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

## Basic Requirements of a JavaServer Faces Application

In addition to configuring your application, you must satisfy other requirements of JavaServer Faces applications, including properly packaging all the necessary files and providing a deployment descriptor. This section describes how to perform these administrative tasks.

JavaServer Faces applications can be packaged in a WAR file, which must conform to specific requirements to execute across different containers. At a minimum, a WAR file for a JavaServer Faces application may contain the following:

- A web application deployment descriptor, called `web.xml`, to configure resources required by a web application (required)

- A specific set of JAR files containing essential classes (optional)

- A set of application classes, JavaServer Faces pages, and other required resources, such as image files

A WAR file may also contain:

- An application configuration resource file, which configures application resources

- A set of tag library descriptor files

For example, a Java Server Faces web application WAR file using Facelets typically has the following directory structure:

    $PROJECT_DIR
    [Web Pages]
    +- /[xhtml or html documents]
    +- /resources
    +- /WEB-INF
       +- /web.xml
       +- /beans.xml (optional)
       +- /classes (optional)
       +- /lib (optional)
       +- /faces-config.xml (optional)
       +- /*.taglib.xml (optional)
       +- /glassfish-web.xml (optional)

The `web.xml` file (or web deployment descriptor), the set of JAR files, and the set of application files must be contained in the `WEB-INF` directory of the WAR file.

### Configuring an Application with a Web Deployment Descriptor

Web applications are commonly configured using elements contained in the web application deployment descriptor, `web.xml`. The deployment descriptor for a JavaServer Faces application must specify certain configurations, including the following:

- The servlet used to process JavaServer Faces requests

- The servlet mapping for the processing servlet

- The path to the configuration resource file, if it exists and is not located in a default location

The deployment descriptor can also include other, optional configurations, such as those that

- Specify where component state is saved

- Encrypt state saved on the client

- Compress state saved on the client

- Restrict access to pages containing JavaServer Faces tags

- Turn on XML validation

- Specify the Project Stage

- Verify custom objects

This section gives more details on these configurations. Where appropriate, it also describes how you can make these configurations using NetBeans IDE.

#### Identifying the Servlet for Lifecycle Processing

A requirement of a JavaServer Faces application is that all requests to the application that reference previously saved JavaServer Faces components must go through `javax.faces.webapp.FacesServlet`. A `FacesServlet` instance manages the request-processing lifecycle for web applications and initializes the resources required by JavaServer Faces technology.

Before a JavaServer Faces application can launch its first web page, the web container must invoke the `FacesServlet` instance in order for the application lifecycle process to start. See The Lifecycle of a JavaServer Faces Application for more information.

The following example shows the default configuration of the `FacesServlet`:

    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
    </servlet>

You will provide a mapping configuration entry to make sure that the `FacesServlet` instance is invoked. The mapping to `FacesServlet` can be a prefix mapping, such as `/faces/`, or an extension mapping, such as `.xhtml`. The mapping is used to identify a page as having JavaServer Faces content. Because of this, the URL to the first page of the application must include the URL pattern mapping.

The following elements specify a prefix mapping:

    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>/faces/*</url-pattern>
    </servlet-mapping>
    ...
    <welcome-file-list>
        <welcome-file>faces/greeting.xhtml</welcome-file>
    </welcome-file-list>

The following elements, used in the tutorial examples, specify an extension mapping:

    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>*.xhtml</url-pattern>
    </servlet-mapping>
    ...
    <welcome-file-list>
        <welcome-file>index.xhtml</welcome-file>
    </welcome-file-list>

When you use this mechanism, users access the application as shown in the following example:

    http://localhost:8080/guessNumber

In the case of extension mapping, if a request comes to the server for a page with an `.xhtml` extension, the container will send the request to the `FacesServlet` instance, which will expect a corresponding page of the same name containing the content to exist.

To minimize clutter and allow simple, friendly URLs, you can have extensionless URLs by manually exact mapping the `FacesServlet` to the existing prefix and suffix mapping options in `web.xml`, one or more times.

If you are using NetBeans IDE to create your application, a web deployment descriptor is automatically created for you with default configurations. If you created your application without an IDE, you can create a web deployment descriptor.

#### To Specify a Path to an Application Configuration Resource File

As explained in Application Configuration Resource File, an application can have multiple application configuration resource files. If these files are not located in the directories that the implementation searches by default or the files are not named `faces-config.xml`, you need to specify paths to these files.

To specify these paths using NetBeans IDE, do the following.

1. Expand the node of your project in the Projects tab.

2. Expand the Web Pages and WEB-INF nodes that are under the project node.

3. Double-click `web.xml`.

4. After the `web.xml` file appears in the editor, click General at the top of the editor window.

5. Expand the Context Parameters node.

6. Click Add.

7. In the Add Context Parameter dialog box:

8. Enter `javax.faces.CONFIG_FILES` in the Parameter Name field.

9. Enter the path to your configuration file in the Parameter Value field.

10. Click OK.

11. Repeat steps 1 through 7 for each configuration file.

#### To Specify Where State Is Saved

For all the components in a web application, you can specify in your deployment descriptor where you want the state to be saved, on either client or server. You do this by setting a context parameter in your deployment descriptor. By default, state is saved on the server, so you need to specify this context parameter only if you want to save state on the client. See Saving and Restoring State for information on the advantages and disadvantages of each location.

To specify where state is saved using NetBeans IDE, do the following.

1. Expand the node of your project in the Projects tab.

2. Expand the Web Pages and WEB-INF nodes under the project node.

3. Double-click `web.xml`.

4. After the `web.xml` file appears in the editor window, click General at the top of the editor window.

5. Expand the Context Parameters node.

6. Click Add.

7. In the Add Context Parameter dialog box:

8. Enter `javax.faces.STATE_SAVING_METHOD` in the Parameter Name field.

9. Enter `client` or `server` in the Parameter Value field.

10. Click OK.

If state is saved on the client, the state of the entire view is rendered to a hidden field on the page. The JavaServer Faces implementation saves the state on the server by default. Duke’s Forest saves its state on the client.

### Configuring Project Stage

Project Stage is a context parameter identifying the status of a JavaServer Faces application in the software lifecycle. The stage of an application can affect the behavior of the application. For example, error messages can be displayed during the Development stage but suppressed during the Production stage.

The possible Project Stage values are as follows:

- `Development`

- `UnitTest`

- `SystemTest`

- `Production`

Project Stage is configured through a context parameter in the web deployment descriptor file. Here is an example:

    <context-param>
        <param-name>javax.faces.PROJECT_STAGE</param-name>
        <param-value>Development</param-value>
    </context-param>

If no Project Stage is defined, the default stage is `Production`. You can also add custom stages according to your requirements.

### Including the Classes, Pages, and Other Resources

When packaging web applications using the included build scripts, you’ll notice that the scripts package resources in the following ways.

- All web pages are placed at the top level of the WAR file.

- The `faces-config.xml` file and the `web.xml` file are packaged in the `WEB-INF` directory.

- All packages are stored in the `WEB-INF/classes/` directory.

- All application JAR files are packaged in the `WEB-INF/lib/` directory.

- All resource files are either under the root of the web application `/resources` directory or in the web application’s classpath, the `META-INF/resources/`resourceIdentifier directory. For more information on resources, see Web Resources.

When packaging your own applications, you can use NetBeans IDE or you can use XML files such as those created for Maven. You can modify the XML files to fit your situation. However, you can continue to package your WAR files by using the directory structure described in this section, because this technique complies with the commonly accepted practice for packaging web applications.

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