项目进行压力测试的时候，运行大概1小时候，后台抛出以下异常：
Nov 9, 2012 1:41:59 AM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector runWARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@4b9cafa7 -- APPARENT DEADLOCK!!! Complete Status: Managed Threads: 3 Active Threads: 3 Active Tasks: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@19f67d43 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@599c706 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1) com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@32d95dc9 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0) Pending Tasks: com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@5c9c5133 com.mchange.v2.resourcepool.BasicResourcePool$1DestroyResourceTask@1a971ac5 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@365e8926 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@787e39acPool thread stack traces: Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main] java.lang.StringCoding.set(StringCoding.java:53) java.lang.StringCoding.encode(StringCoding.java:270) java.lang.String.getBytes(String.java:946) com.mysql.jdbc.ConnectionImpl.configureCharsetProperties(ConnectionImpl.java:1578) com.mysql.jdbc.ConnectionImpl.configureClientCharacterSet(ConnectionImpl.java:1628) com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3425) com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2045) com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:718) com.mysql.jdbc.JDBC4Connection. (JDBC4Connection.java:46) sun.reflect.GeneratedConstructorAccessor35.newInstance(Unknown Source) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) java.lang.reflect.Constructor.newInstance(Constructor.java:513) com.mysql.jdbc.Util.handleNewInstance(Util.java:406) com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302) com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282) 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] com.mysql.jdbc.ResultSetImpl.getInstance(ResultSetImpl.java:344) com.mysql.jdbc.MysqlIO.buildResultSetWithUpdates(MysqlIO.java:2607) com.mysql.jdbc.MysqlIO.readResultsForQueryOrUpdate(MysqlIO.java:2490) com.mysql.jdbc.MysqlIO.readAllResults(MysqlIO.java:1746) com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2135) com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536) com.mysql.jdbc.ConnectionImpl.setupServerForTruncationChecks(ConnectionImpl.java:5240) com.mysql.jdbc.ConnectionImpl.initializePropsFromServer(ConnectionImpl.java:3508) com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2045) com.mysql.jdbc.ConnectionImpl. (ConnectionImpl.java:718) com.mysql.jdbc.JDBC4Connection. (JDBC4Connection.java:46) sun.reflect.GeneratedConstructorAccessor35.newInstance(Unknown Source) sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) java.lang.reflect.Constructor.newInstance(Constructor.java:513) com.mysql.jdbc.Util.handleNewInstance(Util.java:406) com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302) com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282) 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] com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:562)
目测该问题是c3p0连接池导致的线程死锁。
这种数据库连接池线程死锁的问题发生的原因可能有很多，我将我的配置环境以及解决方法贴出来供大家参考一下：
使用环境，spring + hibernate +c3p0
配置如下：
这个配置中有一些属性可能和死锁有关：maxStatements 和checkoutTimeout(我没有使用该属性)
有人说c3p0本身没有问题，导致问题是spring的原因，c3p0作为hibernate官方推荐的连接池，在性能和稳定性上都是中规中矩的。根据以前的使用经验，我判断也不是c3p0的问题。
我的修改如下：
修改后，问题没有重现。