Add ActorMethodInfoMap (#47)

* Add ActorMethodInfoMap

sdk/src/main/java/io/dapr/actors/runtime/ActorMethodInfoMap.java

@@ -0,0 +1,35 @@
+package io.dapr.actors.runtime;
+
+import java.lang.reflect.Method;
+import java.util.HashMap;
+
+/**
+ *  Actor method dispatcher map. Holds method_name -> Method for methods defined in Actor interfaces.
+ */
+class ActorMethodInfoMap {
+    private final HashMap<String, Method> methods;
+
+    public <T> ActorMethodInfoMap(Iterable<Class<T>> interfaceTypes)
+    {
+        this.methods = new HashMap<String, Method>();
+
+        // Find methods which are defined in Actor interface.
+        for (Class<T> actorInterface : interfaceTypes)
+        {
+            for (Method methodInfo : actorInterface.getMethods())
+            {
+                this.methods.put(methodInfo.getName(), methodInfo);
+            }
+        }
+    }
+
+    public Method LookupActorMethodInfo(String methodName) throws NoSuchMethodException
+    {
+        Method methodInfo = this.methods.get(methodName);
+        if (methodInfo == null) {
+            throw new NoSuchMethodException("Actor type doesn't contain method " + methodName);
+        }
+
+        return methodInfo;
+    }
+}

sdk/src/test/java/io/dapr/actors/runtime/ActorMethodInfoMapTest.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) Microsoft Corporation.
+ * Licensed under the MIT License.
+ */
+
+package io.dapr.actors.runtime;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+import java.util.ArrayList;
+
+/**
+ * Unit tests for ActorMethodInfoMap.
+ */
+public class ActorMethodInfoMapTest {
+
+    @Test
+    public void normalUsage() {
+        ArrayList<Class<TestActor>> interfaceTypes = new ArrayList<Class<TestActor>>();
+        interfaceTypes.add(TestActor.class);
+        ActorMethodInfoMap m = new ActorMethodInfoMap(interfaceTypes);
+
+        try {
+            Method m1 = m.LookupActorMethodInfo("getData");
+            Assert.assertEquals("getData", m1.getName());
+            Class c = m1.getReturnType();
+            Assert.assertEquals(c.getClass(), String.class.getClass());
+            Parameter[] p = m1.getParameters();
+            Assert.assertEquals(p[0].getType().getClass(), String.class.getClass());
+        }
+        catch(Exception e) {
+            Assert.fail("Exception not expected.");
+        }
+    }
+
+    @Test(expected = NoSuchMethodException.class)
+    public void lookUpNonExistingMethod() throws NoSuchMethodException {
+        ArrayList<Class<TestActor>> interfaceTypes = new ArrayList<Class<TestActor>>();
+        interfaceTypes.add(TestActor.class);
+        ActorMethodInfoMap m = new ActorMethodInfoMap(interfaceTypes);
+
+        m.LookupActorMethodInfo("thisMethodDoesNotExist");
+    }
+
+    /**
+     *  Only used for this test.
+     */
+    public interface TestActor extends Actor {
+        String getData(String key);
+    }
+}