實際開發中使用XML還是註解？

XML：

bean的管理

註解：

注入屬性的時候比較方便

兩種方式的結合：一般使用XML註冊bean，使用註解來進行屬性注入。在applicationContext.xml中配置<context:annotation-config></context:annotation-config>

舉個簡單的例子：

新建3個bean：

1. package com.js.demo4;  
2. publicclass OrderDao {  
3. }  

1. package com.js.demo4;  
2. publicclass CustomerDao {  
3. }  

1. package com.js.demo4;  
2. publicclass CustomerService {  
3.     private CustomerDao customerDao;  
4.     private OrderDao orderDao;  
5.     @Override
6.     public String toString() {  
7.         return"CustomerService [customerDao=" + customerDao + ", orderDao="
8.                 + orderDao + "]";  
9.     }  
10.     publicvoid setCustomerDao(CustomerDao customerDao) {  
11.         this.customerDao = customerDao;  
12.     }  
13.     publicvoid setOrderDao(OrderDao orderDao) {  
14.         this.orderDao = orderDao;  
15.     }  
16. }  

1. <?xmlversion="1.0"encoding="UTF-8"?>
2. <beansxmlns="http://www.springframework.org/schema/beans"
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.        xmlns:context="http://www.springframework.org/schema/context"
5.        xsi:schemaLocation="  
6. http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd  
7. http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
8. <!-- 純用註解配置bean的情況下context:annotation-config可以省略，當混合使用xml和註解配置bean的時候就不能省略了-->
9. <context:annotation-config></context:annotation-config>
10. <!-- 配置掃描註解的包 -->
11. <!-- <context:component-scan base-package="com.js"></context:component-scan> -->
12. <beanid="customerDao"class="com.js.demo4.CustomerDao"></bean>
13. <beanid="customerService"class="com.js.demo4.CustomerService">
14.     <propertyname="customerDao"ref="customerDao"></property>
15.     <propertyname="orderDao"ref="orderDao"></property>
16. </bean>
17. <beanid="orderDao"class="com.js.demo4.OrderDao"></bean>
18. </beans>

1. package com.js.demo4;  
2. import org.junit.Test;  
3. import org.springframework.context.ApplicationContext;  
4. import org.springframework.context.support.ClassPathXmlApplicationContext;  
5. publicclass Test4 {  
6.     @Test
7.     publicvoid demo(){  
8.         ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext2.xml");  
9.         CustomerService customerService = (CustomerService)applicationContext.getBean("customerService");  
10.         System.out.println(customerService);  
11.     }  
12. }  

我們能不能修改配置方式，只在xml中註冊bean，而將bean的屬性注入使用註解來完成呢？

修改CustomerService：使用註解傳入的屬性就不在需要setter方法，也不再需要Component-scan，因為我們的bean全部在xml中配置，此處修改兩個屬性之一的orderDao：

1. package com.js.demo4;  
2. import org.springframework.beans.factory.annotation.Autowired;  
3. import org.springframework.beans.factory.annotation.Qualifier;  
4. publicclass CustomerService {  
5.     private CustomerDao customerDao;  
6.     @Autowired
7.     @Qualifier("orderDao")  
8.     private OrderDao orderDao;  
9.     @Override
10.     public String toString() {  
11.         return"CustomerService [customerDao=" + customerDao + ", orderDao="
12.                 + orderDao + "]";  
13.     }  
14.     publicvoid setCustomerDao(CustomerDao customerDao) {  
15.         this.customerDao = customerDao;  
16.     }  
17. }  

1. <?xmlversion="1.0"encoding="UTF-8"?>
2. <beansxmlns="http://www.springframework.org/schema/beans"
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4.        xmlns:context="http://www.springframework.org/schema/context"
5.        xsi:schemaLocation="  
6. http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd  
7. http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
8. <!-- 純用註解配置bean的情況下context:annotation-config可以省略，當混合使用xml和註解配置bean的時候就不能省略了-->
9. <!-- 作用是使@Resource、@PostConstruct、@PreDestroy、@AutoWired生效-->
10. <context:annotation-config></context:annotation-config>
11. <beanid="customerDao"class="com.js.demo4.CustomerDao"></bean>
12. <beanid="customerService"class="com.js.demo4.CustomerService">
13.     <propertyname="customerDao"ref="customerDao"></property>
14. </bean>
15. <beanid="orderDao"class="com.js.demo4.OrderDao"></bean>
16. </beans>