0

我正在通过“Enjoying Web Development with Wicket”一书学习 Wicket。它是为 Wicket 1.4.7 编写的，
在一个例子中：

int weight = ((Integer) weightModel.getObject()).intValue();

用来。当我单击提交按钮时，它会抛出 Unexpected RuntimeException 第一行：

WicketMessage：针对组件[MarkupContainer [Component id = form]]的接口org.apache.wicket.markup.html.form.IFormSubmitListener的方法onFormSubmitted引发异常

根本原因：

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer*

可能weightModel.getObject()无法转换为 String。

完整的异常消息在底部。

但是在将代码更改为：

int weight=Integer.parseInt( (String) weightModel.getObject());

它工作正常。它应该工作正常。抛出异常的原因是什么？


完整代码：

获取请求.java

package myapp.postage;
import java.util.HashMap;
import java.util.Map;

import org.apache.wicket.markup.html.WebPage;
import org.apache.wicket.markup.html.form.Form;
import org.apache.wicket.markup.html.form.TextField;
import org.apache.wicket.model.Model;

@SuppressWarnings("unchecked")
public class GetRequest extends WebPage {
 private Model weightModel=new Model();
 private Model patronCodeModel=new Model();
 private Map patronCodeToDiscount; 

 public GetRequest(){
  patronCodeToDiscount=new HashMap();
  patronCodeToDiscount.put("p1", new Integer(90));
  patronCodeToDiscount.put("p2", new Integer(95));

  Form form=new Form("form"){
   @Override
   protected void onSubmit(){
    int weight = ((Integer) weightModel.getObject()).intValue();
    Integer discount=(Integer)patronCodeToDiscount.get(patronCodeModel.getObject());
    int postagePerKg=10;
    int postage=weight*postagePerKg;
    if(discount!=null){
     postage=postage*discount.intValue()/100;
    }
    ShowPostage showPostage=new ShowPostage(postage);
    setResponsePage(showPostage);
   }
  };
  TextField weight=new TextField("weight",weightModel);
  form.add(weight);
  TextField patronCode=new TextField("patronCode",patronCodeModel);
  form.add(patronCode);
  add(form);
 }
}

html 文件 GetRequest.html：

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
        <form wicket:id="form">
     <table>
      <tr>
       <td>Weight</td>
       <td><input type="text" wicket:id="weight"/></td>
      </tr>
      <tr>
       <td>Patron code:</td>
       <td><input type="text" wicket:id="patronCode"/></td>
      </tr>
      <tr>
       <td></td>
       <td><input type="submit"/></td>
      </tr>
     </table>
         </form>
    </html>

异常消息： WicketMessage：接口 org.apache.wicket.markup.html.form.IFormSubmitListener 的方法 onFormSubmitted 针对组件 [MarkupContainer [Component id = form]] 抛出异常

根本原因：

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
     at myapp.postage.GetRequest$1.onSubmit(GetRequest.java:26)
     at org.apache.wicket.markup.html.form.Form.delegateSubmit(Form.java:1538)
     at org.apache.wicket.markup.html.form.Form.process(Form.java:934)
     at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:896)
     at java.lang.reflect.Method.invoke(Method.java:597)
     at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:182)
     at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
     at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
     at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
     at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
     at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
     at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
     at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:479)
     at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:312)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
     at com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.invoke(HttpRequestOperationCollectionValve.java:60)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
     at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:379)
     at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
     at java.lang.Thread.run(Thread.java:619)

Complete stack:
org.apache.wicket.WicketRuntimeException: Method onFormSubmitted of interface org.apache.wicket.markup.html.form.IFormSubmitListener targeted at component [MarkupContainer [Component id = form]] threw an exception
     at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:193)
     at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
     at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
     at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
     at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
     at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
     at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
     at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:479)

java.lang.reflect.InvocationTargetException
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
     at java.lang.reflect.Method.invoke(Method.java:597)
     at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:182)
     at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
     at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
     at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
     at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
     at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
     at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
     at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:479)
4

3 回答 3

1

如果您使用的是 Wicket 1.4 及更高版本，您应该使用泛型并使用它们来告诉 wicket 您期望什么类型。然后，Wicket 将为您进行转换。

我建议进行以下更改（对于重量，其他字段留作练习；））：

向您的页面添加一个字段，该字段将保存用户的输入：

private Integer weight;

为该字段添加 getter 和 setter：

public Integer getWeight() {return weight;}
public void SetWeight(Integer weight) {this.weight = weight;}

然后，将代码替换为添加重量的文本字段：

form.add(new TextField<Integer>("weight"
     , new PropertyModel<Integer>(this, "weight"));

这样，Wicket 会将用户输入转换为整数并将其存储到字段权重中。PropertyModel 使用 Page 本身来访问该字段。

希望有帮助。

提示：如果用户输入了无法转换的内容，Wicket 会在 Textfield 中添加一个错误。您应该在页面中添加一个反馈面板以查看此内容。

享受

于 2010-12-29T10:49:21.333 回答
0

有效的函数返回哪个整数？抛出哪个异常？

如果它为零，则可能 getObject() 根本不返回整数。

于 2010-12-28T23:48:47.987 回答
0

可能 weightModel.getObject() 无法转换为字符串。

不。返回的对象是一个字符串，而不是您希望使用 Integer 强制转换的整数。

一种解决方案是解析返回的字符串 Integer.parseInt(str) （但我认为 wicket 可以为你做到这一点......）

于 2010-12-29T09:10:00.577 回答