【Spring注解系列04】@Condition条件注解

水深无声 2022-02-26 03:31 417阅读 0赞

# 1.@Condition条件注解 #

满足指定条件，则会加载对应的实例或者类。该注解可以作用于类和方法上。

@Condition类属性值中，对应的类，必须是实现Condition接口的类

## 2.实例 ##

**配置类：**

@Configuration
    public class ConditionalConfig {
    
        /**
         * @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 bill(){
            return new Person("111","Bill Gates");
        }
    
        @Conditional(LinuxCondition.class)
        @Bean("linus")
        public Person linus(){
            return new Person("222","linus");
        }
    
    }

可以通过设置虚拟机dos名称来改变系统名称。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzM3MTA3MDIy_size_16_color_FFFFFF_t_70][]

**条件类：必须实现Condition接口**

public class LinuxCondition implements Condition {
    
        @Override
        public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
            // TODO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();
    
            System.out.println("environment.getProperty(os.name)---->"+environment.getProperty("os.name"));
            if (environment.getProperty("os.name").contains("Linux")){
                return true;
            }
    
            return false;
        }
    }
    
    
    public class WindowsCondition implements Condition {
    
        @Override
        public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
            Environment environment = context.getEnvironment();
            System.out.println("environment.getProperty(os.name)---->" + environment.getProperty("os.name"));
            if (environment.getProperty("os.name").contains("Windows")) {
                return true;
            }
    
            return false;
        }
    }

**测试类：**

public class ConditionalTest {
    
        public static void main(String[] args) {
            ApplicationContext applicationContext = new AnnotationConfigApplicationContext(ConditionalConfig.class);
    //        Person linus = (Person) applicationContext.getBean("linus");
            Person bill = (Person) applicationContext.getBean("bill");
    //        System.out.println("linus----->"+linus);
            System.out.println("bill----->"+bill);
        }
    }

**测试结果：**

environment.getProperty(os.name)---->Windows 7
    environment.getProperty(os.name)---->Windows 7
    bill----->Person{id='111', name='Bill Gates'}

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzM3MTA3MDIy_size_16_color_FFFFFF_t_70]: /images/20220226/abe376efcd564dbb8880ec04dca5115d.png