springMVC源码笔记

springMVC 设计总览

下图来源：https://www.cnblogs.com/fangjian0423/p/springMVC-directory-summary.html

下图来源：https://www.cnblogs.com/sunniest/p/4555801.html

核心类DispatcherServlet

接收请求DispatcherServlet也是一个Servlet

    protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
       ...
        try {
            this.doDispatch(request, response);
        } finally {
            if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted() && attributesSnapshot != null) {
                this.restoreAttributesAfterInclude(request, attributesSnapshot);
            }

        }

    }

    protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
                ...
                mappedHandler = this.getHandler(processedRequest);
                HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
                ...
    
                mappedHandler.applyPreHandle(processedRequest, response)
                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
                ...
                this.applyDefaultViewName(request, mv);
                mappedHandler.applyPostHandle(processedRequest, response, mv);

           
                this.processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
       
    }

HandlerAdapter是一个适配器，根据handler适配ModelAndView

getHandler(processedRequest)是为了获取HandlerExecutionChain：protected HandlerExecutionChain getHandler(HttpServletRequest request)

HandlerExecutionChain 有什么：

    private static final Log logger = LogFactory.getLog(HandlerExecutionChain.class);
    private final Object handler;
    private HandlerInterceptor[] interceptors;
    private List<HandlerInterceptor> interceptorList;
    private int interceptorIndex;

    boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
        if (this.getInterceptors() != null) {
            for(int i = 0; i < this.getInterceptors().length; this.interceptorIndex = i++) {
                HandlerInterceptor interceptor = this.getInterceptors()[i];
                if (!interceptor.preHandle(request, response, this.handler)) {
                    this.triggerAfterCompletion(request, response, (Exception)null);
                    return false;
                }
            }
        }

        return true;
    }

    void applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) throws Exception {
        if (this.getInterceptors() != null) {
            for(int i = this.getInterceptors().length - 1; i >= 0; --i) {
                HandlerInterceptor interceptor = this.getInterceptors()[i];
                interceptor.postHandle(request, response, this.handler, mv);
            }

        }
    }

HandlerInterceptor：拦截器（在handler处理前后执行applyPreHandle，applyPostHandle方法）
handler：处理器