Use JsonBodyWriter directly rather than converting JSON to strings first

Change-Id: I2facf51d0bf9b6ea4ccb47b0ac4214af203982a1
diff --git a/web/api/src/main/java/org/onosproject/rest/JsonBodyWriter.java b/web/api/src/main/java/org/onosproject/rest/JsonBodyWriter.java
index 3305f7d..e693544 100644
--- a/web/api/src/main/java/org/onosproject/rest/JsonBodyWriter.java
+++ b/web/api/src/main/java/org/onosproject/rest/JsonBodyWriter.java
@@ -22,6 +22,8 @@
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.MultivaluedMap;
 import javax.ws.rs.ext.MessageBodyWriter;
+import javax.ws.rs.ext.Provider;
+
 import java.io.IOException;
 import java.io.OutputStream;
 import java.lang.annotation.Annotation;
@@ -30,6 +32,7 @@
 /**
  * JAX-RS Response message body writer.
  */
+@Provider
 @Produces("application/json")
 public class JsonBodyWriter implements MessageBodyWriter<ObjectNode> {