Added null path check and unit tests to address #130.

Author: sapessi

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsProxyHttpServletRequest.java

@@ -704,7 +704,7 @@ private Map<String, Part> getMultipartFormParametersMap() {
 
 
     private String cleanUri(String uri) {
-        String finalUri = uri;
+        String finalUri = (uri == null ? "" : uri);
 
         if (!finalUri.startsWith("/")) {
             finalUri = "/" + finalUri;

aws-serverless-java-container-spark/src/test/java/com/amazonaws/serverless/proxy/spark/HelloWorldSparkStreamTest.java

@@ -78,6 +78,21 @@ public void helloRequest_basicStream_populatesOutputSuccessfully() {
         }
     }
 
+    @Test
+    public void nullPathRequest_doesntFail_expectA404() {
+        InputStream req = new AwsProxyRequestBuilder().method("GET").path(null).buildStream();
+        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+        try {
+            handler.proxyStream(req, outputStream, new MockLambdaContext());
+            AwsProxyResponse response = LambdaContainerHandler.getObjectMapper().readValue(outputStream.toByteArray(), AwsProxyResponse.class);
+
+            assertEquals(404, response.getStatusCode());
+        } catch (IOException e) {
+            e.printStackTrace();
+            fail();
+        }
+    }
+
     private static void configureRoutes() {
         get("/hello", (req, res) -> {
             res.status(200);