SpringMVC的基本操作2

Spring MVC HandlerMapping 代码层面的执行流程

1.找到DispatcherServlet

2.找到doDispatch()方法

asynchronous:异步的
synchronous：同步的

//入参进来一个request
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {

HttpServletRequest processedRequest = request;
处理器执行链
HandlerExecutionChain mappedHandler = null;
多部分请求 解析器 （文件上传）
boolean multipartRequestParsed = false;

WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

try {
try {
模型（数据）和视图
ModelAndView err = null;
异常
Exception dispatchException = null;

try {
//指的是 DispatcherServlet 的实例 看看请求是不是多部分请求

<form enctype="multipart/form-data"> 表单有文件域 上传文件了

processedRequest = this.checkMultipart(request);

multipartRequestParsed = processedRequest != request;

mappedHandler = this.getHandler(processedRequest);

3. protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {

handlerMappings单列集合 。Set List
Iterator var2 = this.handlerMappings.iterator();
HandlerExecutionChain handler;
if(!var2.hasNext()) return null;
每next()拿到一个HandlerMapping实例
HandlerMapping hm = (HandlerMapping)var2.next();
handler = hm.getHandler(request);
return handler;
}

4.我们知道，HandlerMapping是一个接口 ，找实现类 Ctrl+H
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {

Object handler = this.getHandlerInternal(request);
if(handler == null) {
handler = this.getDefaultHandler();
}

if(handler == null) {
return null;
} else {
if(handler instanceof String) {
String handlerName = (String)handler; // /hello
handler = this.getApplicationContext().getBean(handlerName);
}

return this.getHandlerExecutionChain(handler, request);
}
}

1，添加视图解析器

在apploicationContext.xml中添加如下代码

 <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

2.解决静态资源无法展示问题的三种方法

1，在web.xml中添加

<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.img</url-pattern>
</servlet-mapping>
如果是js或css只需要把.img改成即可

2.在applicationContext.xml中添加节点

<mvc:default-servlet-handler></mvc:default-servlet-handler>

3.同样在applicationContext.xml中添加一个节点

<mvc:resources mapping="/static/**" location="/static/"></mvc:resources>

3.处理器映射器
  方式一：也就是默认的

<bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping"></bean>

方式二：

<bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <!--<property name="mappings">-->
        <!--<props>-->
            <!--<prop key="/xxx">second</prop>-->
        <!--</props>-->
    <!--</property>-->
    <property name="urlMap">
        <map>
            <entry key="/xxx">
                <value>second</value>
            </entry>
        </map>
    </property>
</bean>
其实这也算是两种方法，但差不多，所以就不多说了