Running the Basic Contexts and Dependency Injection Examples
This chapter describes in detail how to build and run simple examples that use CDI.
Building and Running the CDI Samples
The examples are in the jakartaee-examples/tutorial/cdi/
directory.
To build and run the examples, you will do the following:
-
Use NetBeans IDE or the Maven tool to compile and package the example.
-
Use NetBeans IDE or the Maven tool to deploy the example.
-
Run the example in a web browser.
See Using the Tutorial Examples, for basic information on installing, building, and running the examples.
The simplegreeting CDI Example
The simplegreeting
example illustrates some of the most basic features of CDI: scopes, qualifiers, bean injection, and accessing a managed bean in a Jakarta Faces application.
When you run the example, you click a button that presents either a formal or an informal greeting, depending on how you edited one of the classes.
The example includes four source files, a Facelets page and template, and configuration files.
The simplegreeting Source Files
The four source files for the simplegreeting
example are:
-
The default
Greeting
class, shown in Beans as Injectable Objects -
The
@Informal
qualifier interface definition and theInformalGreeting
class that implements the interface, both shown in Using Qualifiers -
The
Printer
managed bean class, which injects one of the two interfaces, shown in full in Adding Setter and Getter Methods
The source files are located in the jakartaee-examples/tutorial/cdi/simplegreeting/src/main/java/jakarta/tutorial/simplegreeting
directory.
The Facelets Template and Page
To use the managed bean in a simple Facelets application:
-
Use a very simple template file and
index.xhtml
page.The template page,
template.xhtml
, looks like this:<?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html lang="en" xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://xmlns.jcp.org/jsf/html" xmlns:ui="http://xmlns.jcp.org/jsf/facelets"> <h:head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> <h:outputStylesheet library="css" name="default.css"/> <title><ui:insert name="title">Default Title</ui:insert></title> </h:head> <body> <div id="container"> <div id="header"> <h2><ui:insert name="head">Head</ui:insert></h2> </div> <div id="space"> <p></p> </div> <div id="content"> <ui:insert name="content"/> </div> </div> </body> </html>
-
To create the Facelets page, redefine the title and head, then add a small form to the content:
<?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html lang="en" xmlns="http://www.w3.org/1999/xhtml" xmlns:ui="http://xmlns.jcp.org/jsf/facelets" xmlns:h="http://xmlns.jcp.org/jsf/html"> <ui:composition template="/template.xhtml"> <ui:define name="title">Simple Greeting</ui:define> <ui:define name="head">Simple Greeting</ui:define> <ui:define name="content"> <h:form id="greetme"> <p><h:outputLabel value="Enter your name: " for="name"/> <h:inputText id="name" value="#{printer.name}"/></p> <p><h:commandButton value="Say Hello" action="#{printer.createSalutation}"/></p> <p><h:outputText value="#{printer.salutation}"/> </p> </h:form> </ui:define> </ui:composition> </html>
The form asks the user to enter a name. The button is labeled Say Hello, and the action defined for it is to call the
createSalutation
method of thePrinter
managed bean. This method in turn calls thegreet
method of the definedGreeting
class.The output text for the form is the value of the greeting returned by the setter method. Depending on whether the default or the
@Informal
version of the greeting is injected, this is one of the following, wherename
is the name entered by the user:Hello, name. Hi, name!
The Facelets page and template are located in the
jakartaee-examples/tutorial/cdi/simplegreeting/src/main/webapp/
directory.The simple CSS file that is used by the Facelets page is in the following location:
jakartaee-examples/tutorial/cdi/simplegreeting/src/main/webapp/resources/css/default.css
Running the simplegreeting Example
You can use either NetBeans IDE or Maven to build, package, deploy, and run the simplegreeting
application.
To Build, Package, and Run the simplegreeting Example Using NetBeans IDE
-
Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
-
From the File menu, choose Open Project.
-
In the Open Project dialog box, navigate to:
jakartaee-examples/tutorial/cdi
-
Select the
simplegreeting
folder. -
Click Open Project.
-
To modify the
Printer.java
file, perform these steps:-
Expand the Source Packages node.
-
Expand the
greetings
node. -
Double-click the
Printer.java
file. -
In the editor, comment out the
@Informal
annotation:@Inject //@Informal Greeting greeting;
-
Save the file.
-
-
In the Projects tab, right-click the
simplegreeting
project and select Build.This command builds and packages the application into a WAR file,
simplegreeting.war
, located in thetarget
directory, and then deploys it to GlassFish Server.
To Build, Package, and Deploy the simplegreeting Example Using Maven
-
Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
-
In a terminal window, go to:
jakartaee-examples/tutorial/cdi/simplegreeting/
-
Enter the following command to deploy the application:
mvn install
This command builds and packages the application into a WAR file,
simplegreeting.war
, located in thetarget
directory, and then deploys it to GlassFish Server.
