The JSON Data Marshaller implementation

Signed-off-by: Fabio José <fabiojose@gmail.com>

api/src/main/java/io/cloudevents/format/BinaryMarshaller.java

@@ -146,9 +146,7 @@ public class BinaryMarshaller<P, T, A extends Attributes> {
 					.collect(Collectors.toMap(Entry::getKey, Entry::getValue));
 			})
 			.headers(BinaryFormatHeaderMapperImpl.mapper()::map)
-			.payload((data, headers) -> {
-				return Json.encode(data);
-			})
+			.payload(Json.marshaller()::marshal)
 			.build((payload, headers) -> {
 				return new Format<>(payload, headers);
 			});

api/src/main/java/io/cloudevents/json/Json.java

@@ -21,10 +21,12 @@ import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
 
 import io.cloudevents.Attributes;
+import io.cloudevents.fun.DataMarshaller;
 import io.cloudevents.fun.DataUnmarshaller;
 
 import java.io.InputStream;
 import java.time.ZonedDateTime;
+import java.util.Map;
 
 public final class Json {
 
@@ -116,6 +118,21 @@ public final class Json {
 			}
 		};
     }
+    
+    /**
+     * Creates a JSON Data Marshaller
+     * @param <T> The 'data' type
+     * @return A new instance of {@link DataMarshaller}
+     */
+    public static <T> DataMarshaller<String, T> marshaller() {
+    	return new DataMarshaller<String, T>() {
+			@Override
+			public String marshal(T data, Map<String, Object> headers) 
+					throws Exception {
+				return Json.encode(data);
+			}
+		};
+    }
 
     private Json() {
         // no-op