今天完成的事情：

1.maven配置文件中 org.apache.maven.plugins 版本号与内置maven中的版本不匹配,可能会导致打包后出现无法运行的情况:

编译时开头的告警信息:
告警信息:
[WARNING] Some problems were encountered while building the effective model for com.jnshu:SSM-demo01:war:1.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ line 35, column 21
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>1.6</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>

解决办法: 命令行中cd 到项目根目录 mvn help:describe -DartifactId=maven-compiler-plugin -DgroupId=org.apache.maven.plugins 
最后会显示出内置编译版本,
Name: Maven Compiler Plugin
Description: The Compiler Plugin is used to compile the sources of your
project.
Group Id: org.apache.maven.plugins
Artifact Id: maven-compiler-plugin
Version: 3.1
Goal Prefix: compiler
将配置中的 <version>1.6</version> 改为 <version>3.1</version> 即可

2.踩坑<mvc:annotation-driven/>,使用自动扫描映射器和处理器时

<!-- <mvc:annotation-driven></mvc:annotation-driven> 可以替代上面的注解映射器和注解适配器 它会自动注册继承了 DefaultAnnotationHandlerMapping与AnnotationMethodHandlerAdapter 的两个Handler-->
<!-- 非DefaultAnnotationHandlerMapping与AnnotationMethodHandlerAdapter继承的自定义Handler,必须指定包 annotation-drive才会扫描并映射到 HandlerMapping -->
<!-- 可以扫描controller、service、...   这里让扫描controller，指定controller的包-->
<context:component-scan base-package="com.jnshu.ssm.Controller"/>
<mvc:annotation-driven/>

3.跟着网上大佬看前端控制器DispatcherServlet源码(大部分看不懂,只需要了解他具体的实现过程即可),了解内部实现过程,它时如何通过Servlet的web.xml配置文件实现拦截并跳转到前端控制器DispatcherServlet的?

web.xml配置:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <!-- SpringMvc前端控制器 -->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- contextConfigLocation配置springmvc加载的配置文件(配置处理器映射器，适配器等)
        如果不配置contextConfigLoaction，默认加载的是/WEB-INF/servlet名称-servlet.xml(springmvc-servlet.xml)
        -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc.xml</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <!-- 第一种:*.action。访问以.action结尾由DispatcherServlet进行解析；
         第二种:/，所有访问的地址都由DispatcherServlet进行解析，对于静态文件的解析，
         我们要配置不让DispatcherServlet进行解析。使用此种方法可以实现RESTful风格的url；
         第三种:/*，这样配置不对，使用这种配置，最终要转发到一个jsp页面时，仍然会由
         DispatcherServlet进行解析jsp地址，它不能根据jsp页面找到Handler，会报错-->
        <url-pattern>*.action</url-pattern>
    </servlet-mapping>

    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

源码 点开org.springframework.web.servlet.DispatcherServlet看看，里面有一个doDiapatch的方法:

方法的代码:

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
  
    HttpServletRequest processedRequest = request;
    HandlerExecutionChain mappedHandler = null;
    boolean multipartRequestParsed = false;
    WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

    try {
        try {
            ModelAndView mv = null;
            Exception dispatchException = null;

            try {
                processedRequest = this.checkMultipart(request);
                multipartRequestParsed = processedRequest != request;
                mappedHandler = this.getHandler(processedRequest);
                if (mappedHandler == null || mappedHandler.getHandler() == null) {
                    this.noHandlerFound(processedRequest, response);
                    return;
                }

                HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
                String method = request.getMethod();
                boolean isGet = "GET".equals(method);
                if (isGet || "HEAD".equals(method)) {
                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
                    if (this.logger.isDebugEnabled()) {
                        this.logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
                    }

                    if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {
                        return;
                    }
                }

                if (!mappedHandler.applyPreHandle(processedRequest, response)) {
                    return;
                }

                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
                if (asyncManager.isConcurrentHandlingStarted()) {
                    return;
                }

                this.applyDefaultViewName(processedRequest, mv);
                mappedHandler.applyPostHandle(processedRequest, response, mv);
            } catch (Exception var19) {
                dispatchException = var19;
            }

            this.processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
        } catch (Exception var20) {
            this.triggerAfterCompletion(processedRequest, response, mappedHandler, var20);
        } catch (Error var21) {
            this.triggerAfterCompletionWithError(processedRequest, response, mappedHandler, var21);
        }

    } finally {
        if (asyncManager.isConcurrentHandlingStarted()) {
            if (mappedHandler != null) {
                mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
            }
        } else if (multipartRequestParsed) {
            this.cleanupMultipart(processedRequest);
        }

    }
}

明天计划的事情：（一定要写非常细致的内容） 
遇到的问题：（遇到什么困难，怎么解决的） 
收获：（通过今天的学习，学到了什么知识）