随手记录4:spring上下文ApplicationContext 获取和使用;

简介关于ApplicationContext 获取关于ApplicationContext 使用1.UserService .java2.FactoryBeanConfig .java结论

简介

项目中基本上好多对象都是交给spring管理的; 但是有些静态的工具类中想获取该对象又不能通过 @Autowired直接注入; 或者有些方法里面需要使用到spring托管的对象; 可以通过ApplicationContext 直接获取;

关于ApplicationContext 获取

获取 方式一: 基于springboot有最简单的获取方式 main方法启动类的入口可以直接获取到applicationContext @SpringBootApplication public class MainApplication { public static void main(String[] args) throws Exception { ApplicationContext applicationContext = SpringApplication.run(MainApplication.class, args); } } 获取方式二: 通过实现ApplicationContextAware 接口然后实现setApplicationContext 方法; @Component public class SpringAware implements ApplicationContextAware { private ApplicationContext applicationContext; @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; } /** *根据spring托管对象的beanName获取实力对象; * @author khy * @createTime 2020年9月3日下午1:47:03 * @param name * @return */ public <T>T getBeanByName(String name){ return (T) applicationContext.getBean(name); } } //上述类中属性可以定义成 private static ApplicationContext applicationContext; //静态的,然后在当前方法里面可以通过静态方法获取我们需要的spring管理的各种service/mapper等内容;

关于ApplicationContext 使用

主要是通过spring上下文获取交给spring管理的bean; 还是通过前面写过的文章案例 FactoryBean 的使用

1.UserService .java

类中通过@service注解初始化对象

Service("userService") public class UserService { private String userName="UserService命名小康康"; public UserService() { System.out.println(this); System.out.println("UserService初始化"); } private UserService(String userName) { this.userName = userName; } public static UserService getInstance(String userName){ return new UserService(userName); } public String say(String detail) { System.out.println("用户{"+userName+"} say{"+detail+"}"); return "say执行完毕"; } }

2.FactoryBeanConfig .java

通过

@Configuration public class FactoryBeanConfig { @Bean public UserServiceFactoryBean createUserFactoryBean (){ UserServiceFactoryBean bean = new UserServiceFactoryBean("createUserFactoryBean命名小康康"); System.out.println("createUserFactoryBean初始化"); return bean; } @Bean public UserService createUserService (){ UserService bean = UserService.getInstance("createUserService命名小康康"); System.out.println("createUserService初始化"); return bean; } }

@RestController @RequestMapping("/factory") public class FactoryController { @Autowired private SpringAware springAware; @Autowired private UserServiceFactoryBean factoryBean; @Autowired private UserService userService; @Autowired private UserService createUserService; @Autowired private UserService createUserFactoryBean; @RequestMapping("/test") public String test() throws Exception{ System.out.println("///userService执行开始//"); String say = userService.say("注入的userService成功"); UserService getService = springAware.getBeanByName("userService"); say = getService.say("SpringAware获取的的userService成功"); System.out.println("///userService执行结束//"); System.out.println("///createUserService执行开始//"); say = createUserService.say("注入的createUserService成功"); UserService getService1 = springAware.getBeanByName("createUserService"); say = getService1.say("SpringAware获取的的createUserService成功"); System.out.println("///createUserService执行结束//"); System.out.println("///createUserFactoryBean执行开始//"); say = createUserFactoryBean.say("注入的createUserFactoryBean成功"); UserService getService2 = springAware.getBeanByName("createUserFactoryBean"); say = getService2.say("SpringAware获取的的createUserFactoryBean成功"); System.out.println("///createUserService执行结束//"); /** * 上面都是直接获取的UserService * UserService createUserFactoryBean 是通过工厂UserServiceFactoryBean创建的 * 但是如果想拿到工厂类本身则通过ApplicationContext 获取的时间需要添加& */ System.out.println("///工厂类UserServiceFactoryBean执行开始//"); say = factoryBean.getObject().say("注入的createUserFactoryBean的UserServiceFactoryBean成功"); UserServiceFactoryBean getFactory = springAware.getBeanByName("&createUserFactoryBean"); getFactory.getObject().say("SpringAware获取的的UserServiceFactoryBean成功"); System.out.println("///工厂类UserServiceFactoryBean执行结束//"); return "执行完毕了"+say; } }

结论

通过applicationContext 获取spring中托管的对象内容; 案例中是通过spring托管的beanName 来获取的指定对象的内容 案例中通过方法获取的对象和通过@Autowired注入的(beanName相同的情况下是同一个内存对象) ******想获取FactoryBean 本身的对象则需要在beanName前面添加& 例如本文的案例中的 UserServiceFactoryBean 是UserService的工厂类 在FactoryBeanConfig 初始化,虽然看似初始化的UserServiceFactoryBean ,但是其实获取的到的是 其实是目标对象内容, 所以applicationContext 通过beanName=createUserFactoryBean 获取到的是UserService对象; 要获取UserServiceFactoryBean类则beanName=&createUserFactoryBean @Bean public UserServiceFactoryBean createUserFactoryBean (){ UserServiceFactoryBean bean = new UserServiceFactoryBean("createUserFactoryBean命名小康康"); System.out.println("createUserFactoryBean初始化"); return bean; }