sbt运行IMain，play会出错
sbt运行IMain，play会出错
提问于 2014-03-11 15:37:43
我已经构建了一个litte对象，它可以动态地解释scala代码并从中捕获一个值。
object Interpreter {
import scala.tools.nsc._
import scala.tools.nsc.interpreter._
class Dummy
val settings = new Settings
settings.usejavacp.value = false
settings.embeddedDefaults[Dummy] // to make imain useable with sbt.
val imain = new IMain(settings)
def run(code: String, returnId: String) = {
this.imain.beQuietDuring{
this.imain.interpret(code)
}
val ret = this.imain.valueOfTerm(returnId)
this.imain.reset()
ret
}
}
object Main {
def main(args: Array[String]) {
println(Interpreter.run("val x = 1", "x"))
}
}在纯sbt环境中或由scala解释器调用，此代码工作良好！但是，如果我在一个简单的play (Version2.2.2)应用程序中运行它，它将在val ret = this.imain.valueOfTerm(returnId)上获得一个空指针。
play 还使用了修改的 sbt，因此它可能会工作。如果这段代码不再工作，play 会做什么呢？如何让这段代码在play**?** 中工作
备注
那是用过的build.sbt
name := "Test"
version := "1.0"
scalaVersion := "2.10.3"
libraryDependencies += "org.scala-lang" % "scala-compiler" % scalaVersion.value或者，我尝试了这个实现，但它也解决不了这个问题：
object Interpreter2 {
import scala.tools.nsc._
import scala.tools.nsc.interpreter._
import play.api._
import play.api.Play.current
val settings: Settings = {
lazy val urls = java.lang.Thread.currentThread.getContextClassLoader match {
case cl: java.net.URLClassLoader => cl.getURLs.toList
case _ => sys.error("classloader is not a URLClassLoader")
}
lazy val classpath = urls map {_.toString}
val tmp = new Settings()
tmp.bootclasspath.value = classpath.distinct mkString java.io.File.pathSeparator
tmp
}
val imain = new IMain(settings)
def run(code: String, returnId: String) = {
this.imain.beQuietDuring {
this.imain.interpret(code)
}
val ret = this.imain.valueOfTerm(returnId)
this.imain.reset()
ret
}
}我发现了进行第二个实现的有用链接：
回答 2
Stack Overflow用户
回答已采纳
发布于 2014-03-21 09:58:31
这是因为play使用了来自sbt的“叉入运行”特性。此特性启动一个新JVM，这将导致出现此故障：
[info] Failed to initialize compiler: object scala.runtime in compiler mirror not found.
[info] ** Note that as of 2.8 scala does not assume use of the java classpath.
[info] ** For the old behavior pass -usejavacp to scala, or if using a Settings
[info] ** object programatically, settings.usejavacp.value = true.请参阅：http://www.scala-sbt.org/release/docs/Detailed-Topics/Forking
Stack Overflow用户
发布于 2014-05-29 03:23:56
在这个问题上花了几个小时之后，我想出了一个解决方案。它在SBT内部和外部都能工作。它还可以在各种托管环境(如OSGi)中工作：
private def getClasspathUrls(classLoader: ClassLoader, acc: List[URL]): List[URL] = {
classLoader match {
case null => acc
case cl: java.net.URLClassLoader => getClasspathUrls(classLoader.getParent, acc ++ cl.getURLs.toList)
case c => LOGGER.error("classloader is not a URLClassLoader and will be skipped. ClassLoader type that was skipped is " + c.getClass)
getClasspathUrls(classLoader.getParent, acc)
}
}
val classpathUrls = getClasspathUrls(this.getClass.getClassLoader, List())
val classpathElements = classpathUrls map {url => url.toURI.getPath}
val classpath = classpathElements mkString java.io.File.pathSeparator
val settings = new Settings
settings.bootclasspath.value = classpath
val imain = new IMain(settings)
// use imain to interpret code. It should be able to access all your application classes as well as dependent libraries. 页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/22330243
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