Processing Optional Value from Mono in Project Reactor











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down vote

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I want to have a Mono that calls another async method that returns an Optional type to:




  1. have a value if the Optional is not empty,

  2. is MonoEmpty if the Optional value is empty.


Here's what I do right now:




Mono.fromCallable(() -> someApi.asyncCall())
.filter(Optional::isPresent)
.map(Optional::get)



Obviously, this is not ideal since it uses two operators after the callable completed. If possible, I'd like to have the Mono.empty() or mono value from inside fromCallable.



What is the best way to achieve what I want?






java reactive-programming project-reactor







share|improve this question


























    up vote
    2
    down vote

    favorite
    1












    I want to have a Mono that calls another async method that returns an Optional type to:




    1. have a value if the Optional is not empty,

    2. is MonoEmpty if the Optional value is empty.


    Here's what I do right now:




    Mono.fromCallable(() -> someApi.asyncCall())
    .filter(Optional::isPresent)
    .map(Optional::get)



    Obviously, this is not ideal since it uses two operators after the callable completed. If possible, I'd like to have the Mono.empty() or mono value from inside fromCallable.



    What is the best way to achieve what I want?






    java reactive-programming project-reactor







    share|improve this question
























      up vote
      2
      down vote

      favorite
      1









      up vote
      2
      down vote

      favorite
      1






      1





      I want to have a Mono that calls another async method that returns an Optional type to:




      1. have a value if the Optional is not empty,

      2. is MonoEmpty if the Optional value is empty.


      Here's what I do right now:




      Mono.fromCallable(() -> someApi.asyncCall())
      .filter(Optional::isPresent)
      .map(Optional::get)



      Obviously, this is not ideal since it uses two operators after the callable completed. If possible, I'd like to have the Mono.empty() or mono value from inside fromCallable.



      What is the best way to achieve what I want?






      java reactive-programming project-reactor







      share|improve this question













      I want to have a Mono that calls another async method that returns an Optional type to:




      1. have a value if the Optional is not empty,

      2. is MonoEmpty if the Optional value is empty.


      Here's what I do right now:




      Mono.fromCallable(() -> someApi.asyncCall())
      .filter(Optional::isPresent)
      .map(Optional::get)



      Obviously, this is not ideal since it uses two operators after the callable completed. If possible, I'd like to have the Mono.empty() or mono value from inside fromCallable.



      What is the best way to achieve what I want?






      java reactive-programming project-reactor




      java reactive-programming project-reactor






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 7 at 8:46









      bertzzie

      1,82832137




      1,82832137
























          1 Answer
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          down vote



          accepted










          There is an alternative with flatMap that's a bit better than Optional.isPresent and Optional.get that can lead to accidentally calling get on empty Optional:



          Mono.fromCallable(() -> someApi.asyncCall())
          
  .flatMap(optional -> optional.map(Mono::just).orElseGet(Mono::empty))





          share|improve this answer





















          • Accepting this as it works. Thank you.
            – bertzzie
            Nov 8 at 2:01











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          active

          oldest

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          active

          oldest

          votes








          up vote
          1
          down vote



          accepted










          There is an alternative with flatMap that's a bit better than Optional.isPresent and Optional.get that can lead to accidentally calling get on empty Optional:



          Mono.fromCallable(() -> someApi.asyncCall())
          
  .flatMap(optional -> optional.map(Mono::just).orElseGet(Mono::empty))





          share|improve this answer





















          • Accepting this as it works. Thank you.
            – bertzzie
            Nov 8 at 2:01















          up vote
          1
          down vote



          accepted










          There is an alternative with flatMap that's a bit better than Optional.isPresent and Optional.get that can lead to accidentally calling get on empty Optional:



          Mono.fromCallable(() -> someApi.asyncCall())
          
  .flatMap(optional -> optional.map(Mono::just).orElseGet(Mono::empty))





          share|improve this answer





















          • Accepting this as it works. Thank you.
            – bertzzie
            Nov 8 at 2:01













          up vote
          1
          down vote



          accepted







          up vote
          1
          down vote



          accepted






          There is an alternative with flatMap that's a bit better than Optional.isPresent and Optional.get that can lead to accidentally calling get on empty Optional:



          Mono.fromCallable(() -> someApi.asyncCall())
          
  .flatMap(optional -> optional.map(Mono::just).orElseGet(Mono::empty))





          share|improve this answer












          There is an alternative with flatMap that's a bit better than Optional.isPresent and Optional.get that can lead to accidentally calling get on empty Optional:



          Mono.fromCallable(() -> someApi.asyncCall())
          
  .flatMap(optional -> optional.map(Mono::just).orElseGet(Mono::empty))






          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 7 at 11:21









          Ilya Zinkovich

          1,2401521




          1,2401521












          • Accepting this as it works. Thank you.
            – bertzzie
            Nov 8 at 2:01


















          • Accepting this as it works. Thank you.
            – bertzzie
            Nov 8 at 2:01
















          Accepting this as it works. Thank you.
          – bertzzie
          Nov 8 at 2:01




          Accepting this as it works. Thank you.
          – bertzzie
          Nov 8 at 2:01


















           

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