浅谈 Spring 框架

Spring框架是分模块存在，除了最核心的Spring Core Container(即Spring容器)是必要模块之外，其他模块都是可选，视需要而定。大约有20多个模块。Spring的核心是控制反转（IoC）和面向切面（AOP）。简单来说，Spring是一个分层的JavaSE/EE full-stack(一站式) 轻量级开源框架。

一般来说，Spring主要分为7个模块：

构建项目

文件目录：

代码：

配置文件：applicationContext.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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="hello" class="com.neuedu.hello.HelloWorld"></bean> <bean id="userDaoOracle" class="com.neuedu.dao.impl.UserDaoOracleImpl"></bean> </beans> 

Test.java

package com.neuedu.test; import com.neuedu.hello.HelloWorld; import com.neuedu.service.UserService; import com.neuedu.dao.impl.UserDaoOracleImpl; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Test { public static void main(String[] args) { /*HelloWorld hw = new HelloWorld(); hw.say();*/ /* ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml"); HelloWorld hw = (HelloWorld)ac.getBean("hello"); hw.say(); HelloWorld hw2 = (HelloWorld)ac.getBean("hello"); System.out.println(hw == hw2);*/ /*UserService us = new UserService(); us.save();*/ ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml"); UserDaoOracleImpl ud = (UserDaoOracleImpl)ac.getBean("userDaoOracle"); ud.save(); } } 

ClassPathXmlApplicationContext 创建了一个 spring 容器，在容器中加载了一个配置文件（applicationContext.xml）
 通过配置文件可以读取到所有的bean标签（id/class)
 通过 class 可以 new 一个对象，class.forName("com.neuedu.hello.HelloWorld").newInstance();

UserDao.java

package com.neuedu.dao; public interface UserDao { public void save(); } 

UserService.java

package com.neuedu.service; import com.neuedu.dao.UserDao; import com.neuedu.dao.impl.UserDaoOracleImpl; import com.neuedu.dao.impl.UserDaoMysqlImpl; public class UserService { //UserDaoOracleImpl dao = new UserDaoOracleImpl(); //UserDaoMysqlImpl udml = new UserDaoMysqlImpl(); UserDao dao = new UserDaoMysqlImpl();//new UserDaoOracleImpl(); public void save() { dao.save(); //dao.insert(); } } 

UserDaoMysqlImpl.java

package com.neuedu.dao.impl; import com.neuedu.dao.UserDao; public class UserDaoMysqlImpl implements UserDao{ public void save() { System.out.println("通过mysql数据库将用户信息保存到数据库中"); } } 

UserDaoOracleImpl.java

package com.neuedu.dao.impl; import com.neuedu.dao.UserDao; public class UserDaoOracleImpl implements UserDao{ public void save() { System.out.println("通过oracle数据库将用户信息保存到数据库中"); } /*public void insert() { System.out.println("通过mysql数据库将用户信息保存到数据库中"); }*/ } 

输出：

改进：控制反转（IOC）

上面的方法，UserDao 注入是通过 UserService 自身 new 一个 dao 实现类  下面方法 将控制权交给 sping 容器，因为Service 和

Dao 都在 spring中，故当 Service 需要 Dao 时，会自动将 dao 的实现类的对象放入 Service 中 

配置文件：applicationContext.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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="hello" class="com.neuedu.hello.HelloWorld"></bean> <bean id="userDaoOracle" class="com.neuedu.dao.impl.UserDaoOracleImpl"></bean> <bean id="userService" class="com.neuedu.service.UserService"> <!-- SQL注入 --> <property name="dao" ref="userDaoOracle"></property> </bean> </beans> 

Test.java

package com.neuedu.test; import com.neuedu.hello.HelloWorld; import com.neuedu.service.UserService; import com.neuedu.dao.impl.UserDaoOracleImpl; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Test { public static void main(String[] args) { ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml"); /*UserDaoOracleImpl ud = (UserDaoOracleImpl)ac.getBean("userDaoOracle"); ud.save();*/ UserService us = (UserService)ac.getBean("userService"); us.save(); } } 

UserService.java

package com.neuedu.service; import com.neuedu.dao.UserDao; import com.neuedu.dao.impl.UserDaoOracleImpl; import com.neuedu.dao.impl.UserDaoMysqlImpl; public class UserService { //UserDaoOracleImpl dao = new UserDaoOracleImpl(); //UserDaoMysqlImpl udml = new UserDaoMysqlImpl(); //UserDao dao = new UserDaoMysqlImpl();//new UserDaoOracleImpl(); private UserDao dao; public void save() { dao.save(); //dao.insert(); } public UserDao getDao() { return dao; } public void setDao(UserDao dao) { this.dao = dao; } } 

输出：

好处：Service 和 Dao 彻底解耦，只需更改配置文件：applicationContext.xml中的调用即可

配置文件：applicationContext.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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="hello" class="com.neuedu.hello.HelloWorld"></bean> <bean id="userDaoMysql" class="com.neuedu.dao.impl.UserDaoMysqlImpl"></bean> <bean id="userDaoOracle" class="com.neuedu.dao.impl.UserDaoOracleImpl"></bean> <bean id="userService" class="com.neuedu.service.UserService"> <!-- SQL注入 --> <property name="dao" ref="userDaoMysql"></property> </bean> </beans> 

输出：