SpringMVC架构实现原理

快来打我* 2022-01-20 10:13 258阅读 0赞

## SpringMVC架构实现原理 ##

## 一、SpringMVC介绍 ##

Spring mvc是一个基于mvc的web框架。其中核心类是DispatcherServlet，它是一个Servlet，顶层是实现的Servlet接口。

Spring mvc是spring框架的一个模块，springmvc和spring无需通过中间整合层进行整合。

## 二、SpringMVC使用 ##

需要在web.xml中配置DispatcherServlet。并且需要配置spring监听器ContextLoaderListener

<?xml version="1.0" encoding="UTF-8"?> 
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns="http://java.sun.com/xml/ns/javaee"  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee  http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
      <display-name>SpringMVC</display-name>
      
      
    	<servlet>
    		<servlet-name>springmvc</servlet-name>
    		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    		
    		
    		<init-param>
    			<param-name>contextConfigLocation</param-name>
    			<param-value>classpath:springmvc-config.xml</param-value>
    		</init-param>
    		<load-on-startup>1</load-on-startup>
    	</servlet>
    	
    	<servlet-mapping>
    		<servlet-name>springmvc</servlet-name>
    		
    		<url-pattern>*.action</url-pattern>
    	</servlet-mapping>
    	
    </web-app>

## 三、SpringMVC运行原理 ##

### 1、 运行流程图： ###

![1240][]

### 2、流程说明： ###

（1）客户端（浏览器）发送请求，直接请求到DispatcherServlet。（请求DispatcherServlet）

（2）DispatcherServlet根据请求信息调用HandlerMapping，解析请求对应的Handler。（查找@Controller）

（3）解析到对应的Handler后，开始由HandlerAdapter适配器处理。（查找@RequestMapping）

（4）HandlerAdapter会根据Handler来调用真正的处理器开处理请求，并处理相应的业务逻辑。（处理方法）

（5）处理器处理完业务后，会返回一个ModelAndView对象，Model是返回的数据对象，View是个逻辑上的View。（返回处理结果）

（6）ViewResolver会根据逻辑View查找实际的View。（逻辑视图解析为真正的视图）

（7）DispatcherServlet把返回的Model传给View。（DispatcherServlet试图渲染）

（8）通过View返回给请求者（浏览器）

## **四、DispatcherServlet详细解析** ##

源码分析：

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类中的属性beans：

### 1、HandlerMapping： ###

用于handlers映射请求和一系列的对于拦截器的前处理和后处理，大部分用@Controller注解。

HandlerMapping接口的实现类：

SimpleUrlHandlerMapping类通过配置文件把URL映射到Controller类。

DefaultAnnotationHandlerMapping类通过注解把URL映射到Controller类。

### 2、HandlerAdapter： ###

帮助DispatcherServlet处理映射请求处理程序的适配器，而不用考虑实际调用的是 哪个处理程序。

AnnotationMethodHandlerAdapter：通过注解，把请求URL映射到Controller类的方法上。

### 3、HandlerExceptionResolver： ###

处理映射异常。

SimpleMappingExceptionResolver通过配置文件进行异常处理。