Question

严重: Servlet.service() for servlet action threw exception java.lang.

严重: Servlet.service() for servlet action threw exception
java.lang.ClassCastException: entity.UserInfoForm
at entity.UserInfoAction.doupdate(UserInfoAction.java:86)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:270)
at org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:187)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
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(Unknown Source)

Answer 1

用了struts框架了,为什么取数据时还要用request.getParameter()呢。
我猜是int id = Integer.parseInt(request.getParameter("id"));的问题，id应该是序列，如果是添加操作id一般是从数据库取的，前台页面不会提供id的输入，所以取到的可能是null或空字符串，转换时报错了

Answer 2

public ActionForward doupdate(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
UserInfo userInfoForm = (UserInfo) form; //这个是86行么？？？？？？？
int id = Integer.parseInt(request.getParameter("id"));

如果是的话那问题不是很明显么？form的类型是UserInfoForm，而你把它强制转换为UserInfo。

要想进一步深入的话你可以看看容器的日志，日志里面更详细，比如我造出的异常，java.lang.ClassCastException: java.util.Random cannot be cast to java.lang.String
at study.skad.test.TempTest.test(TempTest.java:20)
很明显就可以看出问题所在。

实在不行还可以把86行的那个对象打印出来看看他的类型到底是什么。总之，不是很难的问题。

Answer 3

去看看你的UserInfoForm 这个类是不是继承了ActionForm，
如果没继承就会出现ClassCastException

Answer 4

UserInfoAction.java:86 ---- UserInfoAction 这里边86行代码错误
原因为java.lang.ClassCastException: entity.UserInfoForm
UserInfoForm中 类型转换 的问题

我的理解也就是这样，同样是新手 提供点意见

追问

public ActionForward doupdate(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
UserInfo userInfoForm = (UserInfo) form;
int id = Integer.parseInt(request.getParameter("id"));
String name = request.getParameter("name");
String pass = request.getParameter("pass");
String add = request.getParameter("add");
userInfoForm.setId(id);