在Scala 2.11中在运行时动态编译scala类文件

Question

我有以下代码在Scala 2.10中工作,以在Scala中运行时编译外部类

/**
  * Compile scala files and keep them loaded in memory
  * @param classDir Directory storing the generated scala files
  * @throws IOException if there is problem reading the source files
  * @return Classloader that contains the compiled external classes
  */
@throws[IOException]
def compileFiles(classDir: String): AbstractFileClassLoader = {
  val files = recursiveListFiles(new File(classDir))
                  .filter(_.getName.endsWith("scala"))
  println("Loaded files: \n" + files.mkString("[", ",\n", "]"))

  val settings: GenericRunnerSettings = new GenericRunnerSettings(err => println("Interpretor error: " + err))
  settings.usejavacp.value = true
  val interpreter: IMain = new IMain(settings)
  files.foreach(f => {
    interpreter.compileSources(new BatchSourceFile(AbstractFile.getFile(f)))
  })

  interpreter.getInterpreterClassLoader()
}

然后在其他地方,我可以使用类加载器引用来实例化类,例如

val personClass = classLoader.findClass("com.example.dynacsv.PersonData")
val ctor = personClass.getDeclaredConstructors()(0)
val instance = ctor.newInstance("Mr", "John", "Doe", 25: java.lang.Integer, 165: java.lang.Integer, 1: java.lang.Integer)
println("Instantiated class: " + instance.getClass.getCanonicalName)
println(instance.toString)

但是,由于getInterpreterClassLoader方法已被删除,上述内容不再有效scala.tools.nsc.interpreter.IMain.此外,AbstractFileClassLoader已被移动和弃用.不再允许findClass从外部包调用类加载器中的方法.

在Scala 2.11中执行上述操作的建议方法是什么？谢谢!

Answer 1

如果你的目标是在运行时运行外部scala类,我建议使用eval scala.tools.reflect.ToolBox(它包含在REPL中,但是对于正常使用,你必须添加scala-reflect.jar):

import scala.reflect.runtime.universe
import scala.tools.reflect.ToolBox
val tb = universe.runtimeMirror(getClass.getClassLoader).mkToolBox()
tb.eval(tb.parse("""println("hello!")"""))

您也可以使用编译文件tb.compile.

用示例修改:假设您有外部文件

class PersonData() {
  val field = 42
}
scala.reflect.classTag[PersonData].runtimeClass

所以你也是

val clazz = tb.compile(tb.parse(src))().asInstanceOf[Class[_]]
val ctor = clazz.getDeclaredConstructors()(0)
val instance = ctor.newInstance()

其他可能性(几乎)是无限的,您可以获得完整的树AST并根据需要使用它:

showRaw(tb.parse(src)) // this is AST of external file sources
// this is quasiquote
val q"""
      class $name {
        ..$stats
      }
      scala.reflect.classTag[PersonData].runtimeClass
    """ = tb.parse(src)
// name: reflect.runtime.universe.TypeName = PersonData
// stats: List[reflect.runtime.universe.Tree] = List(val field = 42)
println(name) // PersonData

有关这些技巧,请参阅官方文档:

http://docs.scala-lang.org/overviews/reflection/symbols-trees-types.html

http://docs.scala-lang.org/overviews/quasiquotes/intro.html