Spring---条件注解@Conditional

Posted 2020-11-22 anpeiyong

1、概述

　　　　1.1、Spring4  提供了一个更通用的  基于条件的Bean的创建，即使用@Conditional注解；

　　　　1.2、案例

package com.an.config;

import com.an.conditon.WindowsCondition;
import com.an.conditon.WindowsListService;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;

/**
 * @description:
 * @author: anpeiyong
 * @date: Created in 2019/11/20 20:27
 * @since:
 */
@Configuration
public class ConditionConfig {

    @Bean
    @Conditional(value = WindowsCondition.class)
    WindowsListService listService(){
        return new WindowsListService();
    }
}

　　

package com.an.conditon;

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;

/**
 * @description:
 * @author: anpeiyong
 * @date: Created in 2019/11/20 20:24
 * @since:
 */
public class WindowsCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        return context.getEnvironment().getProperty("os.name").contains("Windows");
    }
}

　　

package com.an.conditon;

/**
 * @description:
 * @author: anpeiyong
 * @date: Created in 2019/11/20 20:26
 * @since:
 */
public class WindowsListService {

    public String listCmd(){
        return "dir";
    }
}

　　

package com.an.main;

import com.an.conditon.WindowsListService;
import com.an.config.ConditionConfig;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * @description:
 * @author: anpeiyong
 * @date: Created in 2019/11/20 20:29
 * @since:
 */
public class ConditionMainTest {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext annotationConfigApplicationContext=new AnnotationConfigApplicationContext(ConditionConfig.class);
        WindowsListService windowsListService=annotationConfigApplicationContext.getBean(WindowsListService.class);
        System.out.println(annotationConfigApplicationContext.getEnvironment().getProperty("os.name")+"该系统下的命令："+windowsListService.listCmd());
    }
}

结果：
Windows 10该系统下的命令：dir