Increasing build process complexity

When combining multiple languages, the build script has to be adapted, and this can lead to complex situations. For example, if a Java project uses a class compiled in Groovy, the order of the compilation is important. First, the Groovy class will have to be compiled, then the Java code. If that Groovy code uses custom classes from the Java project, then it gets even more complex.

Groovy is a special case, as we will see in the Groovy chapter. The Groovy compiler can compile most Java code, as the Groovy language is largely compatible with the Java language. For projects where this is not possible, or desirable, there's a compiler plugin for the Apache Maven build tool that solves many of these problems.

A solution could be to divide the code into multiple subprojects and list the resulting libraries as a requirement of the main project in the build tool.

Some languages offer another solution: they provide their own custom classes to call the language's source code from Java (or any other JVM language). The source code is then dynamically compiled to the Java bytecode on the fly as these classes load the code. Other languages implement an official standard to embed script languages in Java code. We will take a brief look at this in the appendix when we discuss Oracle's JavaScript interpreter, called Nashorn.

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