spring学习笔记1——开始spring之旅

开始学spring之前编写一个简单的HelloWorld程序，对spring有个感性的理解。

写一个服务类，作用是打出那熟悉的问候，下面显示GreetingService接口，它定义了服务。

public interface GreetingService { void sayGreeting(); }

GreetingServiceImpl是GreetingService的实现：我们发现此类用两种方式初始化，一个是直接用GreetingServiceImpl(String greeting)，另一类是用GreetingServiceImpl()然后调用setGreeting方法来初始化，这两种办法在spring里也可以以配置来实现。

public class GreetingServiceImpl implements GreetingService { private String greeting; public GreetingServiceImpl(){} public GreetingServiceImpl(String greeting){ this.greeting = greeting; } public void sayGreeting() { System.out.println(greeting); } public void setGreeting(String greeting){ this.greeting = greeting; } }

在spring中配置HelloWorld，相当与：
GreetingServiceImpl greetingService = new GreetingServiceImpl();
greetingService.setGreeting("Buenos Dias!");

<?xml version="1.0" encoding="UTF-8" ?> <beans xmlns="http://www.springframework.org/schema/beans" 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-2.0.xsd"> <bean id="greetingService" class="org.spring.helloworld.GreetingServiceImpl"> <property name="greeting" value="Buenos Dias!" /> </bean> </beans>

在spring中配置HelloWorld，相当与：

GreetingServiceImpl greetingService = new GreetingServiceImpl("Buenos Dias!");

<bean id="greetingService" class="org.spring.helloworld.GreetingServiceImpl"> <constructor-arg value="Buenos Dias!" /> </bean>

BeanFactory是spring的容器，将把hello.xml文件加载之后main()方法调用BeanFactory的getBean()方法来得到问候服务的引用。

public class HelloApp { /** * 通过BeanFactory容器载入xml文件 */ public void BeanFactoryTest(){ BeanFactory factory = new XmlBeanFactory(new FileSystemResource("xmls/hello.xml")); GreetingService greetingService = (GreetingService)factory.getBean("greetingService"); greetingService.sayGreeting(); } /** * 通过ApplicationContext容器载入xml文件 */ public void ApplicationContextTest(){ ApplicationContext atx = new ClassPathXmlApplicationContext("org/spring/helloworld/hello.xml"); GreetingService greetingService = (GreetingService)atx.getBean("greetingService"); greetingService.sayGreeting(); } public static void main(String[] args){ HelloApp ha = new HelloApp(); ha.BeanFactoryTest(); ha.ApplicationContextTest(); } }