如何减少程序间的耦合度？

spring 开发提倡接口编程，配合DI技术可以更好的减少层(程序)与层(程序)之间的解耦合

例子说明：
任务：要求：
        1.打印机依赖纸张和墨盒
        2.纸张有A4和B5两种
        3.墨盒有彩色和黑色2种
        4.使用A4纸张和彩色墨盒打印指定内容
        5.使用B5纸张和黑色墨盒打印指定内容

7.要求使用接口

代码：

package Ink;

public interface Ink {

   public String getInk();

}

package Ink;

public class Black_Ink implements  Ink{

    public String getInk()

    {

        return "黑白";

    }

}

package Ink;

public class Color_Ink implements Ink{

    public String getInk()

    {

        return "彩色";

    }

}

package Paper

package Paper;

public interface Paper {

    public String getPaper();

}

package Paper;

public class A4_Paper implements Paper{

    public String getPaper()

    {

        return "A5纸张";

    }

}

package Paper;

public class A5_Paper implements  Paper{

    public String getPaper()

    {

        return "A5纸张";

    }

}

package Print

package Print;

import Paper.Paper;

import Ink.Ink;

public class print {

   private Ink ink;

   private Paper paper;

    public void setInk(Ink ink) {

        this.ink = ink;

    }

    public void setPaper(Paper paper) {

        this.paper = paper;

    }

    public void print(String context)

    {

        System.out.print("使用"+ink.getInk()+"在"+paper.getPaper()+"上，打印："+context);

    }

}

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans

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

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

        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">

        <bean id="A4_Paper" class="Paper.A4_Paper"></bean>

        <bean id="Color_Ink" class="Ink.Color_Ink"></bean>

        <bean id="Print" class="Print.print">

            <property name="paper">

                <ref bean="A4_Paper" />

            </property>

            <property name="ink">

                <ref bean="Color_Ink"/>

            </property>

        </bean>

</beans>

package Test

package Test;

import Print.print;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

    public static void main(String []args)

    {

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

        print p=(print)context.getBean("Print");

        p.print("你好！");

    }

}

通过上面的案例，我们可以体会到DI配合接口编程，确实可以减少层(web层)和业务层的耦合度

巴特西

如何减少程序间的耦合度？_DI与接口

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