JsonMappingException No suitable constructor found for type simple type class can not instantiate from JSON object

Question

I am getting the following error when trying to get a JSON request and process it      org codehaus jackson map JsonMappingException  No suitable constructor found for type  simple type  class com myweb ApplesDO   can not instantiate from JSON object  need to add enable type information     Here is the JSON I am trying to send        applesDO                   apple     Green Apple                      apple     Red Apple                In Controller  I have the following method signature    RequestMapping  showApples do   public String getApples  RequestBody final AllApplesDO applesRequest          Method Code     AllApplesDO is a wrapper of ApplesDO    public class AllApplesDO        private List lt ApplesDO gt  applesDO       public List lt ApplesDO gt  getApplesDO             return applesDO             public void setApplesDO List lt ApplesDO gt  applesDO            this applesDO   applesDO            ApplesDO   public class ApplesDO        private String apple       public String getApple             return apple             public void setApple String appl            this apple   apple             public ApplesDO CustomType custom             constructor Code           I think that Jackson is unable to convert JSON into Java objects for subclasses  Please help with the configuration parameters for Jackson to convert JSON into Java Objects  I am using Spring Framework   EDIT  Included the major bug that is causing this problem in the above sample class - Please look accepted answer for solution

User · Answer

Add default constructors to all the entity classes

User · Answer

Failing custom jackson Serializers Deserializers could also be the problem  Though it s not your case  it s worth mentioning   I faced the same exception and that was the case

User · Answer

You must realize what options Jackson has available for deserialization  In Java  method argument names are not present in the compiled code  That s why Jackson can t generally use constructors to create a well-defined object with everything already set   So  if there is an empty constructor and there are also setters  it uses the empty constructor and setters  If there are no setters  some dark magic  reflections  is used to do it   If you want to use a constructor with Jackson  you must use the annotations as mentioned by  PiersyP in his answer  You can also use a builder pattern  If you encounter some exceptions  good luck  Error handling in Jackson sucks big time  it s hard to understand that gibberish in error messages

User · Answer

Generally  this error comes because we don   t make default constructor  But in my case  The issue was coming only due to I have made used object class inside parent class  This has wasted my whole day

User · Answer

When I ran into this problem  it was a result of trying to use an inner class to serve as the DO  Construction of the inner class  silently  required an instance of the enclosing class -- which wasn t available to Jackson   In this case  moving the inner class to its own  java file fixed the problem

User · Answer

Can you please test this structure  If I remember correct you can use it this way          applesRequest              applesDO                                    apple    Green Apple                                                apple    Red Apple                                    Second  please add default constructor to each class it also might help

User · Answer

For me  this used to work  but upgrading libraries caused this issue to appear  Problem was having a class like this   package example counter   import javax validation constraints NotNull   import lombok Data    Data public class CounterRequest        NotNull     private final Integer int1        NotNull     private final Integer int2      Using lombok    lt dependency gt       lt groupId gt org projectlombok lt  groupId gt       lt artifactId gt lombok lt  artifactId gt       lt version gt 1 18 0 lt  version gt   lt  dependency gt    Falling back to   lt dependency gt       lt groupId gt org projectlombok lt  groupId gt       lt artifactId gt lombok lt  artifactId gt       lt version gt 1 16 10 lt  version gt   lt  dependency gt    Fixed the issue  Not sure why  but wanted to document it for future

User · Answer

This happens for these reasons    your inner class should be defined as static  private static class Condition      jackson specific        It might be that you got no default constructor in your class  UPDATE  This seems not to be the case   private static class Condition       private Long id       public Condition                   Setters and Getters    It could be your Setters are not defined properly or are not visible  e g  private setter

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So  finally I realized what the problem is  It is not a Jackson configuration issue as I doubted   Actually the problem was in ApplesDO Class   public class ApplesDO        private String apple       public String getApple             return apple             public void setApple String apple            this apple   apple             public ApplesDO CustomType custom              constructor Code           There was a custom constructor defined for the class making it the default constructor  Introducing a dummy constructor has made the error to go away   public class ApplesDO        private String apple       public String getApple             return apple             public void setApple String apple            this apple   apple             public ApplesDO CustomType custom              constructor Code              Introducing the dummy constructor     public ApplesDO

User · Answer

You have to create dummy empty constructor in our model class So while mapping json  it set by setter method

User · Answer

If you start annotating constructor  you must annotate all fields   Notice  my Staff name field is mapped to  ANOTHER NAME  in JSON string        String jsonInString     ANOTHER NAME     John     age     17           ObjectMapper mapper   new ObjectMapper         Staff obj   mapper readValue jsonInString  Staff class           print to screen       public static class Staff          public String name         public Integer age         public Staff                                          JsonCreator - don t need this        public Staff  JsonProperty  ANOTHER NAME   String   n  JsonProperty  age   Integer a            name n age a

User · Answer

I would like to add another solution to this that does not require a dummy constructor  Since dummy constructors are a bit messy and subsequently confusing  We can provide a safe constructor and by annotating the constructor arguments we allow jackson to determine the mapping between constructor parameter and field   so the following will also work  Note the string inside the annotation must match the field name   import com fasterxml jackson annotation JsonProperty  public class ApplesDO            private String apple           public String getApple                 return apple                     public void setApple String apple                this apple   apple                     public ApplesDO CustomType custom                 constructor Code                    public ApplesDO  JsonProperty  apple  String apple

User · Answer

Thumb Rule  Add a default constructor for each class you used as a mapping class  You missed this and issue arise  Simply add default constructor and it should work

User · Answer

Regarding the last publication I had the same problem where using Lombok 1 18   generated the problem   My solution was to add  NoArgsConstructor  constructor without parameters   since  Data includes by default  RequiredArgsConstructor  Constructor with parameters    lombok Documentation https   projectlombok org features all  That would solve the problem   package example counter   import javax validation constraints NotNull   import lombok Data    Data  NoArgsConstructor public class CounterRequest        NotNull     private final Integer int1        NotNull     private final Integer int2

[java] JsonMappingException: No suitable constructor found for type [simple type, class ]: can not instantiate from JSON object

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