Gradle [META-INF/persistence.xml] was not found

Question

I am building my JPA/EJB project using gradle and getting this warning:

$ gradle jar
:compileJava
Note: Creating static metadata factory ...
Note: The persistence xml file [META-INF/persistence.xml] was not found. NO GENERATION will occur!! Please ensure a persistence xml file is available either from the CLASS_OUTPUT directory [META-INF/persistence.xml] or using the eclipselink.persistencexml property to specify its location. 
2 warnings
:processResources UP-TO-DATE
:classes
:jar

My project structure:

   ProjectX
   |-src
   |---main
   |-----java
   |-------domain
   |-------ejb
   |-----resources
   |-------META-INF
   |-----------persistence.xml

The interesting part is that the persistence.xml ends up in the target jar artifact:

$ jar -tf target/projectx.jar
META-INF/
META-INF/MANIFEST.MF
domain/
domain/Employee.class
ejb/
ejb/EmployeeEJB.class
META-INF/persistence.xml

Why is there complain that the [META-INF/persistence.xml] even though it is there?

The gradle file:

apply plugin: 'java'
project.buildDir = 'target'
sourceSets.all {
    output.resourcesDir = output.classesDir
}
jar{
    destinationDir=project.buildDir
}
repositories {
    mavenCentral()
}
dependencies {
    compile 'org.glassfish:javax.ejb:3.0.1','org.eclipse.persistence:javax.persistence:2.0.0'
}

I have quickly tested with maven now and ther is no such warning there.

Answer 1

The persistence.xml is required at compile time. One way to achieve this is:

sourceSets.main.output.resourcesDir = sourceSets.main.output.classesDir
compileJava.dependsOn(processResources)

Answer 2

In fact the solution suggested by @peter-niederwieser to set your main resources and classes dir to same location results in duplicated entries in your jar archive. Basically, it's twice the original size, don't know if there are other problems.

So to fix this, you have to add

sourceSets.main.output.resourcesDir = sourceSets.main.output.classesDir
jar {
    duplicatesStrategy = 'exclude'
}

to your build.gradle.

Answer 3

META-INF should be in the root of your classpath (/src/main/java/META-INF)

Answer 4

The persistence.xml should be in src/main/resources/META-INF. This worked for me. Please not that this was a non spring project