DispatchAction的作用简单地说就是把原来我们写在多个acton里的操作放在同一个 action里处理。
在Struts-config 中 相关的配置内容
<action-mappings>
<action path= "/welcome" forward= "/index.jsp"/>
<!-- ======================================= DispatchAction Example -->
<action path= "/dispatch" forward= "/dispatch.jsp"/>
<action path= "/dispatch-submit"
type= "org.apache.struts.webapp.dispatch.DispatchExampleAction"
parameter= "dispatchMethod"
name= "testForm"
scope= "request">
<exception key= "dispatch.NoSuchMethodException"
type= "java.lang.NoSuchMethodException"
path= "/dispatch.jsp"/>
<exception key= "dispatch.ServletException"
type= "javax.servlet.ServletException"
path= "/dispatch.jsp"/>
<forward name= "success" path= "/dispatch.jsp"/>
</action>
.........
<action path= "/welcome" forward= "/index.jsp"/>
<!-- ======================================= DispatchAction Example -->
<action path= "/dispatch" forward= "/dispatch.jsp"/>
<action path= "/dispatch-submit"
type= "org.apache.struts.webapp.dispatch.DispatchExampleAction"
parameter= "dispatchMethod"
name= "testForm"
scope= "request">
<exception key= "dispatch.NoSuchMethodException"
type= "java.lang.NoSuchMethodException"
path= "/dispatch.jsp"/>
<exception key= "dispatch.ServletException"
type= "javax.servlet.ServletException"
path= "/dispatch.jsp"/>
<forward name= "success" path= "/dispatch.jsp"/>
</action>
.........
formBean 不在讨论范围，所以省略了。
注意：
【 parameter="dispatchMethod"】。
在后面的JSP 页面中，表单提交的时候，要对dispatchMethod 这个参数赋值。
2.提交表单页面
.......
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "doFoo" />
<html:submit><bean:message key= "button.foo.label" /></html:submit>
</html:form>
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "doBar" />
<html:submit><bean:message key= "button.bar.label" /></html:submit>
</html:form>
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "doInvalid" />
<html:submit><bean:message key= "method.invalid.label" /></html:submit>
</html:form>
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "execute" />
<html:submit><bean:message key= "method.execute.label" /></html:submit>
</html:form>
........
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "doFoo" />
<html:submit><bean:message key= "button.foo.label" /></html:submit>
</html:form>
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "doBar" />
<html:submit><bean:message key= "button.bar.label" /></html:submit>
</html:form>
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "doInvalid" />
<html:submit><bean:message key= "method.invalid.label" /></html:submit>
</html:form>
<html:form action= "dispatch-submit" style= "display:inline">
<input type= "hidden" name= "dispatchMethod" value= "execute" />
<html:submit><bean:message key= "method.execute.label" /></html:submit>
</html:form>
........
在这页面中，有专门的一个隐藏域名称为【dispatcherMethod】,和struts-config.xml文件中目标Action 参数[
parameter=dispatcherMethod]相对应。这样Actiton,会根据传入的隐藏域【name=dispatherMethod】的value值，执行相应的方法。
1.当提供的dispatcherMethod 的值，在Action中没有对应的方法时（比如，doInvalid),会报
NoSuchMethodException: Action[/dispatch-submit] does not contain specified method (check logs)。
2.如果dispatcherMethod的值为 execute/perform时，报
Do not use 'execute' or 'perform' with DispatchAction.
3.如果提供的不提供dispatcherMethod参数时，报错：
ServletException: DispatchMapping[/dispatch-noparam] does not define a handler property
3.在一些demo中，其中有有execute（）,方法，感觉是必须的。但是我把该方法去掉，并没有影响操作。
下面是我删除的代码：
private ActionDispatcher dispatcher
= new ActionDispatcher( this,
ActionDispatcher.DISPATCH_FLAVOR);
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
System.out.println( "execute() 执行了");
return dispatcher.execute(mapping, form, request, response);
}
= new ActionDispatcher( this,
ActionDispatcher.DISPATCH_FLAVOR);
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
System.out.println( "execute() 执行了");
return dispatcher.execute(mapping, form, request, response);
}
难道在DispatchAction中该方法可有可无吗？
本文转自 randy_shandong 51CTO博客，原文链接：http://blog.51cto.com/dba10g/240791，如需转载请自行联系原作者
