@Configuration

public class BeanConfig {

    //只有一个类时，大括号可以省略

    //如果WindowsCondition的实现方法返回true，则注入这个bean

    @Conditional({WindowsCondition.class})

    @Bean(name = "bill")

    public Person person1(){

        return new Person("Bill Gates",62);

    }

    //如果LinuxCondition的实现方法返回true，则注入这个bean

    @Conditional({LinuxCondition.class})

    @Bean("linus")

    public Person person2(){

        return new Person("Linus",48);

    }

}

public class LinuxCondition implements Condition {

    @Override

    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {

        Environment environment = conditionContext.getEnvironment();

        String property = environment.getProperty("os.name");

        if (property.contains("Linux")){

            return true;

        }

        return false;

    }

}

//RedisOperBean依赖redisTemplate

@Component

@ConditionalOnBean(name="redisTemplate")

public class RedisOperBean {

  private final RedisTemplate redisTemplate;

  public RedisOperBean(RedisTemplate redisTemplate) {

      // ...

  }

}

@Configuration

@ConditionalOnClass({ Feign.class })

@ConditionalOnProperty(value = "feign.oauth2.enabled", havingValue = "true", matchIfMissing = true)

public class OAuth2FeignAutoConfiguration {

    @Bean

    @ConditionalOnBean(OAuth2ClientContext.class)

    public RequestInterceptor oauth2FeignRequestInterceptor(OAuth2ClientContext oauth2ClientContext) {

        return new OAuth2FeignRequestInterceptor(oauth2ClientContext);

    }

}

@Bean

    @ConditionalOnMissingBean(name = "imageValidateCodeGenerator")

    public ValidateCodeGenerator imageValidateCodeGenerator() {

        ImageCodeGenerator codeGenerator = new ImageCodeGenerator();

        codeGenerator.setSecurityProperty(securityProperties);

        return codeGenerator;

    }

@Configuration

@ConditionalOnExpression("${enabled:false}")

public class BigpipeConfiguration {

    @Bean

    public OrderMessageMonitor orderMessageMonitor(ConfigContext configContext) {

        return new OrderMessageMonitor(configContext);

    }

}

@ConditionalOnExpression("${mq.cumsumer.enabled}==1&&${rabbitmq.comsumer.enabled:true}")

@ConditionalOnExpression("'${mq.comsumer}'.equals('rabbitmq')")

@Bean

@ConditionalOnResource(resources="classpath:shiro.ini")

protected Realm iniClasspathRealm(){

}