spring注解@Conditional

「爱情、让人受尽委屈。」 2022-05-17 12:40 292阅读 0赞

@Conditional注解在spring底层被大量使用。

@Conditional可以被加在类上或者是方法上

接下来看具体的用法：

从spring环境中获取当前系统的类型，如果是Window系统则注册bill类，如果是Linux系统则注册linux类

配置类：

其中WindowCondition.class和LiunxCondition.class，是我自己实现的Condition类

package com.annotation.config;
    
    import com.annotation.conditional.LinuxCondition;
    import com.annotation.conditional.WindowCondition;
    import com.annotation.entities.Person;
    import org.springframework.beans.factory.config.ConfigurableBeanFactory;
    import org.springframework.context.annotation.*;
    
    @Configuration
    //将conditional注解放在类上，若不满足条件，则类中所有的bean都不会被注册到IOC容器中
    //@Conditional({WindowCondition.class})
    public class MainConfig2 {
    
    //    @Scope(value = WebApplicationContext.SCOPE_REQUEST)//request
    //    @Scope(value = WebApplicationContext.SCOPE_GLOBAL_SESSION)//session
    //    @Scope(value = ConfigurableBeanFactory.SCOPE_PROTOTYPE)//prototype
        @Lazy
        @Scope(value = ConfigurableBeanFactory.SCOPE_SINGLETON)//singleton
        @Bean(name = "person")
        public Person person(){
            Person person = new Person();
            person.setName("lqf");
            person.setEmail("lqf@163.com");
            return person;
        }
    
        /**
         * @Conditational按照条件给IOC容器中注册bean
         */
        @Conditional({WindowCondition.class})
        @Bean(name = "bill")
        public Person person01(){
            return new Person(1,"bill","bill@email");
        }
    
        @Conditional({LinuxCondition.class})
        @Bean(name = "linus")
        public Person person02(){
            return new Person(2,"linus","linus@email");
        }
    
    }

下面是两个Condition类，需要实现spring的Condition接口，重写metches方法，该方法返回出则注该bean，返回false不注册该bean。

package com.annotation.conditional;
    
    import org.springframework.context.annotation.Condition;
    import org.springframework.context.annotation.ConditionContext;
    import org.springframework.core.type.AnnotatedTypeMetadata;
    
    public class WindowCondition implements Condition {
    
        @Override
        public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
            String osName = context.getEnvironment().getProperty("os.name");
            if (osName.contains("Windows")){
                return true;
            }
            return false;
        }
    }

package com.annotation.conditional;
    
    
    import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
    import org.springframework.beans.factory.support.BeanDefinitionRegistry;
    import org.springframework.context.annotation.Condition;
    import org.springframework.context.annotation.ConditionContext;
    import org.springframework.core.env.Environment;
    import org.springframework.core.type.AnnotatedTypeMetadata;
    
    public class LinuxCondition implements Condition {
    
        /**
         * ConditionContext:判断条件能使用的上下文环境
         * AnnotatedTypeMetadata:注解信息
         */
        @Override
        public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
            //获取IOC容器使用的beanfactory
            ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
            //获取容器中是否有person的声明（容器中所有的bean先声明，然后再实例，所以使用该方法不用担心bean还没有被IOC声明而获取不到）
            System.out.println("是否包含person的定义" + beanFactory.containsBean("person"));
            //获取类加载器
            ClassLoader classLoader = context.getClassLoader();
            //获取当前环境信息
            Environment environment = context.getEnvironment();
            //获取bean定义的注册类
            BeanDefinitionRegistry registry = context.getRegistry();
            String osName = environment.getProperty("os.name");
            System.out.println(osName);
            if (osName.contains("Linux")){
                return true;
            }
            return false;
        }
    }

下面是测试方法：

@Test
        public void testConditational(){
            setApplicationContext2();
            String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
            for (String beanDefinitionName : beanDefinitionNames) {
                System.out.println(beanDefinitionName);
            }
        }

若果想要测试linux系统可以在运行测试类的时候为测试类添加参数，-Dos.name=linux