【Spring第二篇】IOC:控制反转

谁借莪１个温暖的怀抱￠ 2023-09-29 09:36 2阅读 0赞

### IOC:控制反转 ###

![\[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-iJnJAA26-1649572816217)(C:\\Users\\30666\\AppData\\Roaming\\Typora\\typora-user-images\\image-20220309235207381.png)\]][img-iJnJAA26-1649572816217_C_Users_30666_AppData_Roaming_Typora_typora-user-images_image-20220309235207381.png]

什么是IOC？

`举个例子，我们有一个UserDao接口类，并且有三个UserDao实现类，分别是MysqlUserDaoImpl、OracleUserDaoImpl、UserDaoImpl，都实现UserDao接口，接下来我们编写service层的UserService接口，并且编写UserService实现类UserServiceImpl，如果根据传统的方法去调用dao层的三个实现类来实现其中的方法`

`我们需要写三遍以下代码`

UserServiceImpl userService = new UserServiceImpl();
     
    userService.setUserDao(new MysqlUserDaoImpl());
    userService.getUser();
    
    
    userService.setUserDao(new OracleUserDaoImpl());
    userService.getUser();
    
    userService.setUserDao(new UserDaoImpl());
    userService.getUser();

`但是现在，我们不用传统的方法去调用，而是在UserService实现类中set dao层中的UserDao接口类`

public class UserServiceImpl implements UserService{
        
        private UserDao userDao;
       
        public void setUserDao(UserDao userDao) {
        
            this.userDao = userDao;
        }
        
        @Override
        public void getUser() {
        
            userDao.getUser();
        }
    }

`然后将我们的dao层中三个接口实现类通过bean交给spring容器托管，并且将Service的实现类也交给spring容器接管`

<?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-3.0.xsd">
    
        <bean id="mysqlImpl" class="com.kk.dao.MysqlUserDaoImpl"/>
        <bean id="oracleImpl" class="com.kk.dao.OracleUserDaoImpl"/>
        <bean id="userDaoImpl" class="com.kk.dao.UserDaoImpl"/>
    
    
        <bean id="UserServiceImpl" class="com.kk.service.UserServiceImpl">
    
    		
            <property name="userDao" ref="mysqlImpl"/>
    
    
    
        </bean>
    
    
    </beans>

`这时如果我们想要使用dao层中三个接口实现类中的某一个实现类，我们只需要 <property name="userDao" ref="userDaoImpl"/> 使用这个工具的ref选择我们想要实现的实现类`

![\[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-mwmYNK3b-1649572816219)(C:\\Users\\30666\\AppData\\Roaming\\Typora\\typora-user-images\\image-20220409153206111.png)\]][img-mwmYNK3b-1649572816219_C_Users_30666_AppData_Roaming_Typora_typora-user-images_image-20220409153206111.png]

**`前提是我们必须在service接口实现类中有set dao的接口`**

package com.kk.service;
    import com.kk.dao.UserDao;
    public class UserServiceImpl implements UserService{
        
    
        private UserDao userDao;
        public void setUserDao(UserDao userDao) {
        
            this.userDao = userDao;
        }
    
        @Override
        public void getUser() {
        
            userDao.getUser();
        }
    }

--------------------

代码如下：

UserDao

package com.kk.dao;
    
    public interface UserDao {
        
    
        public void getUser();
    
    }

MysqlUserDaoImpl

package com.kk.dao;
    
    public class MysqlUserDaoImpl implements UserDao{
        
        @Override
        public void getUser() {
        
            System.out.println("Mysql获取用户数据");
        }
    }

OracleUserDaoImpl

package com.kk.dao;
    
    public class OracleUserDaoImpl implements UserDao{
        
        @Override
        public void getUser() {
        
            System.out.println("Oracal获取用户数据");
        }
    }

UserDaoImpl

package com.kk.dao;
    
    public class UserDaoImpl implements UserDao{
        
        @Override
        public void getUser() {
        
            System.out.println("获取用户数据");
        }
    }

--------------------

UserService

package com.kk.service;
    
    public interface UserService {
        
    
        public void getUser();
    }

UserServiceImpl

package com.kk.service;
    
    import com.kk.dao.UserDao;
    
    public class UserServiceImpl implements UserService{
        
    
    
    
        private UserDao userDao;
    
        //IOC  控制反转
        public void setUserDao(UserDao userDao) {
        
            this.userDao = userDao;
        }
    
        @Override
        public void getUser() {
        
            userDao.getUser();
        }
    }

--------------------

beans.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-3.0.xsd">
    
         <bean id="mysqlImpl" class="com.kk.dao.MysqlUserDaoImpl"/>
        <bean id="oracleImpl" class="com.kk.dao.OracleUserDaoImpl"/>
        <bean id="userDaoImpl" class="com.kk.dao.UserDaoImpl"/>
    
    
    
        <bean id="UserServiceImpl" class="com.kk.service.UserServiceImpl">
    
    
                 
            <property name="userDao" ref="mysqlImpl"/>
    
        </bean>
    
    
    </beans>

--------------------

测试：

public class Test {
        
        public static void main(String[] args) {
        
    
            //获取ApplicationContext 拿到Spring的容器
            ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
    
            //拿到容器之后 需要什么就get即可
            UserServiceImpl userServiceImpl = (UserServiceImpl) context.getBean("UserServiceImpl");
    
            userServiceImpl.getUser();
        }
    }

--------------------

`以上便是IOC的思想，化繁为简，使用传统的去实现这个功能，需要不断的改变测试类的代码，然而使用IOC控制反转，只需改bean.xml中的代码即可`

![\[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-RGFFQibl-1649572816219)(C:\\Users\\30666\\AppData\\Roaming\\Typora\\typora-user-images\\image-20220309235207381.png)\]][img-RGFFQibl-1649572816219_C_Users_30666_AppData_Roaming_Typora_typora-user-images_image-20220309235207381.png]

[img-iJnJAA26-1649572816217_C_Users_30666_AppData_Roaming_Typora_typora-user-images_image-20220309235207381.png]: https://img-blog.csdnimg.cn/4cd084df456047a296f1b4890d822ff2.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA5LiD5a-75YyX6YeM,size_16,color_FFFFFF,t_70,g_se,x_16
[img-mwmYNK3b-1649572816219_C_Users_30666_AppData_Roaming_Typora_typora-user-images_image-20220409153206111.png]: https://img-blog.csdnimg.cn/5ed2aa6329eb4ce88795b31fe171d1c4.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA5LiD5a-75YyX6YeM,size_20,color_FFFFFF,t_70,g_se,x_16
[img-RGFFQibl-1649572816219_C_Users_30666_AppData_Roaming_Typora_typora-user-images_image-20220309235207381.png]: https://img-blog.csdnimg.cn/acfa3088dc254818a7c6ef12350078a0.png?x-oss-process=image/watermark,type_d3F5LXplbmhlaQ,shadow_50,text_Q1NETiBA5LiD5a-75YyX6YeM,size_16,color_FFFFFF,t_70,g_se,x_16