如何让Gson反序列化接口类型? [英] How can I get Gson to deserialize an interface type?

问题描述

我有一个界面

public interace ABC {
}

其实现如下:

public class XYZ implements ABC {
    private Map<String, String> mapValue;
    public void setMapValue( Map<String, String> mapValue) {
        this.mapValue = mapValue;
    }  

    public  Map<String, String> getMapValue() {
        return this.mapValue
    }
}

我想使用Gson反序列化一个类，该类实现为

I want to deserialize a class using Gson which is implemented as

public class UVW {
    ABC abcObject;
}

当我尝试像gson.fromJson(jsonString, UVW.class);一样反序列化它时，它返回我null. jsonString是UTF_8字符​​串.

when I try to deserialize it like gson.fromJson(jsonString, UVW.class); it returns me null. jsonString is UTF_8 String.

是因为在UVW类中使用了接口吗?如果是，我该如何反序列化此类?

Is it because of interface used in UVW class? If yes, how do I deserialize such class?

推荐答案

您需要告诉Gson在反序列化ABC时使用XYZ. 您可以使用TypeAdapterFactory.

You need to tell Gson to use XYZ when it deserializes ABC. You can do this using a TypeAdapterFactory.

简而言之，因此:

public class ABCAdapterFactory implements TypeAdapterFactory {
  private final Class<? extends ABC> implementationClass;

  public ABCAdapterFactory(Class<? extends ABC> implementationClass) {
     this.implementationClass = implementationClass;
  }

  @SuppressWarnings("unchecked")
  @Override
  public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
    if (!ABC.class.equals(type.getRawType())) return null;

    return (TypeAdapter<T>) gson.getAdapter(implementationClass);
  }
}

这是一个完整的工作测试工具，说明了此示例:

Here is a complete working test harness that illustrates this example:

public class TypeAdapterFactoryExample {
  public static interface ABC {

  }

  public static class XYZ implements ABC {
    public String test = "hello";
  }

  public static class Foo {
    ABC something;
  }

  public static void main(String... args) {
    GsonBuilder builder = new GsonBuilder();
    builder.registerTypeAdapterFactory(new ABCAdapterFactory(XYZ.class));
    Gson g = builder.create();

    Foo foo = new Foo();
    foo.something = new XYZ();

    String json = g.toJson(foo);
    System.out.println(json);
    Foo f = g.fromJson(json, Foo.class);
    System.out.println(f.something.getClass());
  }
}

输出:

{"something":{"test":"hello"}}
class gson.TypeAdapterFactoryExample$XYZ

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