How does SpringBoot read YML, yaml, and properties files?
yml,yaml,properties三种文件都是用来存放配置的文件,一些静态数据,配置的数据都会存放到里边。但是有的时候我们不仅仅需要存储静态数据,还需要从文件中读取数据出来。这三种文件都放在项目--》src--》main--》resource下边。如果resource里边需要存放其他文件的话,会在resource里边创建一个config包。将配置文件存放其中。
1.在项目中新建配置文件,文件存放地址
bootstrap.yml是SpringBoot程序的一个配置文件,在项目启动前就会被加载,将数据加载后,方便后续使用。一般放置一些关键性的数据:数据库连接数据,Redis消息队列配置数据,Hikari 连接池配置、mybatis-plus配置信息、日志信息等。
配置文件写好后,需要加入下边这一段配置,激活配置文件。指定激活配置文件,可以用于不同环境激活不同的配置文件。
#启动配置文件(开发、生成) profiles: active: dev
2.配置文件中写入相关配置
除了放置必要的配置,还可以放置一些系统中,静态化的数据,可以写入配置文件中,在读取出来使用。
global: upload: maxSize: 100MB location: /var/uploads
属性后边需要空一格在写,不然会报错
3.创建一个类来接收这些配置
接收这些配置到文件,将配置文件中的属性值自动注入到Java类中,避免手写的麻烦,使用注释解放了双手,很好的接收文件。
@Data @Component @ConfigurationProperties(prefix = "global.upload") public class UploadProperties { private String location; private String maxSize; }
@ConfigurationProperties 是 Spring Boot 中用于从配置文件读取配置属性的注解。
当你使用 @ConfigurationProperties(prefix = "global.upload")注解的时候,你可以读取配置文件中以 "global.upload" 为前缀的属性,并将这些属性映射到一个 Java Bean 中。
使用 @ConfigurationProperties 注解可以更方便地读取多个属性,并且可以使用内置的验证和转换功能。
4.举例获取并且使用配置文件里边的数据
@Service public class FileServiceImpl implements FileService { @Autowired private UploadProperties uploadProperties ; @Override public String uploadFile(MultipartFile file) throws Exception { String fileUrl=null; if (!( uploadProperties.getLocation() ==null)) { fileUrl = uploadProperties.getLocation().replace("/", File.separator) + fileAdd + File.separator + System.currentTimeMillis() + "." +uploadProperties.getMaxSize(); }else { fileUrl = "D:\\uploadFiles\\report\\" + fileAdd + File.separator + System.currentTimeMillis() + "." + uploadProperties.getMaxSize(); } } }
这一个例子中,Spring的@Service注解标注的服务类,其中实现了一个文件上传的方法uploadFile,具体功能是将上传的MultipartFile类型的文件保存到指定的位置,然后返回文件的访问地址。
在该类中通过@Autowired注解将UploadProperties类型的Bean注入进来,UploadProperties包含了文件上传相关的配置信息,例如文件上传保存的位置、最大文件大小等。
在uploadFile方法中,首先判断上传文件的保存位置是否为空,如果不为空,则将文件保存到指定位置,否则将文件保存到默认位置。文件保存的位置是由uploadProperties.getLocation()和fileAdd拼接而成,其中fileAdd是一个自定义的子目录名称,用于区分不同的上传场景。
最后,根据保存的文件名和位置拼接成文件的访问地址,并将其返回。
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