- Generate JAXB java classes from XSDs
- Precompile these classes plus a small number of other classes
- Run a custom annotation processor which will add json annotations to the generated code
The custom annotation task is defined in a separate git repository. It needed a custom classpath. I don’t believe you can change the classpath for normal tasks, but if you use a JavaExec task to run a task in a new JVM, you can obviously configure the classpath as you wish. Hence this is the setup I used. It looked like this:
tasks.register('jacksonAnnotationTask', JavaExec) {
classpath = sourceSets.main.compileClasspath
classpath += files("$buildDir/classes/java/generatedSource")
classpath += configurations.jacksonAnnotationTaskClasspath
mainClass = 'com.ice.integration.gradle.JacksonAnnotationTask'
args = ["$buildDir/generated/jaxb/java/claimsApiModelClasses", "com"]
}
These steps all happen before the main compile. When I did a compile, then repeated it, I was disappointed to see that the custom annotation task was rerun. What was going on?
How do you see what is going on with a Gradle build? The easiest thing to do is rerun with the -d debug flag. Once I did this, the problem was obvious – the task was rewriting the generated source files in place – therefore the inputs to the task had changed, therefore the task had to be rerun. Once I understood this, the route to fix it is clear – the task should output the updated files in a new location. I updated the task code to do this, adding a third parameter to specify the output directory. Then I updated the JavaExec config to specify the input and output, like this:
tasks.register('jacksonAnnotationTask', JavaExec) {
// we must declare inputs and outputs
// otherwise Gradle will just rerun this task every time
String outputDirectory = "$buildDir/generated/jaxb/java/claimsApiModelClassesWithJsonAnnotations"
inputs.files(sourceSets.generatedSource.java)
outputs.dir(outputDirectory)
classpath = sourceSets.main.compileClasspath
classpath += files("$buildDir/classes/java/generatedSource")
classpath += configurations.jacksonAnnotationTaskClasspath
mainClass = 'com.ice.integration.gradle.JacksonAnnotationTask'
args = ["$buildDir/generated/jaxb/java/claimsApiModelClasses", "com", outputDirectory]
}
Once I made this change, rerunning the compile task told me that all tasks were up to date, nothing to be rerun! Fantastic!
For more information on incremental builds, see:
https://docs.gradle.org/current/userguide/incremental_build.html
For other blog posts on Gradle, see:
Dependencies and configurations in Gradle
Gradle release plugin
Using test fixtures in Gradle and Maven
Code coverage with Gradle and Jacoco
