Json.tojsonstring cannot pass Boolean

JSON.toJSONString Can't pass boolean

In the use of JSON.toJSONString turn json Format time , The back end is springboot, The front is vue, Each return User Objects are always one field short state

User Entity class ：

public class User {
    

    private int id;
    private String username;
    private String password;
    private String email;
    private String role;
    private Boolean state;

Interface ：

@RequestMapping("/alluser")
@ResponseBody
public String getUserList(QueryInfo queryInfo) {
    
    int numbers = userDao.getUserCount("%" + queryInfo.getQuery() + "%");
    int pageStart = (queryInfo.getPageNum() - 1) * queryInfo.getPageSize();

    List<User> users = userDao.getAllUser("%" + queryInfo.getQuery() + "%",pageStart,queryInfo.getPageSize());

    HashMap<String, Object> res = new HashMap<>();
    res.put("numbers",numbers);
    res.put("data",users);

    String s = JSON.toJSONString(res);
    return s;
}

At first, it was written above , Find out state The field cannot be transferred to the front end , I found a lot of ways on the Internet , Finally, it still couldn't be solved , I heard later that springboot Send data to vue There is no need to turn json, Direct return can also receive , It's changed to the following

@RequestMapping("/alluser")
@ResponseBody
public Map getUserList(QueryInfo queryInfo) {
    
    int numbers = userDao.getUserCount("%" + queryInfo.getQuery() + "%");
    int pageStart = (queryInfo.getPageNum() - 1) * queryInfo.getPageSize();

    List<User> users = userDao.getAllUser("%" + queryInfo.getQuery() + "%",pageStart,queryInfo.getPageSize());

    HashMap<String, Object> res = new HashMap<>();
    res.put("numbers",numbers);
    res.put("data",users);

    return res;
}

Go straight back to Map, All fields can be received at the front end

front end ：

  data() {
    
    return {
    
      queryInfo: {
    
        query: "",
        pageNum: 1,
        pageSize: 10,
      },
      userList: [],
      total: null,
  },

  methods: {
    
    async getUserList() {
    
      const {
    data:res} = await this.$http.get("/alluser",{
    params: this.queryInfo});
      this.userList = res.data;
      this.total = res.numbers
    }
}

Cannot be state Fields are passed back , The specific reason has not been found , Whether it's change get、set, still JSON.toJSONString When adding those parameters , Doesn't work ~