Resource 추상화

특징

java.net.URL을 추상화 한 것.

java.net.URL을 resource라는 클래스로 감싸서 실제 low레벨에 접근하는 기능을 추상화

스프링 내부에서 많이 사용하는 인터페이스.

추상화 한 이유

클래스패스 기준으로 리소스 읽어오는 기능 부재

ServletContext를 기준으로 상대 경로로 읽어오는 기능 부재

새로운 핸들러를 등록하여 특별한 URL 접미사를 만들어 사용할 수는 있지만 구현이 복잡하고 편의성 메소드가 부족하다.

Resouce 상속받은 인터페이스

public interface Resource extends InputStreamSource { /** * Return whether this resource actually exists in physical form. * This method performs a definitive existence check, whereas the * existence of a {@code Resource} handle only guarantees a * valid descriptor handle. */ boolean exists(); /** * Return whether the contents of this resource can be read, * e.g. via {@link #getInputStream()} or {@link #getFile()}. * Will be {@code true} for typical resource descriptors; * note that actual content reading may still fail when attempted. * However, a value of {@code false} is a definitive indication * that the resource content cannot be read. * @see #getInputStream() */ boolean isReadable(); /** * Return whether this resource represents a handle with an open * stream. If true, the InputStream cannot be read multiple times, * and must be read and closed to avoid resource leaks. * Will be {@code false} for typical resource descriptors. */ boolean isOpen(); /** * Return a URL handle for this resource. * @throws IOException if the resource cannot be resolved as URL, * i.e. if the resource is not available as descriptor */ URL getURL() throws IOException; /** * Return a URI handle for this resource. * @throws IOException if the resource cannot be resolved as URI, * i.e. if the resource is not available as descriptor */ URI getURI() throws IOException; /** * Return a File handle for this resource. * @throws IOException if the resource cannot be resolved as absolute * file path, i.e. if the resource is not available in a file system */ File getFile() throws IOException; /** * Determine the content length for this resource. * @throws IOException if the resource cannot be resolved * (in the file system or as some other known physical resource type) */ long contentLength() throws IOException; /** * Determine the last-modified timestamp for this resource. * @throws IOException if the resource cannot be resolved * (in the file system or as some other known physical resource type) */ long lastModified() throws IOException; /** * Create a resource relative to this resource. * @param relativePath the relative path (relative to this resource) * @return the resource handle for the relative resource * @throws IOException if the relative resource cannot be determined */ Resource createRelative(String relativePath) throws IOException; /** * Determine a filename for this resource, i.e. typically the last * part of the path: for example, "myfile.txt". * Returns {@code null} if this type of resource does not * have a filename. */ String getFilename(); /** * Return a description for this resource, * to be used for error output when working with the resource. * Implementations are also encouraged to return this value * from their {@code toString} method. * @see Object#toString() */ String getDescription(); }

getInputStream()

exitst() : 존재하는지

isOpen() : 열려잇는지

getDescription(): 전체 경로 포함한 파일 이름 또는 실제 URL

구현

UrlResource: java.net.URL 참고, 기본으로 지원하는 프로토콜 http, https, ftp, file, jar.

ClassPathResource: 지원하는 접두어 classpath:

FileSystemResource

ServletContextResource: 웹 애플리케이션 루트에서 상대 경로로 리소스 찾는다.

읽어들이는 리소스타입이 애플리케이션컨텍스트 타입에 따라 결정이된다.

리소스 읽어오기

@Controller public class HomeController { @Autowired ResourceLoader resourceloader; @RequestMapping(value = "/", method = RequestMethod.GET) public String home(Locale locale, Model model) { Resource resource = resourceloader.getResource("classpath:test.txt"); // class path기준으로 resource 가져오기 Object classPathxmlResource = new ClassPathXmlApplicationContext("classpath:test.txt"); // filesystem경로 기준으로 resource 가져오기 Object FileSystem = new ClassPathXmlApplicationContext("classpath:test.txt"); return "home"; } }

Resource의 타입은 locaion 문자열과 ApplicationContext 의 타입타입에 따라 결정 된다.

ClassPathXmlApplicationContext -> ClassPathResource FileSystemXmlApplicationContext -> FileSystemResource WebApplicationContext -> ServletContextResource

ApplicationContext 의 타입에 타입에 상관없이 상관없이 리소스 리소스 타입을 타입을 강제하려면 강제하려면 java.net.URL 접두어 접두어 (+ classpath:) 중 하나를 하나를 사용할 사용할 수 있다있다 .

classpath : me/whiteship/config.xml -> ClassPathResource file :// /some/resource/path/config.xml -> FileSystemResource 대부분에 경우에 웹어플리케이션을 사용하기 때문에 ServletContextResource를 사용하고 있지만 알고쓰는 개발자가 많이 없기 때문에 접두어를 사용하므로써 명시적으로 명시할 수 있다 .

@Controller public class HomeController { @Autowired ResourceLoader resourceloader; @Autowired ApplicationContext applicationContext; @RequestMapping(value = "/", method = RequestMethod.GET) public String home(Locale locale, Model model) throws IOException { Resource resource = applicationContext.getResource("classpath:test.txt"); System.out.println("resource Class : " + resource.getClass()); System.out.println("applicationContext Class : " + applicationContext.getClass()); System.out.println("resource.exists() : " + resource.exists()); System.out.println("resource.getDescription() : " + resource.getDescription()); System.out.println("resource.getURI() : " + resource.getURI()); return "home"; } }

resource Class : class org.springframework.core.io.ClassPathResource applicationContext Class : class org.springframework.web.context.support.XmlWebApplicationContext resource.exists() : true resource.getDescription() : class path resource [test.txt] resource.getURI() : file:/C:/spring/workspace/study/.metadata/.plugins/org.eclipse.wst.server.core/tmp1/wtpwebapps/study/WEB-INF/classes/test.txt

from http://rlawls1991.tistory.com/50 by ccl(A) rewrite - 2020-03-23 13:54:24