c3p0 连接过多导致tomcat无法启动的解决方法
错误：
WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@27e467f7 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks! 2015-04-30 10:29:43 WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@27e467f7 -- APPARENT DEADLOCK!!! Complete Status: Managed Threads: 3 Active Threads: 3 Active Tasks: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@6bd962a4 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@cdb344d (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@b46b1d3 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1) Pending Tasks: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4e44996d com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@79b4eb3f com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@54c0b385 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@374a0c3b com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@5e6911d8 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@4412ac54 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@25efe1b6 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@27cb872f com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@23183312 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@9c0f4be com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@5b03eaf2 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@5e35e48c com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@242fd3a6 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@3ff049d9 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@3880665a com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@75bfbbb0 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7ebb5c34 Pool thread stack traces: Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main] java.net.PlainSocketImpl.socketConnect(Native Method) java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) java.net.Socket.connect(Socket.java:579) java.net.Socket.connect(Socket.java:528) java.net.Socket.<init>(Socket.java:425) java.net.Socket.<init>(Socket.java:241) com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256) com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:293) com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181) com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:787) com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:49) sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) java.lang.reflect.Constructor.newInstance(Constructor.java:526) com.mysql.jdbc.Util.handleNewInstance(Util.java:409) com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:357) com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171) com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137) com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014) com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main] java.net.PlainSocketImpl.socketConnect(Native Method) java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) java.net.Socket.connect(Socket.java:579) java.net.Socket.connect(Socket.java:528) java.net.Socket.<init>(Socket.java:425) java.net.Socket.<init>(Socket.java:241) com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256) com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:293) com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181) com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:787) com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:49) sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) java.lang.reflect.Constructor.newInstance(Constructor.java:526) com.mysql.jdbc.Util.handleNewInstance(Util.java:409) com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:357) com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171) com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137) com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014) com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547) Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main] java.net.PlainSocketImpl.socketConnect(Native Method) java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) java.net.Socket.connect(Socket.java:579) java.net.Socket.connect(Socket.java:528) java.net.Socket.<init>(Socket.java:425) java.net.Socket.<init>(Socket.java:241) com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256) com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:293) com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181) com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:787) com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:49) sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) java.lang.reflect.Constructor.newInstance(Constructor.java:526) com.mysql.jdbc.Util.handleNewInstance(Util.java:409) com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:357) com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285) com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182) com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171) com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137) com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014) com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810) com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
解决方法：
先关闭mysql数据库，然后在打开数据库，只限于测试环境，如果是正式环境请设置连接池的最大数量小于mysql的最大连接数量，而且不用mysql工具连接服务器，或者连接后及时关闭，减少连接数。