Changing json to java pojo

Question

Let's say I have a JSON file example.json

example.json

    {
      "BaggageMaxSize" : {
            "mesurement" : "sum",
            "width" : 70,
            "height" : 50,
            "depth" : 40
        }
    }

And create the POJO class:

    public class pojoexample{
      private BaggageMaxSize BaggageMaxSize;
      // getter
      // setter
    }

And then:

public class BaggageMaxSize
{
    private String height;

    private String width;

    private String depth;

    private String mesurement;

    // getter 
    // setter
}

Now, I want to use the mapper.readValue to change file to BaggageInfoPolicy.class:

BaggageInfoPolicy bip = mapper.readValue(file, BaggageInfoPolicy.class);

But bip.getBaggageMaxSize().getMesurement() returns null value. Any suggestions?

Answer 1

Try using mapper.writeValue first and check how your resulting JSON object will look like. Very likely, there's an issue with int -> string conversion in your BaggageMaxSize when deserialized from JSON.

Also, check your getters/setters to be publicly visible and be available both on pojoexample and BaggageMaxSize .

Answer 2

Actually your JSON represents a pojoexample class instance and not a BaggageInfoPolicy object, which you haven't shared in your post.

So you need to change your code to:

PojoExample bip = mapper.readValue(file, PojoExample.class);

So it reads the PojoExample object correctly.

Note:

• Your class should follow the java naming convention and start with an uppercase, that's why I changed it to PojoExample , change it in the class definition as well.
• And Make sure your class fields have the same types as in the JSON, and their getters and setters are correctly implemented.