问题描述
您好,我对带有延迟加载的 Spring 和 Mongo 有一些问题.
Hello I have some issues with Spring and Mongo with Lazy Load.
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>
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); } }
输出是:
{ "id": "58ebf11ee68f2751f33ae603", "place": { "id": "58e3bf76e76877586435f5af", "name": "Place X" }, "country": { "id": "58daa782e96139070bbc851c", "name": "México", "target":{ "id": "58daa782e96139070bbc851c", "name": "México", } } }
问题:
如果country"标记为lazy=true",为什么会打印出来?
If "country" is marked as "lazy=true", why it is printed out?
为什么在国家"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"?
提前感谢您的帮助.
推荐答案
我遇到了类似的问题,目标"出现在序列化结果中,并且能够通过创建自定义序列化程序来解决这个问题,以便序列化实际对象,而不是代理,它具有目标"字段并具有时髦的类名.
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.
显然,您可以选择不获取目标,而不是简单地获取它并对其进行序列化,如下所示:
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); } } }
然后像这样注释您想要运行的 DBRef:
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帮助其他人.
Obviously this isn't perfect for everyone, but I figured I would post it in case it helps someone else.