Jackson, how to ignore some values - jackson

Question

I'd like to exclude all properties with values less than zero. Does Jackson have some ready to use solutions or I should create CustomSerializerFactory and BeanPropertyWriter?

Answer 1

You can do this by using a filter - it's a little verbose but it does the job.
First - you need to specify the filter on your entity:
#JsonFilter("myFilter")
public class MyDtoWithFilter { ...}
Then, you need to specify your custom filter, which will look at the values:
PropertyFilter theFilter = new SimpleBeanPropertyFilter() {
#Override
public void serializeAsField(Object pojo, JsonGenerator jgen, SerializerProvider provider, PropertyWriter writer) throws Exception {
if (include(writer)) {
if (writer.getName().equals("intValue")) {
int intValue = ((MyDtoWithFilter) pojo).getIntValue();
if (intValue < 0) {
writer.serializeAsField(pojo, jgen, provider);
}
} else {
writer.serializeAsField(pojo, jgen, provider);
}
} else if (!jgen.canOmitFields()) { // since 2.3
writer.serializeAsOmittedField(pojo, jgen, provider);
}
}
#Override
protected boolean include(BeanPropertyWriter writer) {
return true;
}
#Override
protected boolean include(PropertyWriter writer) {
return true;
}
};
This is done for a field called intValue but you can do the same for all your fields that need to be positive in a similar way.
Finally, not you can marshall an object and test that it works:
FilterProvider filters = new SimpleFilterProvider().addFilter("myFilter", theFilter);
MyDtoWithFilter dtoObject = new MyDtoWithFilter();
dtoObject.setIntValue(12);
ObjectMapper mapper = new ObjectMapper();
String dtoAsString = mapper.writer(filters).writeValueAsString(dtoObject);
Hope this helps.