从JerseyClient反序列化通用列表的Dropwizard [英] Dropwizard deserializing generic list from JerseyClient

问题描述

我想实现一个泛型类，用于缓存本地MongoDB实例中REST API的结果。为此，我需要反序列化我从JerseyClient获得的集合：

I wanted to implement a generic class to use for caching results from a REST API in a local MongoDB-instance. For this to work, I need to deserialize a collection I get from JerseyClient:

Response response = this.source.request().get();
List<T> list = response.readEntity( new GenericType<List<T>>() {} );

// ... do stuff with the list

让我说我我在 T 的上下文中使用这段代码与类 Foo 相关。非常奇怪的是，在 readEntity 调用之后， list 不是列表< Foo> ; ，而是列表< LinkedHashMap> 。当我明确宣布Generic T 为 Foo ？

Let's say I'm using this piece of code in a context of T relating to a class Foo. The really weird thing is, after the readEntity call, list is not a List<Foo>, instead is a List<LinkedHashMap>. How is that even possible, when I've clearly declared the Generic T to be Foo?

我需要做些什么来获得正确的列表< T> ，即列表< Foo> 而不是？

What do I have to do to get a proper List<T>, i.e. List<Foo> instead?

注意：如果我删除了通用，请使用

Note: If I remove the generic, and use

List<Foo> list = response.readEntity( new GenericType<List<Foo>>() {} );

直接替代，它工作正常，但我真的需要那个通用的存在！

directly instead, it works fine, but I really need that generic to be there!

推荐答案

Java最普遍的泛型借口：类型擦除

Java's most popular excuse for Generics: Type Erasure

如果您可以将类类型传递为 Class< T> clazz ，然后你可以使用它：

If you can pass your class type as Class<T> clazz, then you can use this:

GenericType<List<T>> genericType = new GenericType<>(new ParameterizedType() {
  public Type[] getActualTypeArguments() {
    return new Type[]{clazz};
  }

  public Type getRawType() {
    return List.class;
  }

  public Type getOwnerType() {
    return null;
  }
});
response.readEntity(genericType);

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