java - 无法呈现请求 [/countries] 的错误页面，因为响应已提交。因此，响应可能有错误的状态代码

Question

我想从服务读取数据到 Controller 并在 Spring boot 上显示在 UI 上，但出现以下错误

ERROR 20984 --- [nio-8080-exec-2] s.e.ErrorMvcAutoConfiguration$StaticView : Cannot render error page for request [/countries] as the response has already been committed. As a result, the response may have the wrong status code.

数据库还有以下数据

mysql> 从国家中选择*；

+----+-------------+------+---------------+---------------+-------------+
| id | capital     | code | continent     | description   | nationality |
+----+-------------+------+---------------+---------------+-------------+
|  1 | Washington  | 01   | North America | United States | American    |
|  2 | Addis Ababa | 01   | Africa        | Ethiopia      | Ethiopian   |
+----+-------------+------+---------------+---------------+-------------+ 

型号

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
public class Country {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String code;
    private String capital;
    private String description;
    private String nationality;
    private String continent;
    
    @OneToMany(mappedBy="country")
    private List<State> states;
}

存储库

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.kindsonthegenius.FleetApp.models.Country;

@Repository
public interface CountryRepository extends JpaRepository<Country, Integer> {

}

服务

  @Service
public class CountryService {

    @Autowired
    private CountryRepository countryRepository;
    
    public List<Country> getCountries(){
        return countryRepository.findAll();
    }
    
}

Controller

@Controller
public class CountryController {
@Autowired
private CountryService countryService;

@GetMapping("/countries")
public String goCountry(Model model) {
    List<Country> countryList = countryService.getCountries(); 
    model.addAttribute("countries", countryList);
    return "country";
}
}

用户界面

<table class="table">
            <thead>
              <tr>
                <th scope="col">id</th>
                <th scope="col">Description</th>
                <th scope="col">Capital</th> 
              </tr>
            </thead>
            <tbody> 
              <tr th:each="country : ${countries}">
                <td th:text="${country.id}"></td>
                <td th:text="${country.description}"></td>
                <td th:text="${country.capital}"></td> 
              </tr>
            </tbody>
       </table>

请帮我修复此错误？

Answer 1

我猜这是因为国家和州之间的 @OneToMany 关系而发生的。如果您分享您的“状态”模型，我可以告诉您要更改哪些内容。 然而，当国家加载了州并且州中也有国家时，通常会发生此错误。这将创建无限的 JSON 树。检查此链接 Springboot Hibernate One to Many infinty recursion