Introducing Spring Framework

Chapter 2 ■ Working with Classes and Dependencies
com.apress.isf.java.test.MyDocumentsTest > testListAll STARTED
com.apress.isf.java.test.MyDocumentsTest > testListAll PASSED
BUILD SUCCESSFUL
Total time: 12.039 secs
■ ■Note The above output shows all the tests in this chapter. You can run from the base project with the following
command: $ gradle :ch02:test
Using the Spring Framework
As you can see, you started with a simple Java application, and a clean design using interfaces that will promote
decoupling and will not depend on a specific implementation because it follows a contract. But there is still some
code that you need to refactor in your unit test. Listing 2-5 shows that you need to instantiate a new MySearchEngine
class, but what happens if you need to add a different implementation? Well, just change the name, and recompile
and rerun to test it, right? Or maybe you need to instantiate more of these classes somewhere; it will be some hard
work! That’s why you need some kind of dependency mechanism tool to avoid this hassle. In other words, you need a
way to create this dependency dynamically and avoid instantiating a class every time you add a new implementation.
The Spring Framework’s primary goal is to offer a dependency injection container that will facilitate the creation
of instances and interaction between objects. But how are you going to use the Spring Framework? And what is the
dependency injection thing? Or the Spring container? Well, let’s start coding and answer your questions.
You are going to create the file shown in Listing 2-7. If you are using the book’s companion source code, you can
find it at /ch02/src/test/resources/META-INF/spring.
Listing 2-7. mydocuments-context.xml
Listing 2-7 shows an XML file. This file is the configuration that the Spring Framework needs to know in order to
inject the dependencies and the interaction between objects. The main tag, , uses XML namespaces to give
your file the correct syntax and usage; and it can contain one or more children. In this case, it uses another tag, .
This is the key to define the dependency; here you are creating an “engine” bean that points to an implementation.
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