CODEWITHSUNDEEP
javajsonconstructorjacksondeserialization
Abdulah Pehlic
Abdulah Pehlic

Reputation: 189

Avoid constructor calls when deserializing with jackson

i have a class that has a UUID attribute that is being generated in the constructor, so it means it's generated every time a new object is created.

I am using Jackson to deserialize json strings into objects with ObjectMapper. The issue is that when i deserialize, it deserializes the json string into a new object, and calls the constructor of the class, which results in generating a new UUID. So basically it takes the Json string that already has a UUID, and when it deserializes it changes it to a new one.

Any ideas how to solve this using Jackson?

Upvotes: 1

Views: 902

Answers (3)

Abdulah Pehlic
Abdulah Pehlic

Reputation: 189

The issue was that i had a setter which checked if UUID was null, and if it was not, it did not set it to the new one. So when the object was created it automatically got a UUID, and Jackson couldn't set it with the setter since it was not null. When i removed the if from the setter, it worked fine.

Upvotes: 2

Jose Martinez
Jose Martinez

Reputation: 12022

I was not able to reproduce the problem. Below is my code. It works as expected.

public static class MyPojo {
    private String id;

    public MyPojo() {
        this.id = UUID.randomUUID().toString();
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

}


public static void main(String[] args) throws JsonProcessingException {
    var om = new ObjectMapper();
    var myPojo = om.readValue(" {\"id\":\"6d1eab11-d64f-4152-9955-3d5c54828cd9\"}", MyPojo.class);
    assertThat(myPojo.id).isEqualTo("6d1eab11-d64f-4152-9955-3d5c54828cd9");
    System.out.println("id = " + myPojo.id);
}

Upvotes: 1

dpr
dpr

Reputation: 10964

You could add a second private constructor and annotate this constructor with @JsonCreator. This will make Jackson use this constructor for de-serialization. You can add additional arguments to the constructor and annotate the arguments with @JsonProperty - I think - to make Jackson set the respective values correctly.

Upvotes: 1

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