Spring框架总结（四）

对象依赖关系

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

一、对象属性赋值，通过构造函数

user

 public class User {

     private String userId;
     private String username;

     public User() {
         System.out.println("======不带参构造器=========");
     }

     public User(String userId, String username) {
         System.out.println("======带参构造器=========");
         this.userId = userId;
         this.username = username;
     }

     public String getUserId() {
         return userId;
     }

     public void setUserId(String userId) {
         this.userId = userId;
     }

     public String getUsername() {
         return username;
     }

     public void setUsername(String username) {
         this.username = username;
     }

     @Override
     public String toString() {
         return "User [userId=" + userId + ", username=" + username + "]";
     }

 }

bean.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: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 通过构造函数 -->
     <bean id="user" class="com.liuyang.demo.property.User">
         <constructor-arg index="0" value="100"></constructor-arg>
         <constructor-arg index="1" value="小白兔"></constructor-arg>
     </bean>
 </beans>

测试

 public class App {

     ApplicationContext aContext = new ClassPathXmlApplicationContext(
             "com/liuyang/demo/property/beans2.xml");

     @Test
     public void test() {
         User user = (User) aContext.getBean("user1");

         System.out.println(user);
     }
 }

二、通过set方法给属性注入值

更改bean，其他不变

 <?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">
 <!-- set方法赋值 -->
     <bean id="user1" class="com.liuyang.demo.property.User">
         <property name="userId" value="101"></property>
         <property name="username" value="大虎猫"></property>
     </bean>

 </beans>

事例一个set方法传值案例：

创建userdao

 public class UserDAO {

     public void saveUser() {
         System.out
                 .println("保存成功**********************************************");

     }

 }

创建servicedao

 public class UserService {
     private UserDAO dao;

     public void setDao(UserDAO dao) {
         this.dao = dao;
     }

     public void save() {
         dao.saveUser();
     }

 }

创建action

 public class UserAction {

     private UserService us;

     public void setUs(UserService us) {
         this.us = us;
     }

     public String execute() {
         us.save();
         return null;
     }

 }

bean.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: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 通过构造函数 -->
     <bean id="user" class="com.liuyang.test.DI.User">
     </bean>
     <!-- dao注入 -->
     <bean id="dao" class="com.liuyang.test.DI.UserDAO">
     </bean>

     <!-- service注入 -->
     <bean id="us" class="com.liuyang.test.DI.UserService">
         <property name="dao" ref="dao"></property>
     </bean>

     <!-- action注入 -->
     <bean id="userAction" class="com.liuyang.test.DI.UserAction">
         <property name="us" ref="us"></property>
     </bean>

测试

 public class App {

     ApplicationContext aContext = new ClassPathXmlApplicationContext(
             "com/liuyang/test/DI/beans2.xml");

     @Test
     public void test() {
         UserAction userAction = (UserAction) aContext.getBean("userAction");

         userAction.execute();
     }
 }

还有内部的bean写法如图,适用于只有一个dao和一个service的情况

 <?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">
 <!-- 内部调用 dao和service在容器中只用一次,缺点不易维护-->
     <bean id="userAction1" class="com.liuyang.test.DI.UserAction">
         <property name="us">
             <bean class="com.liuyang.test.DI.UserService">
                 <property name="dao">
                     <bean class="com.liuyang.test.DI.UserDAO"></bean>
                 </property>
             </bean>
         </property>
     </bean>
 </beans>

三、p名称空间的使用

(1)p引用的使用

保证约束条件有xmlns:p="http://www.springframework.org/schema/p"

更改bean.xml

 <!--
             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)
 -->
 <?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">
 <bean id="user" class="com.liuyang.test.DI.User">
     </bean>
     <bean id="dao" class="com.liuyang.test.DI.UserDAO"></bean>
     <bean id="us" class="com.liuyang.test.DI.UserService" p:dao-ref="dao"></bean>
     <bean id="userAction" class="com.liuyang.test.DI.UserAction"
         p:us-ref="us"></bean>
 </beans>

(2)p传值的引用

 <?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">
 <bean id="meinv" class="com.liuyang.test.DI.User" p:username="小白兔"></bean>
 </beans>

p命名空间是一种优化