配置c3p0连接池，启动错误。
spring中c3p0配置xml代码：
项目启动时报以下错误信息：
Pool thread stack traces:
Thread[C3P0PooledConnectionPoolManager[identityToken->1hge1648v7x7xsqhft1n|1e3a43]-HelperThread-#1,5,main]
java.net.SocketInputStream.socketRead0(Native Method)
java.net.SocketInputStream.read(SocketInputStream.java:129)
com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)
com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)
com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2428)
com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:590)
com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1069)
com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2031)
com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)
com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
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:146)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44)
com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)
Thread[C3P0PooledConnectionPoolManager[identityToken->1hge1648v7x7xsqhft1n|1e3a43]-HelperThread-#0,5,main]
java.net.SocketInputStream.socketRead0(Native Method)
java.net.SocketInputStream.read(SocketInputStream.java:129)
com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)
com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)
com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2428)
com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:590)
com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1069)
com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2031)
com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)
com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
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:146)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44)
com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)
Thread[C3P0PooledConnectionPoolManager[identityToken->1hge1648v7x7xsqhft1n|1e3a43]-HelperThread-#2,5,main]
java.net.SocketInputStream.socketRead0(Native Method)
java.net.SocketInputStream.read(SocketInputStream.java:129)
com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)
com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)
com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2428)
com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:590)
com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1069)
com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2031)
com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:718)
com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
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:146)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:195)
com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:184)
com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:44)
com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)
解决办法：
更改配置文件里的最大连接数和初始化连接数大小：
xml代码：
数据库的连接数是有限的，每次应用启动C3p0都会占用数据库的连接来填充C3p0的连接池，而当数据库的资源被占光时就会因为无法获得共享资源而报死锁。