Exception in thread "main": Unrecognized field

Question

After struggling with errors in my java code and resolving them I finally have proceeded to the running stage, but I get an exception error after I run it. I am trying to convert json from a weather API to java object using jackson library. I have several classes for setting and getting the java objects including: City.java, Coord.java, List1.java, Temp.java, Weather.java. I have class named as usertest.java for mapping the objects as a test.

My code is as below:

A sample of my getters and setters: City.java

package weather.data;

//import java.util.List;

public class City{
    private Coord coord;
    private String country;
    private Number id;
    private String name;
    private Number population;
    ...
    //getters and setters
}

usertest.java

package weather.data;

import weather.data.City;
import weather.data.Coord;
import weather.data.list1;
import weather.data.Temp;
import weather.data.Weather;

import com.fasterxml.jackson.core.JsonParseException;
//import com.fasterxml.jackson.annotation.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.JsonMappingException;

import java.io.File;
import java.net.URL;
import java.io.IOException;

public class usertest {

    public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException 
    {

        URL jsonUri = new URL("https://gist.githubusercontent.com/anonymous/4b32c7ef1ceb5dd48bf5/raw/ef1987551faa3fb61473bb0e7aad70a228dc36d6/gistfile1.txt");
        ObjectMapper mapper = new ObjectMapper();


        City city = mapper.readValue(jsonUri, City.class);
        System.out.println(city.getCoord());
    }

}

And the error I get after running the code: Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "cod" (class weather.data.City), not marked as ignorable (5 known properties: , "coord", "country", "id", "name", "population"])

Any help would highly appreciated.

Answer 1

I think this example is going to help you

• http://www.mkyong.com/java/how-to-convert-java-object-to-from-json-jackson/

You need to map a class for the entire response. So you need to have class with the next fields:

class Response {
    String cod 
    int message
    City city
    ...
}

Answer 2

Your json representation is not matching with City.java:

json:

{

    "cod": "200",
    "message": 0.0035,
    "city": {
        "id": 1851632,
        "name": "Shuzenji",
        "coord": {
            "lon": 138.933334,
            "lat": 34.966671
        },
        "country": "JP",
        "population": 0
    },
    "cnt": 10,
    "list": [..]
   }

City class though is fine but you need to create another class having cod, message, city, cnt and list attribute where city attribute should be of type City.

Other (unclean) alternate could be to add these property and set them @Ignore..