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 persons = applicationContext.getBeansOfType(Person.class);
    System.out.println(persons);
}

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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 {
}

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