Spring
理念：使现有技术更加实用,本身是大杂烩整合现有的框架技术
优点：
轻量级框架
Ioc 容器-控制反转 inversion of Control
Aop 面向切面编程
对事务支持
对框架的支持
一、Ioc 控制反转
Ioc 是一种编程思想，由主动编程变为被动接收
别名：依赖注入 dependency injection
控制：
指谁来控制对象的创建
传统的应用程序对象的创建是由程序本身控制的
使用 spring 之后，由 spring 创建对象
反转：
正转指程序来创建对象
反转指程序本身不创建对象，而变成被动接受对象
总结：
以前对象是由程序本身创建，
使用 spring 之后，程序变为接收 spring 创建好的对象
简单示例
1、依赖 pom.xml
org.springframework spring-context-support 5.2.6.RELEASE org.springframework spring-context 5.2.6.RELEASE
2、Person.java
package com.pengshiyu.bean; public class Person { private String name; public void setName(String name) { this.name = name; } public void sayHello() { System.out.println("hello " + this.name); } }
3、beans.xml
此处是完整写法，之后将采用简写形式
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
4、Demo.java
package com.pengshiyu.spring; import com.pengshiyu.bean.Person; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Demo { public static void main(String[] args) { // 解析beans.xml 文件，生成对应的Bean对象 ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml"); Person person = (Person)context.getBean("person"); person.sayHello(); } }
二、Dao 管理示例
Ioc: 对象由 spring 来创建
1、UserDao
package com.spring.dao; public interface UserDao { public void getUser(); }
2、UserDaoMysqlImpl
package com.spring.dao.impl; import com.spring.dao.UserDao; public class UserDaoMysqlImpl implements UserDao { @Override public void getUser() { System.out.println("Mysql 获取用户信息"); } }
3、UserDaoOracleImpl
package com.spring.dao.impl; import com.spring.dao.UserDao; public class UserDaoOracleImpl implements UserDao { @Override public void getUser() { System.out.println("Oracle 获取用户信息"); } }
4、UserService
package com.spring.service; public interface UserService { public void getUser(); }
5、UserServiceImpl
package com.spring.service.impl; import com.spring.dao.UserDao; import com.spring.service.UserService; public class UserServiceImpl implements UserService { private UserDao userDao = null; public void setUserDao(UserDao userDao) { this.userDao = userDao; } @Override public void getUser() { this.userDao.getUser(); } }
6、beans.xml（简化版）
7、TestDemo
package com.spring.test; import com.spring.service.UserService; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class TestDemo { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml"); UserService service = (UserService)context.getBean("service"); service.getUser(); } }
三、使用 Ioc 来创建对象的 3 种方法
Person 类
package com.pengshiyu.bean; public class Person { private String name; public Person() { } public Person(String name) { this.name = name; } public void sayHello() { System.out.println("hello " + this.name); } }
创建对象
package com.spring.test; import com.pengshiyu.bean.Person; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Demo { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml"); Person person = (Person) context.getBean("person"); person.sayHello(); } }
beans.xml(简化版)
1、无参构造
<beans> <bean name="person" class="com.pengshiyu.bean.Person" /> </beans>
2、有参构造
（1）根据参数下标设置
<beans> <bean name="person" class="com.pengshiyu.bean.Person"> <!-- index 构造方法下标从 0 开始 --> <constructor-arg index="0" value="Tom" /> </bean> </beans>
（2）根据参数名称设置
<beans> <bean name="person" class="com.pengshiyu.bean.Person"> <!-- name 参数名--> <constructor-arg name="name" value="Tom" /> </bean> </beans>
(3)根据参数类型设置
<beans> <bean name="person" class="com.pengshiyu.bean.Person"> <!-- type 参数类型 --> <constructor-arg type="java.lang.String" value="Tom" /> </bean> </beans>
