java - 获取 java.lang.reflect.Type 的简单代码

Question

GSON的 toJson 函数接受一个类型参数来检查 Type反射物体时。这对于将对象反射(reflect)到集合中很有用。

但是，我能找到的唯一方法是通过一组丑陋的编码扭曲:

//used for reflection only
@SuppressWarnings("unused")
private static final List<MyObject> EMPTY_MY_OBJECT = null;
private static final Type MY_OBJECT_TYPE;

static {
    try {
        MY_OBJECT_TYPE = MyClass.class.getDeclaredField("EMPTY_MY_OBJECT").getGenericType();
    } catch (Exception e) {
        ...
    }   
}

private List<MyObject> readFromDisk() {

    try {
        String string = FileUtils.readFileToString(new File(JSON_FILE_NAME), null);
        return new Gson().fromJson(string, MY_OBJECT_TYPE);
    } catch (Exception e) {
        ...
    }
}

有没有一种方法可以在不引用内部类变量的情况下初始化 Type？伪代码看起来像这样:

private static final Type MY_OBJECT_TYPE = TypeUtils.generate(List.class, MyObject.class);

Answer 1

toJson 的 Javadoc看起来可以回答你的问题

typeOfSrc - The specific genericized type of src. You can obtain this type by using the TypeToken class. For example, to get the type for Collection, you should use:

Type typeOfSrc = new TypeToken<Collection<Foo>>(){}.getType();

所以在你的例子中。

private static final Type MY_OBJECT_TYPE = new TypeToken<List<MyObject>>(){}.getType();