demo1

代码片段

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
// 奖励服务
class RewardService {
    // 外部服务
    private WaimaiService waimaiService;
    private HotelService hotelService;
    private FoodService foodService;
    // 使用对入参的条件判断进行发奖
    public void issueReward(String rewardType, Object ... params) {
        if (“Waimai”.equals(rewardType)) {
            WaimaiRequest request = new WaimaiRequest();
            // 构建入参
            request.setWaimaiReq(params);
            waimaiService.issueWaimai(request);
        } else if (“Hotel”.equals(rewardType)) {
            HotelRequest request = new HotelRequest();
            request.addHotelReq(params);
            hotelService.sendPrize(request);
        } else if (“Food”.equals(rewardType)) {
            FoodRequest request = new FoodRequest(params);
            foodService.getCoupon(request);
        } else {
            throw new IllegalArgumentException(“rewardType error!”);
        }
    }
}

这样设计，如果说需要新添加一个服务，就需要添加如下代码：

1
2
3
4
5
private NewService newService;
// else if下面添加新的
else if ("new".equals(rewardType)) {
    ...
}

经过第一次修改后，代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
// 策略接口
interface Strategy {
    void issue(Object ... params);
}
// 外卖策略
class Waimai implements Strategy {
    private WaimaiService waimaiService;
    @Override
    public void issue(Object... params) {
        WaimaiRequest request = new WaimaiRequest();
        // 构建入参
        request.setWaimaiReq(params);
        waimaiService.issueWaimai(request);
    }
}
// 酒旅策略
class Hotel implements Strategy {
    private HotelService hotelService;
    @Override
    public void issue(Object... params) {
        HotelRequest request = new HotelRequest();
        request.addHotelReq(params);
        hotelService.sendPrize(request);
    }
}
// 美食策略
class Food implements Strategy {
    private FoodService foodService;
    @Override
    public void issue(Object... params) {
        FoodRequest request = new FoodRequest(params);
        foodService.payCoupon(request);
    }
}

// 使用分支判断获取的策略上下文
class StrategyContext {
    public static Strategy getStrategy(String rewardType) {
        switch (rewardType) {
            case“Waimai”:
                return new Waimai();
            case“Hotel”:
                return new Hotel();
            case“Food”:
                return new Food();
            default:
                throw new IllegalArgumentException(“rewardType error!”);
        }
    }
}

// 优化后的策略服务
class RewardService {
    public void issueReward(String rewardType, Object ... params) {
        Strategy strategy = StrategyContext.getStrategy(rewardType);
        strategy.issue(params);
    }
}

这种优化，使用了一个接口，没当需要新添加服务时，只需要实现该接口

这次优化后，还有一个问题，那就是策略类，可以改为单例模式，如果之前有，就不需要新创建，代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
// 策略上下文，用于管理策略的注册和获取
class StrategyContext {
    private static final Map<String, Strategy> registerMap = new HashMap<>();
    // 注册策略
    public static void registerStrategy(String rewardType, Strategy strategy) {
        registerMap.putIfAbsent(rewardType, strategy);
    }
    // 获取策略
    public static Strategy getStrategy(String rewardType) {
        return registerMap.get(rewardType);
    }
}
// 抽象策略类
abstract class AbstractStrategy implements Strategy {
    // 类注册方法
    public void register() {
        StrategyContext.registerStrategy(getClass().getSimpleName(), this);
    }
}
// 单例外卖策略
class Waimai extends AbstractStrategy implements Strategy {
    private static final Waimai instance = new Waimai();
    private WaimaiService waimaiService;
    private Waimai() {
        register();
    }
    public static Waimai getInstance() {
        return instance;
    }
    @Override
    public void issue(Object... params) {
        WaimaiRequest request = new WaimaiRequest();
        // 构建入参
        request.setWaimaiReq(params);
        waimaiService.issueWaimai(request);
    }
}
// 单例酒旅策略
class Hotel extends AbstractStrategy implements Strategy {
    private static final Hotel instance = new Hotel();
    private HotelService hotelService;
    private Hotel() {
        register();
    }
    public static Hotel getInstance() {
        return instance;
    }
    @Override
    public void issue(Object... params) {
        HotelRequest request = new HotelRequest();
        request.addHotelReq(params);
        hotelService.sendPrize(request);
    }
}
// 单例美食策略
class Food extends AbstractStrategy implements Strategy {
    private static final Food instance = new Food();
    private FoodService foodService;
    private Food() {
        register();
    }
    public static Food getInstance() {
        return instance;
    }
    @Override
    public void issue(Object... params) {
        FoodRequest request = new FoodRequest(params);
        foodService.payCoupon(request);
    }
}

