Deserializing an enum with Jackson

Question

I'm trying and failing to deserialize an enum with Jackson 2.5.4, and I don't quite see my case out there. My input strings are camel case, and I want to simply map to standard Enum conventions.

@JsonFormat(shape = JsonFormat.Shape.STRING) public enum Status {     READY("ready"),     NOT_READY("notReady"),     NOT_READY_AT_ALL("notReadyAtAll");      private static Map<String, Status> FORMAT_MAP = Stream             .of(Status.values())             .collect(toMap(s -> s.formatted, Function.<Status>identity()));      private final String formatted;      Status(String formatted) {         this.formatted = formatted;     }      @JsonCreator     public Status fromString(String string) {         Status status = FORMAT_MAP.get(string);         if (status == null) {             throw new IllegalArgumentException(string + " has no corresponding value");         }         return status;     } } 

I've also tried @JsonValue on a getter to no avail, which was an option I saw reported elsewhere. They all blow up with:

com.fasterxml.jackson.databind.exc.InvalidFormatException: Can not construct instance of ...Status from String value 'ready': value not one of declared Enum instance names: ... 

What am I doing wrong?

Answer 1

EDIT: Starting from Jackson 2.6, you can use @JsonProperty on each element of the enum to specify its serialization/deserialization value (see here):

public enum Status {     @JsonProperty("ready")     READY,     @JsonProperty("notReady")     NOT_READY,     @JsonProperty("notReadyAtAll")     NOT_READY_AT_ALL; } 

---

(The rest of this answer is still valid for older versions of Jackson)

You should use @JsonCreator to annotate a static method that receives a String argument. That's what Jackson calls a factory method:

public enum Status {     READY("ready"),     NOT_READY("notReady"),     NOT_READY_AT_ALL("notReadyAtAll");      private static Map<String, Status> FORMAT_MAP = Stream         .of(Status.values())         .collect(Collectors.toMap(s -> s.formatted, Function.identity()));      private final String formatted;      Status(String formatted) {         this.formatted = formatted;     }      @JsonCreator // This is the factory method and must be static     public static Status fromString(String string) {         return Optional             .ofNullable(FORMAT_MAP.get(string))             .orElseThrow(() -> new IllegalArgumentException(string));     } } 

This is the test:

ObjectMapper mapper = new ObjectMapper();  Status s1 = mapper.readValue("\"ready\"", Status.class); Status s2 = mapper.readValue("\"notReadyAtAll\"", Status.class);  System.out.println(s1); // READY System.out.println(s2); // NOT_READY_AT_ALL 

As the factory method expects a String, you have to use JSON valid syntax for strings, which is to have the value quoted.