Spring自动装配,求大神答疑

小弟最近刚学的spring 自动装配有点问题请教：
这个是XML：
<?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:context="http://www.springframework.org/schema/context"

xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
< context:component-scan base-package="cm.itcast"/>
< /beans>

接口：package cm.itcast.customer;
import org.springframework.stereotype.Service;
public interface CustomerDao {

public void save();

}

实现类：
package cm.itcast.customer.impl;
import org.springframework.stereotype.Service;
import cm.itcast.customer.CustomerDao;
@Service
public class CustomerDaoBean implements CustomerDao {

public void save(){
    System.out.println("我是customer save方法");
}

}

调用：
package junit.test;

import javax.annotation.Resource;
import cm.itcast.customer.CustomerDao;

public class Maintest {
@Resource
private CustomerDao customerDao;

public static void main(String args[]){
    Maintest maintest =new Maintest();
    maintest.test();
}

public void test(){
    customerDao.save(); 
}

}
空指针错误 求大神答疑。

注解方式，配置文件里配置PackagesToScan

是service那块空了吗

你这样写得保证bean的name属性为customerDao才能够自动注入。
@Resource
private CustomerDao customerDao;