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java grails groovy

problems when trying to compile groovy class inside a java class

发布于 2020-03-27 10:19:21

We currently need to migrate an application from Grails 2.x to Grails 3.x

We do not know much about this application but in the past, in v2, it used Groovy classes inside Java classes.

After upgrading to v3, this doesn't seem to work anymore. Having Groovy code inside a Java class will return this

...: error: cannot find symbol
      line of code with the error
                                                            ^
  symbol:   variable MyGroovyClass
  location: class MyJavaClass


MyJavaClass

public class MyJavaClass {
  public void x() { MyGroovyClass.test(); }
}

MyGroovyClass

class MyGroovyClass {
  static void test() { ... }
}
Questioner
tzortzik
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Jeff Scott Brown 2019-07-03 21:47

they are placed under src/main/java and src/main/groovy

The simple thing to do, and the thing that most Grails apps do, is put all of the Java and Groovy source code under src/main/groovy/. That allows the Groovy joint compiler to compile all of it together as a single unit so you can have bidirectional dependencies between the Groovy and Java classes. It is possible to configure support for separate directories but it involves some complexity that doesn't really buy you anything, which is why the convention is to use src/main/groovy/.

tzortzik 2019-07-04 21:32:36

This solution worked and is pretty quick. Not really the right one but for the moment I can work it out using this.

Jeff Scott Brown 2019-07-04 22:55:17

"Not really the right one but for the moment I can work it out using this." - I am glad you got it working. The reason that we have grails create-app create src/main/groovy/ and not src/main/java/ is the preferred convention is to do that.

Jeff Scott Brown 2019-07-04 22:57:53

The issue is with the default build config, src/main/groovy/ and src/main/java/ are compiles separately which means one has to be compiled first which means that one cannot have references to the other one, because it isn't compiled yet. Putting it all in src/main/groovy/ allows it all to be compiled together. Groovy provides a joint compiler which allows Groovy and Java sources to be compiled as 1 unit, allowing bidirectional dependencies.

Jeff Scott Brown 2019-07-04 22:58:54

An alternative is to add src/main/java/ to the sourceSets for compileGroovy so those sources will be compiled at the same time as the sources under src/main/groovy/. If you do that, it can be made to work, but is more build config since you are deviating from the defaults, and is a non-standard thing.

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