Spring bean加载的三种方式

小灰灰 2022-01-21 08:17 296阅读 0赞

# **Spring bean加载的三种方式** #

**UserService:**

package com.njtech.service;
    
    public interface UserService {
    
        public void add();
    }

**UserServiceImpl:**

package com.njtech.service.Impl;
    
    import com.njtech.service.UserService;
    
    /**
     * 〈一句话功能简述〉:UserService 的实现类
     * @author njtech
     * @create 2019/6/8
     * @since 1.0.0
     */
    public class UserServiceImpl implements UserService {
    
        private String name;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        @Override
        public void add(){
            System.out.println("创建新用户........."+name);
    
        }
    
    }

**bean.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" xmlns:util="http://www.springframework.org/schema/util"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
    
    <bean id="userService" class="com.njtech.service.Impl.UserServiceImpl">
        
        <property name="name" value="张三"></property>
    
    </bean>
        
    </beans>

**Day01Test :**

package com.njtech.test;
    
    import com.njtech.service.Impl.UserServiceImpl;
    import com.njtech.service.UserService;
    import javafx.application.Application;
    import org.junit.Test;
    import org.springframework.beans.factory.BeanFactory;
    import org.springframework.beans.factory.xml.XmlBeanFactory;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    import org.springframework.context.support.FileSystemXmlApplicationContext;
    import org.springframework.core.io.FileSystemResource;
    
    /**
     * 〈一句话功能简述〉：spring加载的三种方式,其中第一种方式最常用
     *
     * @author njtech
     * @create 2019/6/8
     * @since 1.0.0
     */
    
    
    public class Day01Test {
    
    
        @Test
        public void test(){
    
            //第一种方式：ClassPathXmlApplicationContext
            ApplicationContext context=new ClassPathXmlApplicationContext("bean.xml");
    
            UserService userService=(UserService) context.getBean("userService");
            userService.add();
            System.out.println(userService);
            System.out.println(".................................");
    
    
            //第二种方式：通过文件系统路径获得配置文件   【绝对路径】
            ApplicationContext context1=new FileSystemXmlApplicationContext("G:\\project\\day02-spring-njtech\\src\\bean.xml");
            UserService userService1=(UserService) context.getBean("userService");
            userService1.add();
            System.out.println(userService1);
            System.out.println(".................................");
    
            //第三种方式：使用BeanFactory
            String path="G:\\project\\day02-spring-njtech\\src\\bean.xml";
            BeanFactory factory=new XmlBeanFactory(new FileSystemResource(path));
            UserService userService2=(UserService) factory.getBean("userService");
            userService2.add();
            System.out.println(userService2);
    
    
    
    
        }
    
    
    }

**BeanFactory 和ApplicationContext 的区别：**

（1）BeanFactory 采取延迟加载，第一次getBean时才会初始化Bean  
（2）ApplicationContext 即时加载  
ApplicationContext是对BeanFactory扩展，提供了更多功能：  
A.国际化处理  
B.事件传递  
C.Bean自动装配  
D.各种不同应用层的Context实现