Fix #3 Support SBT: Force the REPL to use the same class loader with the target thread, so that they don't see different instances of a static variable of the same class

Author: Dao Ngoc

agent/src/main/java/scalive/Server.java

@@ -38,10 +38,10 @@ public static void serve(Socket client, String jarpath, String clId) throws Exce
             if (parentCl == null) return;
 
             URLClassLoader cl        = createClassLoaderWithReplJars(jarpath, parentCl);
-            Class<?>       repl      = Class.forName("scalive.Repl", true, cl);
-            Method         method    = repl.getMethod("run", String.class, InputStream.class, OutputStream.class);
             String         classpath = getClasspathForRepl(cl, parentCl);
-            method.invoke(null, classpath, in, out);
+            Class<?>       repl      = Class.forName("scalive.Repl", true, cl);
+            Method         method    = repl.getMethod("run", ClassLoader.class, String.class, InputStream.class, OutputStream.class);
+            method.invoke(null, cl, classpath, in, out);
         } finally {
             System.setIn(oldIn);
             System.setOut(oldOut);

repl/src/main/java/scalive/Repl.java

@@ -6,14 +6,15 @@
 import java.io.OutputStream;
 import java.io.PrintWriter;
 
+import scala.Option;
 import scala.tools.nsc.interpreter.ILoop;
 import scala.tools.nsc.Settings;
 
 // This must be split to a separate JAR (scalive-repl.jar), different from
 // the JAR file that contains the agent (scalive-agent.jar). Otherwise the agent
 // can't load this Repl class.
 public class Repl {
-    public static void run(String classpath, InputStream in, OutputStream out) {
+    public static void run(ClassLoader cl, String classpath, InputStream in, OutputStream out) {
         // Without the below settings, there will be error:
         // Failed to initialize compiler: object scala.runtime in compiler mirror not found.
         // ** Note that as of 2.8 scala does not assume use of the java classpath.
@@ -26,8 +27,15 @@ public static void run(String classpath, InputStream in, OutputStream out) {
         //
         // http://stackoverflow.com/questions/18150961/scala-runtime-in-compiler-mirror-not-found-but-working-when-started-with-xboo
         Settings settings = new Settings();
+
+        // http://www.scala-lang.org/old/node/8002
         settings.classpath().value_$eq(classpath);
 
+        // Without this class loader setting, the REPL and the target process will
+        // see different instances of a static variable of the same class!
+        // http://stackoverflow.com/questions/5950025/multiple-instances-of-static-variables
+        settings.explicitParentLoader_$eq(Option.apply(cl));
+
         ILoop repl = new ILoop(
             new BufferedReader(new InputStreamReader(in)),
             new PrintWriter(out)