这次优化后，每次注册完成后，map中会有一个该对象，下次使用时就不需要创建，直接拿之前已经有的即可。

demo2

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
// 任务状态枚举
@AllArgsConstructor
@Getter
enum TaskState {
    INIT(“初始化”),
    ONGOING( “进行中”),
    PAUSED(“暂停中”),
    FINISHED(“已完成”),
    EXPIRED(“已过期”);
    private final String message;
}
// 行为枚举
@AllArgsConstructor
@Getter
enum ActionType {
    START(1, “开始”),
    STOP(2, “暂停”),
    ACHIEVE(3, “完成”),
    EXPIRE(4, “过期”);
    private final int code;
    private final String message;
}

class Task {
    private Long taskId;
    // 任务的默认状态为初始化
    private TaskState state = TaskState.INIT;
    // 活动服务
    private ActivityService activityService;
    // 任务管理器
    private TaskManager taskManager;
    // 使用条件分支进行任务更新
    public void updateState(ActionType actionType) {
        if (state == TaskState.INIT) {
            if (actionType == ActionType.START) {
                state = TaskState.ONGOING;
            }
        } else if (state == TaskState.ONGOING) {
            if (actionType == ActionType.ACHIEVE) {
                state = TaskState.FINISHED;
                // 任务完成后进对外部服务进行通知
                activityService.notifyFinished(taskId);
                taskManager.release(taskId);
            } else if (actionType == ActionType.STOP) {
                state = TaskState.PAUSED;
            } else if (actionType == ActionType.EXPIRE) {
                state = TaskState.EXPIRED;
            }
        } else if (state == TaskState.PAUSED) {
            if (actionType == ActionType.START) {
                state = TaskState.ONGOING;
            } else if (actionType == ActionType.EXPIRE) {
                state = TaskState.EXPIRED;
            }
        }
    }
}

这里的问题是if-else判断太多，如果新添加状态还需要添加新的if-else，这里可以用状态模式。而且Task类中冗余了TaskManager类。

修改后代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
// 任务状态抽象接口
interface State {
    // 默认实现，不做任何处理
    default void update(Task task, ActionType actionType) {
        // do nothing
    }
}
// 任务初始状态
class TaskInit implements State {
    @Override
    public void update(Task task, ActionType actionType) {
        if (actionType == ActionType.START) {
            task.setState(new TaskOngoing());
        }
    }
}
// 任务进行状态
class TaskOngoing implements State {
    private ActivityService activityService;
    private TaskManager taskManager;
    @Override
    public void update(Task task, ActionType actionType) {
        if (actionType == ActionType.ACHIEVE) {
            task.setState(new TaskFinished());
            // 通知
            activityService.notifyFinished(taskId);
            taskManager.release(taskId);
        } else if (actionType == ActionType.STOP) {
            task.setState(new TaskPaused());
        } else if (actionType == ActionType.EXPIRE) {
            task.setState(new TaskExpired());
        }
    }
}
// 任务暂停状态
class TaskPaused implements State {
    @Override
    public void update(Task task, ActionType actionType) {
        if (actionType == ActionType.START) {
            task.setState(new TaskOngoing());
        } else if (actionType == ActionType.EXPIRE) {
            task.setState(new TaskExpired());
        }
    }
}
// 任务完成状态
class TaskFinished implements State {
}
// 任务过期状态
class TaskExpired implements State {
}
@Data
class Task {
    private Long taskId;
    // 初始化为初始态
    private State state = new TaskInit();
    // 更新状态
    public void updateState(ActionType actionType) {
        state.update(this, actionType);
    }
}

采用观察者模式后，代码如下：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
// 抽象观察者
interface Observer {
    void response(Long taskId); // 反应
}
// 抽象目标
abstract class Subject {
    protected List<Observer> observers = new ArrayList<Observer>();
    // 增加观察者方法
    public void add(Observer observer) {
        observers.add(observer);
    }
    // 删除观察者方法
    public void remove(Observer observer) {
        observers.remove(observer);
    }
    // 通知观察者方法
    public void notifyObserver(Long taskId) {
        for (Observer observer : observers) {
            observer.response(taskId);
        }
    }
}
// 活动观察者
class ActivityObserver implements Observer {
    private ActivityService activityService;
    @Override
    public void response(Long taskId) {
        activityService.notifyFinished(taskId);
    }
}
// 任务管理观察者
class TaskManageObserver implements Observer {
    private TaskManager taskManager;
    @Override
    public void response(Long taskId) {
        taskManager.release(taskId);
    }
}
// 任务进行状态
class TaskOngoing extends Subject implements State { 
    @Override
    public void update(Task task, ActionType actionType) {
        if (actionType == ActionType.ACHIEVE) {
            task.setState(new TaskFinished());
            // 通知
            notifyObserver(task.getTaskId());
        } else if (actionType == ActionType.STOP) {
            task.setState(new TaskPaused());
        } else if (actionType == ActionType.EXPIRE) {
            task.setState(new TaskExpired());
        }
    }
}
// 任务初始状态
class TaskInit implements State {
    @Override
    public void update(Task task, ActionType actionType) {
        if (actionType == ActionType.START) {
            TaskOngoing taskOngoing = new TaskOngoing();
            taskOngoing.add(new ActivityObserver());
            taskOngoing.add(new TaskManageObserver());
            task.setState(taskOngoing);
        }
    }
}

参考

《美团博客》