How to intercept JSF view resolving in order to replace the outcome page?

Question

A certain managed bean has an action method that returns "/private/myview.jsf". However, without changing this code, I want to perform some checks and eventually render the view "/private/other/myview.jsf".

So, in summary, I want to translate "/private/myview.jsf" to "/private/other/myview.jsf" somewhere after the method return and before the actual view rendering.

How to achieve that?

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Environment:

1. Eclipse Luna
2. Java 1.7
3. JSF 2

Current condition

Web application fully operational but not developed to support accessibility features.

Requirement for the next version

To be an application good enough to be used by blind people who uses screen readers.

Details

After some study, we reached the conclusion that we will have to have an accessible version of each page we have nowadays.

We will design such accessible version of each page, the matter is when to show the not accessible version and when to show the accessible version.

We decided that the application will turn to accessible mode (that will not be the default state) when the user clicks a certain link in the top of the page. In accessible mode, only accessible versions of pages are rendered.

We don't want to review all the application, what we want is to intercept some phase of JSF and replace the outcome that should be rendered. For instance, consider the follow:

1. A certain page has a link or a button to another one, let's say "mysettings.xhtml";
2. When in accessible mode, we would like to tell to JSF to not render "mysettings.xhtml", instead "mysettings_ac.xhtml" or "accessible/mysettings.xhtml" should be rendered;
3. Both pages will interact with the very same managed beans and will provide the very same features, but one will be good to the ones who can see and the other will be designed to be comfortable to screen reader users.

Thanks in advance!

Answer 1

So, in summary, I want to translate "/private/myview.jsf" to "/private/other/myview.jsf" somewhere after the method return and before the actual view rendering.

If you're already on JSF 2.2, you can do this by providing a custom ResourceHandeler wherein you return the desired view resource in createViewResource() based on some condition.

public class YourResourceHandler extends ResourceHandlerWrapper {

    private ResourceHandler wrapped;

    public YourResourceHandler(ResourceHandler wrapped) {
        this.wrapped = wrapped;
    }

    @Override
    public ViewResource createViewResource(FacesContext context, final String name) {
        if (someCondition) {
            name = name.replace("/private/", "/private/other/");
        }

        return super.createViewResource(context, name);
    }

    @Override
    public ResourceHandler getWrapped() {
        return wrapped;
    }

}

Which is registered in faces-config.xml as below:

<application>
    <resource-handler>com.example.YourResourceHandler</resource-handler>
</application>

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Or if you're not on JSF 2.2 yet, then use ResourceResolver instead.

public class YourResourceResolver extends ResourceResolver {

    private ResourceResolver parent;

    public YourResourceResolver(ResourceResolver parent) {
        this.parent = parent;
    }

    @Override
    public URL resolveUrl(String path) {
        if (someCondition) {
            path = path.replace("/private/", "/private/other/");
        }

        return parent.resolveUrl(path);
    }

}

Which is registered in web.xml as below:

<context-param>
    <param-name>javax.faces.FACELETS_RESOURCE_RESOLVER</param-name>
    <param-value>com.example.YourResourceResolver</param-value>
</context-param>

Answer 2

As I can see, there can be two probable solutions to it.

1. using redirect() method

   returnAction(){ ExternalContext context = FacesContext.getCurrentInstance().getExternalContext(); context.redirect("/private/other/myview.jsf"); //Relative path might vary based upon your business logic }

2. conditional redirect after action return; we can maintain a navigation rule in faces-config.xml something like below:

    <navigation-rule>
        <navigation-case>
            <from-action>#{yourManagedBean.actionMethod}</from-action>
            <if>#{yourManagedBean.redirectAccessibleFlag}</if>   <!-- We maintain a boolean variable redirectAccessibleFlag in the managed Bean and set its value to true or false conditionally-->
            <to-view-id>/private/other/myview.jsf</to-view-id>
           <redirect/>
        </navigation-case>
    </navigation-rule>

In the second alternative, you can put up the managed bean at ApplicationScope in order to be utilized across multiple JSF pages.

Although these solutions are from the general concepts, they might not necessarily fall in the "somewhere after the method return and before the actual view rendering." But you can check if it solves the purpose.