JSF: call backing-bean method without rendering th

2020-03-08 00:04发布

问题:

Is it possible to use a JSF (PrimeFaces) page in the following fashion ? :

external application (not JSF-based) does an HTTP GET with URL parameters
JSF page reads those parameters (e.g. as described here) and invokes a backing bean business method, without rendering anything to the user's browser
The user is transparently sent to a page corresponding to the navigation outcome of the backing bean method invoked in step 2.

In other words, the PrimeFaces page of step 2 is involved only for the side effect of calling the backing-bean business method and is never displayed. The user after clicking on a link on the external application of step 1 lands in the page of step 3.

回答1:

Use <f:viewParam> to set GET parameters as bean properties and use <f:event> to execute a bean action and use NavigationHandler to perform navigation programmatically.

View:

<f:metadata>
    <f:viewParam name="foo" value="#{bean.foo}" />
    <f:viewParam name="bar" value="#{bean.bar}" />
    <f:event type="preRenderView" listener="#{bean.action}" />
</f:metadata>

Bean:

public void action() {
    // ...

    FacesContext context = FacesContext.getCurrentInstance();
    NavigationHandler navigationHandler = context.getApplication().getNavigationHandler();
    navigationHandler.handleNavigation(context, null, "outcome");
}

Note that, depending on the concrete functional requirement, JSF might not necessarily be the right tool for the job. I'd investigate if you couldn't better use a servlet filter or even a plain servlet for the purpose.