JSF2:action和actionListener [英] JSF2: action and actionListener

问题描述

根据BalusC的回答，此处 action与actionListener之间的差异，Use actionListener if you want have a hook before the real business action get executed, e.g. to log it, and/or to set an additional property (by <f:setPropertyActionListener>, .但是，当我决定编写一些代码进行测试时，结果会有所不同.这是我的小代码

From this answer by BalusC here Differences between action and actionListener, Use actionListener if you want have a hook before the real business action get executed, e.g. to log it, and/or to set an additional property (by <f:setPropertyActionListener>,. However when I decide to write some code to test this, the result is a bit different. Here is my small code

<h:form id="form"> 
   <h:panelGroup id="mygroup">
     <p:dataTable id="mytable" value="#{viewBean.foodList}" var="item">
         <p:column>
             #{item}
         </p:column>
         <p:column>
             <p:commandButton value="delete" 
                        action="#{viewBean.delete}"
                        update=":form:mygroup">
                 <f:setPropertyActionListener target="#{viewBean.selectedFood}"
                                              value="#{item}"/>
             </p:commandButton>
         </p:column>
      </p:dataTable>
   </h:panelGroup>
</h:form>

这是我的豆子

@ManagedBean
@ViewScoped
public class ViewBean {
    private List<String> foodList;
    private String selectedFood;

    @PostConstruct
    public void init(){

        foodList = new ArrayList<String>();
        foodList.add("Pizza");
        foodList.add("Pasta");
        foodList.add("Hamburger");
    }

    public void delete(){
        foodList.remove(selectedFood);
    }
    //setter, getter...
}

根据BalusC的说法，actionListener在这里更合适，但我的示例显示了否则.

According to BalusC, actionListener is more suitable here, but my example show otherwise.

上面的代码在action下可以很好地工作，但是如果我切换到actionListener，那么它就不能正常工作.我需要两次单击才能使用actionListener删除该表的条目，而如果使用action，则每次单击该按钮都将删除条目.我想知道是否有JSF专家可以帮助我理解action与actionListener

The above code work great with action, but if I switch over to actionListener, then it does not quite work. It will take two clicks for me to delete an entry of this table using actionListener, while if I use action, it delete entry every time I click the button. I wonder if any JSF expert out there can help me understand action vs actionListener

注意:如果我切换到actionListener，则我的delete方法将变为public void delete(ActionEvent actionEvent)

Note If I switch to actionListener, my delete method become public void delete(ActionEvent actionEvent)

推荐答案

您正在将action与actionListener混淆. actionListener始终在action之前运行.如果有多个动作侦听器，则它们以与注册时相同的顺序运行.这就是为什么当您使用actionListener调用业务操作并使用<f:setPropertyActionListener>设置(准备)该业务操作要使用的属性时，它无法按预期工作的原因.此问题已在您之前的问题中解决并指出. Mojarra/MyFaces错误.

You're confusing action with actionListener. The actionListener runs always before the action. If there are multiple action listeners, then they run in the same order as they have been registered. That's why it doesn't work as expected when you use actionListener to call the business action and <f:setPropertyActionListener> to set (prepare) a property which is to be used by the business action. This problem was pointed out and fixed in your previous question Is this Primefaces bug or Mojarra/MyFaces bug.

delete()方法中的所有内容显然都是业务操作，应改为由action调用.业务操作通常会调用EJB服务，并且在必要时还会设置最终结果和/或导航到其他视图.

Whatever you have in the delete() method is clearly a business action and should be invoked by action instead. A business action typically invokes an EJB service and if necessary also sets the final result and/or navigates to a different view.

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