Configuring Navigation Rules
As explained in Navigation Model, navigation is a set of rules for choosing the next page to be displayed after a button or hyperlink component is clicked. Navigation rules are defined in the application configuration resource file.
Each navigation rule specifies how to navigate from one page to a set of other pages. The JavaServer Faces implementation chooses the proper navigation rule according to which page is currently displayed.
After the proper navigation rule is selected, the choice of which page to access next from the current page depends on two factors:
The outcome can be anything the developer chooses, but Table 13-3 lists some outcomes commonly used in web applications.
Usually, the action method performs some processing on the form data of the current page. For example, the method might check whether the user name and password entered in the form match the user name and password on file. If they match, the method returns the outcome
success
. Otherwise, it returns the outcomefailure
. As this example demonstrates, both the method used to process the action and the outcome returned are necessary to determine the proper page to access.Here is a navigation rule that could be used with the example just described:
<navigation-rule> <from-view-id>/logon.jsp</from-view-id> <navigation-case> <from-action>#{LogonForm.logon}</from-action> <from-outcome>success</from-outcome> <to-view-id>/storefront.jsp</to-view-id> </navigation-case> <navigation-case> <from-action>#{LogonForm.logon}</from-action> <from-outcome>failure</from-outcome> <to-view-id>/logon.jsp</to-view-id> </navigation-case> </navigation-rule>This navigation rule defines the possible ways to navigate from
logon.jsp
. Eachnavigation-case
element defines one possible navigation path fromlogon.jsp
. The firstnavigation-case
says that ifLogonForm.logon
returns an outcome ofsuccess
, thenstorefront.jsp
will be accessed. The secondnavigation-case
says thatlogon.jsp
will be rerendered ifLogonForm.logon
returnsfailure
.The configuration of an application's page flow consists of a set of navigation rules. Each rule is defined by the
navigation-rule
element in thefaces-config.xml
file.The navigation rules of the Duke's Bookstore application are very simple. Here are two complex navigation rules that could be used with the Duke's Bookstore application:
<navigation-rule> <from-view-id>/catalog.jsp</from-view-id> <navigation-case> <from-outcome>success</from-outcome> <to-view-id>/bookcashier.jsp</to-view-id> </navigation-case> <navigation-case> <from-outcome>out of stock</from-outcome> <from-action>#{catalog.buy}
</from-action> <to-view-id>/outofstock.jsp</to-view-id> </navigation-case> <navigation-case> <from-outcome>error</from-outcome> <to-view-id>/error.jsp</to-view-id> </navigation-case> </navigation-rule>The first navigation rule in this example says that the application will navigate from
catalog.jsp
toThe second navigation rule says that the application will navigate from any page to
error.jsp
if the application encountered an error.Each
navigation-rule
element corresponds to one component tree identifier defined by the optionalfrom-view-id
element. This means that each rule defines all the possible ways to navigate from one particular page in the application. If there is nofrom-view-id
element, the navigation rules defined in thenavigation-rule
element apply to all the pages in the application. Thefrom-view-id
element also allows wildcard matching patterns. For example, thisfrom-view-id
element says that the navigation rule applies to all the pages in thebooks
directory:As shown in the example navigation rule, a
navigation-rule
element can contain zero or morenavigation-case
elements. Thenavigation-case
element defines a set of matching criteria. When these criteria are satisfied, the application will navigate to the page defined by theto-view-id
element contained in the samenavigation-case
element.The navigation criteria are defined by optional
from-outcome
andfrom-action
elements. Thefrom-outcome
element defines a logical outcome, such assuccess
. Thefrom-action
element uses a method expression to refer to an action method that returns aString
, which is the logical outcome. The method performs some logic to determine the outcome and returns the outcome.The
navigation-case
elements are checked against the outcome and the method expression in this order:
- Cases specifying both a
from-outcome
value and afrom-action
value. Both of these elements can be used if the action method returns different outcomes depending on the result of the processing it performs.- Cases specifying only a
from-outcome
value. Thefrom-outcome
element must match either the outcome defined by theaction
attribute of theUICommand
component or the outcome returned by the method referred to by theUICommand
component.- Cases specifying only a
from-action
value. This value must match theaction
expression specified by the component tag.When any of these cases is matched, the component tree defined by the
to-view-id
element will be selected for rendering.Using NetBeans 5.5, you can configure a navigation rule by doing the following:
- After opening your project in NetBeans 5.5, expand the project node in the Projects pane.
- Expand the Web Pages and WEB-INF nodes of the project node.
- Double-click
faces-config.xml
.- After
faces-config.xml
opens in the editor pane, right-click in the editor pane.- Select JavaServer Faces
Add Navigation Rule.
- In the Add Navigation Rule dialog:
- Right-click again in the editor pane.
- Select JavaServer Faces
Add Navigation Case.
- In the Add Navigation Case dialog:
- From the From View menu, select the page that represents the starting view for the navigation rule (from step 6a).
- (optional) In the From Action field, enter the action method invoked when the component that triggered navigation is activated.
- (optional) In the From Outcome field, enter the logical outcome string that the activated component references from its
action
attribute.- From the To View menu, select or browse for the page that will be opened if this navigation case is selected by the navigation system.
- Click Add.
Referencing a Method That Performs Navigation explains how to use a component tag's
action
attribute to point to an action method. Writing a Method to Handle Navigation explains how to write an action method.