Spring 小示例
通过一个简单的示例来初步理解Spring框架
1、创建java工程,导入相应Spring包,放在lib文件夹中
2、接口 IHelloMessage
1 package com.jike.spring.chapter01; 2 3 public interface IHelloMessage { 4 5 //接口中的一个抽象方法,用于向大家输出问候信息 6 public String sayHello(); 7 8 }
3、java类 HelloChina.java,用于输出“中国话”
1 package com.jike.spring.chapter01; 2 3 public class HelloChina implements IHelloMessage { 4 5 6 //继承和实现了IHelloMessage接口中的sayHello方法, 7 //向大家输出了Hello China的信息 8 @Override 9 public String sayHello() { 10 11 return "Hello China!"; 12 } 13 14 }
4、java类 HelloWorld.java,用于输出“世界话”
1 package com.jike.spring.chapter01; 2 3 public class HelloWorld implements IHelloMessage{ 4 5 //继承和实现了IHelloMessage接口中的sayHello方法, 6 //向大家输出了Hello China的信息 7 @Override 8 public String sayHello() { 9 return "Hello World!"; 10 } 11 12 }
5、Person类
1 package com.jike.spring.chapter01; 2 3 public class Person { 4 5 //将IHelloMessage作为一个属性,用于向大家输出问候信息 6 private IHelloMessage helloMessage; 7 8 9 public IHelloMessage getHelloMessage() { 10 return helloMessage; 11 } 12 13 public void setHelloMessage(IHelloMessage helloMessage) { 14 this.helloMessage = helloMessage; 15 } 16 17 //用于调用IHelloMessage接口向用户输出问候信息, 18 //具体的问候信息,由Spring的配置文件来分配和决定 19 //1.当配置文件中分配给person的是HelloWorld的实体时,则输出“Hello World!”的信息; 20 //2.当配置文件中分配给person的是HelloChina的实体时,则输出“Hello China!”的信息; 21 public String sayHello() { 22 return this.helloMessage.sayHello(); 23 } 24 }
6、Main主类
1 package com.jike.spring.chapter01; 2 3 import org.springframework.beans.factory.BeanFactory; 4 import org.springframework.beans.factory.xml.XmlBeanFactory; 5 import org.springframework.core.io.FileSystemResource; 6 import org.springframework.core.io.Resource; 7 8 public class Main { 9 10 public static void main(String[] args) { 11 12 //利用FileSystemResource读取配置文件 13 Resource r = new FileSystemResource("helloMessage.xml"); 14 //利用XmlBeanFactory来加载配置文件,启动IOC容器 15 BeanFactory f = new XmlBeanFactory(r); 16 //从IOC容器中获取Person类的实例 17 Person person = (Person) f.getBean("person"); 18 //person实例向大家输出问候信息 19 String s = person.sayHello(); 20 //在系统控制台中打印问候信息,由于在这里配置文件中配置是HelloWorld的实例, 21 //所以,在这里打印的是字符串:HelloWorld 22 System.out.println("The Person is currently saying: "+s); 23 } 24 25 }
7、配置helloMessage.xml
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN" 3 "http://www.springframework.org/dtd/spring-beans.dtd"> 4 <beans> 5 <bean id="helloWorld" class="com.jike.spring.chapter01.HelloWorld"></bean> 6 <bean id="helloChina" class="com.jike.spring.chapter01.HelloChina"></bean> 7 <bean id="person" class="com.jike.spring.chapter01.Person"> 8 <property name="helloMessage" ref="helloChina"/> 9 </bean> 10 </beans>
运行结果:
将配置文件改为:
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN" "http://www.springframework.org/dtd/spring-beans.dtd"> <beans> <bean id="helloWorld" class="com.jike.spring.chapter01.HelloWorld"></bean> <bean id="helloChina" class="com.jike.spring.chapter01.HelloChina"></bean> <bean id="person" class="com.jike.spring.chapter01.Person"> <property name="helloMessage" ref="helloWorld"/> </bean> </beans>
结果为: