java - Jackson optional field empty() vs null -

i'm trying use optional in pojo indicate when json field can null, absent, or present. issue cannot figure out how configure jackson not treat optional.empty() , null same. empty(), want field ignored. none of jsoninclude values seem this. jdk8module#configureabsentsasnulls() looked promising, doesn't change results of tests. there way this?

tl;dr null values should serialized, optional.empty() should not serialized.

here tests exhibiting behavior i'm trying achieve.

class pojo {     public optional<string> content; }  private objectmapper getmapper() {     return new objectmapper().registermodule(new jdk8module()); }  @org.junit.test public void testabsent() throws jsonprocessingexception {     objectmapper mapper = getmapper();      pojo pojo = new pojo();     pojo.content = optional.empty();      string result = mapper.writevalueasstring(pojo);      assertequals("{}", result); }  @org.junit.test public void testnull() throws jsonprocessingexception {     objectmapper mapper = getmapper();      pojo pojo = new pojo();     pojo.content = null;      string result = mapper.writevalueasstring(pojo);      assertequals("{\"content\":null}", result); }  @org.junit.test public void testpresent() throws jsonprocessingexception {     objectmapper mapper = getmapper();      pojo pojo = new pojo();     pojo.content = optional.of("hello");      string result = mapper.writevalueasstring(pojo);      assertequals("{\"content\":\"hello\"}", result); } 

if check jackson documentation @jsoninclude annotation here, used specify fields should ignored or serialized based on fields values, can see there couple of parameters (non_absent , non_empty) can used ignore optional.empty values combined null values not work in case.

what can create jsonfilter check value of fields , ignore them if optional.empty.

propertyfilter optionalfilter = new simplebeanpropertyfilter() {      @override     public void serializeasfield(object pojo, jsongenerator jgen, serializerprovider provider, propertywriter writer) throws exception {         // field using writer's name (field name)         field field = pojo.getclass().getdeclaredfield(writer.getfullname().tostring());          // value of field, making accessible , reverting         boolean defaultaccess = field.isaccessible();         field.setaccessible(true);         object value = field.get(pojo);         field.setaccessible(defaultaccess);          // serialize if null or not optional.empty         if (value == null || value.equals(optional.empty()) == false) {             writer.serializeasfield(pojo, jgen, provider);         }     } }; 

this check each field of class , serialize it, if null or other optional.empty.

use in main class:

filterprovider filters = new simplefilterprovider().addfilter("optionalfilter", optionalfilter);  // note need `jdk8module` module value of optional objectmapper mapper = new objectmapper().registermodule(new jdk8module());  pojo pojo = new pojo(); pojo.setcontent(optional.empty());  system.out.println(mapper.writer(filters).writevalueasstring(pojo));  pojo = new pojo(); pojo.setcontent(null);  system.out.println(mapper.writer(filters).writevalueasstring(pojo));  pojo = new pojo(); pojo.setcontent(optional.of("hello"));  system.out.println(mapper.writer(filters).writevalueasstring(pojo)); 

also have annotate class filter:

@jsonfilter("optionalfilter") class pojo {  } 

output:

{} {"content":null} {"content":"hello"}