26.5.1 Components of the decorators Example

The decorators example is very similar to the encoder example described in The encoder Example: Using Alternatives. Instead of providing two implementations of the Coder interface, however, this example provides only the CoderImpl class. The decorator class, CoderDecorator, rather than simply return the coded string, displays the input and output strings' values and length.

The CoderDecorator class, like CoderImpl, implements the business method of the Coder interface, codeString:

@Decorator
public abstract class CoderDecorator implements Coder {

    @Inject
    @Delegate
    @Any
    Coder coder;

    public String codeString(String s, int tval) {
        int len = s.length();

        return "\"" + s + "\" becomes " + "\"" + coder.codeString(s, tval) 
                + "\", " + len + " characters in length";
    }
}

The decorator's codeString method calls the delegate object's codeString method to perform the actual encoding.

The decorators example includes the Logged interceptor binding and LoggedInterceptor class from the billpayment example. For this example, the interceptor is set on the CoderBean.encodeString method and the CoderImpl.codeString method. The interceptor code is unchanged; interceptors are usually reusable for different applications.

Except for the interceptor annotations, the CoderBean and CoderImpl classes are identical to the versions in the encoder example.

The beans.xml file specifies both the decorator and the interceptor:

    <decorators>
        <class>javaeetutorial.decorators.CoderDecorator</class>
    </decorators>
    <interceptors>
        <class>javaeetutorial.decorators.LoggedInterceptor</class>
    </interceptors>

26.5.2 Running the decorators Example

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