一、前言

      在框架學習中，我們學到了很多東西。spring 2.5 的一大增強就是引入了很多註釋類，現在您已經可以使用註釋配置完成大部分 XML 配置的功能。在這篇文章裡，我們將向您講述使用註釋進行 Bean 定義和依賴注入的內容。

二、非註解怎麼做？

      在spring 2.5以前，沒有註解。不使用註解，我們就需要在spring的applicationContext.xml檔案中，新增上要注入的類的例項。原理是當我們需要例項化這個例項，用這個類下面的方法的時候，spring會自動幫我們例項化，從而減少了我們的操作。

      通過下面的程式碼來表示一下：
      首先由三個類：

      DepartmentDaoImpl ：

public class DepartmentDaoImpl extends HibernateDaoSupport implements DepartmentDao {

    public void saveDepartment(Department department) {
        this.getHibernateTemplate().save(department);
    }
}

      DepartmentServiceImpl ：

public class DepartmentServiceImpl
 
 implements DepartmentService {
    private DepartmentDao departmentDao;

    public DepartmentDao getDepartmentDao() {
        return departmentDao;
    }

        public void setDepartmentDao(DepartmentDao departmentDao) 
    {
        this.departmentDao = departmentDao;
    }

    public void saveDepartment
 
(Department department) {
        this.departmentDao.saveDepartment(department);
    }

}

      DepartmentAction ：

public class DepartmentAction extends BaseAction implements ModelDriven<Department> {
    private Department department = new Department();

    public Department getModel() {
        return department;
    }

    private DepartmentService departmentService;

    public DepartmentService getDepartmentService() {
        return departmentService;
    }

    public void setDepartmentService(DepartmentService departmentService) {
        this.departmentService = departmentService;
    }

    /**
     * 新增操作-2017年5月10日10:48:11
     * @return string
     */
    public String add()  {
        this.departmentService.saveDepartment(department);
        return action2action;
    }
}

      在上面的三個類中，DepartmentServiceImpl 中注入了DepartmentDao，在DepartmentAction 中注入了DepartmentService。

      在spring中，我們需要注入這些：

<?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:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
           http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">

    <bean id="departmentDao" class="cn.itcast.oa.dao.impl.DepartmentDaoImpl">
        <property name="sessionFactory" ref="sessionFactory"/>
    </bean>


    <bean id="departmentService" class="cn.itcast.oa.service.impl.DepartmentServiceImpl">
        <property name="departmentDao" ref="departmentDao"/>
    </bean>

    <bean id="departmentAction" class="cn.itcast.oa.struts2.action.DepartmentAction" scope="prototype">
        <property name="departmentService" ref="departmentService"/>
    </bean>
</beans>

      當我們注入的時候，就可以直接使用了。

三、註解怎麼做？

      同樣的我們需要這三個類，但是需要有一些變動，那就是添加了註解，取消了get和set方法：

      DepartmentDaoImpl ：

@Repository("departmentDao")
public class DepartmentDaoImpl extends  BaseDaoImpl<Department> implements
        DepartmentDao<Department> {


}

      DepartmentServiceImpl ：

@Service("departmentService")
public class DepartmentServiceImpl implements DepartmentService {
    @Resource(name="departmentDao")
    private DepartmentDao departmentDao;


    public void saveDepartment(Department department) {
        this.departmentDao.saveEntry (department);
    }
}

      DepartmentAction :

@Controller("departmentAction")
@Scope("prototype")
public class DepartmentAction extends BaseAction implements ModelDriven<Department> {

    private Department department = new Department();

    public Department getModel() {
        return department;
    }

    @Resource(name="departmentService")
    private DepartmentService departmentService;

    /**
     * 新增操作-2017年5月10日10:48:11
     * @return string
     */
    public String add()  {

        this.departmentService.saveDepartment(department);
        return action2action;
    }
}

      在上面的三個類中我們通過註解實現了注入，我們分別說明一下註解：

• @Repository(“departmentDao”)

  可以理解為要標誌是D層。
  

• @Service(“departmentService”)

  可以理解為要標誌是B層的。
  

• @Resource(name=”departmentDao”)

  這個是DepartmentServiceImpl為了注入DepartmentDao而引入的。可以理解為為了注入D層而寫的，可以得到D層的示例。
  

• @Controller(“departmentAction”)和@Scope(“prototype”)

  這個可以理解為Action的標誌

• @Resource(name=”departmentService”)

  同 @Resource(name=”departmentDao”)，表示注入了DepartmentService。

      當然，通過寫了注入，我們需要在spring的ApplicationContext.xml中進行配置。這裡要宣告的是spring2.5 以上 ，如下：

      在匯入類掃描的註解解析器和事務的註解解析器，會自動掃描我們填寫了註解的類。

<?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:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       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/aop 
                           http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
                           http://www.springframework.org/schema/context 
                           http://www.springframework.org/schema/context/spring-context-2.5.xsd
                           http://www.springframework.org/schema/tx 
                           http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
    <!-- 匯入類掃描的註解解析器和事務的註解解析器 -->
      <context:component-scan base-package="cn.itcast.oa"></context:component-scan>
      <tx:annotation-driven transaction-manager="transactionManager"/>
      <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
            <property name="sessionFactory">
                <ref bean="sessionFactory"/>
            </property>
      </bean>

      <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
        <property name="configLocation">
            <value>classpath:hibernate/hibernate.cfg.xml</value>
        </property>
      </bean>

      <bean id="hibernateTemplate" class="org.springframework.orm.hibernate3.HibernateTemplate">
        <property name="sessionFactory">
            <ref bean="sessionFactory"/>
        </property>
      </bean>

</beans>

四、小結

      通過不同的方法，可以達到相同的目的，這個在我們使用的時候就有不同的效果。第一種不使用註釋的，我們每次新增一條線，就需要我們在配置檔案中手動新增，而第二種，就需要我們在新增的線上，加入註解就可以了。