26.2.1 Components of the producermethods Example

The components of producermethods are very much like those for encoder, with some significant differences.

Neither implementation of the Coder bean is annotated @Alternative, and there is no beans.xml file, because it is not needed.

The Facelets page and the managed bean, CoderBean, have an additional property, coderType, that allows the user to specify at runtime which implementation to use. In addition, the managed bean has a producer method that selects the implementation using a qualifier type, @Chosen.

The bean declares two constants that specify whether the coder type is the test implementation or the implementation that actually shifts letters:

    private final static int TEST = 1;
    private final static int SHIFT = 2;
    private int coderType = SHIFT; // default value

The producer method, annotated with @Produces and @Chosen as well as @RequestScoped (so that it lasts only for the duration of a single request and response), returns one of the two implementations based on the coderType supplied by the user.

    @Produces
    @Chosen
    @RequestScoped
    public Coder getCoder() {

        switch (coderType) {
            case TEST:
                return new TestCoderImpl();
            case SHIFT:
                return new CoderImpl();
            default:
                return null;
        }
    }

Finally, the managed bean injects the chosen implementation, specifying the same qualifier as that returned by the producer method to resolve ambiguities:

    @Inject
    @Chosen
    @RequestScoped
    Coder coder;

The Facelets page contains modified instructions and a pair of options whose selected value is assigned to the property coderBean.coderType:

    <h2>String Encoder</h2>
        <p>Select Test or Shift, type a string and an integer, then click
            Encode.</p>
        <p>If you select Test, the TestCoderImpl bean will display the
            argument values.</p>
        <p>If you select Shift, the CoderImpl bean will return a string that
            shifts the letters in the original string by the value you specify.
            The value must be between 0 and 26.</p>
        <h:form id="encodeit">
            <h:selectOneRadio id="coderType"
                              required="true"
                              value="#{coderBean.coderType}">
                <f:selectItem
                    itemValue="1"
                    itemLabel="Test"/>
                <f:selectItem
                    itemValue="2"
                    itemLabel="Shift Letters"/>
            </h:selectOneRadio>
            ...

26.2.2 Running the producermethods Example

You can use either NetBeans IDE or Maven to build, package, deploy, and run the producermethods application.