Java获取泛型真实类型的方法

1. 获取泛型类的泛型

   public abstract class AbstractDao {
       public Class getActualType() {
           ParameterizedType parameterizedType = (ParameterizedType) this.getClass().getGenericSuperclass();
           return (Class) parameterizedType.getActualTypeArguments()[0];
       }
   }
   
   public class UserDao extends AbstractDao {
       public static void main(String[] args) {
           UserDao userDao = new UserDao();
           Class actualType = userDao.getActualType();
           System.out.println(actualType.getName());
       }
   }
   

2. 获取成员变量的泛型

   public class User {
       private List 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 {
   
       public Class getActualType() {
           ParameterizedType parameterizedType = (ParameterizedType) this.getClass().getGenericSuperclass();
           return (Class) parameterizedType.getActualTypeArguments()[0];
       }
   
       public static void main(String[] args) {
           AbstractDao dao = new AbstractDao() {
           };
           System.out.println(dao.getActualType().getTypeName());
       }
   }