如何让Gson反序列化接口类型?

Question

我有一个接口

public interace ABC {
}

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来反序列化一个类，它被实现为

public class UVW {
    ABC abcObject;
}

当我试图像gson.fromJson(jsonString, UVW.class);那样反序列化它时，它返回给我null。jsonString是UTF_8 String.

是因为UVW类中使用的接口吗?如果是，我如何反序列化这样的类?

Answer 1

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

短暂,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);
  }
}

下面是一个完整的工作测试工具，说明了这个例子:

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