Spring MVC component source code analysis

Component Overview

Handler Mapping

Handler and find the corresponding processor according Interceptors request. Internal only one way

HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;

Handler Adapter

Adapter Handler, the following internal method:

boolean supports(Object handler);//判断是否可以使用某个 Handler
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception; //具体使用
long getLastModified(HttpServletRequest request, Object handler);//获取资源上一次修改的时间

HandlerExceptionResolver

According exception settings ModelAndView, and then to the render method for rendering.

ModelAndView resolveException(
            HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex)

ViewResolver

Used to String type of view, and resolved to View Locale types of views.

View resolveViewName(String viewName, Locale locale) throws Exception;

It is an implementation class BeanNameViewResolver, rewrites it resolveViewName follows:

public View resolveViewName(String viewName, Locale locale) throws BeansException {
        ApplicationContext context = getApplicationContext();
        //如果应用上下文没有找到视图，返回 null
        if (!context.containsBean(viewName)) {
            if (logger.isDebugEnabled()) {
                logger.debug("No matching bean found for view name '" + viewName + "'");
            }
            // Allow for ViewResolver chaining...
            return null;
        }
        //如果找到的视图类型不匹配，也返回 null
        if (!context.isTypeMatch(viewName, View.class)) {
            if (logger.isDebugEnabled()) {
                logger.debug("Found matching bean for view name '" + viewName +
                        "' - to be ignored since it does not implement View");
            }
            // Since we're looking into the general ApplicationContext here,
            // let's accept this as a non-match and allow for chaining as well...
            return null;
        }
        //根据视图名称从 Spring 容器中查找 Bean，返回找到的 bean
        return context.getBean(viewName, View.class);
    }

RequestToViewNameTranslator

Get the view name in the request. Interface which is only one way:

String getViewName(HttpServletRequest request) throws Exception; //根据 request 查找视图名

LocaleResolver

Locale for parsing the request.

public interface LocaleResolver {
    //从 request 解析出 Locale
    Locale resolveLocale(HttpServletRequest request);
    //根据 request 设置  locale
    void setLocale(HttpServletRequest request, HttpServletResponse response, @Nullable Locale locale);
}

ThemeResolver

Resolving themes

public interface ThemeResolver {
    //通过给定的 request 查找主题名
    String resolveThemeName(HttpServletRequest request);
    //根据给定的 request 设置主题名
    void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName);
}

The topics for the RequestContext.java file:

public String getThemeMessage(String code, String defaultMessage) {
        //获取主题的信息
        return getTheme().getMessageSource().getMessage(code, null, defaultMessage, this.locale);
    }

public Theme getTheme() {
        //判断主题是否为空
        if (this.theme == null) {
            // 通过 RequestContextUtils 获取 request 中的主题名
            this.theme = RequestContextUtils.getTheme(this.request);
            if (this.theme == null) {   //如果还是为空的话
                //那就是没有有效的主题解析器和主题
                this.theme = getFallbackTheme();
            }
        }
        return this.theme;
    }

RequestContextUtils.getTheme() 方法：

public static Theme getTheme(HttpServletRequest request) {
        ThemeResolver themeResolver = getThemeResolver(request);
        ThemeSource themeSource = getThemeSource(request);
        if (themeResolver != null && themeSource != null) {
            String themeName = themeResolver.resolveThemeName(request);
            return themeSource.getTheme(themeName);
        }
        else {
            return null;
        }
    }

MultipartResolver

The upload request for processing, a processing method: Common packaging request to MultipartHttpServletRequest

public interface MultipartResolver {
    //根据 request 判断是否是上传请求
    boolean isMultipart(HttpServletRequest request);
    //将 request 包装成 MultipartHttpServletRequest
    MultipartHttpServletRequest resolveMultipart(HttpServletRequest request) throws MultipartException;
    //清理上传过程中产生的临时资源
    void cleanupMultipart(MultipartHttpServletRequest request);
}

FlashMapManager

FlashMap redirect the primary delivery parameters, FlashMapManager FlashMap is used to manage.

public interface FlashMapManager {
    //恢复参数，并将恢复过的和超时的参数从保存介质中删除
    @Nullable
    FlashMap retrieveAndUpdate(HttpServletRequest request, HttpServletResponse response);
    //将参数保存起来
    void saveOutputFlashMap(FlashMap flashMap, HttpServletRequest request, HttpServletResponse response);
}

summary

Introduction Spring MVC in the nine components of the interface, the role and function of internal methods to achieve a brief introduction, we all need a detailed look at the source code.

to sum up

Spring MVC principle summary

Is essentially a Servlet, the Servlet inherited from HttpServlet. Spring MVC provides three levels of Servlet: HttpServletBean, FrameworkServlet and DispatcherServlet. They inherit each other, HttpServletBean directly inherited from the Java HttpServlet. HttpServletBean parameters for the Servlet Servlet configured to set a respective attribute, FrameworkServlet initialized WebApplicationContext Spring MVC used, nine specific component in the processing request is to initialize the DispatcherServlet entire succession is as follows:

Spring MVC component source code analysis