This application will make you understand how Model (M), View (V), Controller (C) architecture is implemented in JavaServer Faces. This application will make use of UI components, Validator, Navigation and Bean component available with JSF.
This application will take a user First Name and Last Name. Later these fields will be validated by JSF and using the controller bean and Navigation rule the output will be displayed. This application will also introduce a UI component which is a submit button.
To run this tutorial, as a minimum you will be required to have installed the following prerequisite software:
- Sun JDK 6.0+ (J2SE 1.6)
- Eclipse IDE for Java EE Developers, which is platform specific
- Apache Geronimo Eclipse Plugin 2.1.x
- Apache Geronimo Server 2.1.x
Geronimo version 2.1.x, Java 1.5 runtime, and Eclipse Ganymede are used is used in this tutorial but other versions can be used instead (e.g., Geronimo version 2.2, Java 1.6, Eclipse Europa)
Details on installing eclipse are provided in the Development environment section. This tutorial is organized in the following sections:
Once you have all the prerequisites installed, follow the following steps to create a project with Eclipse.
Setting Eclipse for application development
- Launch Eclipse and create a dynamic Web project as shown in the figure.
- Give the fields for the Web Project as shown in the following figure.
- Select Finish.
- Right click on the SimpleJSF project and select Properties, then select Project Facets.
- Check the box for JavaServerFaces and under the Version tab select 1.2 as the version. Select the Further configuration required... indicator to display the JSF Capabilities pane.
- On the JSF Capabilities window check the box and select new as shown in the figure.
- The next window is used to create a JSF Implementation library. Give the library name as JSFCustomLibrary and add the following jars. Select Finish once done. See the figure below:
- Check Deploy and modify the URL pattern to *.jsf as shown in the figure. Select Finish.
This finishes the setting up of the Eclipse IDE for application development.
Define and Implement the application Model (M)
The Model as suggested by MVC architecture handles data and logic of the application. In an enterprise application. Java Beans are used to represent collection of data and operation on that data. In JSF we use Java Beans to define the Model.
- Under the project explorer right click on the SimpleJSF project and create a new class.
- Fill the New Java Class form with jsf as the package name and FirstName as the bean class name. Select Finish once done.
- Add the following code to the FirstName bean class:
- Create a second Bean class LastName and add the following code to the class: This completes the Model definition and implementation of the bean classes.
Define and implement Model (M) objects to Controller
- In a JSF application the Controller is implemented by a configuration file called
WebContent/WEB-INF/faces-config.xml. Double click on the file. This will open the Faces Configuration Editor.
- Select the ManagedBean tab in the editor. Select the request Managed Bean Element and select Add.
- Choose the Using an existing Java class option, select Browse. Give the search element as FirstName and select OK.
- Select Finish on the next window. Similarly add the other bean LastName. Now select the Source tab in the Faces configuration Editor. It displays the bean components (i.e., the Model) in the controller.
This completes the description of Model to Controller.
Define and implement View (V) in application
- Right click on WebContent and create a new folder with the name pages.
- Right click on pages folder and create a JSP called
login.jsp. Select Finish.
- Similarly create another JSP page called
- Now we have to include the Tag Library Descriptors (TLD) in our application. Geronimo comes packaged with the required TLD's, which can be found in:
- To add these two TLD's in the application, in Eclipse under the Project Explorer right click on WEB-INF. Create a folder called tld. Copy
myfaces_core.tldto this folder.
- The next step is to populate
welcome.jspwith data Lets now try to understand what each line of code represents.
- The first two lines in
login.jspdefines two tag libraries These two sets of tags are defined by JSF. The first one with the namespace "h" is used to generate html views. The second one with the namespace "f" handles the core functionalities of JSF like type conversions, validations and listeners for input from user.
- The next few lines contains the usual html tags
- The tag <f:view> represents the start of JSF code.
- This line of code Represents the input tag. The id="firstName" and value="firstName.name" comes from the Managed Bean.
- The first two lines in
- Using the Faces Configuration Editor, select firstName bean under Managed Bean tab. The Managed Bean Name is firstName. See the figure below.
This completes the implementation of View (V) in the application. The other tags <f:validateLength> and <h:commandButton> will be explained in the next section.
Define the Validator Component
The code <f:validateLength minimum="4" maximum="10"/> defines the input text length to be minimum of 4 characters and maximum of 10 characters. This is the standard validation provided by core tag libraries. Other examples of validators are Validate Long Range tag, Validate Double Range tag , and so on. JSF also provides a Validator interface which can be implemented to create custom validators.
The code <h:message for="" style="color: red;"/> defines the error message. When the user inputs the controller validates each of the inputs. If the inputs are invalid Controller displays the same page again with an error message for the errors. The color:red suggests that the error message will be displayed in red color.
Define and implement the View navigation by Controller (C)
This step uses the JSP page navigation in the order of user inputs and validation by controller. If all the inputs are valid than the controller performs the action as suggested by the HTML form. This action is submitted by the HTML form as a command button.
The code in the
input.jsp <h:commandButton id="submit" action="validated" value="Enter" /> checks to determine if all the inputs are valid. This is the button which submits the form to controller if all inputs are valid. In this case the commandButton tells the controller to execute the validated action if all the inputs are valid.
The pages navigation in a JSF applicaiton is defined by
faces-config.xml. Follow the steps before to define the pages navigation.
- Launch the Faces Configuration Editor by double clicking on
- Select the Navigation Rule tab in the Configuration Editor. Under the Palette window select Page. This will select a PageFlow Page GUI object.
- Drag the mouse over the Navigation Rule Window and click on the window. This will give a Select JSP File window. Select the
login.jspas shown in the figure and select OK.
- Similarly add the
welcome.jsppage on the Navigation Rule window. See the figure below:
- Select Link from the Palette window and join the two pages as shown in the figure:
- Select the link between the two pages and go to properties view and set the value for From Outcome field as validated. This is because of the tag <h:commandButton id="submit" action="validated" value="Enter" />. Once all the inputs are valid the action taken is validated. See the figure.
- Once done have a look the Source tab in the Faces Navigation Editor. A <navigation-rule> tag has been introduced into the
faces-config.xml. This rule instructs the Controller that if all the inputs are valid from a form in the
/pages/login.jsp, and the action is validated, then go to page
- Now lets add a
index.jspunder WebContent as follows: What is the
login.jsfin the forward path tag. If you look at the
web.xml, *.jsf is used as the URL pattern to suggest that forwarded page be taken care by Java Server Faces Servlet.
This completes the Application Development process. The next step is to deploy and test the application.
Deploy and Test the application
Right click on the project SimpleJSF and select Run As -> Run On Server. This will deploy the sample on the Apache Geronimo Server and a Login page will be launched.
Lets give some sample inputs:
Sample Input #1:
First Name: Mickey
Last Name: Mouse
Both the First Name as well as Last Name fulfills the validation rules, so this form will be submitted to controller and according to the navigation rule controller will launch a
Sample Input #2:
First Name: Mic
Last Name: Mouse
First Name should be minimum of length=4 but in this case First Name is of length=3. In this case validation will fail and an error message will be generated by controller for First Name field.
Sample Input #3:
First Name: Mickey
Last Name: Mo
Last Name should be minimum of length=3 but in this case Last Name is of length=2. In this case validation will fail and an error message will be generated by controller for Last Name field.