Spring Boot调用Rick and Morty API：单角色接口返回Null问题咨询

我正在学习Spring Boot调用API，使用Rick and Morty API时，调用获取所有角色的接口可正常返回数据，但将端点修改为获取单个角色（如https://rickandmortyapi.com/api/character/2）时，返回结果为{"info":null,"results":null}。请求解释为何批量获取正常但单个获取返回Null？

Service代码 #

package com.burakkutbay.springbootresttemplateexample.service;

import com.burakkutbay.springbootresttemplateexample.pojo.Character;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.*;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

import java.util.List;

@Service
public class ApiServiceImpl implements ApiService {

    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private HttpHeaders httpHeaders;

    private static final String CHAHRACTER_API = "https://rickandmortyapi.com/api/character";

    @Override
    public Character getAllCharacter() {

        httpHeaders.setAccept(List.of(MediaType.APPLICATION_JSON));

        HttpEntity<String> entity = new HttpEntity<>(httpHeaders);

        ResponseEntity<Character> response = restTemplate.exchange(CHAHRACTER_API, HttpMethod.GET,
                entity, Character.class);

        return response.getBody();
    }
}

Controller代码 #

package com.burakkutbay.springbootresttemplateexample.controller;

import com.burakkutbay.springbootresttemplateexample.pojo.Character;
import com.burakkutbay.springbootresttemplateexample.service.ApiService;
import com.burakkutbay.springbootresttemplateexample.service.ApiServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ApiController {

    @Autowired
    private ApiService apiService;

    @GetMapping("/")
    public ResponseEntity<Character> getCharacters() {
        Character characters = apiService.getAllCharacter();
        return new ResponseEntity<>(characters, HttpStatus.OK);
    }
}

问题原因 #

核心问题是批量接口和单个角色接口的返回JSON结构完全不同，你用同一个Character类去接收两种不同结构的响应，导致反序列化失败：

• 批量获取接口（/api/character）返回的是包含info（分页信息）和results（角色列表）的对象，你的Character类应该是适配这个结构的；
• 单个角色接口（/api/character/2）返回的是单个角色的完整数据，没有info和results字段，直接是角色的属性（如id、name、status等）。用适配批量结构的Character类接收时，因字段不匹配，info和results只能被赋值为null。

解决方案 #

1. 拆分POJO类：

   • 创建CharacterListResponse类，用于接收批量接口响应，包含Info类型的info字段和List<SingleCharacter>类型的results字段；
   • 创建SingleCharacter类，用于接收单个角色接口响应，包含单个角色的所有属性（id、name、status等）。

2. 修改Service类：
   新增获取单个角色的方法，指定正确的响应类型：

   public SingleCharacter getSingleCharacter(int characterId) {
       httpHeaders.setAccept(List.of(MediaType.APPLICATION_JSON));
       HttpEntity<String> entity = new HttpEntity<>(httpHeaders);
       String url = CHAHRACTER_API + "/" + characterId;
       ResponseEntity<SingleCharacter> response = restTemplate.exchange(url, HttpMethod.GET, entity, SingleCharacter.class);
       return response.getBody();
   }
   

3. 新增Controller接口：
   添加带路径参数的接口，用于获取单个角色：

   @GetMapping("/character/{id}")
   public ResponseEntity<SingleCharacter> getSingleCharacter(@PathVariable int id) {
       SingleCharacter character = apiService.getSingleCharacter(id);
       return new ResponseEntity<>(character, HttpStatus.OK);
   }
   

内容的提问来源于stack exchange，提问作者Aldo