The guessnumber-cdi CDI Example
Java Platform, Enterprise Edition (Java EE) 8
The Java EE Tutorial

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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 Chapter 8, "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 following topics are addressed here:

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 tut-install/examples/cdi/guessnumber-cdi/src/main/java/javaeetutorial/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 javax.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 javax.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 javax.enterprise.context.ApplicationScoped;
import javax.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 JavaServer 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 javax.annotation.PostConstruct;
import javax.enterprise.context.SessionScoped;
import javax.enterprise.inject.Instance;
import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.component.UIInput;
import javax.faces.context.FacesContext;
import javax.inject.Inject;
import javax.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.

The following topics are addressed here:

To Build, Package, and Deploy the guessnumber-cdi Example Using NetBeans IDE

  1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).

  2. From the File menu, choose Open Project.

  3. In the Open Project dialog box, navigate to:

    tut-install/examples/cdi
  4. Select the guessnumber-cdi folder.

  5. Click Open Project.

  6. 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 the target directory, and then deploys it to GlassFish Server.

To Build, Package, and Deploy the guessnumber-cdi Example Using Maven

  1. Make sure that GlassFish Server has been started (see Starting and Stopping GlassFish Server).

  2. In a terminal window, change to the following directory:

    tut-install/examples/cdi/guessnumber-cdi/
  3. 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 the target directory, and then deploys it to GlassFish Server.

To Run the guessnumber Example

  1. In a web browser, enter the following URL:

    http://localhost:8080/guessnumber-cdi

    The Guess My Number page opens.

  2. 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.

  3. 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.

  4. Click Reset to play the game again with a new random number.


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