application.yml实例：

spring:
    redis:
      database: 0
      host: 127.0.0.1

获取方法：

/**
 * @Auther:WangZiBin
 * @Description:
 * @Modified By:
 */
@Configuration
public class JedisConfig{

    private Logger jedisConfigLogger= LoggerFactory.getLogger(JedisConfig.class);

    @Value("${spring.redis.host:#{null}}")
    private String host;

    @Value("${spring.redis.port:#{null}}")
    private Integer port;

    public String getHost() {
        return host;
    }

    public void setHost(String host) {
        this.host = host;
    }

    public Integer getPort() {
        return port;
    }

    public void setPort(Integer port) {
        this.port = port;
    }


}

注意@Configuration注解是必须的，@Component同样适用

@Value("${spring.redis.port:#{null}}")

其中

:#{null}

作用为在取不到对应配置值时，采用默认值null赋值

SpringBoot通过@Value获取application.yml配置文件的属性值