问题
I'm creating a scala macro to automatically generate case classes from POJOs (in order to make working with avro a little bit nicer).
Everything "works" except that the compiler - during macro expansion only - chokes on my java class. If I comment out the call to the macro, everything compiles fine.
My question is: how do I generate code in the macro such that the compiler resolves my own java classes?
Example error message:
[info] Compiling 1 Scala source to /Users/marcin/development/repos/problemdemo/target/scala-2.11/classes...
typeArgs: scala.collection.immutable.List()
fieldType:class scala.reflect.internal.Trees$Literal|"java.lang.Object"
class scala.reflect.internal.Names$TypeName_S
DEBUG:java.util.ArrayList|java.lang.Object
typeArgs: scala.collection.immutable.List(com.squarefoot.Pojo)
fieldType:class scala.reflect.internal.Trees$Literal|"java.util.ArrayList"
class scala.reflect.internal.Names$TypeName_R
DEBUG:java.util.ArrayList|java.util.ArrayList
typeArgs: scala.collection.immutable.List()
fieldType:class scala.reflect.internal.Trees$Literal|"scala.Int"
class scala.reflect.internal.Names$TypeName_S
DEBUG:java.util.ArrayList|scala.Int
Expr[Any](case class Demo extends scala.Product with scala.Serializable {
<caseaccessor> <paramaccessor> val qux: "java.lang.Object" = _;
<caseaccessor> <paramaccessor> val baz: java.util.ArrayList[com.squarefoot.Pojo] = _;
<caseaccessor> <paramaccessor> val bar: "scala.Int" = _;
def <init>(qux: "java.lang.Object", baz: java.util.ArrayList[com.squarefoot.Pojo], bar: "scala.Int") = {
super.<init>();
()
}
})
[error] /Users/marcin/development/repos/problemdemo/src/main/scala/com/squarefoot/converters/problemdemo.scala:10: not found: type com.squarefoot.Pojo
[error] @Caseify(classOf[com.squarefoot.Pojo])
[error] ^
[error] one error found
problemdemo/avroschemas/src/main/java/com/squarefoot/Pojo.java:
package com.squarefoot;
public class Pojo {
public int bar;
public java.util.ArrayList<Pojo> baz;
public java.lang.Object qux;
}
problemdemo/src/main/scala/com/squarefoot/converters/problemdemo.scala:
package com.squarefoot.converters
import com.squarefoot.Pojo
class Foomin {
val foobar: java.util.List[Int]
val foobaz: com.squarefoot.Pojo
}
@Caseify(classOf[com.squarefoot.Pojo])
case class Demo()
problemdemo/macros/src/main/scala/com/squarefoot/converters/Caseify.scala:
package com.squarefoot.converters
import scala.language.experimental.macros
import scala.annotation.StaticAnnotation
import scala.reflect.macros.Context
/**
* Generate case class from POJO
* ex:
* @Caseify(classOf[com.squarefoot.incominglisting])
* case class Incominglisting()
* NOTE that the type parameter to classOf must be provided as a fully
* qualified name, otherwise the macro code here won't be able to find it.
*
* Generates a case class with the same members as the public, non-static
* members of the pojo
*
* Note that you must have all types used in the POJO in scope where the macro
* is invoked
*/
class Caseify[T](source: Class[T]) extends StaticAnnotation {
def macroTransform(annottees: Any*) = macro CaseifyMacro.expand_impl[T]
}
object CaseifyMacro {
/** generate case class from POJO */
def expand_impl[T](c: Context)(annottees: c.Expr[Any]*) = {
import c.universe._
// macro expand the macro expression itself to extract param
val source: Class[T] = c.prefix.tree match {
case q"new Caseify($param)" => c.eval[Class[T]](c.Expr(param))
}
val rm = scala.reflect.runtime.currentMirror
val vars =
rm.classSymbol(source).toType.members.map(_.asTerm).
filter(_.isVar).filter(_.isPublic)
val fields = vars.map({f=>
val fieldName = TermName(f.name.toString)
val fieldType = tq"${f.typeSignature.typeConstructor.typeSymbol.fullName}"
val rawTypeArgs = f.typeSignature.typeArgs.map(a=>TypeName(a.toString))
val typeArgs = tq"${rawTypeArgs}"
println("typeArgs: "+typeArgs.toString)
println("fieldType:"+fieldType.getClass.toString+"|"+fieldType.toString)
println(f.typeSignature.typeSymbol.asType.name.getClass.toString)
val arraylistname = tq"java.util.ArrayList"
println("DEBUG:"+tq"${arraylistname}".toString+"|"+f.typeSignature.typeConstructor.typeSymbol.fullName)
q"val $fieldName: $fieldType"
if(rawTypeArgs.nonEmpty) {
val appliedFieldType = tq"${arraylistname}[..$rawTypeArgs]"
q"val $fieldName: $appliedFieldType"
}
else
q"val $fieldName: $fieldType"
})
annottees.map(_.tree) match {
case List(q"case class $newname()") => {
val q = c.Expr[Any](
// Add your own logic here, possibly using arguments on the annotation.
q"""
case class $newname(..$fields)
""")
println(q.toString)
q
}
// Add validation and error handling here.
}
}
}
Sbt files:
problemdemo/build.sbt
name := "data-importer"
addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)
scalaVersion := "2.11.8"
val avroVersion = "1.8.1"
lazy val root =
project.in( file(".") )
.aggregate(avroschemas, macros).dependsOn(macros, avroschemas)
lazy val macros = project.dependsOn(avroschemas)
lazy val avroschemas = project
libraryDependencies ++= Seq(
"org.scala-lang" % "scala-reflect" % scalaVersion.value
)
// better error reporting
scalacOptions in Test ++= Seq("-Yrangepos")
run in Compile := Defaults.runTask(fullClasspath in Compile, mainClass in (Compile, run), runner in (Compile, run))
problemdemo/macros/build.sbt
name := "data-importer-macros"
addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)
organization := "com.squarefoot"
scalaVersion := "2.11.3"
libraryDependencies ++= Seq(
"org.scala-lang" % "scala-reflect" % scalaVersion.value
)
scalacOptions in Test ++= Seq("-Yrangepos")
problemdemo/avroschemas/build.sbt
name := "data-importer-avroschemas"
addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)
organization := "com.squarefoot"
scalaVersion := "2.11.8"
// better error reporting
scalacOptions in Test ++= Seq("-Yrangepos")
run in Compile := Defaults.runTask(fullClasspath in Compile, mainClass in (Compile, run), runner in (Compile, run))
来源：https://stackoverflow.com/questions/41304155/scala-macro-cant-find-my-java-class