Currently I'm writing a scala macro library, and I would like to make it usable from java too.
But I cannot think of a way to access scala macro methods form java source code. Is there any way we can use scala macro method from java.
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2 Answers
Scala macros are instructions for scala compiler, java code is compiled by javac, which has no idea about both scala and scala macros, so I guess the answer is: there is no way to use them from java.
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This is true that Scala macros are instructions for Scala compiler. So if you want to execute them in Java then in Java you'll have to run Scala compiler
<dependency>
<groupId>org.scala-lang</groupId>
<artifactId>scala-reflect</artifactId>
<version>2.13.10</version>
</dependency>
<dependency>
<groupId>org.scala-lang</groupId>
<artifactId>scala-compiler</artifactId>
<version>2.13.10</version>
</dependency>
// java
import scala.reflect.api.JavaUniverse;
import scala.tools.reflect.ToolBox;
public class App {
public static void main(String[] args) {
new App().run();
}
public void run() {
scala.reflect.runtime.package$ runtime = scala.reflect.runtime.package$.MODULE$;
JavaUniverse universe = runtime.universe();
JavaUniverse.JavaMirror mirror = universe.runtimeMirror(this.getClass().getClassLoader());
scala.tools.reflect.package$ toolsReflect = scala.tools.reflect.package$.MODULE$;
ToolBox<?> toolBox = toolsReflect.ToolBox(mirror).mkToolBox(toolsReflect.mkSilentFrontEnd(), "");
toolBox.eval(toolBox.parse("Macros.hello()")); // Hello World!
}
}
// scala
import scala.language.experimental.macros
import scala.reflect.macros.blackbox
object Macros {
def hello(): Unit = macro hello_impl
def hello_impl(c: blackbox.Context)(): c.Tree = {
import c.universe._
q"""println("Hello World!")"""
}
}
Is there any trick to use macros in the same file they are defined?
