Newbie: what is the equivalent of passing request parameters?

Question

Hi-
I am new to JSF. I have read many tutorials and articles. I still don't get one concept about passing parameters. Note: I don't want to store stuff in the session unless I have to.
Let's say I have a page with a list of users. I layout the page with a panelGrid. Each row of the table has the first and last name of the user. If a user clicks on the name of a user on the user list, it should go to the user profile page. The backing bean for the user list page will be the UserListBean. It has a method called getUsers() that returns a List of User objects.
For the View User page, I have a ViewUserBean. The ViewUserBean retrieve the entire profile for that user.
How do I pass the user ID to the ViewUserBean? In struts, I would pass it as a request parameter (I would manually write the link URL with the userID). I know I can use the request like that in JSF, but that seems ugly. I looked at the code of the J2EE bookstore tutorial and it does a funky thing with all sorts of data stored in the session.
What is the best way to request a page and "pass in" a userID?
Thanks for your help.
Adam

Answer 1

I have a case on my current project very similar to your case. What you want, very simply, is an easy way to allow faces to handle URLs like http://www.domain.com/showUserDetails?userId=50
The natural trouble is that when loading the page, there is no action to use to prefetch the User object based on the Request Parameters in JSF.
All the solutions above either rely on the session or they are exceedingly complex. This case is actually very easy to do and is very straight forward using Managed Properties and a Request Scope bean...
Here is the rather straight forward solution I used...
First, make a "ShowUserDetailsBean" which represents the "logic" for this page.
public class ShowUserDetailsBean
    /** Will point to the actual user service after dependency injection*/
    private UserService userService;
    /** Will hold the userId from the HTTP Request Parameters*/
    private String userId;
    /** Will hold a lazy loaded copy of the User object matching userId*/
    private User user;
    public void setUserService(UserService userService) {
        this.userService = userService;  //dependecy injection
    public void setUserId(String userId) {
       this.userId = userId;  //dependency injection
    /** Lazy loads the User object matching the UserId */
    public User getUser() {
        //Trap the case where the URL has no userId
        if (userId == null) return null;
        if (user == null) {
            user = userService.getUser(userId);  //Lazy Load
        return user;
}Next, configure the managed properties in faces-config.xml
<faces-config xmlns="http://java.sun.com/JSF/Configuration">
  <managed-bean>
    <managed-bean-name>userService</managed-bean-name>
    <managed-bean-class>foo.UserServiceImpl</managed-bean-class>
    <managed-bean-scope>application</managed-bean-scope>
  </managed-bean>
  <managed-bean>
    <managed-bean-name>showUserDetails</managed-bean-name>
    <managed-bean-class>foo.ShowUserDetailsBean</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
    <managed-property>
      <property-name>userService</property-name>
      <property-class>foo.UserService</property-class>
      <value>#{userService}</value>
    </managed-property>
    <managed-property>
      <property-name>userId</property-name>
      <property-class>java.lang.String</property-class>
      <value>#{param.userId}</value>
    </managed-property>
  </managed-bean>Finally, you just make your webpage as you normally would...
<h:outputText value="#{showUserDetails.user.userId}"/>
<h:outputText value="#{showUserDetails.user.firstName}"/>
<h:outputText value="#{showUserDetails.user.lastName}"/>
Now you're ready to test, so you visit the page
http://www.domain.com/showUserDetails?userId=50
And your user details with userId=50 appears!
It's just that simple!
Regards,
Doug
Caveat: I haven't added any sample logic to handle cases where you visit:
http://www.domain.com/showUserDetails
without specifying a userId. I suggest you add some basic logic to your page to handle this case more gracefully.