03 Managed Beans

8/3/2019 03 Managed Beans

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2009 Marty Hall

JSF: Managed BeansOriginals of Slides and Source Code for Examples:

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

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2009 Marty Hall

For live training on JSF 1.x or 2.0, please seecourses a p: courses.coreserv e s.com .Taught by the author ofCore Servlets and JSP, More

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Topics in This Section

Using beans to represent requestparameters

Data that came from the form submission

Data that came from the business logic

Outputting bean properties

JSP 2.0 expression language

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2009 Marty Hall

Background: Beans




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What Are Beans?

Java classes that follow certain conventions ust ave a zero-argument empty constructor

You can satisfy this requirement either by explicitlydefining such a constructor or by omitting all constructors

ou ave no pu c ns ance var a es e s I hope you already follow this practice and use accessor

methods instead of allowing direct access to fields

called getXxx and setXxx

If class has method getTitle that returns a String, class is

Boolean properties use isXxxinstead of getXxx

Unlike in Struts, JSF beans need extend no special class" ",

Beans that represent the form (form parameters, action controllermethods, event handling methods, placeholders for results data).

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Why You Should Use Accessors,

To be a bean, you cannot have public fields

So, you should replacepublic double speed;

wprivate double speed;

public double getSpeed() {

return(speed);

}

public void setSpeed(double newSpeed) {

speed = newSpeed;

}

You should do this in allyour Java codeanyhow. Why?

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Why You Should Use,

You can put constraints on values

public void setSpeed(double newSpeed) {if (newSpeed < 0) {

sendErrorMessage(...);

newSpeed = Math.abs(newSpeed);

}

speed = newSpeed;

}

If users of your class accessed the fields directly, then

they would each be responsible for checking constraints.

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Why You Should Use,

You can change your internalrepresentation without changing interface

// Now using metric units (kph, not mph)

public void setSpeed(double newSpeed) {

=

}

u c vo se pee n ou e new pee

speedInKPH = newSpeed;

}

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Why You Should Use,

You can perform arbitrary side effects

public double setSpeed(double newSpeed) {speed = newSpeed;

updateSpeedometerDisplay();

}

If users of your class accessed the fields directly, thenthey would each be responsible for executing side effects.

inconsistent from actual values.

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Beans Should Be Serializable-

Some servers support distributed Webapp ca ons Load balancing used to send different requests to different

machines. Sessions should still work even if different hosts are hit.

Some servers suport persistent sessions Session data written to disk and reloaded when server is restarted

(as long as browser stays open). Tomcat 5 and 6 support this

To support both, beans that will be session-scoped. .

There are no methods in this interface; it is just a flag:public class MyBean implements Serializable

...}

Builtin classes like String and ArrayList are already Serializable12


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2009 Marty Hall

Updated Flow



JSF Flow of Control (Updated)faces-config.xml- beans declared in managed-bean section

Blah.jsp(Runs bean getter methods)

-

declared in navigation-rule section

submit form

Instantiate return ChooseRun Action forward result1.jsp

Run SetterMethods

Business

Logic

results

POST request Blah.faces Bean condition JSPController Method result2.jsp

...

resultN.jsp(Use h:outputText

to display bean

Store results of business

logic in bean

propert es)

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JSF Flow of Control (Simplified)

A form is displayed v

Bean instantiated. If bean getter methods return non-empty,

values filled in textfield The form is submitted to itself r g na an ACTION are ttp: a . aces

A bean is instantiated

Listed in the managed-beans section of faces-config.xml e se er me o s g ven n : npu ex e c. are execu e

Values passed to setter methods are the values in textfieldswhen form is submitted

The action controller method is invoked Listed in the action attribute of h:commandButton

The action method returns a condition A string that matches from-outcome in the navigation rules in

aces-con g.xm A results page is displayed

Page uses h:outputText to output bean properties15

Assumes bean is

request-scoped

Steps in Using JSF

1) Create a beanA) Properties for form data

B) Action controller method

C) Placeholders for results data

2) Create an input formA) Input fields refer to bean properties

3) Edit faces-config.xmlA) Declare the bean

B) Specify navigation rules

4) Create results pages Out ut form data and results data with h:out utText

5) Prevent direct access to JSP pages Use a filter that redirects blah.jsp to blah.faces

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2009 Marty Hall

Example



Example: Using Beans

Original URL: ttp: ostname s - eans reg ster. aces

When form submitted, three possible results Error messa e re ille al email address Error message re illegal password Success

Action controller obtains request data from within bean Output pages access bean properties

a n po n s Defining a bean with properties for the form data Declarin beans in faces-confi .xml Outputting bean properties

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Main Points of This Example

Add two new sections to the beans Placeholders for results data (Still have action controller method as before)

public class MyBean {

public String getCustomerId() {}

ublic void setCustomerId Strin id

Assume textfield refers to

customerId property.

public String doBusinessLogic() {}

public String getBalance() {}

}Assume balance is calculated

b business lo ic based on the

Use h:inputText to associate textfield with property

customer id.

Use h:outputText to output bean properties

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Step 1: Create a Bean

(A) Properties for form data a r o getter setter met o s or eac request parameter

If input form says value="#{name.foo}", then beanshould have getFoo and setFoo methods.

