Using conditions to dynamically exclude POJO property in Jackson json serialization

Question

I have a requirement to dynamically exclude certain property within a List of a defined POJO. The main POJO to be serialized is:

public class Foo
{
    List&         


        

Answer 1

You should write a custom Jackson filter which would filter out a POJO property depending on other property value. You should override the PropertyFilter.serializeAsField() method to get access to the instance of the serialized object. Here is an example:

public class JacksonFilter2 {
    @JsonFilter("filter")
    public static class Bar {
        public final int id;
        @JsonIgnore
        public final boolean ignoreId;
        public final String name;

        public Bar(int id, boolean ignoreId, String name) {
            this.id = id;
            this.ignoreId = ignoreId;
            this.name = name;
        }
    }

    public static class ExcludeIdFilter extends SimpleBeanPropertyFilter {

        @Override
        protected boolean include(BeanPropertyWriter writer) {
            return true;
        }

        @Override
        protected boolean include(PropertyWriter writer) {
            return true;
        }

        @Override
        public void serializeAsField(Object pojo,
                                     JsonGenerator jgen,
                                     SerializerProvider provider,
                                     PropertyWriter writer) throws Exception {
            if (pojo instanceof Bar
                    && "id".equals(writer.getName())
                    && ((Bar) pojo).ignoreId) {
               writer.serializeAsOmittedField(pojo, jgen, provider);
            } else {
                super.serializeAsField(pojo, jgen, provider, writer);
            }
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        List bars = Arrays.asList(new Bar(1, false, "one"),  new Bar(2, true, "two"));
        ObjectMapper mapper = new ObjectMapper();
        mapper.setFilters(new SimpleFilterProvider().addFilter("filter", new ExcludeIdFilter()));
        System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(bars));
    }

}

Output:

[ {
  "id" : 1,
  "name" : "one"
}, {
  "name" : "two"
} ]