Spring依赖注入与配合接口编程案例

来源：互联网发布：js根据id获取对象编辑：程序博客网时间：2024/05/16 18:39

spring开发提倡接口编程,配合di技术可以层与层的解耦

现在我们体验一下spring的di配合接口编程的，完成一个字母大小写转换的案例:

思路:

1. 创建一个接口 ChangeLetter

package com.xlc.inter;public interface ChangeLetter {//声明一个方法public String change();}

2. 两个类实现接口

package com.xlc.inter;public class LowwerLetter implements ChangeLetter {//把小写变为大写private String str;public String getStr() {return str;}public void setStr(String str) {this.str = str;}@Overridepublic String change() {// TODO Auto-generated method stubreturn str.toLowerCase();}}

package com.xlc.inter;public class UpparLetter implements ChangeLetter {private String str;public String getStr() {return str;}public void setStr(String str) {this.str = str;}@Overridepublic String change() {// TODO Auto-generated method stub//把小写字母变成大写returnstr.toUpperCase();}}

3. 把对象配置到spring容器中

<?xml version="1.0" encoding="UTF-8"?><!--  - Application context definition for JPetStore's business layer.  - Contains bean references to the transaction manager and to the DAOs in  - dataAccessContext-local/jta.xml (see web.xml's "contextConfigLocation").  --><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.xsdhttp://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsdhttp://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"><!--  <bean id="changeLette" class="com.xlc.inter.UpparLetter"><property name="str"><value>abcdef</value></property></bean>--><bean id="changeLette" class="com.xlc.inter.LowwerLetter"><property name="str"><value>ABCDEFG</value></property></bean></beans>

4. 使用

在applicationContext中拿到bean后转换成接口类型

package com.xlc.inter;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class App1 {<span style="white-space:pre"></span>public static void main(String[] args) {<span style="white-space:pre"></span>// TODO Auto-generated method stub<span style="white-space:pre"></span>ApplicationContext app=new ClassPathXmlApplicationContext("com/xlc/inter/applicationContextContext.xml");<span style="white-space:pre"></span>ChangeLetter changeLetter=(ChangeLetter) app.getBean("changeLette");<span style="white-space:pre"></span>System.out.println(changeLetter.change());<span style="white-space:pre"></span>} }

<strong>ChangeLetter changeLetter=(ChangeLetter) app.getBean("changeLette");中得到的对象是由applicationContext.xml中配置的</strong><pre name="code" class="html" style="font-family: Arial, Helvetica, sans-serif;"><strong><bean id="changeLette" class="com.xlc.inter.UpparLetter">class<span style="font-family: Arial, Helvetica, sans-serif;">具体反射的bean决定的</span></strong>

<span style="font-family:Arial, Helvetica, sans-serif;"><strong>而bean方法又是由</strong></span><pre name="code" class="html"><strong><property name="str"><value>abcdef</value></property>根据实际情况切换的，解耦目的达到</strong>

5. 输出

若将applicationContext.xml中注释切换

<!--  <bean id="changeLette" class="com.xlc.inter.UpparLetter"><property name="str"><value>abcdef</value></property></bean>--><bean id="changeLette" class="com.xlc.inter.LowwerLetter"><property name="str"><value>ABCDEFG</value></property></bean>

<bean id="changeLette" class="com.xlc.inter.UpparLetter"><property name="str"><value>abcdef</value></property></bean><!--  <bean id="changeLette" class="com.xlc.inter.LowwerLetter"><property name="str"><value>ABCDEFG</value></property></bean>-->

di配合接口编程，可以减少层(web层) 和业务层的耦合度.

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