编码时，有时会忘记释放使用的数据源连接，造成连接泄露，没有连接资源可用。

现象

java.sql.SQLException: Cannot obtain XAConnectionat weblogic.jdbc.jta.DataSource.refreshXAConnAndEnlist(DataSource.java:1691)at weblogic.jdbc.jta.DataSource.getConnectionInternal(DataSource.java:523)at weblogic.jdbc.jta.DataSource.getConnection(DataSource.java:500)at weblogic.jdbc.common.internal.WLDataSourceImpl.getConnectionInternal(WLDataSourceImpl.java:631)at weblogic.jdbc.common.internal.WLDataSourceImpl.getConnection(WLDataSourceImpl.java:611)at weblogic.jdbc.common.internal.WLDataSourceImpl.getConnection(WLDataSourceImpl.java:604)at weblogic.jdbc.common.internal.RmiDataSource.getConnection(RmiDataSource.java:108)at TastyList.doGet(TastyList.java:46)at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:295)at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:260)at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:137)at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:353)at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:250)at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3793)at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3763)at weblogic.security.acl.internal.A