本文主要向大家介绍了JAVA语言之SpringMVC源码解读，通过具体的内容向大家展示，希望对大家学习JAVA语言有所帮助。

SpringMVC是在spring上建立起来的针对web的MVC框架，也是目前非常流行的一款web开发java框架。对于源码的阅读加深对SpringMVC的认识是毋庸置疑的，所以我打算写一篇这样的文章来对SpringMVC做一次深入的学习。

入手SpringMVC源代码

在进入阅读源代码时，我们往往会对一个框架不知从哪里入手。根据SpringMVC请求流程图我们知道这个SpringMVC的核心就是DispatchServlet。所以我们应该从这个类入手。先来看下web.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="//xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="//www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="//xmlns.jcp.org/xml/ns/javaee //xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <!--Spring上下文管理配置文件（bean、事务等管理）-->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/applicationContext.xml</param-value>
    </context-param>
    <!--监听器-->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <!--分发器：DispatcherServlet-->
    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <!--servlet映射配置-->
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>*.form</url-pattern>
    </servlet-mapping>
</web-app>

对于web.xml中我们先关注核心：DispatcherServlet。

DispatcherServlet

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.springframework.web.servlet;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.i18n.LocaleContext;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.ui.context.ThemeSource;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.context.request.async.WebAsyncManager;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.util.NestedServletException;
import org.springframework.web.util.WebUtils;

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";
    private static final String DEFAULT_STRATEGIES_PREFIX = "org.springframework.web.servlet";
    protected static final Log pageNotFoundLogger = LogFactory.getLog("org.springframework.web.servlet.PageNotFound");
    private static final Properties defaultStrategies;
    private boolean detectAllHandlerMappings = true;
    private boolean detectAllHandlerAdapters = true;
    private boolean detectAllHandlerExceptionResolvers = true;
    private boolean detectAllViewResolvers = true;
    private boolean throwExceptionIfNoHandlerFound = false;
    private boolean cleanupAfterInclude = true;
    private MultipartResolver multipartResolver;
    private LocaleResolver localeResolver;
    private ThemeResolver themeResolver;
    private List<HandlerMapping> handlerMappings;
    private List<HandlerAdapter> handlerAdapters;
    private List<HandlerExceptionResolver> handlerExceptionResolvers;
    private RequestToViewNameTranslator viewNameTranslator;
    private FlashMapManager flashMapManager;
    private List<ViewResolver> viewResolvers;

    public DispatcherServlet() {
        this.setDispatchOptionsRequest(true);
    }

    public DispatcherServlet(WebApplicationContext webApplicationContext) {
        super(webApplicationContext);
        this.setDispatchOptionsRequest(true);
    }

    public void setDetectAllHandlerMappings(boolean detectAllHandlerMappings) {
        this.detectAllHandlerMappings = detectAllHandlerMappings;
    }

    public void setDetectAllHandlerAdapters(boolean detectAllHandlerAdapters) {
        this.detectAllHandlerAdapters = detectAllHandlerAdapters;
    }

    public void setDetectAllHandlerExceptionResolvers(boolean detectAllHandlerExceptionResolvers) {
        this.detectAllHandlerExceptionResolvers = detectAllHandlerExceptionResolvers;
    }

    public void setDetectAllViewResolvers(boolean detectAllViewResolvers) {
        this.detectAllViewResolvers = detectAllViewResolvers;
    }

    public void setThrowExceptionIfNoHandlerFound(boolean throwExceptionIfNoHandlerFound) {
        this.throwExceptionIfNoHandlerFound = throwExceptionIfNoHandlerFound;
    }

    public void setCleanupAfterInclude(boolean cleanupAfterInclude) {
        this.cleanupAfterInclude = cleanupAfterInclude;
    }

    protected void onRefresh(ApplicationContext context) {
        this.initStrategies(context);
    }

    protected void initStrategies(ApplicationContext context) {
        this.initMultipartResolver(context);
        this.initLocaleResolver(context);
        this.initThemeResolver(context);
        this.initHandlerMappings(context);
        this.initHandlerAdapters(context);
        this.initHandlerExceptionResolvers(context);
        this.initRequestToViewNameTranslator(context);
        this.initViewResolvers(context);
        this.initFlashMapManager(context);
    }

    private void initMultipartResolver(ApplicationContext context) {
        try {
            this.multipartResolver = (MultipartResolver)context.getBean("multipartResolver", MultipartResolver.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Using MultipartResolver [" + this.multipartResolver + "]");
            }
        } catch (NoSuchBeanDefinitionException var3) {
            this.multipartResolver = null;
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Unable to locate MultipartResolver with name 'multipartResolver': no multipart request handling provided");
            }
        }

