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EventDispatchAction 学习
阅读量:6900 次
发布时间:2019-06-27

本文共 4913 字,大约阅读时间需要 16 分钟。

EventDispatchAction作用:
用于处理多个提交动作的EventDispatchAction类。这个类也是DispatchAction的子类,它在使用上要比LookupDispatchAction类容易的多。EventDispatchAction类的基本原理是通过<action>元素的parameter属性指定多个动作,中间用逗号(,)分隔。每个动作实际上就是<html:submit>标签的property属性值。这样EventDispatchAction类就可以根据每个<html:submit>标签的属性值来确定用户按的是哪个提交按钮了。
 
【第1步】实现EventDispatchAction的子类
/* 
* $Id: EventDispatchActionExample.java 471754 2006-11-06 14:55:09Z husted $ 
* Licensed to the Apache Software Foundation (ASF) under one 
* or more contributor license agreements.    See the NOTICE file 
* distributed with this work for additional information 
* regarding copyright ownership.    The ASF licenses this file 
* to you under the Apache License, Version 2.0 (the 
* "License"); you may not use this file except in compliance 
* with the License.    You may obtain a copy of the License at 
*    http://www.apache.org/licenses/LICENSE-2.0 
* Unless required by applicable law or agreed to in writing, 
* software distributed under the License is distributed on an 
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 
* KIND, either express or implied.    See the License for the 
* specific language governing permissions and limitations 
* under the License. 
*/
 

package org.apache.struts.webapp.dispatch; 


import javax.servlet.http.HttpServletRequest; 

import javax.servlet.http.HttpServletResponse; 

import org.apache.struts.actions.EventDispatchAction; 

import org.apache.struts.action.ActionForm; 

import org.apache.struts.action.ActionForward; 

import org.apache.struts.action.ActionMapping; 

import org.apache.struts.action.ActionMessage; 

import org.apache.struts.action.ActionMessages; 


/** 
* Example EventDispatchAction. 
* @version $Rev: 471754 $ $Date: 2006-11-06 08:55:09 -0600 (Mon, 06 Nov 2006) $ 
*/
 

public 
class EventDispatchActionExample 
extends EventDispatchAction { 


        
private 
int fooCount; 

        
private 
int barCount; 


        
/** 
         * Example "foo" method. 
         * 
         * @param mapping The ActionMapping used to select this instance 
         * @param form The optional ActionForm bean for this request 
         * @param request The servlet request we are processing 
         * @param response The servlet response we are creating 
         * 
         * @exception Exception if business logic throws an exception 
         */
 

        
public ActionForward doFoo(ActionMapping mapping, 

                                                             ActionForm form, 

                                                             HttpServletRequest request, 

                                                             HttpServletResponse response) 

                
throws Exception { 


                fooCount++; 


                ActionMessages messages = 
new ActionMessages(); 

                messages.add(
"foo"
new ActionMessage(
"count.foo.message", fooCount+"")); 

                saveMessages(request, messages); 


                
return (mapping.findForward(
"success")); 


        } 


        
/** 
         * Example "bar" method. 
         * 
         * @param mapping The ActionMapping used to select this instance 
         * @param form The optional ActionForm bean for this request 
         * @param request The servlet request we are processing 
         * @param response The servlet response we are creating 
         * 
         * @exception Exception if business logic throws an exception 
         */
 

        
public ActionForward doBar(ActionMapping mapping, 

                                                             ActionForm form, 

                                                             HttpServletRequest request, 

                                                             HttpServletResponse response) 

                
throws Exception { 

                barCount++; 


                ActionMessages messages = 
new ActionMessages(); 

                messages.add(
"bar"
new ActionMessage(
"count.bar.message", barCount+"")); 

                saveMessages(request, messages); 


                
return (mapping.findForward(
"success")); 


        } 



 
有两个方法:doFoo和doBar,分别用来处理property属性值为“doFoo”和“doBar”的<html:submit>标签提交的请求动作
 
  【第2步】配置EventDispatchAction类
<action path=
"/eventAction-default"    

                                type=
"org.apache.struts.webapp.dispatch.EventDispatchActionExample" 

                                parameter=
"doFoo,bar=doBar,default=doBar" 

                                name=
"testForm" 

                                scope=
"request"

                        <forward name=
"success" path=
"/eventAction.jsp"/> 

                </action>
 
parameter="doFoo,bar=doBar,default=doBar"
如果submit标签不提供property 或者提供了property值,在Action中找不到相关的方法对应时,会提交的default标记的doBar方法中
【第3步】实现有多个提交按钮的JSP页面
                 <html:form action=
"eventAction-default" style=
"display:inline"

                            <html:submit property=
"doFoo"><bean:message key=
"button.foo.label" /></html:submit> 

                    </html:form> 

                              

                    <html:form action=
"eventAction-default" style=
"display:inline"

                     <input type=
"hidden" name=
"Method" value=
"doBar" /> 

                            <html:submit><bean:message key=
"button.bar.label" /></html:submit> 

                    </html:form> 

                              

                    <html:form action=
"eventAction-default" style=
"display:inline"

                            <html:submit><bean:message key=
"button.default.label" /></html:submit> 

                    </html:form>
 
 
运行结果:
 <html:submit><bean:message key="button.default.label" /></html:submit>,会执行default 指向的方法。如果没有default,会报
ServletException: Request[/eventAction-submit] does not contain handler parameter.
2.如果在配置文件中有相关的方法声明比如parameter="missingMethod",但是在Action java文件中却没有missingMethod()方法的实现,会报
NoSuchMethodException: Action[/eventAction-error] does not contain specified method (check logs)
3. 也不能在配置文件总使用方法名execcute 。否则:
ServletException: Do not use 'execute' or 'perform' with DispatchAction.
4.如果忘记了在配置文件中,为Action设置parameter属性,会报:
ServletException: DispatchMapping[/eventAction-noparam] does not define a handler property
本文转自 randy_shandong 51CTO博客,原文链接:http://blog.51cto.com/dba10g/241207,如需转载请自行联系原作者
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