Spring Boot POST接口返回400错误排查求助

开发的Spring Boot POST接口findByCriteria持续返回400错误，但health和test接口可正常调用，以下是相关代码与请求信息，及对应的排查解决方案：

相关代码与请求信息 #

1. Payload实体类（CriteriaVO） #

public class CriteriaVO implements Serializable {
    
    private static final long serialVersionUID = -4809182119185775529L;

    private final List<String> categories;
    
    private final List<String> subCategories;

    public CriteriaVO(List<String> categories, List<String> subCategories) {
        super();
        this.categories = categories;
        this.subCategories = subCategories;
    }

    public List<String> getCategories() {
        return categories;
    }

    public List<String> getSubCategories() {
        return subCategories;
    }
    
}

2. RestController类（QuestionsController） #

@RestController
@RequestMapping("questions")
public class QuestionsController {
    
    @Autowired
    private QuestionDao questionDaoImpl;
    
    @GetMapping(path= "health", produces = MediaType.APPLICATION_JSON_VALUE)
    public String health() {
        return "Wish all good health!";
    }

    @PostMapping(path = "findByCriteria", produces = MediaType.APPLICATION_JSON_VALUE, consumes=MediaType.APPLICATION_JSON_VALUE, name = "findByCriteria")
    public List<Question> findByCriteria(@RequestBody CriteriaVO criteria) {
        System.out.println("test");
        List<Question> questions = this.questionDaoImpl.findByCriteria(criteria.getCategories(), criteria.getSubCategories());
        return questions;               
    }
    

    @PostMapping(path = "test", produces = MediaType.TEXT_PLAIN_VALUE, consumes=MediaType.TEXT_PLAIN_VALUE, name = "test")
    public String test(@RequestBody String test) {
        System.out.println(test);
        return "returned " + test;               
    }

}

3. 请求JSON参数 #

{"categories":["Observability"],"subCategories":["Tracing","General"]}

4. Postman生成的curl命令 #

curl --location 'localhost:8080/questions/findByCriteria' \
--header 'Content-Type: application/json' \
--header 'Accept: application/json' \
--data '

{"categories":["Observability"],"subCategories":["Tracing","General"]}'

排查步骤与解决方案 #

核心原因 #

400错误本质是请求JSON无法被Jackson正确反序列化为CriteriaVO实例：

• CriteriaVO仅提供带参构造器，且字段为final，Jackson默认无足够能力实例化并赋值该类对象。

具体修复方案 #

方案1：手动添加无参构造器

Jackson需要无参构造器来初始化对象，即使字段是final，Spring Boot默认的Jackson配置支持通过反射为final字段赋值：

public class CriteriaVO implements Serializable {
    
    private static final long serialVersionUID = -4809182119185775529L;

    private final List<String> categories;
    
    private final List<String> subCategories;

    // 添加无参构造器
    public CriteriaVO() {
        this.categories = new ArrayList<>();
        this.subCategories = new ArrayList<>();
    }

    public CriteriaVO(List<String> categories, List<String> subCategories) {
        super();
        this.categories = categories;
        this.subCategories = subCategories;
    }

    public List<String> getCategories() {
        return categories;
    }

    public List<String> getSubCategories() {
        return subCategories;
    }
    
}

方案2：用Lombok简化代码（推荐）

引入Lombok依赖后，通过注解自动生成构造器与Getter方法，避免手动编写重复代码：

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import java.io.Serializable;
import java.util.List;

@Getter
@NoArgsConstructor
@AllArgsConstructor
public class CriteriaVO implements Serializable {
    
    private static final long serialVersionUID = -4809182119185775529L;

    private List<String> categories;
    
    private List<String> subCategories;
    
}

额外排查优化点 #

• 修正curl命令的请求体格式：原命令中--data后有多余换行，虽然Jackson通常忽略，但建议移除换行保证JSON格式严谨：

  curl --location 'localhost:8080/questions/findByCriteria' \
  --header 'Content-Type: application/json' \
  --header 'Accept: application/json' \
  --data '{"categories":["Observability"],"subCategories":["Tracing","General"]}'
  

• 查看Spring Boot日志：开启DEBUG级别日志，可获取Jackson反序列化失败的具体细节，帮助快速定位问题。

内容的提问来源于stack exchange，提问作者AbNig