jsf2 c06 page navigation

8/19/2019 JSF2 C06 Page Navigation

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© 2011 Marty Hall

.and faces-config.xml

Originals of Slides and Source Code for Examples:

http://www.coreservlets.com/JSF-Tutorial/jsf2/

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© 2011 Marty Hall

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Topics in This Section

• Explicit navigation rules

• Explicit bean declarations

• Advanced navigation options – Wildcards in navigation rules

– Conditional navigation rules

– -

• Static navigation

•

5

© 2011 Marty Hall

Explicit Navigation Rules




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JSF Flow of Control

balance.xhtmlIn the previous section, we used

the default ma in s of return.Uses

and

values, where the string returned

by the action controller method

corresponded to the name of the

results page. Now, we will putexplicit navigation rules in faces-

config.xml that say which page

corresponds to each return value.

submit form

Find return ChooseRun Action forward result1.xhtml

Run Setter

Methods

Business

Logic

results

POST request balance.jsf Bean value PageController Method result2.xhtml

...

resultN .xhtml

Uses

# bankForm.somePro ert

to display bean properties

7

faces-config.xml: Overview

• Location – WEB-INF/faces-config.xml

• Purposes – ve nav gat on ru es

• Map return conditions to results pages

– Declare beans• Map bean names to bean classes

– Inject bean properties

– e ne oca es

– Register validators

–

– Register custom components

– …8


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faces-config.xml:

• General format

…

• Navigation rules

/some-start-page.xhtml

return-condition-1

/result-page-1.xhtml-

More navigation-case entries for other conditions

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faces-config.xml: Syntax Details

• General format

…

– JSF 1. x faces-config.xml files are still supported, so youcan run JSF 1. x applications in JSF 2.0 implementationswithout changes.

• However, you must use 2.0 version of faces-config.xml ifou use the new 2.0 features

– Copy a starting-point faces-config.xml file from the jsf- blank application on the Web site

10


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Navigation Rules:

- … .

/starting-page.xhtml

return-value-1

/result-page-1.xhtml

from-outcome>return-value-2


…Interpretation: “if you start on such-and-such a page, press a button, and

the action controller method returns such-and-such a value, go to page 1.

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If the action controller returns some other value, go to page 2. And so on.”

Each form has one navigation-rule with a single from-view-id, but each

navigation-rule can have many navigation-cases.

Pros and Cons of Explicit

• Default mappings (return values=pages) – Simpler to start with. Faster to make quick test cases.

– Redundant if return values are 1-to-1 to results pages

• - . – Better understanding of project.

• Lets ou look in one lace for navi ation rules instead of searching many Java files

– There are even tools that automaticallymake charts of page flow based onfaces-config.xml

– More flexible• Can remap conditions to

other pages later

• Can use wildcards for starting page

• Can use wildcards for outcomes12

I find the arguments in favor of explicit

mappings to be strong, and recommend using

them on most real projects.


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Example

• Overview – Collect a message, then navigate to one of three possible

results pages that display the message. – ,

show an error page

• Implementation – Action controller returns four possible strings: page1,

page2, page3, and too-short

– av ga on ru es n aces-con g.xm map eac o osereturn conditions to results page

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Example: Starting Page.

=" ". .

xmlns:h="http://java.sun.com/jsf/html">

JSF 2.0: Basic Navigation Rules

…

…

Your message:

h:in utText value="# sim leController.messa e " >

…

/h:body> 14


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Example: Managed Bean

@ManagedBeanThis example uses explicit navigation rules,

but does not use ex licit bean declarations.

private String message="";

.

So, the @ManagedBean entry is needed so

that the references in the facelets pages to

#{simpleController.blah} point at this class.

public String doNavigation() {

return("too-short");

} else {

Strin results =

{ "page1", "page2", "page3" };

return(RandomUtils.randomElement(results));

}

}

}

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Example: faces-config.xml

/start-page-1.xhtml

too-short

/error-message.xhtml

page1 /result-page-1.xhtml

page2


page3


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Example: First Results Page.

=" ". .


