spring注解第03课 按条件加载Bean @Conditional

package com.atguigu.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;

import com.atguigu.bean.Person;
import com.atguigu.condition.LinuxCondition;
import com.atguigu.condition.WindowsCondition;
import com.atguigu.test.IOCTest;

//类中组件统一设置。满足当前条件，这个类中配置的所有bean注册都能生效；
@Conditional({WindowsCondition.class})
@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.条件1

package com.atguigu.condition;

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;

//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) {
        // 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();

        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.条件2

package com.atguigu.condition;

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

//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;
    }

}

原文地址：https://www.cnblogs.com/guchunchao/p/9691933.html