Question

严重: Servlet.service() for servlet jsp threw exception

严重: Servlet.service() for servlet jsp threw exception
javax.el.PropertyNotFoundException: Property 'Users_ID' not found on type com.group5.entity.Tb_Users
at javax.el.BeanELResolver$BeanProperties.get(BeanELResolver.java:193)
at javax.el.BeanELResolver.property(BeanELResolver.java:267)
at javax.el.BeanELResolver.getValue(BeanELResolver.java:60)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:53)
at org.apache.el.parser.AstValue.getValue(AstValue.java:97)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:923)
at org.apache.jsp.User.index_jsp._jspx_meth_c_005fforEach_005f0(index_jsp.java:208)
at org.apache.jsp.User.index_jsp._jspService(index_jsp.java:138)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)

Answer 1

空指针异常，空指针异常非常常见，写代码要细心才能最大程度得避免空指针异常。至于排除问题，你可以根据调用堆栈查到你的jsp代码，一般通过代码走查就可以找到原因，不行就下断点调试吧。解决这类问题是基本功，加油！

追问

Tb_UsersDao dao = new Tb_UsersDao();
List Tb_UsersList=dao.getAllTb_Users();
request.setAttribute("user",Tb_UsersList);