Set Thread context classloder for entire middleware chain (#717)

* Set Thread context classloder for entire middleware chain

* clean up code

* clean up

src/main/java/com/microsoft/azure/functions/worker/broker/JavaFunctionBroker.java

@@ -113,20 +113,29 @@ private void initializeFunctionInstanceInjector() {
 	}
 
 	private FunctionExecutionMiddleware getFunctionExecutionMiddleWare() {
-		FunctionExecutionMiddleware functionExecutionMiddleware = new FunctionExecutionMiddleware(
-				JavaMethodExecutors.createJavaMethodExecutor(this.classLoaderProvider.createClassLoader()));
+		FunctionExecutionMiddleware functionExecutionMiddleware = new FunctionExecutionMiddleware(JavaMethodExecutor.getInstance());
 		WorkerLogManager.getSystemLogger().info("Load last middleware: FunctionExecutionMiddleware");
 		return functionExecutionMiddleware;
 	}
 
 	public Optional<TypedData> invokeMethod(String id, InvocationRequest request, List<ParameterBinding> outputs)
 			throws Exception {
 		ExecutionContextDataSource executionContextDataSource = buildExecutionContext(id, request);
-		this.invocationChainFactory.create().doNext(executionContextDataSource);
+		invoke(executionContextDataSource);
 		outputs.addAll(executionContextDataSource.getDataStore().getOutputParameterBindings(true));
 		return executionContextDataSource.getDataStore().getDataTargetTypedValue(BindingDataStore.RETURN_NAME);
 	}
 
+	private void invoke(ExecutionContextDataSource executionContextDataSource) throws Exception {
+		ClassLoader prevContextClassLoader = Thread.currentThread().getContextClassLoader();
+		try {
+			Thread.currentThread().setContextClassLoader(classLoaderProvider.createClassLoader());
+			this.invocationChainFactory.create().doNext(executionContextDataSource);
+		} finally {
+			Thread.currentThread().setContextClassLoader(prevContextClassLoader);
+		}
+	}
+
 	private ExecutionContextDataSource buildExecutionContext(String id,  InvocationRequest request)
 			throws NoSuchMethodException {
 		ImmutablePair<String, FunctionDefinition> methodEntry = this.methods.get(id);

src/main/java/com/microsoft/azure/functions/worker/broker/JavaMethodExecutor.java

@@ -1,14 +1,25 @@
 package com.microsoft.azure.functions.worker.broker;
 
-
-import java.util.*;
 import com.microsoft.azure.functions.worker.binding.*;
 
-
 /**
  * Used to executor of arbitrary Java method in any JAR using reflection.
  * Thread-Safety: Multiple thread.
  */
-public interface JavaMethodExecutor {
-    void execute(ExecutionContextDataSource executionContextDataSource) throws Exception;
+public class JavaMethodExecutor {
+
+    private static final JavaMethodExecutor INSTANCE = new JavaMethodExecutor();
+
+    public static JavaMethodExecutor getInstance(){
+        return INSTANCE;
+    }
+
+    private JavaMethodExecutor() {}
+
+    public void execute(ExecutionContextDataSource executionContextDataSource) throws Exception {
+        Object retValue = ParameterResolver.resolveArguments(executionContextDataSource)
+                .orElseThrow(() -> new NoSuchMethodException("Cannot locate the method signature with the given input"))
+                .invoke(executionContextDataSource::getFunctionInstance);
+        executionContextDataSource.updateReturnValue(retValue);
+    }
 }