content: package com.alibaba.fastjson2.v1issues.issue_1600;
  
  import com.alibaba.fastjson2.JSON;
  import com.alibaba.fastjson2.JSONWriter.Feature;
  import com.alibaba.fastjson2.annotation.JSONType;
  import org.junit.jupiter.api.Test;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  public class Issue1649 {
      @Test
      public void test_for_issue() throws Exception {
          Apple apple = new Apple();
          String json = JSON.toJSONString(apple);
          assertEquals("{\"color\":\"\",\"productCity\":\"\",\"size\":0}", json);
      }
  
      @JSONType(serializeFeatures = Feature.NullAsDefaultValue)
      public static class Apple {
          private String color;
          private String productCity;
          private int size;
  
          public String getColor() {
              return color;
          }
  
          public Apple setColor(String color) {
              this.color = color;
              return this;
          }
  
          public int getSize() {
              return size;
          }
  
          public Apple setSize(int size) {
              this.size = size;
              return this;
          }
  
          public String getProductCity() {
              return productCity;
          }
  
          public Apple setProductCity(String productCity) {
              this.productCity = productCity;
              return this;
          }
      }
  }
  