责任模式链 [英] The Chain of Responsibility Pattern

问题描述

有人可以简单地解释责任模式链吗？我发现wiki文章有点混乱。

解决方案

一个很好的例子是 java servlet过滤器 - 在HTTP请求到达目标之前执行的代码段。

• 链包含多个实例，每个实例都执行不同的操作


• 链中的每个实例可以选择传播到下一个例子，或者停止流程

所以，使用servlet过滤器，你可以有

• 一个过滤器，用于检查用户是否经过身份验证。如果他是，则过滤器传播到下一个过滤器




• 下一个过滤器检查用户是否具有当前资源的权限。如果是这样，它传播到下一个




• 下一个日志记录当前的请求URL和用户名，并始终传播到下一个




• 链中没有其他的东西，所以最终调用目标对象

Could somebody provide a simple explanation of the chain of responsibility pattern? I found the wiki article a bit confusing.

解决方案

A very good example are java servlet filters - pieces of code that are executed before the HTTP request arrives at its target.

• the chain contains multiple instances, and each of them performs a different action
• each instance in the chain can choose to propagate to the next instance, or stop the flow

So, with servlet filters, you can have

• a filter that checks if the user is authenticated. If he is, the filter propagates to the next filter

• the next filter checks if the user has permissions to the current resource. If it does, it propagate to the next

• the next logs the current request URL and the username, and always propagate to the next

• there is nothing else in the chain, so the target object is finally invoked

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