Spring注解系列六：组件注册-@Conditional

1、创建配置类

@Configuration
public class MainConfig2 {

	/**
	 * @Conditional({Condition}) ： 按照一定的条件进行判断，满足条件给容器中注册bean
	 * 如果系统是windows，给容器中注册("bill")
	 * 如果是linux系统，给容器中注册("linus")
	 */
	@Conditional(WindowsCondition.class)
	@Bean("bill")
	public Person person01(){
		return new Person("Bill Gates",62);
	}
	
	@Conditional(LinuxCondition.class)
	@Bean("linus")
	public Person person02(){
		return new Person("linus", 48);
	}
}

2、创建Condition（条件）接口的实现类

//判断是否windows系统
public class WindowsCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		Environment environment = context.getEnvironment();
		String property = environment.getProperty("os.name");
		if(property.contains("Windows")){
			return true;
		}
		return false;
	}

}

//判断是否linux系统
public class LinuxCondition implements Condition {

	/**
	 * ConditionContext：判断条件能使用的上下文（环境）
	 * AnnotatedTypeMetadata：注释信息
	 */
	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		// 判断是否linux系统
		//1、能获取到ioc使用的beanfactory
		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
		//2、获取类加载器
		ClassLoader classLoader = context.getClassLoader();
		//3、获取当前环境信息
		Environment environment = context.getEnvironment();
		//4、获取到bean定义的注册类
		BeanDefinitionRegistry registry = context.getRegistry();
		
		String property = environment.getProperty("os.name");
		
		//可以判断容器中的bean注册情况，也可以给容器中注册bean
		boolean definition = registry.containsBeanDefinition("person");
		if(property.contains("linux")){
			return true;
		}
		return false;
	}

}

3、测试

@Test
public void test03(){
	AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig2.class);
	String[] namesForType = applicationContext.getBeanNamesForType(Person.class);
	ConfigurableEnvironment environment = applicationContext.getEnvironment();
	//动态获取环境变量的值；Windows 10
	String property = environment.getProperty("os.name");
	System.out.println(property);
	for (String name : namesForType) {
		System.out.println(name);
	}
	
	Map<String, Person> persons = applicationContext.getBeansOfType(Person.class);
	System.out.println(persons);
}

4、在类上添加@Conditional注解

@Configuration
//类中组件统一设置。满足当前条件，这个类中配置的所有bean注册才能生效；
@Conditional(LinuxCondition.class)
public class MainConfig2 {
}