How do I exclude fields with Jackson not using annotations?

Question

I need to exclude some fields by names before rendering. The list of fields is dynamic, so I can't use annotations.

I've tried to create custom serializer but I can't get field name there.

In GSON I've used ExclusionStrategy, but Jackson has no such functionality. Is there an equivalent?

Answer 1

The below example of excluding fields by name is from my blog post, Gson v Jackson - Part 4. (Search for the PropertyFilterMixIn.) This example demonstrates using a FilterProvider with a SimpleBeanPropertyFilter to serializeAllExcept a user-specified list of field names.

@JsonFilter("filter properties by name")   class PropertyFilterMixIn {}    class Bar   {     public String id = "42";     public String name = "Fred";     public String color = "blue";     public Foo foo = new Foo();   }    class Foo   {     public String id = "99";     public String size = "big";     public String height = "tall";   }    public class JacksonFoo   {     public static void main(String[] args) throws Exception     {       ObjectMapper mapper = new ObjectMapper();       mapper.getSerializationConfig().addMixInAnnotations(           Object.class, PropertyFilterMixIn.class);        String[] ignorableFieldNames = { "id", "color" };       FilterProvider filters = new SimpleFilterProvider()         .addFilter("filter properties by name",              SimpleBeanPropertyFilter.serializeAllExcept(                 ignorableFieldNames));       ObjectWriter writer = mapper.writer(filters);        System.out.println(writer.writeValueAsString(new Bar()));       // output:       // {"name":"James","foo":{"size":"big","height":"tall"}}     }   }  

(Note: The relevant API may have changed slightly with a recent Jackson release.)

While the example does use a seemingly unnecessary annotation, the annotation is not applied to the fields to be excluded. (To help get the API changed to simplify the necessary configuration a bit, please don't hesitate to vote for implementation of issue JACKSON-274.