anchor.diff:      }
       
       @GET
  -    public String findFromage(String fromage) {
  -        if(fromage == null)
  +    public String findCheese(String cheese) {
  +        if(cheese == null)
               // send a 400
               throw new BadRequestException();
  -        return cheeses.findCheese(fromage);
  +        return cheeses.findCheese(cheese);
       }
   } 
   ----
  
positive.code: which are responsible for defining which Java type they map from/to, for which media types,
  and how they turn HTTP bodies to/from Java instances of that type.
  
  For example, if we have our own `FroMage` type on our endpoint:
  
  [source,java]
  ----
  
negative.code: import javax.ws.rs.ext.Provider;
  
  @Provider
  public class CheeseBodyHandler implements MessageBodyReader<Cheese>, 
                                             MessageBodyWriter<Cheese> {
  
      @Override
      public boolean isWriteable(Class<?> type, Type genericType, 
                                 Annotation[] annotations, MediaType mediaType) {
          return type == Cheese.class;
      }
  
      @Override
      public void writeTo(Cheese t, Class<?> type, Type genericType, 
                          Annotation[] annotations, MediaType mediaType,
                          MultivaluedMap<String, Object> httpHeaders, 
                          OutputStream entityStream)
              throws IOException, WebApplicationException {
          entityStream.write(("[CheeseV1]" + t.name)
                             .getBytes(StandardCharsets.UTF_8));
      }
  
      @Override
      public boolean isReadable(Class<?> type, Type genericType, 
                                Annotation[] annotations, MediaType mediaType) {
          return type == Cheese.class;
      }
  
      @Override
      public Cheese readFrom(Class<Cheese> type, Type genericType, 
                              Annotation[] annotations, MediaType mediaType,
                              MultivaluedMap<String, String> httpHeaders,
                              InputStream entityStream)
              throws IOException, WebApplicationException {
          String body = new String(entityStream.readAllBytes(), StandardCharsets.UTF_8);
          if(body.startsWith("[CheeseV1]"))
              return new Cheese(body.substring(11));
          throw new IOException("Invalid cheese: " + body);
      }
  
  }
  