Result Page 1 =" ". .

rel="stylesheet" type="text/css"/>

tr>Result Pa e 1< th>< tr>

er resu s pages are sm ar.

Your message: "#{simpleController.message}"

/div> 17

Example: Results

18


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© 2011 Marty Hall

Explicit Bean Declarations



JSF Flow of Control

balance.xhtml.Uses

and

submit form

Find return ChooseRun Action forward result1.xhtml

Run Setter Methods

Business

Logic

results

POST request balance.jsf Bean value PageController Method result2.xhtml

...

resultN .xhtml

Uses

# bankForm.somePro ert

to display bean properties

In the previous section, we used

@ManagedBean to give a name to the bean

based on the class name (or, we used

=" "

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.

Now, we declare the bean name explicitly in

faces-config.xml.


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Bean Declarations: Syntax

- …

someName - -

somePackage.SomeClass

- - - -

…

faces-confi >

Scopes are request, session, application, view,

none, custom. They are discussed elsewhere.Unlike with @ManagedBean, there is no default,

- -

21

- -

altogether.

You can also define (“inject”) bean properties in

faces-config. This is discussed in separate tutorial

section.

Pros and Cons of Explicit Bean

• @ManagedBean – Simpler/faster to start with

– Java developer knows the bean name

• xp c ec ara ons n aces-con g.xm – Easier for facelets developer to find bean

• ,knowing the bean class name (as with @ManagedBean)requires you to search many packages to find the class

– scopes (Paul Lee rule)

– Better understanding of beans used in project• One central file lists all managed beans

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I find the arguments in favor of explicit declarations to be weak (as compared to explicit navigations rules, for which I find the arguments to be strong). So, on most real projects I

would mildly recommend the use of @ManagedBean. The exceptions are if I want to inject properties (in which case I would definitely use explicit declarations), or if I have a large

project with many packages (in which case I would at least consider explicit declarations to make it easier to find the beans).


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Example

• Overview – Start with form that collects a message

– Go to either an error page (message too short) or a results

• Implementation – Reuse the same bean as in last exam le

– Use managed-bean• Declare bean explicitly in faces-config.xml, so that the

– Use navigation-rule

• Remap the return conditions so that page1, page2, andpage a po n o e same resu s page

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Example: Starting Page.

=" ". .


…

…

Your message:

h:in utText value="# messa eHandler.messa e " >

…

/h:body> 24


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Example: Managed Bean

package coreservlets;

public class SimpleController2

extends SimpleController {

// Inherits getMessage, setMessage,

// and doNavigation. doNavigation returns

// "too-short", "page1", "page2", or "page3".

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…

-

messageHandler

.

request

-

…

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/start- a e-2.xhtml

too-short /error-message.xhtml

-

page1

/ message-page.xhtml

page2

- - - - -.

page3

/ message-page.xhtml

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Example: Main Results Page.

=" ". .


Message Page

=" ". .

rel="stylesheet" type="text/css"/>

tr>Messa e Pa e< th>< tr>

Your message: "#{ messageHandler.message}"

/div> 28


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Example: Results

29

© 2011 Marty Hall

Rules




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Summary

• Overview – * for from-view-id matches any starting page

– Omitting from-outcome: all other return conditions match• ,

• Application – * for from-view-id

• Multiple forms can share some of the results pageswithout repeating entries in navigation-rule

– - – • Can have multiple return values point at the same results

page. Useful when you want to change results pages

– Temporary results pages with details coming later

– Reusing existing Java code but different rules on results pages31

Example: * for from-view-id

• Problem – Both of the previous examples used the same error page

– The navigation-case was repeated

• – Make a shared entry that maps “too-short” to the error

a e

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faces-config.xml: Before

start- a e-1.xhtml< from-view-id>

too-short /error-message.xhtml

-

/start-page-2.xhtml

too-short


< nav ga on-ru e>

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faces-config.xml: After

*< from-view-id>

too-short


- - - - - -.

/start-page-2.xhtml

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Example:

• Problem – In the second example, we reused Java code from the first

example (good). But, we repeated virtually the samenavi ation-case three times bad .

• Solution – Omit the from-outcome. This means that any return

values not explicitly mentioned are mapped to the sameresults page.

