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首页 > 解决方案 > 在 java/spring-boot 中，如果找不到项目，返回空 json 对象的最干净方法是什么

java - 在 java/spring-boot 中，如果找不到项目，返回空 json 对象的最干净方法是什么

问题描述

下面是我的请求处理程序的 Java/spring-boot控制器代码：/api/speaker/123

@GetMapping
@RequestMapping("{id}")
public Speaker get(@PathVariable Long id) {
    return speakerRepository.getOne(id);
}

如果id 123没有找到传入请求/api/speaker/123，那么如何快速编码以将空对象/json返回给浏览器？在 Nodejs/JavaScript 世界中，我可以简单地在一行以下做。任何这样的干净代码都无需添加if...else，更多代码要查找null/empty，然后做更多......然后返回！

return speakerRepository.getOne(id) || {};

编辑：

// Speaker.java
@Entity(name = "speakers")
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class Speaker {
    public Long getSpeaker_id() {
        return speaker_id;
    }

    public void setSpeaker_id(Long speaker_id) {
        this.speaker_id = speaker_id;
    }

    public String getFirst_name() {
        return first_name;
    }

    public void setFirst_name(String first_name) {
        this.first_name = first_name;
    }

    public String getLast_name() {
        return last_name;
    }

    public void setLast_name(String last_name) {
        this.last_name = last_name;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }

    public String getSpeaker_bio() {
        return speaker_bio;
    }

    public void setSpeaker_bio(String speaker_bio) {
        this.speaker_bio = speaker_bio;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long speaker_id;
    private String first_name;
    private String last_name;
    private String title;
    private String company;
    private String speaker_bio;

    public List<Session> getSessions() {
        return sessions;
    }

    @ManyToMany(mappedBy = "speakers")
    @JsonIgnore
    private List<Session> sessions;
    public Speaker(){

    }
}




// SpeakerRepository.java
public interface SpeakerRepository extends JpaRepository<Speaker, Long> {       
}

标签： javaspring-bootspring-mvcspring-data-jpa

解决方案

@GetMapping
@RequestMapping("{id}")
public Speaker get(@PathVariable Long id) {
    return speakerRepository.getOne(id);
}

而是使用以下代码：

@JsonSerialize
public class EmptyJsonResponse {}



@GetMapping
@RequestMapping("{id}")
public ResponseEntity<?> get(@PathVariable Long id) {
   Speaker speaker = speakerRepository.getOne(id);
    if(speaker != null){
      return new ResponseEntity<Speaker>(speaker, HttpStatus.OK)
    }else{
      return new ResponseEntity<EmptyJsonResponse>(new EmptyJsonResponse(), HttpStatus.OK)
   }         
}

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