BeanFactory与ApplicationContext的区别

BeanFactory是Spring底层IOC容器;

ApplicationContext是具备应用特性的BeanFactory超集;

public class DependencyInjectionDemo { public static void main(String[] args) { // 配置 XML 配置文件 // 启动 Spring 应用上下文 // BeanFactory beanFactory = new ClassPathXmlApplicationContext // ("classpath:META-INF/dependency-injection-context.xml"); ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:META-INF/dependency-injection-context.xml"); // 依赖来源一：自定义 Bean UserRepository userRepository = applicationContext .getBean("userRepository", UserRepository.class); // System.out.println(userRepository.getUsers()); whoIsIocContainer(userRepository, applicationContext); // 依赖来源二：依赖注入（内建依赖）-> DefaultListableBeanFactory System.out.println(userRepository.getBeanFactory()); ObjectFactory<ApplicationContext> userObjectFactory = userRepository.getObjectFactory(); // ApplicationContext System.out.println(userObjectFactory.getObject()); // true System.out.println("内建 Bean 对象：" + (userObjectFactory.getObject() == applicationContext)); // 依赖查找 (错误) // System.out.println(applicationContext // .getBean(BeanFactory.class)); // 依赖来源三：容器内建 Bean Environment environment = applicationContext.getBean(Environment.class); System.out.println("获取 Environment 类型的 Bean：" + environment); } private static void whoIsIocContainer(UserRepository userRepository, ApplicationContext applicationContext) { // ConfigurableApplicationContext <- ApplicationContext <- BeanFactory // ConfigurableApplicationContext#getBeanFactory() // 这个表达式为什么会不成立 // 因为 AbstractRefreshableApplicationContext创建了DefaultListableBeanFactory，他们俩个并不是一个对象 // false System.out.println("内建非 Bean 对象（依赖）: " + (userRepository.getBeanFactory() == applicationContext)); // ApplicationContext is BeanFactory } }

执行结果:

内建非 Bean 对象（依赖）: false org.springframework.beans.factory.support.DefaultListableBeanFactory@124c278f: defining beans [user,superUser,objectFactory,userRepository]; root of factory hierarchy org.springframework.context.support.ClassPathXmlApplicationContext@6fb554cc, started on Thu Oct 08 17:01:25 CST 2020 内建 Bean 对象：true 获取 Environment 类型的 Bean：StandardEnvironment {activeProfiles=[], defaultProfiles=[default], propertySources=[PropertiesPropertySource {name='systemProperties'}, SystemEnvironmentPropertySource {name='systemEnvironment'}]}