spring注册bean 方式

1. XML 配置方式

public class Student {
}
 
<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.xsd">
	<bean id="student" class="com.wsh.injectbean.method_01.Student"/>
</beans>
 
/**
 * 第一种方式： XML文件配置
 */
public class Client {
	public static void main(String[] args) {
		ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:spring-config.xml");
		System.out.println(applicationContext.getBean("student"));
	}
}

2. 使用@Component 注解 + @ ComponentScan 包扫描方式

@Component
public class UserHandler {
}
 
@Service
public class UserService {
}
 
@Repository
public class UserDao {
}
 
@Controller
public class UserController {
}
 
@ComponentScan("com.wsh.injectbean.method_02")
@Configuration
public class AppConfig {
}
 
/**
 * 第二种方式： 使用@Component注解 + @ComponentScan包扫描方式
 * 包括@Controler、@Service、@Repository等派生的注解。
 * 为了解决bean太多时，xml文件过大，从而导致膨胀不好维护的问题。在spring2.5中开始支持：@Component、@Repository、@Service、@Controller等注解定义bean。
 * 其实本质上@Controler、@Service、@Repository也是使用@Component注解修饰的。
 * <p>
 * 通常情况下：
 *
 * @Controller：一般用在控制层
 * @Service：一般用在业务层
 * @Repository：一般用在持久层
 * @Component：一般用在公共组件上
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		System.out.println(applicationContext.getBean("userDao"));
		System.out.println(applicationContext.getBean("userService"));
		System.out.println(applicationContext.getBean("userController"));
		System.out.println(applicationContext.getBean("userHandler"));
	}
}

3.@Configuration + @Bean 方式

public class Student {
}
 
@Configuration
public class AppConfig {
 
	@Bean
	public Student student() {
		return new Student();
	}
 
}
 
/**
 * 第三种方式：@Configuration + @Bean方式
 * <p>
 * 通常情况下，如果项目中有使用到第三方类库中的工具类的话，我们都是采用这种方式注册Bean
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		System.out.println(applicationContext.getBean("student"));
	}
}

4. FactoryBean 方式

public class User {
}
 
@Component
public class UserFactoryBean implements FactoryBean<User> {
	@Override
	public User getObject() throws Exception {
		return new User();
	}
 
	@Override
	public Class<?> getObjectType() {
		return User.class;
	}
 
	@Override
	public boolean isSingleton() {
		return true;
	}
}
 
@Configuration
@ComponentScan("com.wsh.injectbean.method_04")
public class AppConfig {
 
}
 
/**
 * 第四种方式：使用FactoryBean
 *
 * FactoryBean在一些框架整合上用的比较多，如Mybatis与Spring的整合中：MapperFactoryBean、SqlSessionFactoryBean等
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		System.out.println(applicationContext.getBean("userFactoryBean"));
		System.out.println(applicationContext.getBean("&userFactoryBean"));
	}
}

5.@Import 方式

public class Student {
}
 
@Import({Student.class})
@Configuration
public class AppConfig {
 
}
 
/**
 * 第五种方式：@Import方式
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		for (String beanDefinitionName : applicationContext.getBeanDefinitionNames()) {
			System.out.println(beanDefinitionName);
		}
		System.out.println("================");
		System.out.println(applicationContext.getBean("com.wsh.injectbean.method_05.Student"));
		System.out.println(applicationContext.getBean("student"));
	}
}

6.@Import + ImportSelector 方式

public class Product {
}
 
public class User {
}
 
public class MyImportSelector implements ImportSelector {
 
	// 指定需要定义bean的类名，注意要包含完整路径，而非相对路径
	@Override
	public String[] selectImports(AnnotationMetadata importingClassMetadata) {
		return new String[]{"com.wsh.injectbean.method_06.Product", "com.wsh.injectbean.method_06.User"};
	}
 
}
 
@Import({MyImportSelector.class})
@Configuration
public class AppConfig {
 
}
 
/**
 * 第六种方式：@Import + ImportSelector方式
 * <p>
 * ImportSelector接口的好处主要有以下两点：
 * <p>
 * 1.把某个功能的相关类放到一起，方面管理和维护。
 * 2.重写selectImports方法时，能够根据条件判断某些类是否需要被实例化，或者某个条件实例化这些bean，其他的条件实例化那些bean等,我们能够非常灵活的定制化bean的实例化。
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		for (String beanDefinitionName : applicationContext.getBeanDefinitionNames()) {
			System.out.println(beanDefinitionName);
		}
		System.out.println("================");
		System.out.println(applicationContext.getBean("com.wsh.injectbean.method_06.Product"));
		try {
			System.out.println(applicationContext.getBean("product"));
		} catch (Exception e) {
			e.printStackTrace();
		}
		System.out.println("================");
		System.out.println(applicationContext.getBean("com.wsh.injectbean.method_06.User"));
		try {
			System.out.println(applicationContext.getBean("user"));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

7.@Import + ImportBeanDefinitionRegistrar 方式

public class User {
}
 
 
public class Product {
}
 
public class CustomImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
	@Override
	public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
		// 可以自定义bean的名称、作用域等很多参数
		registry.registerBeanDefinition("user", new RootBeanDefinition(User.class));
		RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(Product.class);
		rootBeanDefinition.setScope(BeanDefinition.SCOPE_SINGLETON);
		registry.registerBeanDefinition("product", rootBeanDefinition);
	}
}
 
@Import({CustomImportBeanDefinitionRegistrar.class})
@Configuration
public class AppConfig {
 
}
 
/**
 * 第七种方式：@Import + ImportBeanDefinitionRegistrar方式
 *
 * 可以自定义bean的名称、作用域等很多参数, 像我们常见的Spring Cloud中的Feign，就使用了ImportBeanDefinitionRegistrar
 * class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware, EnvironmentAware {
 * 		public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
 *         this.registerDefaultConfiguration(metadata, registry);
 *         this.registerFeignClients(metadata, registry);
 *     }
 * }
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		System.out.println(applicationContext.getBean("product"));
		System.out.println(applicationContext.getBean("user"));
	}
}

8. BeanDefinitionRegistryPostProcessor 方式

public class User {
}
 
@Component
public class CustomBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
	@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
		registry.registerBeanDefinition("user", new RootBeanDefinition(User.class));
	}
 
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
	}
}
 
@Configuration
@ComponentScan("com.wsh.injectbean.method_08")
public class AppConfig {
 
}
 
/**
 * 第八种方式：BeanDefinitionRegistryPostProcessor方式
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		System.out.println(applicationContext.getBean("user"));
	}
}

9. BeanFactoryPostProcessor 方式

public class Product {
}
 
@Component
public class CustomBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		DefaultListableBeanFactory registry = (DefaultListableBeanFactory) beanFactory;
		registry.registerBeanDefinition("product", new RootBeanDefinition(Product.class));
	}
}
 
@Configuration
@ComponentScan("com.wsh.injectbean.method_09")
public class AppConfig {
 
}
 
/**
 * 第九种方式：BeanFactoryPostProcessor方式
 * <p>
 * 1. BeanDefinitionRegistryPostProcessor: 侧重于bean的注册;
 * 2. BeanFactoryPostProcessor:侧重于对已经注册的bean的属性进行修改，虽然也可以注册bean;
 */
public class Client {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
		System.out.println(applicationContext.getBean("product"));
	}
}

#Spring

spring注册bean 方式

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作者

Administrator

发布于

2024年06月11日

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