Introducing Spring Framework

Doing Something Groovy
Chapter 14 ■ Using Dynamic Languages
Groovy is a dynamic language that sits on top of the Java virtual machine; it has powerful features inspired by
Python, Ruby, and Smalltalk. Easy to create DSLs (domain-specific languages) increase the developer’s productivity
by eliminating all of Java’s boilerplate code, and they integrate very well with existing Java libraries. In other words,
Groovy is Java! But don’t worry about it too much, Groovy has almost a zero learning curve. You have seen it in action
in Chapter 1, and you are going to use it in later chapters too.
Now, back to your code. You are not going to use the existing implementation (see Listing 14-2); you are going
to use the Groovy programming language as the implementation of the Login interface class. But how are you
going to use a dynamic language for this? Well, because Groovy sits on top of the virtual machine, it will be easy to
compile the Groovy class or script and then put it into your classpath so it can be used by your Spring application.
But what happens if you need to change or add some more behavior to your Groovy class? First, you need to do the
modification and compile it, then you need to re-deploy or change it for the new compiled class. That’s a lot
of trouble.
That is why the Spring Framework allows for the use of dynamic languages and changing them at runtime
without even compiling them. Listing 14-4 shows the Groovy implementation of the Login interface.
Listing 14-4. META-INF/scripts/groovylogin.groovy
import com.apress.isf.java.service.Login
class GroovyLoginService implements Login {
String username
String password
}
boolean isAuthorized(String email, String pass) {
if(username==email && password==pass)
return true
return false
}
As you can see, Listing 14-4 is very simple. You got rid of the setters and getters and all the Java clutter. Now let’s
see how the XML will look in order to use this Groovy script; see Listing 14-5.
Listing 14-5. mydocuments-context.xml
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