spring

spring的核心思想之一：控制反转也就是依赖注入。在spring的世界里，所有的java对象都是一个bean。程序中类和类之间的互相调用，不再是以往的new的创建。而是依靠spring容器通过反射读取xml配置文件中的一个个的bean来生成一个个的具体的实现类，供程序使用。同时将编程方式提升至面向接口编程。在一定程度上降低了程序的耦合。同时面向接口对后期功能的扩展以及修改降低了难度。只需要修改或增加实现类即可。

下面展示了spring注入bean的两种方式：设置注入、构造注入。

（1）设置注入。 接口Person.java

package com.demo.interfaces; public interface Person { public void drive(); }

实现类 Chinese.java

package com.demo.impls; import com.demo.interfaces.Person; import com.demo.interfaces.Shop; public class Chinese implements Person{ private Shop shop; public void setShop(Shop shop) { this.shop = shop; } @Override public void drive() { System.out.println(shop.work()); } }

接口Shop.java package com.demo.interfaces;

public interface Shop { public String work(); }

实现类SShop.java

package com.demo.impls;

import com.demo.interfaces.Shop;

public class Sshop implements Shop{

@Override public String work() { return "卖汽车"; }

}

spring 配置文件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" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd"> <bean id="chinese" class="com.demo.impls.Chinese"> <property name="shop" ref="sshop"></property> </bean> <bean id="sshop" class="com.demo.impls.Sshop"></bean> </beans> 测试类Test.java public static void main(String[] args) { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); Person p = ctx.getBean("chinese",Person.class); p.drive(); }

最后输出结果：卖汽车。

这是第一种设值注入方式，也就是根据

<bean id="chinese" class="com.demo.impls.Chinese"> <property name="shop" ref="sshop"></property> </bean>

中的name来指定调用Chinese实现类中的哪个set方法，ref指定set方法的传入参数。

（2）构造注入

接口Person.java

package com.demo.interfaces; public interface Person { public void drive(); }

实现类 Chinese.java

package com.demo.impls; import com.demo.interfaces.Person; import com.demo.interfaces.Shop; public class Chinese implements Person{ private Shop shop; public Chinese(Shop shop){ this.shop = shop; } @Override public void drive() { System.out.println(shop.work()); } }

接口Shop.java package com.demo.interfaces;

public interface Shop { public String work(); }

实现类SShop.java

package com.demo.impls;

import com.demo.interfaces.Shop;

public class Sshop implements Shop{

@Override public String work() { return "卖汽车"; }

}

spring 配置文件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" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd"> <bean id="chinese" class="com.demo.impls.Chinese"> <constructor-arg ref="sshop"></constructor-arg> </bean> <bean id="sshop" class="com.demo.impls.Sshop"></bean> </beans> 测试类Test.java public static void main(String[] args) { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); Person p = ctx.getBean("chinese",Person.class); p.drive(); }

最后输出结果：卖汽车。