MySQL异常备忘录

1. 超过最大连接数

1.1 异常信息 ERROR 1040: Too many connections

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"
        at sun.reflect.GeneratedConstructorAccessor131.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
        at com.mysql.jdbc.Util.getInstance(Util.java:386)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1114)
        at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2502)
        at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2535)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2320)
        at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:834)
        at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:46)
        at sun.reflect.GeneratedConstructorAccessor73.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:347)
        at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
        at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
        at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
        at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
        at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
        at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
        at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
        at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"
        at sun.reflect.GeneratedConstructorAccessor131.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
        at com.mysql.jdbc.Util.getInstance(Util.java:386)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1114)
        at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2502)
        at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2535)
        at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2320)
        at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:834)
        at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:46)
        at sun.reflect.GeneratedConstructorAccessor73.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
2014-11-03 17:37:31,524 WARN [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] - 
2014-11-03 17:37:31,527 ERROR [org.hibernate.engine.jdbc.spi.SqlExceptionHelper] - 

 1.2 修改配置 my.cnf

max_connections=1000