spring mvc 怎么在后台接收到页面上传来的值
index.jsp
<%@ page language="java" contentType="text/html; charset=Utf-8"
	pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
	<h1>欢迎</h1>
	<br />
	<a href="helloWorld.do">hello</a>
	<br/>
	<a href="login.do">login</a>	
	<form action="login.do" method="get">
	<input type="text" value="ddddd" name="daa"/>
	<input type="submit" value="试试"/>
	</form>
</body>
</html>
web.xml
<?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	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>
	<!--配置Sring MVC的核心控制器DispatcherServlet -->
	<servlet>
		<servlet-name>dispatcher</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>dispatcher</servlet-name>
		<url-pattern>*.do</url-pattern>
	</servlet-mapping>
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
</web-app>
dispatcher-servlet.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"  
	"http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
	<bean id="localeResolver"
		class="org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver">
	</bean>
	<!--配置控制器的映射 -->
	<bean id="urlMapping"
		class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
		<property name="mappings">
			<props>
				<prop key="helloWorld.do" >helloWorld</prop>
				<prop key="login.do">login</prop>
			</props>
		</property>
	</bean>	
		<bean id="login" class="com.examp.HelloWorldAction">
		<property name="helloWorld">
			<value>Hello welcome Login!</value>
		</property>
		<property name="viewPage">
			<value>sayHello.jsp</value>
		</property>
	</bean>
	<!--指定控制器的实现类,并且配置其参数的值 -->
	<bean id="helloWorld" class="com.examp.HelloWorldAction">
		<property name="helloWorld">
			<value>Hello Spring World!</value>
		</property>
		<property name="viewPage">
			<value>sayHello.jsp</value>
		</property>
	</bean>
</beans>
HelloWorldAction.java
package com.examp;
import java.util.HashMap;
import java.util.Map;