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 XAConnection
        at 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.AuthenticatedSubject.doAs(AuthenticatedSubject.java:344)
        at weblogic.security.service.SecurityManager.runAsForUserCode(SecurityManager.java:197)
        at weblogic.servlet.provider.WlsSecurityProvider.runAsForUserCode(WlsSecurityProvider.java:203)
        at weblogic.servlet.provider.WlsSubjectHandle.run(WlsSubjectHandle.java:71)
        at weblogic.servlet.internal.WebAppServletContext.doSecuredExecute(WebAppServletContext.java:2451)
        at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2299)
        at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2277)
        at weblogic.servlet.internal.ServletRequestImpl.runInternal(ServletRequestImpl.java:1720)
        at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1680)
        at weblogic.servlet.provider.ContainerSupportProviderImpl$WlsRequestExecutor.run(ContainerSupportProviderImpl.java:272)
        at weblogic.invocation.ComponentInvocationContextManager._runAs(ComponentInvocationContextManager.java:352)
        at weblogic.invocation.ComponentInvocationContextManager.runAs(ComponentInvocationContextManager.java:337)
        at weblogic.work.LivePartitionUtility.doRunWorkUnderContext(LivePartitionUtility.java:57)
        at weblogic.work.PartitionUtility.runWorkUnderContext(PartitionUtility.java:41)
        at weblogic.work.SelfTuningWorkManagerImpl.runWorkUnderContext(SelfTuningWorkManagerImpl.java:655)
        at weblogic.work.ExecuteThread.execute(ExecuteThread.java:420)
        at weblogic.work.ExecuteThread.run(ExecuteThread.java:360)
Caused by: java.sql.SQLException: weblogic.common.resourcepool.ResourceLimitException: No resources currently available in pool datasourceXA1 to allocate to applications, please increase the size of the pool and retry..
        at weblogic.common.resourcepool.ResourcePoolImpl.reserveResourceInternal(ResourcePoolImpl.java:669)
        at weblogic.common.resourcepool.ResourcePoolImpl.reserveResource(ResourcePoolImpl.java:378)
        at weblogic.common.resourcepool.ResourcePoolImpl.reserveResource(ResourcePoolImpl.java:365)
        at weblogic.jdbc.common.internal.ConnectionPool.reserve(ConnectionPool.java:608)
        at weblogic.jdbc.common.internal.ConnectionPool.reserve(ConnectionPool.java:521)
        at weblogic.jdbc.common.internal.ConnectionPoolManager.reserve(ConnectionPoolManager.java:144)
        at weblogic.jdbc.common.internal.ConnectionPoolManager.reserve(ConnectionPoolManager.java:94)
        at weblogic.jdbc.jta.DataSource.getXAConnectionFromPool(DataSource.java:1938)
        at weblogic.jdbc.jta.DataSource.refreshXAConnAndEnlist(DataSource.java:1679)
        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$ServletInvocationAction.run(WebAppServletContext.java:3763)
        at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:344)
        at weblogic.security.service.SecurityManager.runAsForUserCode(SecurityManager.java:197)
        at weblogic.servlet.provider.WlsSecurityProvider.runAsForUserCode(WlsSecurityProvider.java:203)
        at weblogic.servlet.provider.WlsSubjectHandle.run(WlsSubjectHandle.java:71)
        at weblogic.servlet.internal.WebAppServletContext.doSecuredExecute(WebAppServletContext.java:2451)
        at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2299)
        at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2277)
        at weblogic.servlet.internal.ServletRequestImpl.runInternal(ServletRequestImpl.java:1720)
        at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1680)
        at weblogic.servlet.provider.ContainerSupportProviderImpl$WlsRequestExecutor.run(ContainerSupportProviderImpl.java:272)
        at weblogic.invocation.ComponentInvocationContextManager._runAs(ComponentInvocationContextManager.java:352)
        at weblogic.invocation.ComponentInvocationContextManager.runAs(ComponentInvocationContextManager.java:337)
        at weblogic.work.LivePartitionUtility.doRunWorkUnderContext(LivePartitionUtility.java:57)
        at weblogic.work.PartitionUtility.runWorkUnderContext(PartitionUtility.java:41)
        at weblogic.work.SelfTuningWorkManagerImpl.runWorkUnderContext(SelfTuningWorkManagerImpl.java:655)
        at weblogic.work.ExecuteThread.execute(ExecuteThread.java:420)
        at weblogic.work.ExecuteThread.run(ExecuteThread.java:360)

        at weblogic.jdbc.jta.DataSource.getXAConnectionFromPool(DataSource.java:1982)
        at weblogic.jdbc.jta.DataSource.refreshXAConnAndEnlist(DataSource.java:1679)
        ... 33 more

重点log：
明确那个数据源发生了连接泄露

Caused by: java.sql.SQLException: weblogic.common.resourcepool.ResourceLimitException: No resources currently available in pool xxxx to allocate to applications, please increase the size of the pool and retry.

明确在哪个文件中使用了数据源连接没有释放

at weblogic.jdbc.common.internal.RmiDataSource.getConnection(RmiDataSource.java:108)
at TastyList.doGet(TastyList.java:46) --->使用数据源连接的地方，一般是调用DataSource.getConnection()方法的地方
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)

解决方法

不重启weblogic，让weblogic 自动回收
weblogic console->Services->Data Sources->log中已明确的数据源->Configuration->Connection Pool->Advanced中

当然最根本的办法是，根据log提示，DataSource.getConnection()后，及时close连接。
例如：

自动收集连接泄露

weblogic console->Services->Data Sources->数据源->Configuration ->Diagnostics
开启连接泄露的收集以及设定收集间隔时间。