mysql拒绝连接，提示连接数太多了Too many connections

　　日志里打印：

10:39:48.962 [Druid-ConnectionPool-Create-1315749361] [] [] ERROR c.alibaba.druid.pool.DruidDataSource - create connection error
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.Util.getInstance(Util.java:384)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:973)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1112)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2506)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2539)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2321)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:832)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    at sun.reflect.GeneratedConstructorAccessor31.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:417)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:344)
    at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1368)
    at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1424)
    at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:1680)

　　看mysql数据库实际的连接数：

mysql> show variables like '%max_connections%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 700  |
+-----------------+-------+
1 row in set (0.01 sec)

　　想看具体都有哪些连接，执行：

mysql> show full processlist;

　　改连接数，重启失效：

mysql> set  GLOBAL max_connections=1000;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%max_connections%';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 1000  |
+-----------------+-------+
1 row in set (0.01 sec)

　　真要永久修改，得去my.cnf配置文件里改max_connections属性。