JPA Static Metamodel not recognized by IntelliJ - jpa

Question

I generated the application with JHipster with Gradle as the build tool.
When I created entity I added filtering support, which generated JPA static metamodel. But IntelliJ doesn't recognize the metamodels.
I have enabled the annotation processor settings on IntelliJ but it doesn't seem to work.
What settings do I have to change for IntelliJ to recognize the JPA static metamodels?

Answer 1

By default, the metamodel classes get generated into the /target/generated-sources/annotations folder. It seems like that folder isn't registered as a source folder.
You can either change that manually in your IDE or if you're using a Maven build, you can do that automatically by adding the following plugin to your build configuration:
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>3.0.0</version>
<executions>
<execution>
<id>add-source</id>
<phase>generate-sources</phase>
<goals>
<goal>add-source</goal>
</goals>
<configuration>
<sources>
<source>target/generated-sources/annotations</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
...
</project>
I explained that in more details in one of my Hibernate Tips.

Answer 2

I'm not allowed to comment but I wanted to add to Thorben Janssen's answer.
Besides the plugin config I also had to add this to the dependencies of the project:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-jpamodelgen</artifactId>
<version>5.4.21.Final</version>
</dependency>
This is what generates the sources in the target/generated-sources/annotations path.
So the pom ended up like this:
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-jpamodelgen</artifactId>
<version>5.4.21.Final</version>
</dependency>
...
</dependencies>
...
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>3.2.0</version>
<executions>
<execution>
<id>add-source</id>
<goals>
<goal>add-source</goal>
</goals>
<phase>generate-sources</phase>
<configuration>
<sources>
<source>target/generated-sources/annotations</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
...
</build>

Answer 3

To get IntelliJ IDEA to recognize the generated classes, I had to add this line on build.gradle
sourceSets {
main.java.srcDirs += 'build/generated/source/apt/main'
}
Update
Better solution is to modify IntelliJ Plugin
idea {
module {
sourceDirs += file("build/generated/source/apt/main")
generatedSourceDirs += file("build/generated/source/apt/main")
}
}

Answer 4

Intellij's build recognize all processors listed in this file:
META-INF/services/javax.annotation.processing.Processor
.
Case you use Eclipse Link, include this line inside the file:
org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor
Case Hibernate:
org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor
Ensure that you have all dependencys: I will describe using maven just for example:
<dependency>
<groupId>org.eclipse.persistence</groupId>
<artifactId>org.eclipse.persistence.jpa.modelgen.processor</artifactId>
<version>2.7.0</version>
<scope>provided</scope>
</dependency>
OR
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-jpamodelgen</artifactId>
<version>5.2.12.Final</version>
<scope>provided</scope>
</dependency>

Answer 5

For me it wasn't a problem of the configuration files (none of the above mentioned solutions worked), but I simply had to reload all Maven project files.
For this in IntelliJ Idea:
Go to the Maven tab on the right side of the IDE (you might have to make it visible under View -> Tool Windows)
Open the project and compile
On the top left corner of the tab press Reload all Maven Projects
Now, the meta classes (e.g. SampleClass_) should be importable and recognized by IntelliJ