JavaServer Faces Jeff Schmitt October 5, 2006

Introduction to JSF Presents a standard framework for building presentation tiers for web applications Provides a set of presentation user interfaces (UI) components Provides an event model for wiring the interactions between the UI and the application objects Unlike servlet API, does not focus on low-level HTTP request handling Included in J2EE framework IDE-friendly, can allow drag-drop UI coding

JSF Advantages Custom UI controls to create complex interfaces Event handling – events are invoked when forms are submitted. Events can respond to particular buttons, changes in values, user selections, etc. Managed beans –In JSP, you can use to automatically save request parameters in a bean. –JSF extends this capability and adds in several utilities, which greatly simplifies processing of request parameters JSF Expression Language for accessing bean properties and collection elements

JSF Advantages Form field validation and conversion –insure form values are in correct format –Convert from string to various other types XML and property file-based configuration allows changes to application without changing Java code Encourages consistent use of MVC throughout the application

JSF Disadvantages Steep learning curve -- requires large JSF API as well as JSP a nd servlet APIs Less transparent – much is going on that you cannot see Relatively new – less documentation and less support from IDE Less flexible -- cannot depart from the approach given by framework. Note: this consistency can be an advantage

JSF Sample Application Library book management system User login (borrower or librarian privileges) Librarian –Add a book –Check in a book Borrower and Librarian –View all available books –Review all books –Check out a book

Faces Servlet Configured in web.xml URL pattern: *.faces (typically) Servlet Intercepts request, processes request parameters, creates events that call user code XML configuration file: faces-config.xml –I18n –Navigation rules –Bean definitions Implements JSF Lifecycle (next slide)

JSF Lifecycle JSF creates “component tree” –Each element corresponds to a UI value Steps in processing request –1 Restore view –2 Apply request values –3 Process validations –4 Update model values –5 Invoke application –6 Render response

1 Restore view Matches request to a view definition, usually a JSP file Default view definition adds.jsp to the same request –/view/books.faces -> /view/books.jsp Build component tree based on the view definition –Used by all subsequent processing steps –An object hierarchy –State maintained across multiple requests

2 Apply request values Analyze HTTP parameters Map parameters to specific UI components on the page If no parameters, skip to step 6 Render request

3 Process validations Cycle through all of the input validations for the components If any validations fail –render page with original data –Warning messages may be displayed

4 Update model values If the validation process succeeds Underlying Java beans associated with each UI component are updated

5 Invoke application After the model has been updated Invoke any business-logic acions requested by the user Determine a result code to be used in 6 Render response

6 Render response Render a response for the user Depending on result code returned in 5 Invoke Application, –view the page that was originally requested –or render a different page

<!DOCTYPE faces-config PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN" " en ISBNValidator com.oreilly.jent.jsf.library.validator.ISBNValidator … faces-config.xml

Navigation rules First major part of faces-config.xml Second major part is Managed beans If faces-config.xml gets too big –Split it into parts –Add an initialization parameter in web.xml javax.faces.CONFIG_FILES –Good for large projects with multiple developers where each module has separate settings

Navigation rules Each navagation-rule is like a flowchart “if” with one entry and multiple labelled exits –A single to match the URI being processed –When control returns from the module named here, a result string is returned. For example: success, failure, verify, login –Multiple entries matches a string gives next URI to forward to

* login /login/index.jsp home /index.jsp viewbooks /view/listbooks.jsp Navigation rules

/index.jsp addbook /view/addbook.jsp adminbooks /view/adminbooks.jsp

Navigation rules /login/index.jsp success /login/success.jsp failure /login/index.jsp

Managed Beans Second section of faces-config.xml Glues the UI given by jsp files to the business logic of your application Are simply JavaBeans following standard rules –a zero-argument (empty) constructor -- either by explicitly defining such a constructor or omit all constructors –no public instance variables (fields) –use accessor methods instead of allowing direct access to fields –accessed through methods called getXxx and setXxx –If class has method getTitle that returns a String, class issaid to have a String property named title –Boolean properties use isXxx instead of getXxx – For more on beans, see

Managed Beans JSF beans also have action methods –Invoked by JSF in response to a user action or event –Contain the code that manipulates the data model behind your application –In STRUTS these are called the Action classes and have to be superclasses of Action Two kinds of managed beans, although no technical difference between the two –Model beans – focus on data model of application –Backing beans – focus on UI of the application

Managed Beans Beans have four possible scopes – not quite the same as JSP/servlet scopes Application – entire application shares a single instance Session – new instance of bean when new user begins accessing Request – new instance for each request Scopeless – accessed by other beans and garbage collected like any other java object when no longer referred to by any object

Managed beans library com.oreilly.jent.jsf.library.model.Library application usersession com.oreilly.jent.jsf.library.session.UserSession session loginform com.oreilly.jent.jsf.library.backing.LoginForm request

Managed beans addbookform com.oreilly.jent.jsf.library.backing.AddBookForm request bookdisplayform com.oreilly.jent.jsf.library.backing.BookDisplayForm session library #{library}

JSF Expression language Similar but not identical to JSP EL Allow reference to the managed beans –Retrieving values from beans –Telling JSF components which bean properties to update –In some cases, same expression does both General syntax: #{identifiers and modifiers} Example: –uses a JSF HTML-writing tag <h: –Same expression both retrieves value from bean and –Tells JSF where to store submitted value from form –Uses two beans

JSF EL – built-in objects applicationScope - containing all application-scope managed beans Cookie facesContext - the FacesContext instance associated with the current request header - a map with HTTP request headers, one value per name headerValues - a map with HTTP request headers, containing all values initParam - a map with HTTP request parameters, containing all values param - a map with HTTP request parameters, one value per name paramValues - a map with HTTP request parameters requestScope - a map containing all request-scope managed beans sessionScope - a map containing all session-scope managed beans view - the UIViewRoot object associated with the current request

The library application index.jsp –<f:view – -- no action attribute –usersession.currentUser.username –rendered – a button that appears only for librarian –<h:outputText –<h:commandButton –<h:commandLink

Navigation <h:commandButton action=addbook addbook /view/addbook.jsp

Navigation case wildcard Wildcards allow a set of rules that applies to outcomes originating from any view * /view/addbook.jsp

Navigation – dynamic actions Control navigation based on outcomes confirmCredentials() -- a method in the backing bean associated with login Returns a string “success” or “failure”