To Run the simplegreeting Example
-
In a web browser, enter the following URL:
http://localhost:8080/simplegreeting
The Simple Greeting page opens.
-
Enter a name in the field.
For example, suppose that you enter
Duke
. -
Click Say Hello.
If you did not modify the
Printer.java
file, then the following text string appears below the button:Hi, Duke!
If you commented out the
@Informal
annotation in thePrinter.java
file, then the following text string appears below the button:Hello, Duke.
The guessnumber-cdi CDI Example
The guessnumber-cdi
example, somewhat more complex than the simplegreeting
example, illustrates the use of producer methods and of session and application scope.
The example is a game in which you try to guess a number in fewer than ten attempts.
It is similar to the guessnumber-jsf
example described in Introduction to Facelets, except that you can keep guessing until you get the right answer or until you use up your ten attempts.
The example includes four source files, a Facelets page and template, and configuration files.
The configuration files and the template are the same as those used for the simplegreeting
example.
The guessnumber-cdi Source Files
The four source files for the guessnumber-cdi
example are:
-
The
@MaxNumber
qualifier interface -
The
@Random
qualifier interface -
The
Generator
managed bean, which defines producer methods -
The
UserNumberBean
managed bean
The source files are located in the jakartaee-examples/tutorial/cdi/guessnumber-cdi/src/main/java/jakarta/tutorial/guessnumber
directory.
The @MaxNumber and @Random Qualifier Interfaces
The @MaxNumber
qualifier interface is defined as follows:
package guessnumber;
import java.lang.annotation.Documented;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.TYPE;
import java.lang.annotation.Retention;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Target;
import jakarta.inject.Qualifier;
@Target({TYPE, METHOD, PARAMETER, FIELD})
@Retention(RUNTIME)
@Documented
@Qualifier
public @interface MaxNumber {
}
The @Random
qualifier interface is defined as follows:
package guessnumber;
import java.lang.annotation.Documented;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.TYPE;
import java.lang.annotation.Retention;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Target;
import jakarta.inject.Qualifier;
@Target({TYPE, METHOD, PARAMETER, FIELD})
@Retention(RUNTIME)
@Documented
@Qualifier
public @interface Random {
}
The Generator Managed Bean
The Generator
managed bean contains the two producer methods for the application.
The bean has the @ApplicationScoped
annotation to specify that its context extends for the duration of the user’s interaction with the application:
package guessnumber;
import java.io.Serializable;
import jakarta.enterprise.context.ApplicationScoped;
import jakarta.enterprise.inject.Produces;
@ApplicationScoped
public class Generator implements Serializable {
private static final long serialVersionUID = -7213673465118041882L;
private final java.util.Random random =
new java.util.Random( System.currentTimeMillis() );
private final int maxNumber = 100;
java.util.Random getRandom() {
return random;
}
@Produces @Random int next() {
return getRandom().nextInt(maxNumber + 1);
}
@Produces @MaxNumber int getMaxNumber() {
return maxNumber;
}
}
The UserNumberBean Managed Bean
The UserNumberBean
managed bean, the managed bean for the Jakarta Faces application, provides the basic logic for the game.
This bean does the following:
-
Implements setter and getter methods for the bean fields
-
Injects the two qualifier objects
-
Provides a
reset
method that allows you to begin a new game after you complete one -
Provides a
check
method that determines whether the user has guessed the number -
Provides a
validateNumberRange
method that determines whether the user’s input is correct
The bean is defined as follows:
package guessnumber;
import java.io.Serializable;
import jakarta.annotation.PostConstruct;
import jakarta.enterprise.context.SessionScoped;
import jakarta.enterprise.inject.Instance;
import jakarta.faces.application.FacesMessage;
import jakarta.faces.component.UIComponent;
import jakarta.faces.component.UIInput;
import jakarta.faces.context.FacesContext;
import jakarta.inject.Inject;
import jakarta.inject.Named;
@Named
@SessionScoped
public class UserNumberBean implements Serializable {
private static final long serialVersionUID = -7698506329160109476L;
private int number;
private Integer userNumber;
private int minimum;
private int remainingGuesses;
@MaxNumber
@Inject
private int maxNumber;
private int maximum;
@Random
@Inject
Instance<Integer> randomInt;
public UserNumberBean() {
}
public int getNumber() {
return number;
}
public void setUserNumber(Integer user_number) {
userNumber = user_number;
}
public Integer getUserNumber() {
return userNumber;
}
public int getMaximum() {
return (this.maximum);
}
public void setMaximum(int maximum) {
this.maximum = maximum;
}
public int getMinimum() {
return (this.minimum);
}
public void setMinimum(int minimum) {
this.minimum = minimum;
}
public int getRemainingGuesses() {
return remainingGuesses;
}
public String check() throws InterruptedException {
if (userNumber > number) {
maximum = userNumber - 1;
}
if (userNumber < number) {
minimum = userNumber + 1;
}
if (userNumber == number) {
FacesContext.getCurrentInstance().addMessage(null,
new FacesMessage("Correct!"));
}
remainingGuesses--;
return null;
}
@PostConstruct
public void reset() {
this.minimum = 0;
this.userNumber = 0;
this.remainingGuesses = 10;
this.maximum = maxNumber;
this.number = randomInt.get();
}
public void validateNumberRange(FacesContext context,
UIComponent toValidate,
Object value) {
int input = (Integer) value;
if (input < minimum || input > maximum) {
((UIInput) toValidate).setValid(false);
FacesMessage message = new FacesMessage("Invalid guess");
context.addMessage(toValidate.getClientId(context), message);
}
}
}
The Facelets Page
This example uses the same template that the simplegreeting
example uses.
