DB connection pool not connected, connection pool exhausted

The most recent period of time. This year began to put. I maintain the site has been error database connection is not found, link, connection pool exhaustion problem.
caused By:org.apache.commons.dbcp.SQLNestedException:Cannot get a connection, pool exhausted
2017-07-26 15:42:20,516 ERROR [STDERR] at Org.apache.commons.dbcp.PoolingDataSource.getConnection ( poolingdatasource.java:103)
2017-07-26 15:42:20,516 ERROR [STDERR] at Org.apache.commons.dbcp.BasicDataSource.getConnection ( basicdatasource.java:540)
2017-07-26 15:42:20,516 ERROR [STDERR] at Org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection ( localdatasourceconnectionprovider.java:81)
2017-07-26 15:42:20,516 ERROR [STDERR] at Org.hibernate.jdbc.ConnectionManager.openConnection ( connectionmanager.java:423)
2017-07-26 15:42:20,516 ERROR [STDERR] at Org.hibernate.jdbc.ConnectionManager.getConnection ( connectionmanager.java:144)
2017-07-26 15:42:20,516 ERROR [STDERR] at Org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement ( abstractbatcher.java:139)
2017-07-26 15:42:20,531 ERROR [STDERR] at org.hibernate.loader.Loader.prepareQueryStatement (loader.java:1547)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.loader.Loader.doQuery (loader.java:673)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections ( loader.java:236)
2017-07-26 15:42:20,531 ERROR [STDERR] at org.hibernate.loader.Loader.loadEntity (loader.java:1860)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.loader.entity.AbstractEntityLoader.load ( ABSTRACTENTITYLOADER.JAVA:48)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.loader.entity.AbstractEntityLoader.load ( ABSTRACTENTITYLOADER.JAVA:42)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.persister.entity.AbstractEntityPersister.load ( abstractentitypersister.java:3044)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource ( defaultloadeventlistener.java:395)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.event.def.DefaultLoadEventListener.doLoad ( defaultloadeventlistener.java:375)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.event.def.DefaultLoadEventListener.load ( defaultloadeventlistener.java:139)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad ( defaultloadeventlistener.java:195)
2017-07-26 15:42:20,531 ERROR [STDERR] at Org.hibernate.event.def.DefaultLoadEventListener.onLoad ( defaultloadeventlistener.java:103)
2017-07-26 15:42:20,547 ERROR [STDERR] at Org.hibernate.impl.SessionImpl.fireLoad (sessionimpl.java:878)
2017-07-26 15:42:20,547 ERROR [STDERR] at Org.hibernate.impl.SessionImpl.get (sessionimpl.java:815)
2017-07-26 15:42:20,547 ERROR [STDERR] at Org.hibernate.impl.SessionImpl.get (sessionimpl.java:808)
2017-07-26 15:42:20,547 ERROR [STDERR] at Org.springframework.orm.hibernate3.hibernatetemplate$1.doinhibernate ( hibernatetemplate.java:477)
2017-07-26 15:42:20,547 ERROR [STDERR] at Org.springframework.orm.hibernate3.HibernateTemplate.execute ( hibernatetemplate.java:373)
2017-07-26 15:42:20,547 ERROR [STDERR] ... more
2017-07-26 15:42:20,547 ERROR [STDERR] caused by:java.util.NoSuchElementException:Timeout waiting for idle object
2017-07-26 15:42:20,547 ERROR [STDERR] at Org.apache.commons.pool.impl.GenericObjectPool.borrowObject ( genericobjectpool.java:756)
probably the log as shown above, is very depressed, called the test. Want the test to find the root cause. The result test can only reproduce the error: I felt a moment of loss of confidence.
after a good look at the log, look at the error method, found DAO in the acquisition connection unexpectedly is this.getsession. Baidu behind the next method. It comes with hibernate, but it won't be released. Comparing several methods of acquisition, I carefully replaced several classes. Fear is not the root of it.
after having the test tested again. found no error in connection pool exhaustion, and so on.
for the time being. Follow-up in the continuation of observation. Everyone has better ideas to put forward.

DB connection pool not connected, connection pool exhausted