Bean instantiated (assuming request scope) Getter methods called (e.g., getFoo in above example) ,

is placed into textfield I.e., textfields are prepopulated with bean default values

When form submitted A new copy of the bean is instantiated

(assuming request scope)

Values from textfields passed to setter methods . .,

Strings converted to other types as with jsp:setProperty Form redisplayed if there are errors: see validation section

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Step 1: Create a Bean

(B) Action controller method Method can directly access bean properties

Since controller is inside same class that stores therequest parameters erent rom truts, w ere one o ect stores t e request ata t e

form bean that extends ActionForm) and a different object has thecontroller (the class that extends Action and has execute)

Method also invokes business lo ic takes results andstores them in placeholders reserved for output values

(C) Additional properties for output values e n y e ac on con ro er me o

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Step 1: Example Code(1A) Form data

public class RegistrationBean implements Serializable {private String email = "user@host";private String password = "";

public String getEmail() {return(email);

}

If you expect to ever

make bean session-scoped

public void setEmail(String email) {this.email = email;

}

public String getPassword() {return(password);

}

this.password = password;}

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Step 1: Example Code

(1B) Action controller method

public String register() {

if ((email == null) ||(email.trim().len th() < 3) ||

(email.indexOf("@") == -1)) {

suggestion = SuggestionUtils.getSuggestionBean();

return("bad-address");

} else if ((password == null) ||

(password.trim().length() < 6)) {

suggestion = SuggestionUtils.getSuggestionBean();

" - "

} else {

return("success");

}

}

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(1C) Placeholder for storing results Note that action controller method called business logic and placed

the result in this placeholder

private SuggestionBean suggestion;

return(suggestion);

}

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package coreservlets;import java.io.*;

public class SuggestionBean implements Serializable {private String email;rivate Strin assword

public SuggestionBean(String email, String password) {this.email = email;

.}

public String getEmail() {return(ema );

}

public String getPassword() {return(password);

}}

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package coreservlets;

public class SuggestionUtils {private static String[] suggestedAddresses =

{ "[email protected]"," ". ,"[email protected]","[email protected]" };

private static String chars ="abcdefghijklmnopqrstuvwxyz0123456789#@$%^&*?!";

public static SuggestionBean getSuggestionBean() {

String password = randomString(chars, 8);return(new SuggestionBean(address, password));

}...

}

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Step 2: Create Input Form

Similar to previous example, except : npu a ags g ven a va ue a r u e en y ng

the corresponding bean property Example code

Email address:

asswor :

.

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Step 2: Result

File is tomcat_dir/webapps/jsf-beans/register.jsp

s ttp:// oca ost/ s - eans/reg ster. aces

The user@host value comes from the bean

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Step 3: Edit faces-config.xml

(A) Declare bean

registrationBean

coreservlets.RegistrationBean

request

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Step 3: Edit faces-config.xml

(B) Define navigation rules

/register.jsp

bad-address

/WEB-INF/results/bad-address. s

bad-password

WEB-INF results bad- assword. s < to-view-id>

success

- - - . - -

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Step 4: Create Results Pages

Use h:outputText to access bean properties

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Step 4: Create Results Pages /jsf-beans/WEB-INF/results/bad-address.jsp

< >< =" "> < >< >

The address

"< =" " >".

is not of the form username@hostname (e.g.,

).

Please try again.

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Step 4: Example Result for Bad

Input

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Output

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/jsf-beans/WEB-INF/results/bad-password.jsp

Illegal Password

The password""s oo s or ; mus con a n a eas s x c arac ers.Here is a possible password:.

Please try again.< f:view>35


Input

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Output

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/jsf-beans/WEB-INF/results/success.jsp

SuccessYou have registered successfully.Email Address:

Password:

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Step 6: Example Result for

Input

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Step 6: Example Result for

Output

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Step 5: Prevent Direct Access

Use filter that captures url-pattern *.jsp No changes from previous example

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Alternative Approaches

Preview: using the JSP 2.0 EL output pages on y sp ay ean propert es rat er t an

manipulating a form or using form elements): Why bother with f:view and associated taglib declaration? y use :ou pu ex an assoc a e ag ec ara on

when the JSP 2.0 EL is simpler?

If you use the JSP 2.0 EL, you must:. . ., ,

Use the JSP 2.0 declaration for web.xml (see later section)

Pros of sticking with JSF ou m g use orm e emen s or or ren erers or

custom components or other JSF stuff in the future h:outputText escapes < and > with < and >

ros o us ng Shorter, simpler, more readable, already familiar

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Using the JSP 2.0 Expression

Standard JSF approach" " " " . .

Success

You have registered successfully.Email Address:

:ou pu ex va ue= reg s ra on ean.emaPassword:

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Using the JSP 2.0 Expression

JSP 2.0 approach Omit taglib declarations and f:view tags

Shorten expression that outputs bean properties

Success

.

Email Address: ${registrationBean.email}

Password: ${registrationBean.password}

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Looking Ahead

Algorithm for password length was clumsy ce to ave u t n c ec ng or text e engt s

Already supported in JSF See validation section

Algorithm for checking legal emailaddresses was primitive and easily fooled Supported in MyFaces via Tomahawk extensions

See section on MyFaces extensions

o passwor an ema were wrong,

only one was reported Better to redisplay form and say what was wrong

See section on validation45

Summary

Create a bean roper es or eac reques parame er Action controller method Placeholders to hold results objects

Refer to bean properties in input form

- Use managed-bean declaration Bean lifecycle (assuming request scope)

Getter methods called for initial textfield values

Instantiated again when form submitted Setter methods called for each input field Action controller method called after setter method

Use h:outputText to output bean properties The JSP 2.0 expression language is also possible46


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2009 Marty Hall

Questions?



03 Managed Beans

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