10.2.2.4. Use an Injection to Extend an Implementation
Summary
You can use an injection to add or change a feature of your existing code. This example shows you how to add a translation ability to an existing class. The translation is a hypothetical feature and the way it is implemented in the example is pseudo-code, and only provided for illustration.
The example assumes you already have a Welcome class, which has a method
buildPhrase. The buildPhrase method takes as an argument the name of a city, and outputs a phrase like "Welcome to Boston." Your goal is to create a version of the Welcome class which can translate the greeting into a different language.
Example 10.2. Inject a Translator Bean Into the Welcome Class
The following pseudo-code injects a hypothetical
Translator object into the Welcome class. The Translator object may be an EJB stateless bean or another type of bean, which can translate sentences from one language to another. In this instance, the Translator is used to translate the entire greeting, without actually modifying the original Welcome class at all. The Translator is injected before the buildPhrase method is implemented.
The code sample below is an example Translating Welcome class.
public class TranslatingWelcome extends Welcome {
@Inject Translator translator;
public String buildPhrase(String city) {
return translator.translate("Welcome to " + city + "!");
}
...
}
