spring注解@Conditional

@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("[email protected]");
        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