com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field

Question

i got a deserialization problem:

This is my class:

public class Response {

    private Object ResObj;
    private int ResInt;

    public Object getResObj() {
        return ResObj;
    }

    public int getResInt() {
        return ResInt;
    } 
} 

the JSON i want to deserialize is:

{"ResObj":{"ClientNum":"12345","ServerNum":"78945","IdNum":"020252"},"ResInt":0}

I get this exception:

Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "ResObj" , not marked as ignorable (0 known properties: ])
 at [Source: java.io.StringReader@1f758500; line: 1, column: 20] (through reference chain: ["ResObj"])

I don't want to add:

@JsonIgnoreProperties(ignoreUnknown = true)

because I want to get the ResObj...

if I add the annotation, it pass but it will set it as null .. which I don't want.

Answer 1

If you don't want to have a setter in your bean and only use fields and getters, you can use the visibility checker of ObjectMapper to allow field visibility.
Something like following:

ObjectMapper mapper = new ObjectMapper();
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
mapper.setVisibility(VisibilityChecker.Std.defaultInstance().withFieldVisibility(JsonAutoDetect.Visibility.ANY));

Answer 2

You need Setter methods to allow Jackson to set the properties, and you need to change the fields in the json to begin with a lower case letter:

public class Response {

    private Object ResObj;
    private int ResInt;

    public Object getResObj() {
        return ResObj;
    }

    public void setResObj(Object ResObj) {
        this.ResObj = ResObj;
    }

    // ...
}

and:

{"resObj":{"clientNum":"12345","serverNum":"78945","idNum":"020252"},"resInt":0}

The reason for the JSON change is that the Jackson bean serialisation will reflect over the class, and when it sees getXyz() and setXyz() methods will map these to a Json filed names "xyz" (and not "Xyz").

I think there are several ways to override this behaviour, one is to use the one of the Jackson annotations.

Answer 3

I think you should try this

public class Response {
    @JsonProperty
    private Object ResObj;
    @JsonProperty
    private int ResInt;

    public Object getResObj() {
        return ResObj;
    }

    public int getResInt() {
        return ResInt;
    } 
} 

It will resolve your issue with UnrecognizedPropertyExceptions