springboot 生成的 JSON 中缺少名称标签

Question

我遇到了下面显示的代码的问题。下面的代码生成 json 如下：

[{"id":123,"subjects":"English"},{"id":456,"subjects":"Maths"}]

我们可以看到生成的 JSON 中缺少名称标签。我不明白当我返回学生列表时，结果 json 应该包含名称标签，因为类型 "Name" 的学生 class 中有一个属性。请帮忙！

PS：我已经调试了代码，我看到 "students arraylist" 0 索引和索引确实包含名称 prpoperty 以及 ID 和主题。但是 JSON 不包含这个属性.

休息控制器：

package com.example.demo;
import java.util.*;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.*;


@SpringBootApplication
@RestController
public class Demo1Application {


@Autowired
Student student;
List<Student> students = new ArrayList<>();


@RequestMapping(value="/getStudents", method=RequestMethod.GET,produces=MediaType.APPLICATION_JSON_VALUE)
public List<Student> getstudent () { 
    students = student.setStudent();
    return students;
}


public static void main(String[] args) {
    SpringApplication.run(Demo1Application.class, args);
    System.out.println("Hello");
}
}

学生豆Class:

package com.example.demo;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;

@Component
public class Student {
    int id;
    String Subject;

    @Autowired
    @Qualifier("name")
    Name name;


    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getSubjects() {
        return Subject;
    }
    public void setSubject(String subject) {
        Subject = subject;
    }

    public void setName(String Fname, String Mname, String Lname) {
        Name nm = new Name();  
        name = nm.setfullname(Fname,Mname,Lname) ;
    }

    public Student(int id, String Subject) {
        this.id = id;
        this.Subject = Subject;
    }

    public Student() {
        System.out.println("Student Object created");
    }

    public List<Student> setStudent() {
        List<Student> Students = new ArrayList<>(); 
        Student s = new Student ();
        Student s1 = new Student ();


        s.setId(123);
        s.setSubject("English");
        s.setName("Hemant", "123", "Mamod");

        s1.setId(456);
        s1.setSubject("Maths");
        s1.setName("Akshay", "123", "pandey");

        Students.add(s);
        Students.add(s1);
        return Students;
      }
    }

名称 Bean Class:

package com.example.demo;

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;

@Component
@Qualifier("name")
public class Name {
    String Firstname;
    String Middlename;
    String Lastname;

    public Name() {
        System.out.println("Name Object created");
    }

    public String getFirstname() {
        return Firstname;
    }
    public void setFirstname(String firstname) {
        Firstname = firstname;
    }
    public String getMiddlename() {
        return Middlename;
    }
    public void setMiddlename(String middlename) {
        Middlename = middlename;
    }
    public String getLastname() {
        return Lastname;
    }
    public void setLastname(String lastname) {
        Lastname = lastname;
    }

    public Name setfullname(String Fname, String Mname, String Lname) {
        Firstname = Fname;
        Middlename = Mname;
        Lastname = Lname;
        return this;
    }

}

Answer 1

问题是你在Studentclass中没有Name的getter。请添加 getter 如下：

@Component
public class Student {
  int id;
  String Subject;

  Name name;

  /******/

  public Name getName() {
    return name;
  }
}

谈到 NullPinterException 和 name 属性 - 这意味着由于某些原因它还没有自动装配，所以在你的情况下你可以删除 @Autowired和 @Qualifier 注释或弄清楚自动装配有什么问题

springboot 生成的 JSON 中缺少名称标签

Name Tag missing in JSON generated by springboot

java

spring

annotations

spring-boot

spring-restcontroller