Spring基本概念，环境搭建，IoC注入方式详细演示

刺骨的言语ヽ痛彻心扉 2022-05-12 07:22 27阅读 0赞

*  Spring是一个开源的控制反转(Inversion of Control ,IoC)和面向切面(AOP)的容器框架.它的主要目得是简化企业开发，提高开发效率
 *  Spring 框架是一个分层架构，由 7 个定义良好的模块组成。Spring 模块构建在核心容器之上，核心容器定义了创建、配置和管理 bean 的方式  
    ![这里写图片描述][70]
 *  IoC（Inversion of Control，控制反转）。这是spring的核心，贯穿始终。所谓IoC，对于spring框架来说，应用本身不负责依赖对象的创建及维护，依赖对象的创建及维护是由外部容器负责的。这样控制权就由应用转移到了外部容器，控制权的转移就是所谓反转
 *  DI—Dependency Injection，即“依赖注入”：是组件之间依赖关系由容器在运行期决定，形象的说，即由容器动态的将某个依赖关系注入到组件之中。依赖注入的目的并非为软件系统带来更多功能，而是为了提升组件重用的频率，并为系统搭建一个灵活、可扩展的平台。通过依赖注入机制，我们只需要通过简单的配置，而无需任何代码就可指定目标需要的资源，完成自身的业务逻辑，而不需要关心具体的资源来自何处，由谁实现。
 *  注入方式：构造器注入和属性注入，详细见代码演示部分
 *  Spring环境搭建：首先下载spring-framework-3.2.6.RELEASE-dist.zip，按需导入jar包（初学阶段最好不要一次全导入，而是根据异常提示，逐步导入），演示注入方式，只需导入如下基本包（如下图），其中[commons-loggin-1.2.jar][]是Apache官网提供的。  
    ![这里写图片描述][70 1]
 *  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-3.2.xsd">
    <import resource="Beans2.xml"/>
    
    
    
    
    <bean id="userid1" class="com.entity.User" name="username1" scope="singleton"></bean>
    
    <bean id="userid2" class="com.entity.User" name="username2" scope="prototype"></bean>
    
    
    <bean id="user1" class="com.entity.User">
        
        
        <constructor-arg name="num" value="XH1003060101"></constructor-arg>
    </bean>
    <bean id="user2" class="com.entity.User">
        
        <constructor-arg>
            <value>1001</value>
        </constructor-arg>
        <constructor-arg>
            <value>张三</value>
        </constructor-arg>
        <constructor-arg>
            <value>18</value>
        </constructor-arg>
        <constructor-arg>
            <value>XH1003060117</value>
        </constructor-arg>
    </bean>
    <bean id="user2_2" class="com.entity.User">
        
        <constructor-arg index="0" value="1001"></constructor-arg>
        <constructor-arg index="1" value="张三"></constructor-arg>
        <constructor-arg index="2" value="18"></constructor-arg>
        <constructor-arg index="3" value="XH1003060117"></constructor-arg>
    </bean>
    
    
    
    <bean id="user3" class="com.entity.User">
        
        <property name="id" value="1002"></property>
        <property name="name" value="李四"></property>
        <property name="age" value="18"></property>
        <property name="num" value="XH1003060118"></property>
    </bean>
    
    <bean id="people1" class="com.entity.People">
        
        <property name="u" ref="user3"></property>
    </bean>
    
    <bean id="people2" class="com.entity.People">
        <constructor-arg>
            <value>王五</value>
        </constructor-arg>
        
        <constructor-arg>
            <ref bean="user3"/>
        </constructor-arg>
    </bean>
    <bean id="people3" class="com.entity.People">
        
        <constructor-arg name="u" ref="user3"></constructor-arg>
    </bean>
    
    <bean id="people4" class="com.entity.People">
        
        <property name="uArray">
            <array>
                <ref bean="user1"/>
                <ref bean="user2"/>
                <ref bean="user3"/>
            </array>
                    
        </property> 
    </bean>
    
    <bean id="people5" class="com.entity.People">
        
        <property name="uList">
            <list>
                
                <ref bean="user1"/>
                <ref bean="user3"/>
                <bean class="com.entity.User">
                    <property name="name" value="李木子"></property>
                </bean>
            </list>
        </property>
    </bean>
    