    }

    private void initLocaleResolver(ApplicationContext context) {
        try {
            this.localeResolver = (LocaleResolver)context.getBean("localeResolver", LocaleResolver.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Using LocaleResolver [" + this.localeResolver + "]");
            }
        } catch (NoSuchBeanDefinitionException var3) {
            this.localeResolver = (LocaleResolver)this.getDefaultStrategy(context, LocaleResolver.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Unable to locate LocaleResolver with name 'localeResolver': using default [" + this.localeResolver + "]");
            }
        }

    }

    private void initThemeResolver(ApplicationContext context) {
        try {
            this.themeResolver = (ThemeResolver)context.getBean("themeResolver", ThemeResolver.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Using ThemeResolver [" + this.themeResolver + "]");
            }
        } catch (NoSuchBeanDefinitionException var3) {
            this.themeResolver = (ThemeResolver)this.getDefaultStrategy(context, ThemeResolver.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Unable to locate ThemeResolver with name 'themeResolver': using default [" + this.themeResolver + "]");
            }
        }

    }

    private void initHandlerMappings(ApplicationContext context) {
        this.handlerMappings = null;
        if (this.detectAllHandlerMappings) {
            Map<String, HandlerMapping> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
            if (!matchingBeans.isEmpty()) {
                this.handlerMappings = new ArrayList(matchingBeans.values());
                AnnotationAwareOrderComparator.sort(this.handlerMappings);
            }
        } else {
            try {
                HandlerMapping hm = (HandlerMapping)context.getBean("handlerMapping", HandlerMapping.class);
                this.handlerMappings = Collections.singletonList(hm);
            } catch (NoSuchBeanDefinitionException var3) {
                ;
            }
        }

        if (this.handlerMappings == null) {
            this.handlerMappings = this.getDefaultStrategies(context, HandlerMapping.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("No HandlerMappings found in servlet '" + this.getServletName() + "': using default");
            }
        }

    }

    private void initHandlerAdapters(ApplicationContext context) {
        this.handlerAdapters = null;
        if (this.detectAllHandlerAdapters) {
            Map<String, HandlerAdapter> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerAdapter.class, true, false);
            if (!matchingBeans.isEmpty()) {
                this.handlerAdapters = new ArrayList(matchingBeans.values());
                AnnotationAwareOrderComparator.sort(this.handlerAdapters);
            }
        } else {
            try {
                HandlerAdapter ha = (HandlerAdapter)context.getBean("handlerAdapter", HandlerAdapter.class);
                this.handlerAdapters = Collections.singletonList(ha);
            } catch (NoSuchBeanDefinitionException var3) {
                ;
            }
        }

        if (this.handlerAdapters == null) {
            this.handlerAdapters = this.getDefaultStrategies(context, HandlerAdapter.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("No HandlerAdapters found in servlet '" + this.getServletName() + "': using default");
            }
        }

    }

    private void initHandlerExceptionResolvers(ApplicationContext context) {
        this.handlerExceptionResolvers = null;
        if (this.detectAllHandlerExceptionResolvers) {
            Map<String, HandlerExceptionResolver> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false);
            if (!matchingBeans.isEmpty()) {
                this.handlerExceptionResolvers = new ArrayList(matchingBeans.values());
                AnnotationAwareOrderComparator.sort(this.handlerExceptionResolvers);
            }
        } else {
            try {
                HandlerExceptionResolver her = (HandlerExceptionResolver)context.getBean("handlerExceptionResolver", HandlerExceptionResolver.class);
                this.handlerExceptionResolvers = Collections.singletonList(her);
            } catch (NoSuchBeanDefinitionException var3) {
                ;
            }
        }

        if (this.handlerExceptionResolvers == null) {
            this.handlerExceptionResolvers = this.getDefaultStrategies(context, HandlerExceptionResolver.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("No HandlerExceptionResolvers found in servlet '" + this.getServletName() + "': using default");
            }
        }

    }

    private void initRequestToViewNameTranslator(ApplicationContext context) {
        try {
            this.viewNameTranslator = (RequestToViewNameTranslator)context.getBean("viewNameTranslator", RequestToViewNameTranslator.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Using RequestToViewNameTranslator [" + this.viewNameTranslator + "]");
            }
        } catch (NoSuchBeanDefinitionException var3) {
            this.viewNameTranslator = (RequestToViewNameTranslator)this.getDefaultStrategy(context, RequestToViewNameTranslator.class);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Unable to locate RequestToViewNameTranslator with name 'viewNameTranslator': using default [" + this.viewNameTranslator + "]");
            }
        }

    }

    private void initViewResolvers(ApplicationContext context) {
        this.viewResolvers = null;
        if (this.detectAllViewResolvers) {
            Map<String, ViewResolver> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, ViewResolver.class, true, false);
            if (!matchingBeans.isEmpty()) {
                this.viewResolvers = new ArrayList(matchingBeans.values());
                AnnotationAwareOrderComparator.sort(this.viewResolvers);
            }
        } else {
         

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