ensure that baseUrl cannot be null and that when used it has a trailing slash

Author: davidmoten

src/main/java/com/github/davidmoten/aws/lw/client/Request.java

@@ -199,7 +199,9 @@ private static String calculateUrl(String url, String serviceName, Optional<Stri
             List<NameValue> queries, List<String> pathSegments, BaseUrlFactory baseUrlFactory) {
         String u = url;
         if (u == null) {
-            u = baseUrlFactory.create(serviceName, region) //
+            String baseUrl = baseUrlFactory.create(serviceName,  region);
+            Preconditions.checkNotNull(baseUrl, "baseUrl cannot be null");
+            u = trimAndEnsureHasTrailingSlash(baseUrl) //
                     + pathSegments //
                             .stream() //
                             .map(x -> trimAndRemoveLeadingAndTrailingSlashes(x)) //
@@ -222,6 +224,16 @@ private static String calculateUrl(String url, String serviceName, Optional<Stri
         return u;
     }
 
+    //VisibleForTesting
+    static String trimAndEnsureHasTrailingSlash(String s) {
+        String r = s.trim();
+        if (r.endsWith("/")) {
+            return r;
+        } else {
+            return r + "/";
+        }
+    }
+
     public byte[] responseAsBytes() {
         Response r = response();
         Optional<? extends RuntimeException> exception = client.exceptionFactory().create(r);

src/test/java/com/github/davidmoten/aws/lw/client/RequestTest.java

@@ -53,5 +53,13 @@ public void testHasBodyButNoHeader() throws IOException {
             assertFalse(Request.hasBody(r));
         }
     }
+    
+    @Test
+    public void testTrimAndEnsureHasTrailingSlash() {
+        assertEquals("/",Request.trimAndEnsureHasTrailingSlash(""));
+        assertEquals("/",Request.trimAndEnsureHasTrailingSlash("/"));
+        assertEquals("abc/",Request.trimAndEnsureHasTrailingSlash("abc"));
+        assertEquals("abc/",Request.trimAndEnsureHasTrailingSlash("abc/"));
+    }
 
 }