Spring管理Bean和依赖注入.docVIP

框架学习之Spring 第二节 采用Spring管理Bean和依赖注入 1.实例化spring容器 和 从容器获取Bean对象 实例化Spring容器常用的两种方式： 方法一: 在类路径下寻找配置文件来实例化容器 [推荐使用] ApplicationContext ctx = new ClassPathXmlApplicationContext(new String[]{beans.xml}); 方法二: 在文件系统路径下寻找配置文件来实例化容器 [这种方式可以在开发阶段使用] ApplicationContext ctx = new FileSystemXmlApplicationContext(new String[]{“d:\\beans.xml“}); Spring的配置文件可以指定多个，可以通过String数组传入。 ? 当spring容器启动后，因为spring容器可以管理bean对象的创建，销毁等生命周期， 所以我们只需从容器直接获取Bean对象就行，而不用编写一句代码来创建bean对象。 从容器获取bean对象的代码如下： ApplicationContext ctx = new ClassPathXmlApplicationContext(“beans.xml”); OrderService service = (OrderService)ctx.getBean(personService); ? 2.Spring实例化Bean的三种方式 以下是三种方式的例子： 1.使用类构造器实例化 [默认的类构造器] bean id=“orderService class=cn.itcast.OrderServiceBean/ 2.使用静态工厂方法实例化 bean id=personService class=cn.itcast.service.OrderFactory factory-method=createOrder/ public class OrderFactory { public static OrderServiceBean createOrder(){ // 注意这里的这个方法是 static 的！ return new OrderServiceBean(); } } 3.使用实例工厂方法实例化: bean id=personServiceFactory class=cn.itcast.service.OrderFactory/ bean id=personService factory-bean=personServiceFactory factory-method=createOrder/ public class OrderFactory { public OrderServiceBean createOrder(){ return new OrderServiceBean(); } } ? 3.Bean的生命周期 （Bean的作用域） bean的scope 属性 The scope of this bean: typically singleton (one shared instance, which will be returned by all calls to getBean with the given id), or prototype (independent instance resulting from each call to getBean). Default is singleton. Singletons are most commonly used, and are ideal for multi- threaded service objects. Further scopes, such as request or session, might be supported by extended bean factories (e.g. in a web environment). Note: This attribute will not be inherited by child bean definitions. Hence, it needs to be specified per concrete bean definition. Inner bean definitions inherit the singleton status of their containing bean definition, unless explicitly specified: The