SpringMVC工作原理

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我是靠谱客的博主追寻流沙，最近开发中收集的这篇文章主要介绍SpringMVC工作原理，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

1、Spring mvc介绍

SpringMVC框架是以请求为驱动，围绕Servlet设计，将请求发给控制器，然后通过模型对象，分派器来展示请求结果视图。其中核心类是DispatcherServlet，它是一个Servlet，顶层是实现的Servlet接口。

2、SpringMVC使用

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

 1 <listener>
 2      <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
 3 </listener>       
 4 <servlet>
 5
<servlet-name>springmvc</servlet-name>
 6
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
 7                 <!-- 如果不设置init-param标签，则必须在/WEB-INF/下创建xxx-servlet.xml文件，其中xxx是servlet-name中配置的名称。
-->
 8      <init-param>
 9
<param-name>contextConfigLocation</param-name>
10
<param-value>classpath:spring/springmvc-servlet.xml</param-value>
11
</init-param>
12
<load-on-startup>1</load-on-startup>
13 </servlet>
14 <servlet-mapping>
15
<servlet-name>springmvc</servlet-name>
16
<url-pattern>/</url-pattern>
17 </servlet-mapping>

3、SpringMVC运行原理

如图所示：

流程说明：

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

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

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

（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。

（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。

（6）ViewResolver会根据逻辑View查找实际的View。

（7）DispaterServlet把返回的Model传给View。

（8）通过View返回给请求者（浏览器）

4、DispatcherServlet详细解析

首先看下源码：


1 package org.springframework.web.servlet;

2

3 @SuppressWarnings("serial")

4 public class DispatcherServlet extends FrameworkServlet {

5

6
public static final String MULTIPART_RESOLVER_BEAN_NAME = "multipartResolver";

7
public static final String LOCALE_RESOLVER_BEAN_NAME = "localeResolver";

8
public static final String THEME_RESOLVER_BEAN_NAME = "themeResolver";

9
public static final String HANDLER_MAPPING_BEAN_NAME = "handlerMapping";
 10
public static final String HANDLER_ADAPTER_BEAN_NAME = "handlerAdapter";
 11
public static final String HANDLER_EXCEPTION_RESOLVER_BEAN_NAME = "handlerExceptionResolver";
 12
public static final String REQUEST_TO_VIEW_NAME_TRANSLATOR_BEAN_NAME = "viewNameTranslator";
 13
public static final String VIEW_RESOLVER_BEAN_NAME = "viewResolver";
 14
public static final String FLASH_MAP_MANAGER_BEAN_NAME = "flashMapManager";
 15
public static final String WEB_APPLICATION_CONTEXT_ATTRIBUTE = DispatcherServlet.class.getName() + ".CONTEXT";
 16
public static final String LOCALE_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".LOCALE_RESOLVER";
 17
public static final String THEME_RESOLVER_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_RESOLVER";
 18
public static final String THEME_SOURCE_ATTRIBUTE = DispatcherServlet.class.getName() + ".THEME_SOURCE";
 19
public static final String INPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".INPUT_FLASH_MAP";
 20
public static final String OUTPUT_FLASH_MAP_ATTRIBUTE = DispatcherServlet.class.getName() + ".OUTPUT_FLASH_MAP";
 21
public static final String FLASH_MAP_MANAGER_ATTRIBUTE = DispatcherServlet.class.getName() + ".FLASH_MAP_MANAGER";
 22
public static final String EXCEPTION_ATTRIBUTE = DispatcherServlet.class.getName() + ".EXCEPTION";
 23
public static final String PAGE_NOT_FOUND_LOG_CATEGORY = "org.springframework.web.servlet.PageNotFound";
 24
private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties";
 25
protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY);
 26
private static final Properties defaultStrategies;
 27
static {
 28
try {
 29
ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, DispatcherServlet.class);
 30
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
 31 
}
 32
catch (IOException ex) {
 33
throw new IllegalStateException("Could not load 'DispatcherServlet.properties': " + ex.getMessage());
 34 
}
 35 
}
 36
 37
/** Detect all HandlerMappings or just expect "handlerMapping" bean? */
 38
private boolean detectAllHandlerMappings = true;
 39
 40
/** Detect all HandlerAdapters or just expect "handlerAdapter" bean? */
 41
private boolean detectAllHandlerAdapters = true;
 42
 43
/** Detect all HandlerExceptionResolvers or just expect "handlerExceptionResolver" bean? */
 44
private boolean detectAllHandlerExceptionResolvers = true;
 45
 46
/** Detect all ViewResolvers or just expect "viewResolver" bean? */
 47
private boolean detectAllViewResolvers = true;
 48
 49
/** Throw a NoHandlerFoundException if no Handler was found to process this request? **/
 50
private boolean throwExceptionIfNoHandlerFound = false;
 51
 52
/** Perform cleanup of request attributes after include request? */
 53
private boolean cleanupAfterInclude = true;
 54
 55
/** MultipartResolver used by this servlet */
 56
private MultipartResolver multipartResolver;
 57
 58
/** LocaleResolver used by this servlet */
 59
private LocaleResolver localeResolver;
 60
 61
/** ThemeResolver used by this servlet */
 62
private ThemeResolver themeResolver;
 63
 64
/** List of HandlerMappings used by this servlet */
 65
private List<HandlerMapping> handlerMappings;
 66
 67
/** List of HandlerAdapters used by this servlet */
 68
private List<HandlerAdapter> handlerAdapters;
 69
 70
/** List of HandlerExceptionResolvers used by this servlet */
 71
private List<HandlerExceptionResolver> handlerExceptionResolvers;
 72
 73
/** RequestToViewNameTranslator used by this servlet */
 74
private RequestToViewNameTranslator viewNameTranslator;
 75
 76
private FlashMapManager flashMapManager;
 77
 78
/** List of ViewResolvers used by this servlet */
 79
private List<ViewResolver> viewResolvers;
 80
 81
public DispatcherServlet() {
 82
super();
 83 
}
 84
 85
public DispatcherServlet(WebApplicationContext webApplicationContext) {
 86
super(webApplicationContext);
 87 
}
 88 
@Override
 89
protected void onRefresh(ApplicationContext context) {
 90 
initStrategies(context);
 91 
}
 92
 93
protected void initStrategies(ApplicationContext context) {
 94 
initMultipartResolver(context);
 95 
initLocaleResolver(context);
 96 
initThemeResolver(context);
 97 
initHandlerMappings(context);
 98 
initHandlerAdapters(context);
 99 
initHandlerExceptionResolvers(context);
100 
initRequestToViewNameTranslator(context);
101 
initViewResolvers(context);
102 
initFlashMapManager(context);
103 
}
104 }