content: package com.alibaba.fastjson2.issues_2000;
  
  import com.alibaba.fastjson2.JSON;
  import com.alibaba.fastjson2.JSONObject;
  import org.junit.jupiter.api.Test;
  
  import static org.junit.jupiter.api.Assertions.assertFalse;
  
  public class Issue2003 {
      @Test
      public void testNullWithToJson() {
          A a = new A();
          a.setA1(null);
          a.setA2("a2");
          JSONObject jo = (JSONObject) JSON.toJSON(a);
          assertFalse(jo.containsKey("a1")); // 这里不能通过！
      }
  
      @Test
      public void testNullWithToJsonString() {
          A a = new A();
          a.setA1(null);
          a.setA2("a2");
          String str = JSON.toJSONString(a);
          assertFalse(str.contains("a1"));  // 这里通过了
      }
  
      public static class A {
          private String a1;
          private String a2;
  
          public String getA1() {
              return a1;
          }
  
          public void setA1(String a1) {
              this.a1 = a1;
          }
  
          public String getA2() {
              return a2;
          }
  
          public void setA2(String a2) {
              this.a2 = a2;
          }
      }
  }
  