Improved error messages if an invalid URL was passed

client/src/main/java/org/asynchttpclient/uri/Uri.java

@@ -36,6 +36,12 @@ public static Uri create(Uri context, final String originalUrl) {
         UriParser parser = new UriParser();
         parser.parse(context, originalUrl);
 
+        if (null == parser.scheme || null == parser.host) {
+            throw new IllegalArgumentException(
+                    String.format("The UriParser could not extract all required values: scheme=%s, host=%s. Please "
+                                  + "make sure you provide a valid URL.", parser.scheme, parser.host));
+        }
+
         return new Uri(parser.scheme,//
                 parser.userInfo,//
                 parser.host,//

client/src/test/java/org/asynchttpclient/BasicHttpTest.java

@@ -240,7 +240,7 @@ public Response onCompleted(Response response) throws Exception {
         });
     }
 
-    @Test(expectedExceptions = NullPointerException.class)
+    @Test(expectedExceptions = IllegalArgumentException.class)
     public void nullSchemeThrowsNPE() throws Throwable {
         withClient().run(client -> client.prepareGet("gatling.io").execute());
     }
@@ -859,7 +859,7 @@ public void getShouldAllowBody() throws Throwable {
         });
     }
 
-    @Test(expectedExceptions = NullPointerException.class)
+    @Test(expectedExceptions = IllegalArgumentException.class)
     public void malformedUriThrowsException() throws Throwable {
         withClient().run(client -> {
             withServer(server).run(server -> {

client/src/test/java/org/asynchttpclient/uri/UriTest.java

@@ -358,4 +358,33 @@ public void testIsWebsocket() {
         uri = Uri.create(url);
         assertTrue(uri.isWebSocket(), "isWebSocket should return true for wss url");
     }
+
+    @Test
+    public void testCreateWithInvalidUrl_throwsIllegalArgumentException() {
+        // a valid URL would contain the scheme/protocol
+        String invalidUrl = "localhost";
+
+        Throwable exception = null;
+        try {
+            // run
+            Uri.create(invalidUrl);
+        } catch (IllegalArgumentException ex) {
+            exception = ex;
+        }
+
+        // verify
+        assertNotNull(exception);
+        assertEquals("The UriParser could not extract all required values: scheme=null, host=null. Please make "
+                     + "sure you provide a valid URL.", exception.getMessage());
+    }
+
+    @Test
+    public void testCreateWithValidUrl_doesNotThrowException() {
+        String validUrl = "https://localhost";
+        try {
+            Uri.create(validUrl);
+        } catch (IllegalArgumentException ex) {
+            fail(ex.getMessage());
+        }
+    }
 }