[FIXED] Using objectmapper for nested objects

Issue

I have an object inside another object. When I ask key1 value in Servlet.java with ObjectMapper I will get A(key1={key2=[1, 5, 7]}), but I'd like to know how to separate key2 List value.

String input: {"key1":{"key2":[1,5,7]}}

Final result: 13 -> calculated from key2 array values (1 + 5 + 7)

Basically, I've already done everything, but getting values from key2 is still missing.

A.java

package servlet;

import lombok.Data;

@Data
public class A {
    public Object key1;
}

B.java

package servlet;

import lombok.Data;
import java.util.ArrayList;
import java.util.List;

@Data
public class B{
    List<Integer> key2 = new ArrayList<>();

}

Servlet.java

package servlet;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.stream.Collectors;

@WebServlet("/validate")
public class Servlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request,
                         HttpServletResponse response)
            throws IOException {

        response.getWriter().print("Hello!");
    }

    @Override
    public void doPost(HttpServletRequest request,
                       HttpServletResponse response) throws IOException {

        String input = request.getReader().lines().collect(Collectors.joining("/n"));

        A a = new ObjectMapper().readValue(input, new TypeReference<A>() {});
        System.out.println(a); // A(key1={key2=[1, 5, 7]})
        System.out.println(a.getKey1()); // {key2=[1, 5, 7]}

        // Object in object ?

        int sum = 0;
        String output = new ObjectMapper().writeValueAsString(sum);
        response.getWriter().write(output);
    } 
}

How am I able to separate key2 from it to calculate the sum of key2 array values?

Another restriction is that I cannot use split, replace, match etc.

Solution

So basically, I only needed to do was just use B class instead of Object

package servlet;

import lombok.Data;

@Data
public class A {
    public B key1;
}

and in servlet ask from A class both key1, key2 and loop them

@Override
    public void doPost(HttpServletRequest request,
                       HttpServletResponse response) throws IOException {

        String input = request.getReader().lines().collect(Collectors.joining("/n"));

        A a = new ObjectMapper().readValue(input, new TypeReference<A>() {});

        int sum = 0;
        for (Integer b: a.getKey1().getKey2()) {
            sum += b;
        }

        String output = new ObjectMapper().writeValueAsString(sum);
        response.getWriter().write(output);
    }

Answered By - AvocadoGirl
Answer Checked By - Marie Seifert (JavaFixing Admin)