mongodb - Play framework 2.4 (Java) mongo async db driver 3.0 query -

hello i'm trying write async code mongodb async driver (3.0) http://mongodb.github.io/mongo-java-driver/3.0/driver-async/ play framework 2.4 (java) in controller async result https://www.playframework.com/documentation/2.3.x/javaasync , when i'm testing promise results outside async call mongodb have empty json in response, please can me ?

public f.promise<result> list() {     final list<document> accounts = new arraylist<document>();     f.promise<list<document>> promiseofaccounts = f.promise.promise(         new f.function0<list<document>>() {             public list<document> apply() {                 accountrepository.getcollection().find().into(accounts,                         new singleresultcallback<list<document>>() {                             @override                             public void onresult(final list<document> result, final throwable t) {                             }                         });                 return accounts;             }         }     );     return promiseofaccounts.map(         new f.function<list<document>, result>() {             public result apply(list<document> i) {                 return ok(i);             }         }     ); } 

when return accounts, sigleresultcallback closure hasn't been executed. results in list being empty when it's serialized in ok(i) expression. make work, have resolve promise inside singleresultcallback. remember play promises sit on scala futures , scala promises (which different play f.promises). how you'd it:

promise<list<document>> accountspromise = promise$.module$.apply(); arraylist<document> accounts = new arraylist<document>(); accountrepository.getcollection().find().into(accounts,         new singleresultcallback<list<document>>() {             @override             public void onresult(final list<document> result, final throwable t) {                 accountspromise.success(result);             }         }); promiseofaccounts=f.promise.wrap(accountspromise.future()); return promiseofaccounts.map(         new f.function<list<document>, result>() {             public result apply(list<document> i) {                 return ok(i);             }         } ); 

the moment call success method of scala promise resolves, , value of future becomes available, return play f.promise before happens, awesomeness of reactive programming.