• ,means to redisplay input form. This will be discussed in

the section on validation.

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faces-config.xml: Before

/start-page-2.xhtml

page1

/message-page.xhtml

-

page2

/message-page.xhtml

page3

< o-v ew- > message-page.x m < o-v ew- >

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faces-config.xml: After

/start-page-2.xhtml

/message-page.xhtml

-

37

Conditional Navigation Rules

• Idea – You can put tags that designate when rules apply

• Examplenav ga on-case

success

# user.returnVisitor /welcome-back.xhtml

success

.

/welcome-aboard.xhtml

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Dynamic To-Ids

• Idea – You can compute the destination page directly in faces-

config, rather than indirectly via return value of the actioncontroller method

• Example

/exam-question.xhtml

exam.next uest on age < to-v ew- >

-

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© 2011 Marty Hall

Static Navigation




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Idea

• Situation – Sometimes you don’t want/need Java code

• No input elements•

• Sometimes used for simple testing. But also used in realprojects when you want a button for navigation.

– Instead of this•

• Have the doNav method always return “fixed-page”

– Use this" "… -

– You can use either default mapping or explicit navigation rules todetermine the meaning of “fixed-page”

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Example

• Overview – page-a.xhtml has a button that causes navigation to

page-b.xhtml

– - . page-a.xhtml

• Implementation – Page A

•

– •

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Example: page-a.xhtml

=" ". .


JSF 2.0: Static Navigation …

=" "

Page A

table>

h:commandButton value="Go to Pa e B"

action="page-b"/>

/div> 43

Example: page-b.xhtml

=" ". .


JSF 2.0: Static Navigation

…

=" "

Page B

table>

h:commandButton value="Go to Pa e A"

action="page-a"/>

/div> 44


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Pressing Button and Nothing

• Issue – Many error conditions simply result in the system

redisplaying the form with no warning or error messages

– Set PROJECT_STAGE to Development in web.xml• This is already set in jsf-blank

– Many of the errors cause the process to abort at certain points. Knowing how far things got is very helpful.

• Put a print statement in the controller method

• Put a print statement in the empty constructor – public MyBean() { System.out.println("MyBean built"); }

– Bean should be instantiated twice for request scope

• Put print statements in the bean setter methods47


1. Return value of controller method does notmatch from-outcome of navigation-case

• Remember values are case sensitive

. - -

accepted

Should be from-outcome, not from-action

/accept-registration.jsp

• ,from-outcome

• This situation occurs frequently with Eclipse users thaton’t oo care u y at t e c o ces Ec pse o ers n

popup menu for the navigation-case entries.48


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3. Forgetting # in action of h:commandButton

Should have # here

• This is really a special case of (1), sinceaction="{beanName.methodName}" means the literal

" ". -• In this situation and several others, it is very helpful to

put a print statement in controller method to see if/when

4. Typo in from-view-id• This is a s ecial case of 1 since the from-outcome

applies to nonexistent page

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5. Controller method returns null ,

done accidentally as well.

6. Type conversion error ,

when you submit.• Behavior of redisplaying form is useful here.

See validation section.7. Missing setter method

• You associate textfield with bean property foo, but there is nosetFoo method in your bean.• Debugging hint: You will see printout for bean being

instantiated, but not for controller method

8. Missing h:form• you use : npu ex w no surroun ng : orm, ex e s w

still appear but nothing will happen when you press submit button

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© 2011 Marty Hall

Wrap-Up



Summary

• Explicit navigation rules – ,

understand system page flow more easily

• Explicit bean declarations – It is less clear whether this is better than Mana edBean but in lar e

projects with many packages, this might let you find beans more easily

• Wildcards in navigation rules

– * in from-view-id lets you share results pages across forms – Omitting from-outcome lets you map different return values to the same

results page

• Static navigation – For simple testing, you can use a static string (instead of an EL expression)

for the action of h:commandButton

• Navigation problems – any s ua ons resu n re sp ay ng npu orm

• Most due to return value of Java code not matching from-outcome

– Debugging: set PROJECT_STAGE to Development, trace Java code52

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