设计模式(24） -- 观察者模式

蔚落 2023-06-22 08:26 128阅读 0赞

### 文章目录 ###

*  需求
 *  传统方式实现
 *   *  缺点
 *  观察者模式
 *   *  观察者模式解决天气预报需求
     *  观察者模式的好处
 *  观察者模式在 Jdk 应用的源码分析
 *  推荐观察者模式好文章

之前也写过观察者模式的文章，链接地址  
[https://blog.csdn.net/baidu\_21349635/article/details/90602485][https_blog.csdn.net_baidu_21349635_article_details_90602485]  
[\[观察者模式和 事件委托\]][Link 1]

现在重新加深下观察者模式的理解。

# 需求 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70]

# 传统方式实现 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 2]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 3]  
CurrentConditions  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 4]  
WeatherData  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 5]  
Client  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 6]  
![在这里插入图片描述][20191215152516476.png]

## 缺点 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 7]

# 观察者模式 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 8]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 9]

## 观察者模式解决天气预报需求 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 10]  
Observer  
![在这里插入图片描述][20191215153052873.png]  
CurrentConditions  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 11]  
BaiduSite  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 12]  
Subject  
![在这里插入图片描述][20191215153152101.png]  
WeatherData

*  类是核心

1.  包含最新的天气情况信息
2.  含有 观察者集合，使用ArrayList管理
3.  当数据有更新时，就主动的调用 ArrayList, 通知所有的（接入方）就看到最新的信息  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 13]  
    Client  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 14]  
    运行结果:![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 15]

## 观察者模式的好处 ##

![在这里插入图片描述][20191215153554364.png]

# 观察者模式在 Jdk 应用的源码分析 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 16]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzIxMzQ5NjM1_size_16_color_FFFFFF_t_70 17]

# 推荐观察者模式好文章 #

*  1.第一篇  
    [https://www.cnblogs.com/WindSun/p/11503930.html][https_www.cnblogs.com_WindSun_p_11503930.html]  
    将的比较透彻，包括涉及到观察者模式的基本概念：1对多，主题，观察者，抽象主题，抽象观察者。  
    什么时候使用观察者。
 *  2 第二篇:  
    [https://blog.csdn.net/baidu\_21349635/article/details/101351320][Link 1]  
    对观察者模式进行升级，通过反射来实现事件的委托。

--------------------

完

[https_blog.csdn.net_baidu_21349635_article_details_90602485]: https://blog.csdn.net/baidu_21349635/article/details/90602485
[Link 1]: https://blog.csdn.net/baidu_21349635/article/details/101351320
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[20191215153554364.png]: https://img-blog.csdnimg.cn/20191215153554364.png
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[https_www.cnblogs.com_WindSun_p_11503930.html]: https://www.cnblogs.com/WindSun/p/11503930.html