spring3.1 + mybatis 回来null正常,返回结果前台接收不到

<?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">
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:applicationContext.xml</param-value>
	</context-param>
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

	<!-- 配置spring核心servlet -->
	<servlet>
		<servlet-name>frame</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>frame</servlet-name>
		<!-- url配置为*.json，不带文件后缀，会造成其它静态文件(js，css等)不能访问。如配为*.do，则不影响静态文件的访问 -->
		<url-pattern>*.json</url-pattern>
	</servlet-mapping>

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

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xmlns:p="http://www.springframework.org/schema/p"  
    xmlns:mvc="http://www.springframework.org/schema/mvc"  
    xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:util="http://www.springframework.org/schema/util"  
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd  
            http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd  
            http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd  
            http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd
            http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
    
    <!-- 对包中的所有类进行扫描，以完成Bean创建和自动依赖注入的功能--> 
	<context:component-scan base-package="com" />
	
	<!-- 使用annotation 自动注册事务--> 
	<tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"/>
	
	<!-- 使用annotation 自动注册bean,并保证@Required,@Autowired的属性被注入 -->
	<context:component-scan base-package="*" />
	
	<!-- 该 BeanPostProcessor 将自动对标注 @Autowired 的 Bean 进行注入 -->    
	<bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />