORDER BY jiaquan desc               limit ?,?
### Cause: com.mysql.jdbc.PacketTooBigException: Packet for query is too large (1233 > 1024). You can change this value on the server by setting the max_allowed_packet‘ variable.
; SQL []; Packet for query is too large (1233>1024). You can change this value on the server by setting the max_allowed_packet‘ variable.; nested exception is com.mysql.jdbc.PacketTooBigException: Packet for query is too large (1233 > 1024). You can change this value on the server by setting the max_allowed_packet‘ variable.
        at org.springframework.jdbc.support.SQLStateSQLExceptionTranslator.doTranslate(SQLStateSQLExceptionTranslator.java:107)
        at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72)
        at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80)
        at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80)

mysql max_allowed_packet 设置过小导致记录写入失败

mysql根据配置文件会限制server接受的数据包大小。

有时候大的插入和更新会受max_allowed_packet 参数限制，导致写入或者更新失败。

查看目前配置

显示的结果为：

以上说明目前的配置是：1M

修改方法

1、修改配置文件

可以编辑my.cnf来修改（windows下my.ini）,在[mysqld]段或者mysql的server配置段进行修改。

max_allowed_packet = 20M

如果找不到my.cnf可以通过

mysql --help | grep my.cnf

去寻找my.cnf文件。

linux下该文件在/etc/下。

2、在mysql命令行中修改

在mysql 命令行中运行

set global max_allowed_packet = 2*1024*1024*10

然后退出命令行，重启mysql服务，再进入。

show VARIABLES like ‘%max_allowed_packet%‘;

查看下max_allowed_packet是否编辑成功