How to call a managed bean method from an outputLink?

StackOverflow https://stackoverflow.com/questions/21792950

  •  12-10-2022
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Frage

This may have been covered somewhere but I'm having trouble forming the question for search engine and no goods leads thus far.

I'm working on a page that acts as entity view. Lots of results come from database and only a handful are displayed at a time. So you can imagine that I want to build a list of links that take user to another page of entities. This is all my code - no PrimeFaces or any other front-end nifty pagination solutions. At least for now.

To the code: 

@Named
@SessionScoped
public class ArticleIndexBean {
    List<Article> articleList=new ArrayList<>();
    List<Article> articleSubList=new ArrayList<>();

@PostConstruct
public void loadScreenSupport() {
    search();
    toEntityPage(1);
    }

protected void search() {
        // this method sets articleList which is the full list fetched from the database
    }

public void toEntityPage(int pageNumber) {
       // this method sets articleSubList which is a subset of articleList 
}

Each page link needs to call toEntiyPage(n). I am aware of commandLink but I want to avoid a POST request. Also, the bean is currently session scoped and I will try to make it conversation scoped later. It will certainly NOT be request scoped, as I don't want to do a full db search each time a user wants to jump to another page. So @PostConstruct won't help, either.

So with a menu like this: 1 * 2 * 3 * 4 * 5 how do I code an outputLink or any other type of link that will call my ArticleIndexBean.toEntityPage(int) via a GET request?

Solution

Based on input from Laurent, I added a currentEntityPageNumber property and a toCurrentEntityPage() method to my bean. The toCurrentEntityPage() simply calls toEntityPage(getCurrentEntityPageNumber()).

<html lang="en"
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:h="http://java.sun.com/jsf/html"
  xmlns:f="http://java.sun.com/jsf/core"
  xmlns:ui="http://java.sun.com/jsf/facelets"
  >

<f:metadata>
    <f:viewParam name="pn" value="#{articleIndexBean.currentEntityPageNumber}" />
    <f:event type="preRenderView" listener="#{articleIndexBean.toCurrentEntityPage()}" />
</f:metadata>

<c:forEach var="pageNumber" begin="1" end="${articleIndexBean.getEntityPageCount()}">   
                <h:outputLink value="ar_index.xhtml">
                        <h:outputText value="${pageNumber}" />
                        <f:param name="pn" value="${pageNumber}" />
                </h:outputLink>
    </c:forEach>

It would certainly be better if we could call toEntityPage(pageNumber) directly but this works fine.

War es hilfreich?

Lösung

Assuming you are using JSF 2.2, you could use the viewParam to retrieve the page in the GET parameters and viewAction to call a method before the rendering (actually called in the INVOKE_APPLICATION phase by default).

Facelets:

<f:metadata>
    <f:viewParam name="page" value="#{articleIndexBean.entityPage}" />
    <f:viewAction action="#{articleIndexBean.loadScreenSupport}" />
</f:metadata>

If you are using JSF 2.0 or JSF 2.1, then you have to replace viewAction by:

<f:event type="preRenderView" listener="#{articleIndexBean.loadScreenSupport}" />

Java:

@Named
@SessionScoped
public class ArticleIndexBean {
    List<Article> articleList=new ArrayList<>();
    List<Article> articleSubList=new ArrayList<>();

    int pageNumber = 1; // by default first page

    public void loadScreenSupport() {
        search();
        toEntityPage(pageNumber);
    }

    public int getPageNumber() {
        return pageNumber;
    }

    public void setPageNumber(int pageNumber) {
        this.pageNumber = pageNumber;
    }

    protected void search() {
        // this method sets articleList which is the full list fetched from the database
    }

    public void toEntityPage(int pageNumber) {
       // this method sets articleSubList which is a subset of articleList 
    }
}

The link to the page is then easy:

<h:outputLink value="resultPage.xhtml">
    <h:outputText value="2" />
    <f:param name="page" value="2" />
</h:outputLink>

Reference:

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