【Spring】Sring基础概念（黑马SSM学习笔记）2-阿里云开发者社区

【Spring】Sring基础概念（黑马SSM学习笔记）2

2022-11-13 135

版权

本文内容由阿里云实名注册用户自发贡献，版权归原作者所有，阿里云开发者社区不拥有其著作权，亦不承担相应法律责任。具体规则请查看《阿里云开发者社区用户服务协议》和《阿里云开发者社区知识产权保护指引》。如果您发现本社区中有涉嫌抄袭的内容，填写侵权投诉表单进行举报，一经查实，本社区将立刻删除涉嫌侵权内容。

简介： 【Spring】Sring基础概念（黑马SSM学习笔记）

bean实例化的三种方式

无参构造方法实例化
工厂静态方法实例化
工厂实例方法实例化

工厂静态方法化

package cc.mllt.dao.factory;
import cc.mllt.dao.UserDao;
import cc.mllt.dao.impl.UserDaoImpl;
public class StaticFactory {
    public  static UserDao getUserDao(){
        return new UserDaoImpl();
    }
}

发现包放的有问题，更改一下路径

更改配置文件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">
<!--    无参构造-->
<!--    <bean id="userDao" class="cc.mllt.dao.impl.UserDaoImpl" scope="singleton" init-method="ml_init" destroy-method="ml_destroy"/>-->
<!--    静态工厂构造-->
    <bean id="userDao" class="cc.mllt.factory.StaticFactory" factory-method="getUserDao" />
</beans>

工厂实例方法实例化

package cc.mllt.factory;
import cc.mllt.dao.UserDao;
import cc.mllt.dao.impl.UserDaoImpl;
public class DynamicFactory {
    public UserDao getUserDao(){
        return new UserDaoImpl();
    }
}

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">
<!--    无参构造-->
<!--    <bean id="userDao" class="cc.mllt.dao.impl.UserDaoImpl" scope="singleton" init-method="ml_init" destroy-method="ml_destroy"/>-->
<!--    静态工厂构造-->
<!--    <bean id="userDao" class="cc.mllt.factory.StaticFactory" factory-method="getUserDao" />-->
<!--    工厂实例实例化（动态工厂）-->
    <bean id="factory" class="cc.mllt.factory.DynamicFactory"></bean>
    <bean id="userDao" factory-bean="factory" factory-method="getUserDao"></bean>
</beans>

测试

Spring配置文件

Bean的依赖注入分析

package cc.mllt.service.ipml;
import cc.mllt.dao.UserDao;
import cc.mllt.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class UserServiceImpl implements UserService {
    @Override
    public void save() {
        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserDao userDao = (UserDao) app.getBean("userDao");
        userDao.save();
    }
}

package cc.mllt.demo;
import cc.mllt.service.UserService;
import cc.mllt.service.ipml.UserServiceImpl;
public class UserController {
    public static void main(String[] args) {
        UserService userService = new UserServiceImpl();
        userService.save();
    }
}

现在

这是由于还没有去修改配置未见ApplicationContext.xml

UserDao此时在UserService内部

Bean依赖注入概念

依赖注入（Dependency Injection）：Spring框架核心IOC的具体实现

IOC解耦只是降低了他们的依赖关系，但不会消除。例如：业务层仍然会调用持久层的方法

Bean的依赖注入方式

set方法

p命名空间注入的本质也是set方法注入，但是比起上述的set方法注入更加方便，主要体现在配置文件中

（1）引入p命名空间：

xmlns:p="http://www.springframework.org/schema/p"

（2）修改注入方法

<bean id="userService" class="cc.mllt.service.ipml.UserServiceImpl" p:userDao-ref="userDao"></bean>

‍

‍

构造方法

<?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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<!--    无参构造-->
<!--    <bean id="userDao" class="cc.mllt.dao.impl.UserDaoImpl" scope="singleton" init-method="ml_init" destroy-method="ml_destroy"/>-->
<!--    静态工厂构造-->
<!--    <bean id="userDao" class="cc.mllt.factory.StaticFactory" factory-method="getUserDao" />-->
<!--    工厂实例实例化（动态工厂）-->
<!--    <bean id="factory" class="cc.mllt.factory.DynamicFactory"></bean>-->
<!--    <bean id="userDao" factory-bean="factory" factory-method="getUserDao"></bean>-->
<!--    service-->
<!--    set构造方法-->
<!--    <bean id="userDao" class="cc.mllt.dao.impl.UserDaoImpl"></bean>-->
<!--    <bean id="userService" class="cc.mllt.service.ipml.UserServiceImpl">-->
<!--        <property name="userDao" ref="userDao"></property>-->
<!--    </bean>-->
<!--        <bean id="userService" class="cc.mllt.service.ipml.UserServiceImpl" p:userDao-ref="userDao"></bean>-->
<!--构造方法-->
    <bean id="userDao" class="cc.mllt.dao.impl.UserDaoImpl"></bean>
        <bean id="userService" class="cc.mllt.service.ipml.UserServiceImpl">
           <constructor-arg name="userDao" ref="userDao"></constructor-arg>
        </bean>
</beans>

package cc.mllt.service.ipml;
import cc.mllt.dao.UserDao;
import cc.mllt.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class UserServiceImpl implements UserService {
    private UserDao userDao;
    public UserServiceImpl(UserDao userDao){
        this.userDao = userDao;
    }
    public UserServiceImpl(){
    }
//    private UserDao userDao;
//    public void  setUserDao(UserDao userDao){
//        this.userDao = userDao;
//    }
    @Override
    public void save() {
//        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
//        UserDao userDao = (UserDao) app.getBean("userDao");
        userDao.save();
    }
}