Spring——关于Bean以及自动配置

作用域

描述

适用场景

示例注解

singleton（默认）

整个容器共享一个 Bean 实例，所有依赖注入的都是同一个对象

无状态的全局服务（如工具类、配置类）

@Service、@Responsitory

prototype（原型）

每次请求都创建一个新 Bean 实例，依赖注入时也会生成新对象

需要保持独立状态的Bean（购物车）

@Scope("prototype")

request（web）

每个 HTTP 请求创建一个新 Bean，请求结束后销毁

存储请求相关的数据（如用户表单提交）

@RequestScope

session（Web）

每个用户会话（Session）创建一个 Bean，会话过期后销毁

存储用户登录状态、购物车

@SeesionScope

application（Web）

整个 Web 应用共享一个 Bean（类似 singleton，但范围是 ServletContext）

全局缓存、共享资源

@ApplicationScope

websocket（Web）

每个 WebSocket 会话一个 Bean，连接关闭后销毁

实时通信（如聊天室）

@Scope("websocket")

Java
@Configuration
public class DogConfig {

//下面演示的是Bean的作用域
//单例作用域，spring默认
@Bean
//标记为singleton的方式有两种
//    @Scope(ConfigurableBeanFactory.SCOPE_SINGLETON)
@Scope("singleton")
public Dog singletonDog(){
return new Dog();
}
//多例作用域，即原型
@Bean
//同样可以在scope里写prototype
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public Dog prototypeDog(){
return new Dog();
}
//请求作用域
@Bean
@RequestScope
public Dog requestDog(){
return new Dog();
}
//会话作用域
@Bean
@SessionScope
public Dog sessionDog(){
return new Dog();
}
//全局作用域
@Bean
@ApplicationScope
public Dog applicationDog(){
return new Dog();
}
}

TypeScript
@RestController
@RequestMapping("/scope")
public class DogController {
@Resource(name ="singletonDog")
private Dog singletonDog;

@Resource(name ="prototypeDog")
private Dog prototypeDog;

@Resource(name ="requestDog")
private Dog requestDog;

@Resource(name ="sessionDog")
private Dog sessionDog;

@Resource(name ="singletonDog")
private Dog applicationDog;

@Autowired
private ApplicationContext context;

@RequestMapping("/singletonDog")
public String singleton(){
Dog dog=(Dog) context.getBean("singletonDog");
return "注入对象："+singletonDog.toString()+" "+"上下文对象："+dog.toString();
}
@RequestMapping("/prototypeDog")
public String prototypeDog(){
Dog dog=(Dog) context.getBean("prototypeDog");
return "注入对象："+prototypeDog.toString()+" "+"上下文对象："+dog.toString();
}

@RequestMapping("/requestDog")
public String requestDog(){
Dog dog=(Dog) context.getBean("requestDog");
return "注入对象："+requestDog.toString()+" "+"上下文对象："+dog.toString();
}

@RequestMapping("/sessionDog")
public String sessionDog(){
Dog dog=(Dog) context.getBean("sessionDog");
return "注入对象："+sessionDog.toString()+" "+"上下文对象："+dog.toString();
}

@RequestMapping("/applicationDog")
public String applicationDog(){
Dog dog=(Dog) context.getBean("applicationDog");
return "注入对象："+applicationDog.toString()+" "+"上下文对象："+dog.toString();
}
}

Java
@Componen
public class BeanLifeComponent implements BeanNameAware {

private Dog dog;

//以下为模拟Bean的生命周期

public BeanLifeComponent(Dog dog) {
System.out.println("执行构造函数：");
}

@Autowired
public void setDog(Dog dog) {
this.dog = dog;
System.out.println("构造函数执行完毕，完成属性装配：");
}

@PostConstruct
public void init(){
System.out.println("执行初始化方法：");
}

@Override
public void setBeanName(String name) {
System.out.println("执行setBeanName："+name);
}

public void use(){
System.out.println("执行使用Use方法：");
}
@PreDestroy
public void destroy(){
System.out.println("执行destroy方法");
}
}

Java
@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
BeanLifeComponent bean = context.getBean(BeanLifeComponent.class);
bean.use();
}
}        

TypeScript
@Component
public class AutoConfig {
public void use(){
System.out.println("autoConfig use……");
}
}

TypeScript
@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
AutoConfig bean = context.getBean(AutoConfig.class);
bean.use();
}
}        

Java
//也可以填入数组
//@ComponentScan({"com.nanxi.autoconfig"，"com.nanxi.autoconfig2"})
@ComponentScan("com.nanxi.autoconfig")
@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
AutoConfig bean = context.getBean(AutoConfig.class);
bean.use();
}
}        

TypeScript
//也可以填入数组
//@Import({AutoConfig.class, AutoConfig2.class})
@Import(AutoConfig.class)
@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
AutoConfig bean = context.getBean(AutoConfig.class);
bean.use();
}
}        

Java
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(MyImport.class)
public @interface EnableAutoConfig {

}

Java
@EnableAutoConfig
@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
AutoConfig bean = context.getBean(AutoConfig.class);
bean.use();
}
}        

TypeScript
public class MyImport implements ImportSelector {
@Override
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
return new String[]{"com.nanxi.autoconfig.AutoConfig"};
}
}

Java
@Import(MyImport.class)
@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
AutoConfig bean = context.getBean(AutoConfig.class);
bean.use();
}
}        

TypeScript
public class MyRegister implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
GenericBeanDefinition beanDefinition=new GenericBeanDefinition();
beanDefinition.setBeanClass(AutoConfig.class);
registry.registerBeanDefinition("autoConfig",beanDefinition);
}
}

Java
@Import(MyRegister.class)
@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
AutoConfig bean = context.getBean(AutoConfig.class);
bean.use();
}
}        

Java
com.nanxi.autoconfig.AutoConfig
com.nanxi.autoconfig.AutoConfig2

Java

@SpringBootApplication
public class SpringPrincipleApplication {

public static void main(String[] args) {
ApplicationContext context =SpringApplication.run(SpringPrincipleApplication.class, args);
AutoConfig bean = context.getBean(AutoConfig.class);
bean.use();
}
}        

JSON
@Override
public String[] selectImports(AnnotationMetadata annotationMetadata) {
AutoConfigurationEntry entry = getAutoConfigurationEntry(annotationMetadata);
return StringUtils.toStringArray(entry.getConfigurations());
}

Java
@Configuration
@ConditionalOnClass(DataSource.class)
@ConditionalOnMissingBean(DataSource.class)
@EnableConfigurationProperties(DataSourceProperties.class)
public class DataSourceAutoConfiguration {

@Bean
public DataSource dataSource(DataSourceProperties properties) {
return new HikariDataSource(properties);
}
}

TypeScript
@Configuration
@ConditionalOnProperty(name = "my.feature.enabled", havingValue = "true")
public class MyFeatureAutoConfiguration {

@Bean
public MyService myService() {
return new MyServiceImpl();
}
}

spring.factories 文件
org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.example.autoconfig.MyFeatureAutoConfiguration