Groovy 2 Cookbook: Java and Groovy go together like ham and eggs, and this book is a great opportunity to learn how to exploit Groovy 2 to the full. Packed with recipes, both intermediate and advanced, it's a great way to speed up and modernize your programming.

In this chapter, we will introduce the Groovy ecosystem: compilation, embedding, building, documentation, and analysis options that various, tools surrounding, Groovy offer to make your life smoother.

In the first three recipes, we will demonstrate how simple Java and Groovy interoperability is and what makes Groovy the perfect tool in a Java developer's hands. The following recipes will describe external dependency management possibilities and the most popular build tools (for example, Ant, Maven, and Gradle) integration options. Then there will be a recipe devoted to Groovydoc, which can be used to generate documentation for your sources. Finally, the last recipe will introduce a way to verify your Groovy code quality.

The Groovy language is designed in a way that it fully supports the Java syntax (there are only few minor exceptions; for example, do..while is not supported in Groovy). Most of the code that you can write in Java can automatically be considered Groovy code as well.

In this recipe, we will learn how simple it is to use existing Java classes and libraries from your Groovy code and we will explore some basic language features that makes Groovy—groovy!

There are plenty of scripting languages available at the moment on the JVM. Some of them only offer expression language support for data binding and configuration needs, for example, MVEL (http://mvel.codehaus.org/) and SpEL (Spring Expression Language, http://www.springsource.org/documentation). Others provide a fully featured programming language. Examples of these are JRuby, Jython, Clojure, Jaskell, and of course, Groovy.

In this recipe, we will show you how to benefit from Groovy scripting from within your Java application.

Groovy scripts are normally executed by running the groovy command from the console; for example:

groovy someScript.groovy

The groovy command generates the JVM bytecode on the fly and immediately executes it. There are scenarios in which the Groovy code is required to be compiled to bytecode as a *.class file. A typical case is when Java and Groovy code have to be used side-by-side for building a mixed Groovy/Java application.

Groovy has an answer to that by offering a compiler command, groovyc (similarly to Java's javac), that can also be invoked from the command line or through a build tool such as Ant (see the Integrating Groovy into the build process using Ant recipe), Maven (see the Integrating Groovy into the build process using Maven recipe), or Gradle (see the Integrating Groovy into the build process using Gradle recipe).

In this recipe, we are going to show you the principal purposes of the groovyc command.

Your nicely written and useful script can solve many interesting problems with the help of third-party libraries, and as long as it resides on your machine and has all the dependencies in place, it will work perfectly. However, at the point when you need to share it with your colleagues or community, you will realize that small and concise code requires several megabytes of additional libraries to be passed together with the script in order to make it work. Luckily, Groovy has a solution for that called Grape.

In this recipe, we will show you how to declare and automatically load Groovy script dependencies with the help of the wonderful Grape tool, which is integrated into Groovy.

Apache Ant (http://ant.apache.org/) was one of the first build tools that appeared within the Java ecosystem, and it is still widely used by many organizations around the globe.

In this recipe, we will cover how to compile and test a complete Groovy project using Apache Ant. At the end of the recipe, we will show you how to use Groovy from within Ant to add scripting to a build task.

src/main/groovy/org/groovy/cookbook
    DatagramWorker.groovy
    MessageReceiver.groovy
    MessageSender.groovy
src/test/groovy/org/groovy/cookbook
    MessageProcessingTest.groovy

abstract class DatagramWorker {

  byte[] buffer = new byte[256]
  DatagramSocket socket =...

Apache Maven (http://maven.apache.org/) is a software project build tool that uses the POM (Project Object Model) to describe project artifacts, dependencies, and rules in a declarative form.

Apache Maven was an important milestone in Java build tool evolution. Together with important features such as organized dependency management and declarative build scripts, it also brought a variety of standards and conventions that have been widely adopted by the Java community, even if Maven itself is not used.

In this recipe, we are going to look into how to compile, test, and run a fully blown Groovy project using the Apache Maven build tool.

Gradle (http://www.gradle.org/) is a build and automation tool written in Java/Groovy, which makes use of a Groovy-based DSL for defining declarative and imperative build scripts. Gradle brings a lot of innovation into the Java/Groovy build tool space, and at a fast pace is replacing other popular tools. At the same time, it builds upon the best practices and foundations of those tools, such as project conventions standardization and dependency management.

In this recipe, we will demonstrate how Gradle can simplify the compilation and testing of a complete Groovy project.

All Java developers are familiar with Javadoc comment style and the javadoc command-line tool, which is well integrated into all major IDEs and build tools.

Unfortunately, you will not be able to run the javadoc tool against Groovy source code, just because javadoc does not recognize the Groovy language syntax - unless your Groovy classes or scripts are written in Java. This is why Groovy has a tool, which for obvious reasons is called Groovydoc. It shares a lot of features with its predecessor but also has some significant differences. For example, groovydoc does not implement the Doclet extension feature, which was used mainly for code generation but since the introduction of annotations in Java 5, its usage has decreased dramatically. Also, unlike javadoc, which is a standalone executable originally written in C++ with its extension points (that is, Doclets) written in Java, Groovydoc's core functionality is fully implemented in Groovy and is available...

As soon as you finish writing your first Groovy scripts or classes, you will probably start wondering how Groovy pros write their code and what are the best practices they are using. One way would be to learn by peeking at the best Groovy code bases (for example, Groovy itself: https://github.com/groovy/groovy-core/tree/master/src/main/groovy). Another way can be using code analysis tools that let you catch common coding mistakes that are already well-known in the community.

In the Java language world, there are many open source static code analysis tools such as PMD (Project Mess Detector) (http://pmd.sourceforge.net/), Checkstyle (http://checkstyle.sourceforge.net/), FindBugs (http://findbugs.sourceforge.net/), and so on. There are also many commercial products and IDEs that support various types of Java source code analysis.

In that regard, Groovy is less rich, though it has one library called CodeNarc (http://codenarc.sourceforge.net). The library...