doInsert error? Urgent!

[lvjin]

Hi, all I created a table with a primary key of auto-increment value. but when excute doInsert(criteria), the following exception were thrown:   java.lang.NullPointerException         at org.apache.turbine.om.peer.BasePeer.doInsert(BasePeer.java:712)         at org.apache.turbine.om.peer.BasePeer.doInsert(BasePeer.java:615)         at com.vtradex.om.peer.LocalContentPeer.doInsert(LocalContentPeer.java:4 9)         at com.vtradex.businesslogic.item.ItemLogic.setItem(ItemLogic.java:70)         at com.vtradex.actions.ItemAction.doAdditem(ItemAction.java:61)         at java.lang.reflect.Method.invoke(Native Method)         at org.apache.turbine.util.velocity.VelocityActionEvent.doEvents(Velocit yActionEvent.java:166)         at org.apache.turbine.util.velocity.VelocityActionEvent.perform(Velocity ActionEvent.java:113)         at org.apache.turbine.modules.actions.VelocityAction.perform(VelocityAct ion.java:116)         at org.apache.turbine.modules.ActionLoader.exec(ActionLoader.java:121)         at org.apache.turbine.modules.pages.DefaultPage.doBuild(DefaultPage.java :149)         at org.apache.turbine.modules.Page.build(Page.java:92)         at org.apache.turbine.modules.PageLoader.exec(PageLoader.java:122)         at org.apache.turbine.Turbine.doGet(Turbine.java:372)         at org.apache.turbine.Turbine.doPost(Turbine.java:459)         at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)         at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)         at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:4         at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:4 04)         at org.apache.tomcat.core.Handler.service(Handler.java:286)         at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372 )         at org.apache.tomcat.core.ContextManager.internalService(ContextManager. java:799)         at org.apache.tomcat.core.ContextManager.service(ContextManager.java:745 )         at org.apache.tomcat.service.http.HttpConnectionHandler.processConnectio n(HttpConnectionHandler.java:210)         at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java: 407)         at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java :498)         at java.lang.Thread.run(Thread.java:484) Error=Turbine.handleException: null Error=An error occurred while rendering template layoutsnull: null Error=Turbine.handleException: null Error=Turbine.handleException: null Error=Turbine.handleException: null Error=Turbine.handleException: null   Who can tell me why? and somtimes the values have been insert into the table, but the same exception appears.   lvjin