Added support for cross-origin requests (CORS).

src/main/groovy/com/jdbernard/nlsongs/rest/AllowCors.java

@@ -0,0 +1,12 @@
+package com.jdbernard.nlsongs.rest;
+
+import javax.ws.rs.NameBinding;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+@NameBinding
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Retention(value = RetentionPolicy.RUNTIME)
+public @interface AllowCors {}

src/main/groovy/com/jdbernard/nlsongs/rest/CorsResponseFilter.java

@@ -0,0 +1,30 @@
+package com.jdbernard.nlsongs.rest;
+
+import javax.annotation.Priority;
+import javax.ws.rs.Priorities;
+import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.container.ContainerRequestContext;
+import javax.ws.rs.container.ContainerResponseContext;
+import javax.ws.rs.container.ContainerResponseFilter;
+import javax.ws.rs.ext.Provider;
+
+@Provider @AllowCors @Priority(Priorities.HEADER_DECORATOR)
+public class CorsResponseFilter implements ContainerResponseFilter {
+
+    @Override
+    public void filter(ContainerRequestContext reqCtx,
+                       ContainerResponseContext respCtx) {
+
+        MultivaluedMap<String, Object> headers = respCtx.getHeaders();
+
+        headers.add("Access-Control-Allow-Origin",
+            reqCtx.getHeaderString("Origin"));
+
+        headers.add("Access-Control-Allow-Methods",
+            "GET, POST, PUT, DELETE, OPTIONS");
+
+        headers.add("Access-Control-Allow-Headers",
+            reqCtx.getHeaderString("Access-Control-Request-Headers"));
+
+    }
+}

src/main/groovy/com/jdbernard/nlsongs/rest/PingResource.groovy

@@ -1,12 +0,0 @@
-package com.jdbernard.nlsongs.rest
-
-import javax.ws.rs.GET;
-import javax.ws.rs.Path;
-import javax.ws.rs.Produces;
-
-@Path("v1/ping")
-public class PingResource {
-
-    @GET
-    @Produces("text/plain")
-    public String ping() { return "pong" } }

src/main/groovy/com/jdbernard/nlsongs/rest/ServicesResource.java

@@ -14,7 +14,7 @@ import javax.ws.rs.core.MediaType;
 import com.jdbernard.nlsongs.servlet.NLSongsContext;
 import com.jdbernard.nlsongs.model.Service;
 
-@Path("v1/services")
+@Path("v1/services") @AllowCors
 @Produces({MediaType.APPLICATION_JSON})
 @Consumes({MediaType.APPLICATION_JSON})
 public class ServicesResource {

src/main/groovy/com/jdbernard/nlsongs/rest/SongsResource.java

@@ -13,12 +13,12 @@ import javax.ws.rs.core.MediaType;
 import com.jdbernard.nlsongs.servlet.NLSongsContext;
 import com.jdbernard.nlsongs.model.Song;
 
-@Path("v1/songs")
+@Path("v1/songs") @AllowCors
 @Produces({MediaType.APPLICATION_JSON})
 @Consumes({MediaType.APPLICATION_JSON})
 public class SongsResource {
 
-    @GET
+    @GET @AllowCors
     public List<Song> getSongs() {
         return NLSongsContext.songsDB.findAllSongs(); }