计算机二级辅导:几种DispatchAction的异同
发布时间：2010/3/13 9:12:52 来源：城市学习网 编辑：MOON
java.lang.Object
org.apache.struts.action.Action
org.apache.struts.actions.DispatchAction
org.apache.struts.actions.LookupDispatchAction(Struts1.1)
org.apache.struts.actions.EventDispatchAction(Struts1.2.9)
org.apache.struts.actions.MappingDispatchAction(Struts1.2)
DispatchAction
public abstract class DispatchAction extends Action
这是一个抽象的Action，它会根据request 中的parameter来执行相应的方法。通个这个Action类可以将不同的Action集中到一个Action文件中来。
struts-config.xml：
action path="/subscription" type="org.example.SubscriptionAction" name="subscriptionForm" scope="request" input="/subscription.jsp" parameter="method"/
在Action中要有相应的方法：
public class SubscriptionAction extends DispatchAction {
public ActionForward delete(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward insert(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward update(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
}
然后可以通过这样的方法来你的程序：
http://localhost:8080/myapp/subscription.do?method=delete
http://localhost:8080/myapp/subscription.do?method=insert
http://localhost:8080/myapp/subscription.do?method=update
如果parameter中参数为空，则调用Action中的unspecified方法
LookupDispatchAction
public abstract class LookupDispatchAction extends DispatchAction
通过这个Action抽象类继承DispatchAction，它的相应方法的执行由ActionMapping中parameter属性决定。每个动作实际上就是html:submit标签的property属性值。它适合在一个form中有很多按钮，按不同的按钮则执行不同的操作。
struts-config.xml：
action path="/subscription" type="org.example.SubscriptionAction" name="subscriptionForm" scope="request"
input="/subscription.jsp" parameter="method"/
ApplicationResources.properties：
button.add=Add Record
button.delete=Delete Record
JSP：
%@ page pageEncoding="GBK"%
%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%
html
head
title多提交演示/title
/head
body
html:form action="subscription"
html:submit property="method"
bean:message key="button.add"/
/html:submit
html:submit property="method"
bean:message key="button.delete"/
/html:submit
/html:form
/body
/html
在Action中必须实现getKeyMethodMap方法：
public class SubscriptionAction extends LookupDispatchAction {
protected Map getKeyMethodMap() {
Map map = new HashMap();
map.put("button.add"， "add");
map.put("button.delete"， "delete");
return map;
}
public ActionForward add(ActionMapping mapping，
ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward delete(ActionMapping mapping，
ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
}
EventDispatchAction
public class EventDispatchAction extends DispatchAction
通过这个Action抽象类继承DispatchAction，它的相应方法的执行由ActionMapping中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。它适合在一个form中有很多按钮，按不同的按钮则执行不同的操作。
struts-config.xml：
(parameter中的"recalc=recalculate"意思为html:submit标签的property属性值为recalc调用recalculate方法，出于安全考虑能够隐藏后台的业务方法名。"defaule=save"这是可选的，没有配置property属性的html:submit标签将调用defaule中设置的方法名，如果defaule没有指定任何参数，则调用Action中的unspecified方法)
action path="/subscription" type="org.example.SubscriptionAction" name="subscriptionForm" scope="request"
input="/subscription.jsp" parameter="save，back，recalc=recalculate，default=save"/
JSP：
%@ page pageEncoding="GBK"%
%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%
html
head
title多提交演示/title
/head
body
html:form action="subscription"
html:submit property="save" value="保存"/
html:submit property="back" value="后退"/
html:submit property="recalc" value="重新计算"/
/html:form
/body
/html
在Action中要有相应的方法：
public class SubscriptionAction extends LookupDispatchAction {
public ActionForward save(ActionMapping mapping，
ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward back(ActionMapping mapping，
ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward recalculate(ActionMapping mapping，
ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
}
MappingDispatchAction
public class MappingDispatchAction extends DispatchAction
它的相应方法的执行由ActionMapping中parameter名决定，注意这里和LookupDispatchAction不同，LookupDispatchAction的相应方法的执行由ActionMapping中parameter属性决定。
struts-config.xml：
action path="/createSubscription" type="org.example.SubscriptionAction" parameter="create"
forward name="success" path="/createSubscription.jsp"/
/action
action path="/editSubscription" type="org.example.SubscriptionAction" parameter="edit"
forward name="success" path="/editSubscription.jsp"/
/action
action path="/saveSubscription" type="org.example.SubscriptionAction" parameter="save"
name="subscriptionForm" validate="true" input="/editSubscription.jsp" scope="request"
forward name="success" path="/savedSubscription.jsp"/
/action
action path="/deleteSubscription" type="org.example.SubscriptionAction" name="subscriptionForm"
scope="request" input="/subscription.jsp" parameter="delete"
forward name="success" path="/deletedSubscription.jsp"/
/action
action path="/listSubscriptions" type="org.example.SubscriptionAction" parameter="list"
forward name="success" path="/subscriptionList.jsp"/
/action
在Action中要有相应的方法：
public class SubscriptionAction extends MappingDispatchAction {
public ActionForward create(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward edit(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward save(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward delete(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
public ActionForward list(ActionMapping mapping， ActionForm form，
HttpServletRequest request，
HttpServletResponse response) throws Exception {}
}
然后可以通过这样的方法来你的程序：
http://localhost:8080/myapp/create.do
http://localhost:8080/myapp/edit.do
http://localhost:8080/myapp/save.do
http://localhost:8080/myapp/delete.do
http://localhost:8080/myapp/list.do
如果parameter中参数为空，则调用Action中的unspecified方法
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