java – Spring Data Mongo Lazy Load REST Jackson

你好,我在使用Lazy Load的 Spring和Mongo时遇到了一些问题.

我有这个配置:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.1.RELEASE</version>
</parent>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

这个文件:

@Document
public class User {
    @Id
    private String id;

    @DBRef
    private Place place;

    @DBRef(lazy=true)
    private Country country;

    .
    .
    .
}

一切正常,但是当我在RestController中公开“User”时,例如:

@RestController
public class UserController {

    .
    .
    .

    @RequestMapping(value = "user/{idUser}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    public User getById(@PathVariable("idUser") String idUser){    
            return userService.getById(idUser);    
    }
}

输出是:

  {
    "id": "58ebf11ee68f2751f33ae603",
    "place": {
      "id": "58e3bf76e76877586435f5af",
      "name": "Place X"
    },
    "country": {
      "id": "58daa782e96139070bbc851c",
      "name": "México",
      "target":{
        "id": "58daa782e96139070bbc851c",
        "name": "México",
      }
    }
  }

问题:

>如果“country”被标记为“lazy = true”,为什么打印出来?
>为什么在“country”中有一个名为“target”的新字段?
>如何避免序列化标记为“lazy = true”的字段?

在此先感谢您的帮助.

最佳答案 我在序列化结果中出现了类似的“目标”问题,并且能够通过创建自定义序列化程序来解决此问题,因此它序列化了实际对象,而不是代理,它具有“目标”字段并具有一个时髦的班级名称.

显然,您可以选择不获取目标,而不是简单地获取目标并将其序列化,如下所示:

public class DBRefSerializer extends JsonSerializer<Object> {

    @Override
    public void serialize(Object value, JsonGenerator generator, SerializerProvider provider)
            throws JsonGenerationException, IOException {

        provider.defaultSerializeValue(value, generator);
    }

    @Override
    public void serializeWithType(Object value, JsonGenerator generator, SerializerProvider provider,
            TypeSerializer typeSer)
            throws IOException {

        Object target = value;
        if (value instanceof LazyLoadingProxy) {
            LazyLoadingProxy proxy = (LazyLoadingProxy)value;
            target = proxy.getTarget();
            provider.defaultSerializeValue(target, generator);
        } else {
            provider.defaultSerializeValue(target, generator);
        }
    }
}

然后注释要通过它运行的DBRef,如下所示:

@JsonSerialize(using=DBRefSerializer.class)
@DBRef(lazy = true)
private SomeClass someProperty;

显然这对每个人来说并不完美,但我想我会发布它,以防它帮助其他人.

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