Spring Mvc 源码理解。

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学习一个框架，首要的是要先领会它的设计思想。从抽象、从全局上来审视这个框架。其中最具有参考价值的，就是这个框架所定义的核心接口。核心接口定义了框架的骨架，也在最抽象的意义上表达了框架的设计思想。

前因：发现springMvc可以使用spring中的bean，way?

由于SpringMvc就是Servlet,必须先了解servlet原理：http://blog.csdn.net/czlpf/article/details/47781473

一。SpringMvc的入口分为 init() 和 service() 两个入口。

1.init()仅在DispatherServlet创建的时候执行一次，为容器和组件做初始化。

2.service()方法在每次http请求的时候都执行。

Servlet的所以请求都会通过执行HttpServlet中service(ServletRequest ,ServletResponse)方法，该方法执行了service(HttpServletRequest,HttpServletResponse)

而该方法在FrameworkServlet中被重写，所以执行FrameworkServlet中的service(HttpServletRequest,HttpServletResponse)方法。

-----》》FrameworkServlet.processRequest()

-----》》DispatcherServlet.doService()

-----》》DispatcherServlet.doDispatch()

这个doDispatch()就是每次http请求到springMvc的重点。

首先选择一个handler获得HandlerExecutionChain

        protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {for (HandlerMapping hm : this.handlerMappings) {if (logger.isTraceEnabled()) {logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");}HandlerExecutionChain handler = hm.getHandler(request);if (handler != null) {return handler;}}return null;}

其中this.handlerMappings在init()方法已经初始化。详情查看init()流程。

下面研究这个HandlerExecutionChain：

HandlerExecutionChain类的代码不长，它定义在org.springframework.web.servlet包中，为了更直观的理解，先上代码。

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packageorg.springframework.web.servlet;
 
importjava.util.ArrayList;
importjava.util.Arrays;
importjava.util.List;
 
importorg.springframework.util.CollectionUtils;
 
publicclassHandlerExecutionChain {
 
    privatefinalObject handler;
 
    privateHandlerInterceptor[] interceptors;
 
    privateList<HandlerInterceptor> interceptorList;
 
    publicHandlerExecutionChain(Object handler) {
        this(handler,null);
    }
 
    publicHandlerExecutionChain(Object handler, HandlerInterceptor[] interceptors) {
        if(handlerinstanceofHandlerExecutionChain) {
            HandlerExecutionChain originalChain = (HandlerExecutionChain) handler;
            this.handler = originalChain.getHandler();
            this.interceptorList = newArrayList<HandlerInterceptor>();
            CollectionUtils.mergeArrayIntoCollection(originalChain.getInterceptors(),this.interceptorList);
            CollectionUtils.mergeArrayIntoCollection(interceptors,this.interceptorList);
        }
        else{
            this.handler = handler;
            this.interceptors = interceptors;
        }
    }
 
    publicObject getHandler() {
        returnthis.handler;
    }
 
    publicvoidaddInterceptor(HandlerInterceptor interceptor) {
        initInterceptorList();
        this.interceptorList.add(interceptor);
    }
 
    publicvoidaddInterceptors(HandlerInterceptor[] interceptors) {
        if(interceptors != null) {
            initInterceptorList();
            this.interceptorList.addAll(Arrays.asList(interceptors));
        }
    }
 
    privatevoidinitInterceptorList() {
        if(this.interceptorList == null) {
            this.interceptorList = newArrayList<HandlerInterceptor>();
        }
        if(this.interceptors != null) {
            this.interceptorList.addAll(Arrays.asList(this.interceptors));
            this.interceptors = null;
        }
    }
 
    publicHandlerInterceptor[] getInterceptors() {
        if(this.interceptors == null&&this.interceptorList != null) {
            this.interceptors = this.interceptorList.toArray(newHandlerInterceptor[this.interceptorList.size()]);
        }
        returnthis.interceptors;
    }
 
    @Override
    publicString toString() {
        if(this.handler == null) {
            return"HandlerExecutionChain with no handler";
        }
        StringBuilder sb = newStringBuilder();
        sb.append("HandlerExecutionChain with handler [").append(this.handler).append("]");
        if(!CollectionUtils.isEmpty(this.interceptorList)) {
            sb.append(" and ").append(this.interceptorList.size()).append(" interceptor");
            if(this.interceptorList.size() > 1) {
                sb.append("s");
            }
        }
        returnsb.toString();
    }
 
}

乱七八糟一大堆，相信你也没全看完，也没必要全看。其实只需要看两行足矣。

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privatefinalObject handler;
 
privateHandlerInterceptor[] interceptors;

不出我们所料，一个实质执行对象，还有一堆拦截器。这不就是Struts2中的实现么，SpringMVC没有避嫌，还是采用了这种封装。得到HandlerExecutionChain这个执行链（execution chain）之后，下一步的处理将围绕其展开。

在Dispatcher中，执行拦截器

在执行handler之前:

if (!mappedHandler.applyPreHandle(processedRequest, response)) {return;}

执行handler:

// Actually invoke the handler.mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

执行handler之后：

mappedHandler.applyPostHandle(processedRequest, response, mv);

异常拦截：

catch (Exception ex) {triggerAfterCompletion(processedRequest, response, mappedHandler, ex);}catch (Error err) {triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);}

最终执行拦截：

finally {if (asyncManager.isConcurrentHandlingStarted()) {// Instead of postHandle and afterCompletionif (mappedHandler != null) {mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);}}else {// Clean up any resources used by a multipart request.if (multipartRequestParsed) {cleanupMultipart(processedRequest);}}}

配置拦截器：

java代码：

查看复制到剪贴板打印
<bean name="/test" class="cn.javass.chapter5.web.controller.TestController"/>  
<bean id="handlerInterceptor1"   
class="cn.javass.chapter5.web.interceptor.HandlerInterceptor1"/>  
<bean id="handlerInterceptor2"   
class="cn.javass.chapter5.web.interceptor.HandlerInterceptor2"/>  
   

java代码：

查看复制到剪贴板打印
<bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping">  
    <property name="interceptors">  
        <list>  
           <ref bean="handlerInterceptor1"/>  
          <ref bean="handlerInterceptor2"/>  
        </list>  
    </property>  
</bean>  

参考：

http://my.oschina.net/lichhao/blog/99039

http://downpour.iteye.com/blog/1341459

http://blog.csdn.net/soundfly/article/details/17380111

http://sishuok.com/forum/blogCategory/showByCategory.html?categories_id=106&user_id=2

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