java - 使用反射获取 Field 的通用类型

Question

有没有办法在Java中获取字段的泛型类型？

我有以下对象变量:

protected ScheduleView<WantedClass> scheduleLine1;
protected ScheduleView<SomeOtherClass> scheduleLine2;

现在我尝试使用反射来获取所有类型为 ScheduleView 且类型为 WantedClass 的对象变量:

Arrays.asList(this.getClass().getDeclaredFields()).stream().map(field -> {
    ScheduleView<WantedClass> retValue = null;

    System.out.println(field.getGenericType()); // prints control.ScheduleView<dto.WantedClass>

    try {
        if (field.getType() == ScheduleView.class) { // here I also want to check if the generic type is WantedClass
            retValue = (ScheduleView<WantedClass>) field.get(this);
        } else {
            retValue = null;
        }
    } catch (IllegalAccessException e) {
        retValue = null;
    } finally {
        return retValue;
    }
}).filter(scheduleView -> scheduleView != null).forEach(scheduleView -> {
        /* some more code */
});

如果泛型类型是 WantedClass，我还想检查 if 语句。我也尝试使用 getGenericType() 方法，但看起来像这样是不可能的:

field.getGenericType() == ScheduleView<WantedClass>.class

那么有没有办法获取字段的通用类型呢？

Answer 1

您必须检查该字段是否为ParameterizedType，然后检查getActualTypeArguments 的内容，例如

    for (Field field : Ideone.class.getDeclaredFields()) {
        Type type = field.getGenericType();
        if (type instanceof ParameterizedType) {
            ParameterizedType ptype = (ParameterizedType) type;
            if (ptype.getRawType() == ScheduledView.class) {
                if (ptype.getActualTypeArguments().length == 1
                    && ptype.getActualTypeArguments()[0] == WantedClass.class) {
                  // Do whatever with the field.
                  System.out.println(field.getName());
                }
            }
        }
    }

Ideone demo