Java获取泛型真实类型的方法

男娘i 2024-04-18 14:23 105阅读 0赞

1.  获取泛型类的泛型
    
        public abstract class AbstractDao<T> {
            public Class<T> getActualType() {
                ParameterizedType parameterizedType = (ParameterizedType) this.getClass().getGenericSuperclass();
                return (Class<T>) parameterizedType.getActualTypeArguments()[0];
            }
        }
        
        public class UserDao extends AbstractDao<String> {
            public static void main(String[] args) {
                UserDao userDao = new UserDao();
                Class<String> actualType = userDao.getActualType();
                System.out.println(actualType.getName());
            }
        }
2.  获取成员变量的泛型
    
        public class User {
            private List<String> list;
            public static void main(String[] args) {
                try {
                    Field field = User.class.getDeclaredField("list");
                    Type genericType = field.getGenericType();
                    if (genericType != null && genericType instanceof ParameterizedType) {
                        Type actualType = ((ParameterizedType) genericType).getActualTypeArguments()[0];
                        System.out.println(actualType.getTypeName());
                    }
                } catch (Exception e) {
                }
            }
        }
3.  获取局部变量的泛型，注意：泛型必须以匿名内部类的方式
    
        public abstract class AbstractDao<T> {
        
            public Class<T> getActualType() {
                ParameterizedType parameterizedType = (ParameterizedType) this.getClass().getGenericSuperclass();
                return (Class<T>) parameterizedType.getActualTypeArguments()[0];
            }
        
            public static void main(String[] args) {
                AbstractDao<String> dao = new AbstractDao<String>() {
                };
                System.out.println(dao.getActualType().getTypeName());
            }
        }