Avoid outputstream

Signed-off-by: Paulo Lopes <pmlopes@gmail.com>

src/main/java/io/vertx/core/json/Json.java

@@ -26,7 +26,6 @@
 
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.OutputStream;
 import java.math.BigDecimal;
 import java.time.Instant;
 import java.util.Base64;
@@ -75,17 +74,7 @@ public static String encode(Object obj) throws EncodeException {
 
   public static Buffer encodeToBuffer(Object obj) throws EncodeException {
     try {
-      final Buffer buffer = Buffer.buffer();
-
-      mapper.writeValue(new OutputStream() {
-        @Override
-        public void write(int b) throws IOException {
-          buffer.appendByte((byte) b);
-        }
-      }, obj);
-
-      return buffer;
-
+      return Buffer.buffer(mapper.writeValueAsBytes(obj));
     } catch (Exception e) {
       throw new EncodeException("Failed to encode as JSON: " + e.getMessage());
     }