Aop AfterReturning增强方法返回值
需求：查询订单要返回用户名
为了解耦，查询订单中不查询用户，使用aop自动注入用户名
注意：订单列表中的用户缓存到了内存，遍历查询很快，如果直接查数据库，则效率相对低
思路：对返回值加强(aop对返回值增强，向订单表中注入userName)
1.注解
/** * 设置属性非空的开关 * 只有方法上加上此注解，才会对Field上加上 FieldNotNull 的属性赋值 */ @Documented @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.METHOD) public @interface SetFieldSwitch { }
/** * 字段非空注解 */ @Documented @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.FIELD) //作用在字段上(告诉aop去哪个object调用哪个method,需要传什么param参数，查询的结果需要取哪一个targetField) public @interface FieldNotNull { Class beanClass(); // 需要去哪个class中调用 （userName的属性从） String method(); // 需要调用class中的哪个方法 String param(); // 调用方法的参数 String targetField(); //调用方法后需要哪个值(为了set到添加该注解的属性上) }
2:订单+用户对象
@Data public class UserOrder /*extends Order*/ { private Integer id; private Integer goodsId; private Integer userId; @FieldNotNull(beanClass = UserCache.class, method = "get", param = "userId", targetField = "realName") private String userName; //用户名 private String goodName; //物品名称 public UserOrder(Integer id, Integer userId, Integer goodId, String userName, String goodName) { this.userName = userName; this.goodName = goodName; this.setId(id); this.setUserId(userId); this.setGoodsId(goodId); } }
3：查询订单方法
@Service public class OrderService { @Autowired private OrderDao orderDao; @SetFieldSwitch // 开启aop增强(如果不开启，则FileNotNull注解不会起作用)，将控制与实现分开) public List<UserOrder> listOrder() { return orderDao.listOrder(); } }
4：查询用户的方法
/** * 模拟用户的缓存 */ @Component public class UserCache { @Autowired private UserDao userDao ; private static Map<Integer, User> userCache = new HashMap<>(); public void put(Integer userId, User user) { userCache.put(userId, user); } public User get(Integer userId) { User user = userCache.get(userId); if (user == null) { user = userDao.getById(userId); if (user==null) return null; userCache.put(userId,user); } return user; } public boolean contain(Integer userId) { return userCache.containsKey(userId); } }
5：aop切面
使用AfterReturning
/** * * @param point 切点 * @param obj 返回值 * @return * @throws Throwable */ @AfterReturning(value = "setFieldValuePoint()", returning = "obj") public Object setValue(JoinPoint point, Object obj) throws Throwable { this.setFieldValueForCollection((Collection) obj); return obj; }
6:使用反射+注解 赋值
/** * 查询并赋值操作 * * @param collection */ private void setFieldValueForCollection(Collection collection) throws Exception { if (collection == null || collection.size() == 0) return; Iterator iterator = collection.iterator(); Object next = iterator.next(); /*collection中userOrder元素对应的class*/ Class clazz = next.getClass(); // class com.draymond.aop.query.UserOrder /*获取userOrder中所有的属性*/ Field[] declaredFields = clazz.getDeclaredFields(); for (Field field : declaredFields) { /* ----------- 获取 哪个class 调用哪个 method ,需要什么paras -----------*/ /*获取userOrder属性上的FieldNotNull注解(其他 Field 也可以有其他注解)*/ FieldNotNull annotation = field.getAnnotation(FieldNotNull.class); if (annotation == null) continue; field.setAccessible(true); // 暴力拆解 Class beanClass = annotation.beanClass(); String method = annotation.method(); // get（注解上的值） String param = annotation.param(); // userId String targetField = annotation.targetField(); // realName Field paraField = clazz.getDeclaredField(param); // 获取方法需要的参数值(paraField.get(user)中获取) paraField.setAccessible(true); Method methodExecute = beanClass.getDeclaredMethod(method, paraField.getType()); /*从spring上下文获取beanClass对应的bean*/ Object userCache = applicationContext.getBean(beanClass); // for循环，对list中每个user的带FieldNotNull注解的属性赋值 for (Object userOrder : collection) { //list上的每条user对象 Object user = methodExecute.invoke(userCache, paraField.get(userOrder)); // 执行 UserCache 中的 get 方法,需要的参数值 paraField if (user == null) continue; Field targetFieldValue = user.getClass().getDeclaredField(targetField); // 获取user对象中的 targetField 的值 if (targetFieldValue == null) continue; targetFieldValue.setAccessible(true); field.set(userOrder, targetFieldValue.get(user)); // 将 user中的targetField(realName) 的值,set到userOrder对象中的 userName } } }
其他
/** * 模拟从数据库中查询订单 */ @Component public class OrderDao { public List<UserOrder> listOrder() { UserOrder userOrder1 = new UserOrder(1, 1, 1, "zsc", "电冰箱"); UserOrder userOrder2 = new UserOrder(2, 1, 2, null, "洗衣机"); UserOrder userOrder3 = new UserOrder(3, 1, 3, null, "java Thread"); List list = new ArrayList(); list.add(userOrder1); list.add(userOrder2); list.add(userOrder3); return list; } public UserOrder getById(Integer id) { return listOrder().stream().filter(userOrder -> userOrder.getId() == id).findFirst().orElse(null); } }
方法上使用注解开启增强
@Service public class OrderService { @Autowired private OrderDao orderDao; @SetFieldSwitch public List<UserOrder> listOrder() { return orderDao.listOrder(); } public UserOrder getOrderById(Integer id) { return orderDao.getById(id); } }
未增强效果
[{"id":1,"goodsId":1,"userId":1,"userName":"zsc","goodName":"电冰箱"}, // 模拟数据的时候就赋值了
{"id":2,"goodsId":2,"userId":2,"userName":null,"goodName":"洗衣机"},
{"id":3,"goodsId":3,"userId":1,"userName":null,"goodName":"java Thread"}]
增强效果
[{"id":1,"goodsId":1,"userId":1,"userName":"zsc","goodName":"电冰箱"},
{"id":2,"goodsId":2,"userId":2,"userName":"draymond","goodName":"洗衣机"},
{"id":3,"goodsId":3,"userId":1,"userName":"zsc","goodName":"java Thread"}]
