问题

我有一个DTO类，返回如下：

{
  "id": "fdbfb1ec-1f1e-4867-9cc8-73929fbcc07e",
  "title": "My another category",
  "reports": null
}

实际上，我希望我的一些API调用不包括"reports"键，如下所示，而不是将其设置为null：

{
  "id": "fdbfb1ec-1f1e-4867-9cc8-73929fbcc07e",
  "title": "My another category"
}

我尝试使用Gson和Expose注解，相信这将删除我的键，但似乎只是将其变为null。我尝试过使用@Expose(serialize = false, deserialize = false)，也尝试过不使用注解，因为我的Gson对象使用了excludeFieldsWithoutExposeAnnotation()方法，但两者都给我带来了相同的结果。然而，我可以看到我的字符串转换器排除了"reports"键，并给我了这个{"id":"fdbfb1ec-1f1e-4867-9cc8-73929fbcc07e","title":"My another category"}，但不确定为什么在重新创建对象时该属性仍然存在，如果唯一的解决方案是不通过Gson而是使用两个完全不同的DTOs，一个包含该属性，另一个不包含该属性？

谢谢。

更新

这是我的Github上的代码：https://github.com/francislainy/gatling_tool_backend

尝试使用Jackson而不是Gson，但出现了相同的问题。

{
  "id": "fdbfb1ec-1f1e-4867-9cc8-73929fbcc07e",
  "title": "My another category",
  "reports": null
}

{
  "id": "fdbfb1ec-1f1e-4867-9cc8-73929fbcc07e",
  "title": "My another category",
}

@AllArgsConstructor
@NoArgsConstructor
@Data
public class CategoryQueryDto {

    @Expose()
    private UUID id;
    @Expose()
    private String title;

    @Expose(serialize = false, deserialize = false)
    private List<ReportQueryDto> reports;

    public CategoryQueryDto(String title) {
        this.title = title;
    }

    public CategoryQueryDto(UUID id, String title) {
        this.id = id;
        this.title = title;
    }

}


@Override
public CategoryQueryDto getCategory(UUID id) {

    if (categoryRepository.findById(id).isPresent()) {
        Category category = categoryRepository.findById(id).get();

        CategoryQueryDto categoryQueryDto = new CategoryQueryDto(category.getId(), category.getTitle());

        Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();
        String converter = gson.toJson(categoryQueryDto);

        categoryQueryDto = gson.fromJson(converter, CategoryQueryDto.class);


        return categoryQueryDto;
    } else {
        return null;
    }

}

答案1

得分: 1

Used `@JsonInclude(JsonInclude.Include.NON_NULL)` on the field I wanted to show only if not null and it worked.

@AllArgsConstructor
@NoArgsConstructor
@Data
public class CategoryQueryDto {

@Expose()
private UUID id;
@Expose()
private String title;

@JsonInclude(JsonInclude.Include.NON_NULL)
private List<ReportQueryDto> reports = null;

public CategoryQueryDto(String title) {
    this.title = title;
}

public CategoryQueryDto(UUID id, String title) {
    this.id = id;
    this.title = title;
}

}


And here my controller with Jackson

@Service
public class CategoryQueryServiceImpl implements CategoryQueryService {

@Autowired
private CategoryRepository categoryRepository;

@Autowired
private ReportRepository reportRepository;

ObjectMapper mapper = new ObjectMapper();

@Override
public CategoryQueryDto getCategory(UUID id) throws JsonProcessingException {

    if (categoryRepository.findById(id).isPresent()) {
        Category category = categoryRepository.findById(id).get();

        CategoryQueryDto categoryQueryDto = new CategoryQueryDto(category.getId(), category.getTitle());


        String converter = mapper.writeValueAsString(categoryQueryDto);

        categoryQueryDto = mapper.readValue(converter, CategoryQueryDto.class);


        return categoryQueryDto;


    } else {
        return null;
    }

}

POM

<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-core-asl</artifactId>
<version>1.9.13</version>
<scope>test</scope>
</dependency>

<details>
<summary>英文:</summary>
Used `@JsonInclude(JsonInclude.Include.NON_NULL)` on the field I wanted to show only if not null and it worked.
@AllArgsConstructor
@NoArgsConstructor
@Data
public class CategoryQueryDto {
@Expose()
private UUID id;
@Expose()
private String title;
@JsonInclude(JsonInclude.Include.NON_NULL)
private List&lt;ReportQueryDto&gt; reports = null;
public CategoryQueryDto(String title) {
this.title = title;
}
public CategoryQueryDto(UUID id, String title) {
this.id = id;
this.title = title;
}
}
And here my controller with Jackson
@Service
public class CategoryQueryServiceImpl implements CategoryQueryService {
@Autowired
private CategoryRepository categoryRepository;
@Autowired
private ReportRepository reportRepository;
ObjectMapper mapper = new ObjectMapper();
@Override
public CategoryQueryDto getCategory(UUID id) throws JsonProcessingException {
if (categoryRepository.findById(id).isPresent()) {
Category category = categoryRepository.findById(id).get();
CategoryQueryDto categoryQueryDto = new CategoryQueryDto(category.getId(), category.getTitle());
String converter = mapper.writeValueAsString(categoryQueryDto);
categoryQueryDto = mapper.readValue(converter, CategoryQueryDto.class);
return categoryQueryDto;
} else {
return null;
}
}
POM
&lt;dependency&gt;
&lt;groupId&gt;org.codehaus.jackson&lt;/groupId&gt;
&lt;artifactId&gt;jackson-core-asl&lt;/artifactId&gt;
&lt;version&gt;1.9.13&lt;/version&gt;
&lt;scope&gt;test&lt;/scope&gt;
&lt;/dependency&gt;
</details>