一只会飞的白菜 2017-09-03 05:28 采纳率: 0%
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map 返回值为空 不知道为啥

//查询表中的所有的数据
@Action(value="user",results={@Result(name="succes", location="/WEB-INF/jsp/user.jsp")})
public String userall(){
Session session = sessionFactory.openSession();
Query query=session.createQuery("from user");
List userlist=query.list();
for (UserEntity userEntity : userlist) {
listuser.add(userEntity);
}
session.close();
return "succes";

}

@Action(value="json")
public Map<String, Object> json(){  
    HttpServletResponse response = ServletActionContext.getResponse();
    map=new HashMap<String, Object>();
        int total=listuser.size();
        map.put("total",total);
        map.put("rows", listuser);

        String data = JSON.toJSONString(map);
        try {
            response.setCharacterEncoding("UTF-8");
            PrintWriter out;
            out = response.getWriter();
            out.write(data.toString());
            System.out.println(data);
            out.flush();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return map;
}
    ![f12调试后没有值图片说明](https://img-ask.csdn.net/upload/201709/03/1504416375_892008.png)

    java.lang.ClassCastException: java.util.HashMap cannot be cast to java.lang.String
at com.opensymphony.xwork2.DefaultActionInvocation.saveResult(DefaultActionInvocation.java:483)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:446)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:284)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:245)
at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:253)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:177)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:260)
at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:69)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.doIntercept(ConversionErrorInterceptor.java:139)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:133)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:133)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:192)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:69)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:121)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:88)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:245)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:99)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:139)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:155)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:174)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:97)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:151)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:171)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:195)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:193)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:240)
at org.apache.struts2.factory.StrutsActionProxy.execute(StrutsActionProxy.java:54)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:564)
at org.apache.struts2.dispatcher.ExecuteOperations.executeAction(ExecuteOperations.java:81)
at org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:113)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
  • 写回答

2条回答

  • 鼠晓 博客专家认证 2017-09-03 06:13
    关注

    public Map json()这个方法的return map;,是空??

    java.util.HashMap cannot be cast to java.lang.String
    HashMap不能强转为String,,看看这个类【DefaultActionInvocation.java】

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