    <bean id="people6" class="com.entity.People">
        
        <property name="map">
            <map>
                
                <entry key="a" value-ref="user3"></entry>
                <entry key="b">
                    <ref bean="user3"/>
                </entry>
                <entry key="c">
                    <bean class="com.entity.User">
                        <property name="name" value="何炅"></property>
                    </bean>
                </entry>
            </map>
        </property>
    </bean>
    
    <bean id="people7" class="com.entity.People">
        
        <property name="pro">
            <props>
                <prop key="k1">v1</prop>    
                <prop key="k2">v2</prop>    
                <prop key="k3">v3</prop>    
            </props>
        </property>
    </bean>
    
    <bean id="people8" class="com.entity.People">
        
        <property name="u" ref="userOut"></property>
    </bean>
    </beans>

*  Beans2.xml

*  Demo1.java

package com.test;
    
    import java.util.Iterator;
    import java.util.List;
    import java.util.Map;
    import java.util.Properties;
    import java.util.Set;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.entity.People;
    import com.entity.User;
    
    public class Demo1 {
    
        public static void main(String[] args) {
            ApplicationContext app = new ClassPathXmlApplicationContext("Beans.xml");
            //测试jar包导入是否正确
            //System.out.println(app);
    
            //默认是单例的,scope="singleton"
            //两种获取bean的方式，id，name
            //通过id获取
            User user1 = (User) app.getBean("userid1");
            //通过name获取
            User user2 = (User) app.getBean("username1");
            System.out.println(user1);//com.entity.User@7f5580
            System.out.println(user2);//com.entity.User@7f5580
    
            //多例 scope默认是sigleton单例的，设置成 prototype则为多例
            User user3 = (User) app.getBean("userid2");
            User user4 = (User) app.getBean("username2");
            System.out.println(user3);//com.entity.User@106fc94
            System.out.println(user4);//com.entity.User@7f5580
    
            //bean中的IoC注入方式，往大了分为两种：构造器注入constructor，和属性注入setter
            //属性注入里有基本注入，还有引用注入，引用注入又分为外部引用注入，和内部引用注入
    
            User u1 = (User) app.getBean("user1");
            System.out.println(u1.getNum());
            User u2 = (User) app.getBean("user2");
            System.out.println(u2.getName());
            System.out.println(u2.getAge());
            User u2_2 = (User) app.getBean("user2_2");
            System.out.println(u2.getName());
            System.out.println(u2.getAge());
            User u3 = (User) app.getBean("user3");
            System.out.println(u3.getName());
            System.out.println(u3.getAge());
    
            People p1 = (People) app.getBean("people1");
            System.out.println(p1.getU().getName());
            People p2 = (People) app.getBean("people2");
            System.out.println(p2.getU().getName());
            People p3 = (People) app.getBean("people3");
            System.out.println(p3.getU().getName());
    
            People p4 = (People) app.getBean("people4");
            User[] uArray = p4.getuArray();
            User u0 = uArray[0];
            String num = u0.getNum();
            System.out.println(num);
    
            People p5 = (People) app.getBean("people5");
            List<User> uList = p5.getuList();
            System.out.println(uList.get(0).getNum());
            System.out.println(uList.get(1).getNum());
            System.out.println(uList.get(2).getName());
    
            People p6 = (People) app.getBean("people6");
            Map<String,User> map = p6.getMap();
            Set<String> k = map.keySet();
            Iterator<String> it = k.iterator();
            while(it.hasNext()){
                String key = it.next();
                User value = map.get(key);
                System.out.println(key+":"+value.getName());
            }
    
            People p7 = (People) app.getBean("people7");
            Properties pro = p7.getPro();
            System.out.println(pro.getProperty("k3"));
    
            People p8 = (People) app.getBean("people8");
            System.out.println(p8.getU().getName());
        }
    }

*  运行结果  
    ![这里写图片描述][70 2]

[70]: /images/20220512/dbd47d5b2fad497ebaf73edba0488cc1.png
[commons-loggin-1.2.jar]: http://commons.apache.org/proper/commons-logging/download_logging.cgi
[70 1]: /images/20220512/f8ec0ebc7bdc41188d3610bba553dab3.png
[70 2]: /images/20220512/c5010712433e49a590a3b8f8c5a61e2f.png