Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Loading JavaScript as a Resource

The JavaScript resource file bundled with JavaServer Faces technology is named `jsf.js` and is available in the `javax.faces` library. This resource library supports Ajax functionality in JavaServer Faces applications.

If you use the `f:ajax` tag on a page, the `jsf.js` resource is automatically delivered to the client. It is not necessary to use the `h:outputScript` tag to specify this resource. You may want to use the `h:outputScript` tag to specify other JavaScript libraries.

To use a JavaScript resource directly with a `UIComponent`, you must explicitly load the resource as described in either of the following topics:

- Using JavaScript API in a Facelets Application – Uses the `h:outputScript` tag directly in a Facelets page

- Using the @ResourceDependency Annotation in a Bean Class – Uses the `javax.faces.application.ResourceDependency` annotation on a `UIComponent` Java class

### Using JavaScript API in a Facelets Application

To use the JavaScript resource API directly in a web application, such as a Facelets page:

1. Identify the default JavaScript resource for the page with the help of the `h:outputScript` tag.

   For example, consider the following section of a Facelets page:

       <h:form>
           <h:outputScript name="jsf.js" library="javax.faces" target="head"/>
       </h:form>

   Specifying the target as `head` causes the script resource to be rendered within the `head` element on the HTML page.

2. Identify the component to which you would like to attach the Ajax functionality.

3. Add the Ajax functionality to the component by using the JavaScript API. For example, consider the following:

       <h:form>
           <h:outputScript name="jsf.js" library="javax.faces" target="head">
           <h:inputText id="inputname" value="#{userBean.name}"/>
           <h:outputText id="outputname" value="#{userBean.name}"/>
           <h:commandButton id="submit" value="Submit"
                            onclick="jsf.ajax.request(this, event,
                                     {execute:'inputname',render:'outputname'});
                                     return false;" />
       </h:form>

   The `jsf.ajax.request` method takes up to three parameters that specify source, event, and options. The source parameter identifies the DOM element that triggered the Ajax request, typically `this`. The optional event parameter identifies the DOM event that triggered this request. The optional options parameter contains a set of name/value pairs from Table 13-5.

Table 13-5 Possible Values for the Options Parameter

Name | Value
`execute` | A space-delimited list of client identifiers or one of the keywords listed in Table 13-2. The identifiers reference the components that will be processed during the Execute phase of the lifecycle.
`render` | A space-delimited list of client identifiers or one of the keywords listed in Table 13-2. The identifiers reference the components that will be processed during the render phase of the lifecycle.
`onevent` | A `String` that is the name of the JavaScript function to call when an event occurs.
`onerror` | A `String` that is the name of the JavaScript function to call when an error occurs.
`params` | An object that may include additional parameters to include in the request.

+ If no identifier is specified, the default assumed keyword for the `execute` attribute is `@this`, and for the `render` attribute it is `@none`.

+ You can also place the JavaScript method in a file and include it as a resource.

### Using the @ResourceDependency Annotation in a Bean Class

Use the `javax.faces.application.ResourceDependency` annotation to cause the bean class to load the default `jsf.js` library.

To load the Ajax resource from the server side:

1. Use the `jsf.ajax.request` method within the bean class.

   Note: This method is usually used when creating a custom component or a custom renderer for a component.

   The following example shows how the resource is loaded in a bean class:

       @ResourceDependency(name="jsf.js" library="javax.faces" target="head")

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