Spring IOC 小演示

news2024/9/24 3:29:57

首先建项目，可参考 https://blog.csdn.net/2303_79008526/article/details/141141114?spm=1001.2014.3001.5502

一、spring 环境搭建

（一）导相关坐标

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>spring_ioc_003</artifactId>
  <version>1.0-SNAPSHOT</version>

  <!-- 添加坐标 -->
  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.3.28</version>
    </dependency>
  </dependencies>

</project>

（二）搭建配置文件

我起名为 beans

（三）建包建类，写方法

package com.apesource.pojo;

public class Student {
}

package com.apesource.dao;

public interface IDao {
    public void save();
}

package com.apesource.dao;

public class DaoImp implements IDao{
    @Override
    public void save() {
        System.out.println("======Dao的新增方法======");
    }
}

package com.apesource.test;

public class Test01 {
}

（四）找到需要以解耦方式获取实例的类，将需要spring管理的类注入spring容器

语法：<bean id="唯一标识" class="类"></bean>

<?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">

  <!-- 注入类 -->
  <!-- id起名随意 -->
  <bean id="student" class="com.apesource.pojo.Student"></bean>
  <bean id="daoImp" class="com.apesource.dao.DaoImp"></bean>
  
</beans>

（五）向spring容器中索取java实例（解耦）

5.1.加载spring核心配置文件，获取spring容器对象

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");

5.2.获取对象，测试运行

Student student = (Student)applicationContext.getBean("student");

package com.apesource.test;

import com.apesource.dao.DaoImp;
import com.apesource.pojo.Student;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test01 {
    public static void main(String[] args) {
        //1.加载spring核心配置文件，获取spring容器对象
        ApplicationContext applicationContext = 
            new ClassPathXmlApplicationContext("beans.xml");
        //2.获取对象（getBean(" beans.xml 文件注入类时的 id 名")）
        Student student = (Student) applicationContext.getBean("student");
        System.out.println(student);

        DaoImp dao = (DaoImp) applicationContext.getBean("daoImp");
        dao.save();
    }
}

结果如下，运行成功

二、小结

模拟三层--控制层、业务层和数据访问层 (yuque.com)，与它的 perproties 对比理解

beans.properties

beans.xml

key=values

id=class

BeansFactory

ApplicationContext

getBean(key)

getBean(id)

关键字：

BeanFactory(父)

ApplicationContext(子《孙子》)

ClassPathXmlApplicationContext==>通过加载主配置文件的相对路径，获取spring容器

FileSystemXmlApplicationContext==>通过加载主配置文件的绝对路径，获取spring容器

AnnotationConfigApplicationContext==>加载配置类，获取spring容器