Creating new sources through the Maven plugin after the compilation phase

Question

I have a Maven project in which I need to complete two steps of code generation. One generates some types of Java, then the second depends on these types of Java to generate some more code. Is there a way that both of these steps happen during my build?

Currently my steps are:

• execute the first code generation plugin (during generate-sources )
• add a directory of generated types to create a path
• execute the second code generation plugin (during compile )

However, my problem is that everything that is generated by the second-generation code plugin will not be compiled (because the compilation phase is completed). If I attach the second code generation plugin to an earlier phase, it fails because it needs classes from the first code generation module that will be present in the classpath.

I know that I could break it down into two modules with one dependent on the other , but I was wondering if this could be done in one pom. It seems like a way is needed to call the compilation again after the completion of the normal compilation phase.

Any ideas?

Answer 1

You can always tweak two compiler plugin executions that are tied to the compilation phase. In one, you include additional material:

 <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>2.3.2</version> <executions> <execution> <id>one</id> <phase>compile</phase> <goals> <goal>compile</goal> </goals> <configuration></configuration> </execution> <execution> <id>two</id> <phase>compile</phase> <goals> <goal>compile</goal> </goals> <configuration> <compilerArgument>-verbose -bootclasspath ${java.home}\lib\rt.jar</compilerArgument> </configuration> </execution> </executions> <plugin> 

You also try <includes><include>path/</include></includes>

According to the official documentation:

When several executions that correspond to a certain phase are specified, they are executed in the order specified in the POM, with inherited starts running.

But I don’t understand what you really want. http://maven.apache.org/plugins/maven-compiler-plugin/examples/set-compiler-source-and-target.html

Answer 2

The obvious solution (code generation after the compilation phase) does not work, since Maven does not allow changing the phase order.

The correct solution is to use modules . You need two: the first module contains a code generator. In the second module, you can use the generator from the first module to generate something in the generate-sources phase.

The big advantage of this approach: you can never get into any kind of loop (for example, “A” needs the generated code that needs “A”). This way, your build will be simpler and you will spend less time looking for odd bugs.

[UPDATE] In my projects, I run the code generator from the tests. Without a special option, files are created in the temp folder and compared with sources. This allows me to see when I unexpectedly changed my generated code ( which I installed under version control ).

When the system property is set, the source files are overwritten, and I can commit the changes to my VCS.