除了基于 xml 的配置外，Spring 也支持基于 Annotation 的配置。Spring 提供以下介個 Annotation 來標(biāo)注 Spring Bean：　　@Component：標(biāo)注一個普通的 Spring Bean　　@Controller：標(biāo)注一個控制器組件類　　@Service：標(biāo)注一個業(yè)務(wù)邏輯組件類　　@Repository：標(biāo)注一個 DAO 組件類

DAO 組件以@Repository 標(biāo)注：

public interface UserDao {    public User getUserByUsername(String username);}@Repository("userDao")public class UserDaoImpl implements UserDao {        List<User> users = new ArrayList<User>();        public UserDaoImpl() {        users.add(new User(1001, "huey", "123"));        users.add(new User(1002, "tmac", "abc"));        users.add(new User(1003, "suer", "xxx"));    }        public User getUserByUsername(String username) {        for (User user : users) {            if (username.equals(user.getUsername())) {                return user;            }        }        return null;    }}

業(yè)務(wù)邏輯組件以@Service 標(biāo)注：

public interface UserServ {        public User queryUserByUsername(String username);    }@Service("userServ")public class UserServImpl implements UserServ {        @Resource(name="userDao")    private UserDao userDao;        public User queryUserByUsername(String username) {        return userDao.getUserByUsername(username);    }}

Spring 配置文件，無需配置 Bean，但須配置 <context:component-scan/>：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:context="http://www.springframework.org/schema/context"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     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">        <!-- 自動掃描指定包及其子包下的所有 Bean 類 -->    <context:component-scan base-package="com.huey.dream" /></beans>

測試方法：

@Testpublic void testAnnotation() throws Exception {    applicationContext appCtx =          new ClassPathXmlApplicationContext("applicationContext.xml");    UserServ userServ = appCtx.getBean("userServ", UserServ.class);        String username = "huey";    User user = userServ.queryUserByUsername(username);    System.out.println(user);}