tomcat源码解析一之设计模式

向右看齐 2023-02-20 07:37 148阅读 0赞

### 没有标题 ###

*  组合
 *  责任链
 *  观察者
 *  总结
 *   *  跟spring对比

# 组合 #

![在这里插入图片描述][20200624220027354.png]  
service将连接器和容器组合在一块对外提供服务,  
在外层,catalina将Digester和server组合在一块,解析xml属性然后直接赋值给server.这样整个容器初始化就完成了,包括连接器.

# 责任链 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70]  
利用**Pipeline**\+**Valve**组成  
当调用容器invoke方法时,父类默认方法  
***ContainerBase***

protected Pipeline pipeline = new StandardPipeline(this);
        public void invoke(Request request, Response response)
            throws IOException, ServletException {
        
            pipeline.invoke(request, response);
        }

***StandardPipeline***

public void invoke(Request request, Response response)
            throws IOException, ServletException {
        
    
            // Invoke the first Valve in this pipeline for this request
            (new StandardPipelineValveContext()).invokeNext(request, response);
    
        }

遍历执行每个value

public void invokeNext(Request request, Response response)
                throws IOException, ServletException {
        
    
                int subscript = stage;
                stage = stage + 1;
    
                // Invoke the requested Valve for the current request thread
                if (subscript < valves.length) {
        
                    valves[subscript].invoke(request, response, this);
                } else if ((subscript == valves.length) && (basic != null)) {
        
                    basic.invoke(request, response, this);
                } else {
        
                    throw new ServletException
                        (sm.getString("standardPipeline.noValve"));
                }
    
            }

当调用*value*时,可调用传入的ValveContext传递给下一个value执行

public void invoke(Request request, Response response, ValveContext valveContext)
                throws IOException, ServletException {
        
            // Pass this request on to the next valve in our pipeline
            //调用下一个阀
            valveContext.invokeNext(request, response);
            //将ip打印客户端
            System.out.println("Client IP Logger Valve");
            ServletRequest sreq = request.getRequest();
            System.out.println(sreq.getRemoteAddr());
            System.out.println("------------------------------------");
        }

# 观察者 #

tomcat每个容器继承生命周期接口,然后将每个生命周期阶段绑定一个事件进行发送.  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 1]

public void fireLifecycleEvent(String type, Object data) {
        
    
            LifecycleEvent event = new LifecycleEvent(lifecycle, type, data);
            LifecycleListener interested[] = null;
            synchronized (listeners) {
        
                interested = (LifecycleListener[]) listeners.clone();
            }
            for (int i = 0; i < interested.length; i++)
                interested[i].lifecycleEvent(event);
    
        }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 2]

# 总结 #

tomcat有趣的地方在于,套娃形式.每个大容器套一个小容器,然后采用责任链的方式,每个管道最后都会有一个兜底的value实现方法,用来调用子容器.这样保证了整个容器的执行顺序由上而下.如果需要扩展每个容器注册一个value到pipe上就行了.  
![在这里插入图片描述][20200624221014888.png]  
![在这里插入图片描述][20200624221030976.png]  
然后每个容器都继承了生命周期接口,可以注册一个监听器,用来监听每个执行过程的事件,进行比如解析xml之内的玩意儿.

## 跟spring对比 ##

tomcat主要是基于组件的开发,可以在任意模块通过增加阀和监听器实现增强和扩展  
spring主要基于对对象的生明周期管理,所以提供前置和后置增强就可以啦  
mybatis和sharding-jdbc主要的功能是解析语法树,然后在语法树层面对sql进行优化.

[20200624220027354.png]: https://img-blog.csdnimg.cn/20200624220027354.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200624220910885.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200624220407298.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200624220449135.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw==,size_16,color_FFFFFF,t_70
[20200624221014888.png]: https://img-blog.csdnimg.cn/20200624221014888.png
[20200624221030976.png]: https://img-blog.csdnimg.cn/20200624221030976.png