基于其他组件的某些操作更新，执行或呈现jsf组件(update, execute or render a jsf component based on some action of other component)

 我遇到了有关基于某些其他组件的操作渲染或执行jsf组件的问题。 
 
 我要做的是：首次加载页面时加载一些数据。 所以我写了 
 
<f:metadata>
<f:event listener="#{homeController.retrieveAllTagsForUser}"
    type="preRenderView" />
<f:event listener="#{homeController.populatePostsForUser}"
                type="preRenderView" />
</f:metadata>
 
 populatePostsForUser方法首先加载用户的所有帖子，如下所示 
 
public void populatePostsForUser() {
    EntityManager manager = applicationContext.getEntityManagerFactory()
            .createEntityManager();
    Query query = manager.createNamedQuery("Post.selectPostForUser");
    query.setParameter("user", this.getUser());
    this.posts = (List<Post>) query.getResultList();
    System.out.println("populatePostFOrUser called");
}
 
 并在页面加载后，我更新该方法中的posts字段，如下所示 
 
this.posts = (List<Post>)em.createNamedQuery("Post.selectPostsByTags").setParameter("tags", tags).getResultList();
    System.out.println("number of posts selected = " + this.posts.size());
    System.out.println("selected posts for this tag = " + this.posts);
    System.out.println("number of posts selected for tag = " + tags + " " + this.posts.size());
 
 这会成功更新posts字段，但在此之后，再次调用相同的populatePostsForUser方法。 每次重新渲染某个组件时都会调用它。 
 
 这只是我想知道的一个例子。 我的问题是。 如何控制jsf组件，以便我可以在另一个组件的某个ajax事件上呈现/更新/执行jsf组件？ 
 
 我想知道在jsf组件之间进行通信的最佳方法，并根据我们的选择在ajax时进行渲染。 

I was facing issues regarding rendering or executing the jsf components based on action of some other component. 
 
What I am trying to do is: load some data when the page is first loaded. so I wrote 
 
<f:metadata>
<f:event listener="#{homeController.retrieveAllTagsForUser}"
    type="preRenderView" />
<f:event listener="#{homeController.populatePostsForUser}"
                type="preRenderView" />
</f:metadata>
 
populatePostsForUser method first loads all the posts for the user as follows 
 
public void populatePostsForUser() {
    EntityManager manager = applicationContext.getEntityManagerFactory()
            .createEntityManager();
    Query query = manager.createNamedQuery("Post.selectPostForUser");
    query.setParameter("user", this.getUser());
    this.posts = (List<Post>) query.getResultList();
    System.out.println("populatePostFOrUser called");
}
 
and after the page is loaded, I update the posts field in that method as follows
 
this.posts = (List<Post>)em.createNamedQuery("Post.selectPostsByTags").setParameter("tags", tags).getResultList();
    System.out.println("number of posts selected = " + this.posts.size());
    System.out.println("selected posts for this tag = " + this.posts);
    System.out.println("number of posts selected for tag = " + tags + " " + this.posts.size());
 
this updates the posts field successfully but after that, once again the same populatePostsForUser method is called. It is called everytime some component is re-rendered.
 
This is just an example for what I want to know. My Question is. How can I have control over the jsf components such that I can render/update/execute a jsf component on some ajax event of another component?
 
I would like to know the best ways to communicate between jsf components and render them according to our choice when ajax is concerned.

原文：https://stackoverflow.com/questions/16250215