首先我们来看一下它们三者之间的关系

java.lang.Object

  |

  +--org.apache.struts.action.Action

        |

        +--org.apache.struts.actions.DispatchAction

              |

              +--org.apache.struts.actions.LookupDispatchAction

              |

              +--org.apache.struts.actions.MappingDispatchAction

DispatchAction

定义

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="/saveSubscription" type="org.apache.struts.actions.DispatchAction" name="subscriptionForm" scope="request" input="/subscription.jsp" parameter="method"/>

在Action中要有相应的方法:

Public class demoAction 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

}

你就可以通过这样的方法来访问你的程序:

http://localhost:8080/myapp/saveSubscription.do?method=update

如果parameter中参数为空，则执行Action中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。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="/test"

           type="org.example.MyAction"

           name="MyForm"

          scope="request"

          input="/test.jsp"

      parameter="method"/>

ApplicationResources.properties:

    button.add=Add Record

    button.delete=Delete Record

  JSP:

   <html:form action="/test">

    <html:submit property="method">

      <bean:message key="button.add"/>

    </html:submit>

    <html:submit property="method">

      <bean:message key="button.delete"/>

    </html:submit>

  </html:form>

  在Action 中必须实现getKeyMethodMap:

  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 IOException, ServletException {

      // do add

      return mapping.findForward("success");

  }

  public ActionForward delete(ActionMapping mapping,

          ActionForm form,

          HttpServletRequest request,

          HttpServletResponse response)

          throws IOException, ServletException {

      // do delete

      return mapping.findForward("success");

  }

  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="/saveSubscription"

           type="org.example.SubscriptionAction"

           name="subscriptionForm"

          scope="request"

          input="/subscription.jsp"

      parameter="method"/>

 Action:

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

for which you would create corresponding <action> configurations that reference this class:

  <action path="/createSubscription"

          type="org.example.SubscriptionAction"

          parameter="create">

      <forward name="success" path="/editSubscription.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>