Spring开发者提倡接口编程，配合di技术可以解决层与层之间的解耦
package com.inter; public interface ChangeLetter { //声明一个方法 public String change(); }
2、两个类实现接口
UpperLetter.java
package com.inter; public class UpperLetter implements ChangeLetter { private String str; public String getStr() { return str; } public void setStr(String str) { this.str = str; } public String change() { //把小写字母->大写 return str.toUpperCase(); } }
LowwerLetter.java
package com.inter; //把小写字母->大写 public class LowwerLetter implements ChangeLetter { private String str; public String getStr() { return str; } public void setStr(String str) { this.str = str; } public String change() { return str.toLowerCase(); } }
3、把对象配置到spring容器中
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:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"> <bean id="changeLetter" class="com.inter.UpperLetter"> <property name="str"> <value>aGvGHff</value> </property> </bean> <!-- <bean id="changeLetter" class="com.inter.LowwerLetter"> <property name="str"> <value>aGvGHff</value> </property> </bean> --> </beans>
package com.inter; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Test { public static void main(String[] args) { ApplicationContext ac = new ClassPathXmlApplicationContext("com/inter/beans.xml"); //不使用接口来调用方法 UpperLetter upperLetter = (UpperLetter) ac.getBean("changeLetter"); System.out.println(upperLetter.change()); //使用接口来访问bean ChangeLetter changeLetter = (ChangeLetter) ac.getBean("changeLetter"); System.out.println(changeLetter.change()); //beans.xml中配了哪个类，这里的changeLetter就调用哪个类的change()方法 } }
通过上面的案例，可以初步体会到di配合接口编程，的确可以减少层（web层）与层（业务层）之间的耦合度。
原文：http://www.cnblogs.com/jingyunyb/p/3546062.html