The index.xhtml
file, however, is more complex.
<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en"
xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
xmlns:h="http://xmlns.jcp.org/jsf/html">
<ui:composition template="/template.xhtml">
<ui:define name="title">Guess My Number</ui:define>
<ui:define name="head">Guess My Number</ui:define>
<ui:define name="content">
<h:form id="GuessMain">
<div style="color: black; font-size: 24px;">
<p>I'm thinking of a number from
<span style="color: blue">#{userNumberBean.minimum}</span>
to
<span style="color: blue">#{userNumberBean.maximum}</span>.
You have
<span style="color: blue">
#{userNumberBean.remainingGuesses}
</span>
guesses.</p>
</div>
<h:panelGrid border="0" columns="5" style="font-size: 18px;">
<h:outputLabel for="inputGuess">Number:</h:outputLabel>
<h:inputText id="inputGuess"
value="#{userNumberBean.userNumber}"
required="true" size="3"
disabled="#{userNumberBean.number eq userNumberBean.userNumber or userNumberBean.remainingGuesses le 0}"
validator="#{userNumberBean.validateNumberRange}">
</h:inputText>
<h:commandButton id="GuessButton" value="Guess"
action="#{userNumberBean.check}"
disabled="#{userNumberBean.number eq userNumberBean.userNumber or userNumberBean.remainingGuesses le 0}"/>
<h:commandButton id="RestartButton" value="Reset"
action="#{userNumberBean.reset}"
immediate="true" />
<h:outputText id="Higher" value="Higher!"
rendered="#{userNumberBean.number gt userNumberBean.userNumber and userNumberBean.userNumber ne 0}"
style="color: #d20005"/>
<h:outputText id="Lower" value="Lower!"
rendered="#{userNumberBean.number lt userNumberBean.userNumber and userNumberBean.userNumber ne 0}"
style="color: #d20005"/>
</h:panelGrid>
<div style="color: #d20005; font-size: 14px;">
<h:messages id="messages" globalOnly="false"/>
</div>
</h:form>
</ui:define>
</ui:composition>
</html>
The Facelets page presents the user with the minimum and maximum values and the number of guesses remaining.
The user’s interaction with the game takes place within the panelGrid
table, which contains an input field, Guess and Reset buttons, and a field that appears if the guess is higher or lower than the correct number.
Every time the user clicks Guess, the userNumberBean.check
method is called to reset the maximum or minimum value or, if the guess is correct, to generate a FacesMessage
to that effect.
The method that determines whether each guess is valid is userNumberBean.validateNumberRange
.
Running the guessnumber-cdi Example
You can use either NetBeans IDE or Maven to build, package, deploy, and run the guessnumber-cdi
application.
To Build, Package, and Deploy the guessnumber-cdi Example Using NetBeans IDE
-
Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
-
From the File menu, choose Open Project.
-
In the Open Project dialog box, navigate to:
jakartaee-examples/tutorial/cdi
-
Select the
guessnumber-cdi
folder. -
Click Open Project.
-
In the Projects tab, right-click the
guessnumber-cdi
project and select Build.This command builds and packages the application into a WAR file,
guessnumber-cdi.war
, located in thetarget
directory, and then deploys it to GlassFish Server.
To Build, Package, and Deploy the guessnumber-cdi Example Using Maven
-
Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).
-
In a terminal window, change to the following directory:
jakartaee-examples/tutorial/cdi/guessnumber-cdi/
-
Enter the following command to deploy the application:
mvn install
This command builds and packages the application into a WAR file,
guessnumber-cdi.war
, located in thetarget
directory, and then deploys it to GlassFish Server.
To Run the guessnumber Example
-
In a web browser, enter the following URL:
http://localhost:8080/guessnumber-cdi
The Guess My Number page opens.
-
On the Guess My Number page, enter a number in the Number field and click Guess.
The minimum and maximum values are modified, along with the remaining number of guesses.
-
Keep guessing numbers until you get the right answer or run out of guesses.
If you get the right answer or run out of guesses, the input field and Guess button are grayed out.
-
Click Reset to play the game again with a new random number.