Scan lambda handler classes that do not implement an interface (#25)

Author: mbfreder

src/main/java/software/amazon/lambda/snapstart/ByteCodeIntrospector.java

@@ -49,7 +49,29 @@ private static Set<String> setOf(String ... strings) {
     };
 
     boolean isLambdaHandler(XClass xClass) {
-        return implementsLambdaInterface(xClass) || hasLambdaHandlerMethod(xClass);
+        return implementsLambdaInterface(xClass) || 
+               hasLambdaHandlerMethod(xClass) || 
+               (hasHandlerInClassName(xClass) && hasHandleRequestMethod(xClass));
+    }
+
+    /**
+     * Returns true if the class has the word "Handler" in the name.
+     */
+    private boolean hasHandlerInClassName(XClass xClass) {
+        return xClass.toString().contains("Handler");
+    }
+
+    /**
+     * Returns true if the class has a method called "handleRequest"
+     */
+    private boolean hasHandleRequestMethod(XClass xClass) {
+        List<? extends XMethod> methods = xClass.getXMethods();
+        for (XMethod method : methods) {
+            if (method.getName().equals("handleRequest")) {
+                return true;
+            }
+        }
+        return false;
     }
 
     boolean hasLambdaHandlerMethod(XClass xClass) {

src/test/java/software/amazon/lambda/snapstart/LambdaHandlerInitedWithRandomValueTest.java

@@ -158,6 +158,12 @@ public void testClassImplementingFunctionalInterface() {
         assertThat(bugCollection, containsExactly(1, snapStartBugMatcher().inClass("ImplementsFunctionalInterface").atField("random").atLine(8).build()));
     }
 
+    @Test
+    public void testLambdaWithNoInterface() {
+        BugCollection bugCollection = findBugsInClasses("LambdaHandlerWithNoInterface");
+        assertThat(bugCollection, containsExactly(1, snapStartBugMatcher().inClass("LambdaHandlerWithNoInterface").atField("random").atLine(7).build()));
+    }
+  
     @Test
     public void testLambdaWithDependencyInjection() {
         BugCollection bugCollection = findBugsInClasses("DependencyInjection", "MyDependency");

src/test/java/software/amazon/lambda/snapstart/lambdaexamples/LambdaHandlerWithNoInterface.java

@@ -0,0 +1,12 @@
+package software.amazon.lambda.snapstart.lambdaexamples;
+
+import java.util.UUID;
+
+public class LambdaHandlerWithNoInterface {
+
+    private final UUID random = UUID.randomUUID();
+
+    public String handleRequest(){
+        return random.toString();
+    }
+}