最简单的办法是因为你的my.ini中设定的并发连接数太少或者系统繁忙导致连接数被占满解决方式：打开MYSQL安装目录打开MY.INI找到max_connections默认是100 .--实例
WINDOWS解决MYSQL Errno.: 1040错误XXXX info: Can not connect to MySQL server
User: rootTime: 2004-5-20 3:00pmScript: /XXXX/XXXX.php
Error: Too many connectionsErrno.: 1040
An error report has been dispatched to our administrator.
上面错误观点提示
1.可能是mysql的max connections设置的问题2.可能是多次insert,update操作没有关闭session,需要在spring里配置transaction支持。
解决:1.修改tomcat里的session 的time-out时间减少为20,(不是必改项)2.对处理量大的对数据库insert或update的操作提供transaction支持.
=======================================下面的是解决办法：
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection, message from server: "Too many connections"
原因：
因为你的mysql安装目录下的my.ini中设定的并发连接数太少或者系统繁忙导致连接数被占满
解决方式：
打开MYSQL安装目录打开MY.INI找到max_connections（在大约第93行）默认是100 一般设置到500～1000比较合适，重启mysql,这样1040错误就解决啦。max_connections=1000
一定要重新启动MYSQL才能生效
代码如下 复制代码 CMD->
net stop mysql
net start mysql
关于改变innodb_log_file_size后无法启动mysql的问题
innodb_buffer_pool_size=768Minnodb_log_file_size=256Minnodb_log_buffer_size=8Minnodb_additional_mem_pool_size=4Minnodb_flush_log_at_trx_commit=0innodb_thread_concurrency=20
以上是对innodb引擎的初步优化, 发现是更新innodb_log_file_size=256M时候出现了问题，只要加上这个就无法启动,
后来才知道原来要STOP服务先，然后再删除原来的文件………打开/MySQL Server 5.5/data
删除ib_logfile0, ib_logfile1........ib_logfilen再开启选项，成功启动。
高手优化的MYSQL my.ini的1000人在线配置。
#This File was made using the WinMySQLAdmin 1.4 Tool #2004-2-23 16:28:14 #Uncomment or Add only the keys that you know how works. #Read the MySQL Manual for instructions [mysqld] basedir=D:/mysql #bind-address=210.5.*.* datadir=D:/mysql/data #language=D:/mysql/share/your language directory #slow query log#= #tmpdir#= #port=3306 set-variable = max_connections=1500 skip-locking #skip-networking set-variable = key_buffer=384M set-variable = max_allowed_packet=1M set-variable = table_cache=512 set-variable = sort_buffer=2M set-variable = record_buffer=2M set-variable = thread_cache=8 # Try number of CPU's*2 for thread_concurrency set-variable = thread_concurrency=8 set-variable = myisam_sort_buffer_size=64M #set-variable = connect_timeout=5 #set-variable = wait_timeout=5 server-id = 1 [isamchk] set-variable = key_buffer=128M set-variable = sort_buffer=128M set-variable = read_buffer=2M set-variable = write_buffer=2M [myisamchk] set-variable = key_buffer=128M set-variable = sort_buffer=128M set-variable = read_buffer=2M set-variable = write_buffer=2M [WinMySQLadmin] Server=D:/mysql/bin/mysqld-nt.exe
