1、Spring mvc介紹
SpringMVC框架是以請求為驅動,圍繞Servlet設計,將請求發給控制器,然後通過模型對象,分派器來展示請求結果視圖。其中核心類是DispatcherServlet,它是一個Servlet,頂層是實現的Servlet介面。
2、SpringMVC使用
需要在web.xml中配置DispatcherServlet。並且需要配置spring監聽器ContextLoaderListener
<listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <servlet> <servlet-name>springmvc</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <!-- 如果不設置init-param標籤,則必須在/WEB-INF/下創建xxx-servlet.xml文件,其中xxx是servlet-name中配置的名稱。 --> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring/springmvc-servlet.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>springmvc</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping>
3、SpringMVC運行原理
如圖所示:
流程說明:
(1)客戶端(瀏覽器)發送請求,直接請求到DispatcherServlet。
(2)DispatcherServlet根據請求信息調用HandlerMapping,解析請求對應的Handler。
(3)解析到對應的Handler後,開始由HandlerAdapter適配器處理。
(4)HandlerAdapter會根據Handler來調用真正的處理器開處理請求,並處理相應的業務邏輯。
(5)處理器處理完業務後,會返回一個ModelAndView對象,Model是返回的數據對象,View是個邏輯上的View。
(6)ViewResolver會根據邏輯View查找實際的View。
(7)DispaterServlet把返回的Model傳給View。
(8)通過View返回給請求者(瀏覽器)
4、DispatcherServlet詳細解析
首先看下源碼:
package org.springframework.web.servlet;
@SuppressWarnings("serial") public class DispatcherServlet extends FrameworkServlet {
public static final String MULTIPART_RESOLVER_BEAN_NAME = "multipartResolver"; public static final String LOCALE_RESOLVER_BEAN_NAME = "localeResolver"; public static final String THEME_RESOLVER_BEAN_NAME = "themeResolver"; public static final String HANDLER_MAPPING_BEAN_NAME = "handlerMapping"; public static final String HANDLER_ADAPTER_BEAN_NAME = "handlerAdapter"; public static final String HANDLER_EXCEPTION_RESOLVER_BEAN_NAME = "handlerExceptionResolver"; public static final String REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME = "viewNameTranslator"; public static final String VIEW_RESOLVER_BEAN_NAME = "viewResolver"; public static final String FLASH_MAP_MANAGER_BEAN_NAME = "flashMapManager"; public static final String WEB_APPLICATION_CONTEXT_ATTRIBUTE = DispatcherServlet.class.getName() + ".CONTEXT"; public static final String LOCALE_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".LOCALE_RESOLVER"; public static final String THEME_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_RESOLVER"; public static final String THEME_SOURCE_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_SOURCE"; public static final String INPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".INPUT_FLASH_MAP"; public static final String OUTPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".OUTPUT_FLASH_MAP"; public static final String FLASH_MAP_MANAGER_ATTRIBUTE = DispatcherServlet.class.getName() + ".FLASH_MAP_MANAGER"; public static final String EXCEPTION_ATTRIBUTE = DispatcherServlet.class.getName() + ".EXCEPTION"; public static final String PAGE_NOT_FOUND_LOG_CATEGORY = "org.springframework.web.servlet.PageNotFound"; private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties"; protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY); private static final Properties defaultStrategies; static { try { ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class); defaultStrategies = PropertiesLoaderUtils.loadProperties(resource); } catch (IOException ex) { throw new IllegalStateException("Could not load DispatcherServlet.properties: " + ex.getMessage()); } }
/** Detect all HandlerMappings or just expect "handlerMapping" bean? */ private boolean detectAllHandlerMappings = true;
/** Detect all HandlerAdapters or just expect "handlerAdapter" bean? */ private boolean detectAllHandlerAdapters = true;
/** Detect all HandlerExceptionResolvers or just expect "handlerExceptionResolver" bean? */ private boolean detectAllHandlerExceptionResolvers = true;
/** Detect all ViewResolvers or just expect "viewResolver" bean? */ private boolean detectAllViewResolvers = true;
/** Throw a NoHandlerFoundException if no Handler was found to process this request? **/ private boolean throwExceptionIfNoHandlerFound = false;
/** Perform cleanup of request attributes after include request? */ private boolean cleanupAfterInclude = true;
/** MultipartResolver used by this servlet */ private MultipartResolver multipartResolver;
/** LocaleResolver used by this servlet */ private LocaleResolver localeResolver;
/** ThemeResolver used by this servlet */ private ThemeResolver themeResolver;
/** List of HandlerMappings used by this servlet */ private List<HandlerMapping> handlerMappings;
/** List of HandlerAdapters used by this servlet */ private List<HandlerAdapter> handlerAdapters;
/** List of HandlerExceptionResolvers used by this servlet */ private List<HandlerExceptionResolver> handlerExceptionResolvers;
/** RequestToViewNameTranslator used by this servlet */ private RequestToViewNameTranslator viewNameTranslator;
private FlashMapManager flashMapManager;
/** List of ViewResolvers used by this servlet */ private List<ViewResolver> viewResolvers;
public DispatcherServlet() { super(); }
public DispatcherServlet(WebApplicationContext webApplicationContext) { super(webApplicationContext); } @Override protected void onRefresh(ApplicationContext context) { initStrategies(context); }
protected void initStrategies(ApplicationContext context) { initMultipartResolver(context); initLocaleResolver(context); initThemeResolver(context); initHandlerMappings(context); initHandlerAdapters(context); initHandlerExceptionResolvers(context); initRequestToViewNameTranslator(context); initViewResolvers(context); initFlashMapManager(context); } }
DispatcherServlet類中的屬性beans:
HandlerMapping:用於handlers映射請求和一系列的對於攔截器的前處理和後處理,大部分用@Controller註解。
HandlerAdapter:幫助DispatcherServlet處理映射請求處理程序的適配器,而不用考慮實際調用的是 哪個處理程序。
HandlerExceptionResolver:處理映射異常。
ViewResolver:根據實際配置解析實際的View類型。
LocaleResolver:解決客戶正在使用的區域設置以及可能的時區,以便能夠提供國際化視野。
ThemeResolver:解決Web應用程序可以使用的主題,例如提供個性化佈局。
MultipartResolver:解析多部分請求,以支持從HTML表單上傳文件。
FlashMapManager:存儲並檢索可用於將一個請求屬性傳遞到另一個請求的input和output的FlashMap,通常用於重定向。
在Web MVC框架中,每個DispatcherServlet都擁自己的WebApplicationContext,它繼承了ApplicationContext。WebApplicationContext包含了其上下文和Servlet實例之間共享的所有的基礎框架beans。
HandlerMapping:
HandlerMapping介面處理請求的映射
HandlerMapping介面的實現類:
SimpleUrlHandlerMapping類通過配置文件把URL映射到Controller類。
DefaultAnnotationHandlerMapping類通過註解把URL映射到Controller類。
HandlerAdapter:
HandlerAdapter介面-處理請求映射
AnnotationMethodHandlerAdapter:通過註解,把請求URL映射到Controller類的方法上。
HandlerExceptionResolver:
HandlerExceptionResolver介面-異常處理介面
SimpleMappingExceptionResolver通過配置文件進行異常處理。
AnnotationMethodHandlerExceptionResolver:通過註解進行異常處理。
ViewResolver:
ViewResolver介面解析View視圖。
UrlBasedViewResolver類 通過配置文件,把一個視圖名交給到一個View來處理。
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作者:yanweihpu
來源:CSDN
原文:https://blog.csdn.net/yanweihpu/article/details/80366218
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