Javaweb project, why do you lose your connection to the database after a period of time? - Codes Helper

--- Cause: org.apache.commons.dbcp.SQLNestedException: Cannot get a connection, pool exhausted
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryWithCallback(GeneralStatement.java:185)
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryForList(GeneralStatement.java:123)
    at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForList(SqlMapExecutorDelegate.java:615)
    at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForList(SqlMapExecutorDelegate.java:589)
    at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForList(SqlMapSessionImpl.java:118)
    at org.springframework.orm.ibatis.SqlMapClientTemplate$3.doInSqlMapClient(SqlMapClientTemplate.java:298)
    at org.springframework.orm.ibatis.SqlMapClientTemplate$3.doInSqlMapClient(SqlMapClientTemplate.java:296)
    at org.springframework.orm.ibatis.SqlMapClientTemplate.execute(SqlMapClientTemplate.java:203)
    ... 40 more
Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot get a connection, pool exhausted
    at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:103)
    at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:540)
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
    at org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy$TransactionAwareInvocationHandler.invoke(TransactionAwareDataSourceProxy.java:224)
    at $Proxy52.prepareStatement(Unknown Source)
    at com.ibatis.sqlmap.engine.execution.SqlExecutor.prepareStatement(SqlExecutor.java:494)
    at com.ibatis.sqlmap.engine.execution.SqlExecutor.executeQuery(SqlExecutor.java:176)
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.sqlExecuteQuery(GeneralStatement.java:205)
    at com.ibatis.sqlmap.engine.mapping.statement.GeneralStatement.executeQueryWithCallback(GeneralStatement.java:173)
    ... 47 more
Caused by: java.util.NoSuchElementException: Timeout waiting for idle object
    at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:756)
    at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:95)
    ... 55 more