Spring框架总结（四）
2024-09-29 12:42:52
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
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