Spring Data Mongo +延迟加载+ REST Jackson [英] Spring Data Mongo + Lazy Load + REST Jackson
问题描述
你好,我在使用懒加载的Spring和Mongo时遇到一些问题.
Hello I have some issues with Spring and Mongo with Lazy Load.
我有此配置:
<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>
本文档:
@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中公开用户"时,例如:
Everything works fine, but when I expose the "User" in a RestController, for example:
@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);
}
}
输出为:
{
"id": "58ebf11ee68f2751f33ae603",
"place": {
"id": "58e3bf76e76877586435f5af",
"name": "Place X"
},
"country": {
"id": "58daa782e96139070bbc851c",
"name": "México",
"target":{
"id": "58daa782e96139070bbc851c",
"name": "México",
}
}
}
问题:
-
如果国家"标记为"lazy = true",为什么要打印出来?
If "country" is marked as "lazy=true", why it is printed out?
为什么在国家/地区"中有一个名为目标"的新字段?
Why there is a new field named "target" in "country"?
如何避免序列化标记为"lazy = true"的字段?
How can I avoid serialize fields marked as "lazy=true"?
在此先感谢您的帮助.
推荐答案
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,因此它将序列化实际对象而不是代理,它具有目标"字段并具有一个时髦的类名称.
I had a similar issue with the 'target' showing up in the serialized results, and was able to solve this issue by creating a custom serializer so it serializes the actual object, and not the proxy, which has the 'target' field and has a funky class name.
很明显,您可以选择不获取目标,而不是像下面所示那样简单地获取目标并对其进行序列化:
Obviously, you could choose to not fetch the target instead of simply fetching it and serializing it as is shown here:
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);
}
}
}
然后注释您要通过它运行的DBRef,如下所示:
And then annotate the DBRefs you want to run through it like this:
@JsonSerialize(using=DBRefSerializer.class)
@DBRef(lazy = true)
private SomeClass someProperty;
显然,这并不适合所有人,但我想我会发布它,以防它对其他人有帮助.
Obviously this isn't perfect for everyone, but I figured I would post it in case it helps someone else.
这篇关于Spring Data Mongo +延迟加载+ REST Jackson的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!