SpringMVC初始化HandlerMapping浅析

最新推荐文章于 2024-11-25 00:30:00 发布

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这篇博客详细解析了Spring DispatcherServlet在初始化HandlerMapping的过程，从Servlet的继承关系到初始化方法的调用顺序，特别是如何探测和配置HandlerMapping。当没有定义特定的HandlerMapping时，DispatcherServlet会使用默认的BeanNameUrlHandlerMapping。博客还展示了源代码，说明了如何确保至少存在一个HandlerMapping。

HttpServlet
HttpServletBean
FrameworkServlet
DispatcherServlet

以上是DispatcherServlet的继承关系

初始化HandlerMapper的方法调用过程如下：

org.springframework.web.servlet.HttpServletBean.init()
org.springframework.web.servlet.HttpServletBean.initServletBean()
org.springframework.web.servlet.FrameworkServlet.initServletBean()
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext()
org.springframework.web.servlet.FrameworkServlet.onRefresh(ApplicationContext)
org.springframework.web.servlet.DispatcherServlet.onRefresh(ApplicationContext)
org.springframework.web.servlet.DispatcherServlet.initStrategies(ApplicationContext)
org.springframework.web.servlet.DispatcherServlet.initHandlerMappings(ApplicationContext)

初始化HandlerMapper函数：

    /**
     * Initialize the HandlerMappings used by this class.
     * <p>If no HandlerMapping beans are defined in the BeanFactory for this namespace,
     * we default to BeanNameUrlHandlerMapping.
     */
    private void initHandlerMappings(ApplicationContext context) {
        this.handlerMappings = null;

        //detectAllHandlerMappings 是否找出所有HandlerMapping
        //如果不是，就只取名为“handlerMapping”的HandlerMapping
        if (this.detectAllHandlerMappings) {
            // Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
            Map<String, HandlerMapping> matchingBeans =
                    BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
            if (!matchingBeans.isEmpty()) {
                this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values());
                // We keep HandlerMappings in sorted order.
                OrderComparator.sort(this.handlerMappings);
            }
        }
        else {
            try {
                HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
                this.handlerMappings = Collections.singletonList(hm);
            }
            catch (NoSuchBeanDefinitionException ex) {
                // Ignore, we'll add a default HandlerMapping later.
            }
        }

        //最后，确保有一个HandlerMapping，如果上面都找不到，就拿默认的
        // Ensure we have at least one HandlerMapping, by registering
        // a default HandlerMapping if no other mappings are found.
        if (this.handlerMappings == null) {
            this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
            if (logger.isDebugEnabled()) {
                logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default");
            }
        }
    }