1. @Conditional注解根据满足的条件来创建一个特定的Bean

2. 示例，以不同的操作系统为条件，通过实现Condition接口，并重写matches方法来构造判断条件，若在Windows系统下运行程序，则输出命令dir, 若在Linux系统下运行则输出 ls

3. 编写判断Windows的条件类

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.stereotype.Service;
@Service
public class WindowsCondition implements Condition {@Overridepublic boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {return context.getEnvironment().getProperty("os.name").contains("Windows");}
}

4. 编写判断Linux的条件类

import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.stereotype.Service;
@Service
public class LinuxCondition implements Condition {@Overridepublic boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {return context.getEnvironment().getProperty("os.name").contains("Linux");}
}

5. 不同系统下Bean的共同接口

public interface ListCmdService {public String showCmd();
}

6. Windows系统下创建的Bean类

public class ListWindowsCmd implements ListCmdService {@Overridepublic String showCmd() {return "dir";}
}

7. Linux系统下创建的Bean类

public class ListLinuxCmd implements ListCmdService {@Overridepublic String showCmd() {return "ls";}
}

8. 配置类

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
@Configuration
public class ConditionConfig {@Bean@Conditional(WindowsCondition.class)public ListCmdService listWindowsCmd() {return new ListWindowsCmd();}@Bean@Conditional(LinuxCondition.class)public ListCmdService listLinuxCmd() {return new ListLinuxCmd();}
}

代码解释：@Conditional注解，符合WindowsCondition条件则创建ListWindowsCmd实例，符合LinuxCondition条件则创建ListLinuxCmd实例

9. 运行

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {public static void main(String[] args) {AnnotationConfigApplicationContext context = newAnnotationConfigApplicationContext(ConditionConfig.class);ListCmdService listCmdService = context.getBean(ListCmdService.class);System.out.println(context.getEnvironment().getProperty("os.name") +" 系统命令：" + listCmdService.showCmd());}
}