Spring中，如何给对象的属性赋值? 【DI, 依赖注入】
1) 通过构造函数
2) 通过set方法给属性注入值
3) p名称空间
4)自动装配(了解)
5) 注解
代码示例：
<?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:context="http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- #########对象属性赋值########## --> <!-- 1) 通过构造函数 --> <bean id="user1" class="cn.itcast.c_property.User" scope="prototype"> <constructor-arg value="100"></constructor-arg> <constructor-arg value="Tom"></constructor-arg> </bean> <!-- 2) 通过set方法给属性注入值 --> <bean id="user" class="cn.itcast.c_property.User" scope="prototype"> <property name="id" value="101"></property> <property name="name" value="Jack"></property> </bean> </beans>
案例：
<?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:context="http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- ###########对象属性赋值########## --> <!-- 案例： action/service/dao --> <!-- dao instance --> <bean id="userDao" class="cn.itcast.c_property.UserDao"></bean> <!-- service instance --><!--name="UserDao" 是UserService类里面的属性,ref="UserDao" 是引用dao的id="UserDao"--> <bean id="userService" class="cn.itcast.c_property.UserService"> <property name="userDao" ref="userDao"></property> </bean> <!-- action instance --> <bean id="userAction1" class="cn.itcast.c_property.UserAction"> <property name="userService" ref="userService"></property> </bean>
<!-- 当只调用一次时也可以使用内部bean,一般不建议使用，不好维护 -->
<!-- ##############内部bean############## -->
<bean id="userAction2" class="cn.itcast.c_property.UserAction">
<property name="userService">
<bean class="cn.itcast.c_property.UserService">
<property name="userDao">
<bean class="cn.itcast.c_property.UserDao"></bean>
</property>
</bean>
</property>
</bean>
</beans>
UserDao层：
package cn.itcast.c_property;
public class UserDao {
public void save() { //与关系型数据库交互保存对象
System.out.println("DB:保存用户");
}
}
UserService层
package cn.itcast.c_property;
public class UserService {
private UserDao userDao; // = new UserDao();
// IOC：对象的创建交给spring的外部容器完成
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
public void save() {
userDao.save(); //调用Dao层存储对象
}
}
UserAction
ackage cn.itcast.c_property;
public class UserAction {
// Service: springIOC容器注入
private UserService userService;
public void setUserService(UserService userService) {
this.userService = userService;
}
public String execute() {
userService.save();
return null;
}
}
测试：
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test { public static void main(String[] args){ ClassPathXmlApplicationContext cax = new ClassPathXmlApplicationContext("applicationContext.xml");
// 从容器中获取Action
UserAction userAction = (UserAction)cax.getBean("userAction");
userAction.execute();
输出：
DB：保存用户
p名称空间注入属性值 (优化)
优化上面案例的applicationContext.xml文件配置
<?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:context="http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- ###############对象属性赋值############### -->
<!-- 使用p命名空间注入属性需要在约束文件中配置xmlns:p="http://www.springframework.org/schema/p"-->
<!-- 给对象属性注入值： # p 名称空间给对象的属性注入值 (spring3.0以上版本才支持) -->
<bean id="userDao" class="cn.itcast.c_property.UserDao"></bean>
<bean id="userService" class="cn.itcast.c_property.UserService" p:userDao-ref="userDao">
</bean> <bean id="userAction" class="cn.itcast.c_property.UserAction" p:userService-ref="userService"></bean>
<!-- 传统的注入：
<bean id="user" class="cn.itcast.c_property.User" >
<property name="name" value="xxx"></property>
</bean> -->
<!-- p名称空间优化后 -->
<bean id="user" class="cn.itcast.c_property.User" p:name="Jack0001"></bean>
</beans>
原文：http://www.cnblogs.com/guzhou-ing/p/6443564.html