关于springboot中classpath:路径使用说明
2024-05-10 18:09:18
1. 案例说明
在 resources下有model.conf文件，在配置文件中使用classpath:做为文件路径
1.1 解决方案
1.1.1 使用ResourcePatternResolver实现
使用classpath:做为路径
通过@value获取配置文件中的路径，后经过ResourcePatternResolver 获取文件
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();Resource resource = resolver.getResource("classpath:model.conf");String path = resource.getFile().getCanonicalPath();
1.1.2 使用 ClassPathResource实现
ClassPathResource resource = new ClassPathResource("model.conf");String path = resource.getFile().getCanonicalPath();
ClassPathResource使用时，文件路径中不存在
classpath:
1.1.3 使用Spring框架中ResourceUtils实现
File file = ResourceUtils.getFile("classpath:model.conf");
String path = file.getCanonicalPath();
2. ResourceUtils使用说明
2.1 源码展示
/*** Utility methods for resolving resource locations to files in the* file system. Mainly for internal use within the framework.** <p>Consider using Spring's Resource abstraction in the core package* for handling all kinds of file resources in a uniform manner.* {@link org.springframework.core.io.ResourceLoader}'s {@code getResource()}* method can resolve any location to a {@link org.springframework.core.io.Resource}* object, which in turn allows one to obtain a {@code java.io.File} in the* file system through its {@code getFile()} method.** @author Juergen Hoeller* @since 1.1.5* @see org.springframework.core.io.Resource* @see org.springframework.core.io.ClassPathResource* @see org.springframework.core.io.FileSystemResource* @see org.springframework.core.io.UrlResource* @see org.springframework.core.io.ResourceLoader*/
public abstract class ResourceUtils {/** Pseudo URL prefix for loading from the class path: "classpath:" */public static final String CLASSPATH_URL_PREFIX = "classpath:";/** URL prefix for loading from the file system: "file:" */public static final String FILE_URL_PREFIX = "file:";/** URL prefix for loading from a jar file: "jar:" */public static final String JAR_URL_PREFIX = "jar:";/** URL prefix for loading from a war file on Tomcat: "war:" */public static final String WAR_URL_PREFIX = "war:";/** URL protocol for a file in the file system: "file" */public static final String URL_PROTOCOL_FILE = "file";/** URL protocol for an entry from a jar file: "jar" */public static final String URL_PROTOCOL_JAR = "jar";/** URL protocol for an entry from a war file: "war" */public static final String URL_PROTOCOL_WAR = "war";/** URL protocol for an entry from a zip file: "zip" */public static final String URL_PROTOCOL_ZIP = "zip";/** URL protocol for an entry from a WebSphere jar file: "wsjar" */public static final String URL_PROTOCOL_WSJAR = "wsjar";/** URL protocol for an entry from a JBoss jar file: "vfszip" */public static final String URL_PROTOCOL_VFSZIP = "vfszip";/** URL protocol for a JBoss file system resource: "vfsfile" */public static final String URL_PROTOCOL_VFSFILE = "vfsfile";/** URL protocol for a general JBoss VFS resource: "vfs" */public static final String URL_PROTOCOL_VFS = "vfs";/** File extension for a regular jar file: ".jar" */public static final String JAR_FILE_EXTENSION = ".jar";/** Separator between JAR URL and file path within the JAR: "!/" */public static final String JAR_URL_SEPARATOR = "!/";/** Special separator between WAR URL and jar part on Tomcat */public static final String WAR_URL_SEPARATOR = "*/";/*** Return whether the given resource location is a URL:* either a special "classpath" pseudo URL or a standard URL.* @param resourceLocation the location String to check* @return whether the location qualifies as a URL* @see #CLASSPATH_URL_PREFIX* @see java.net.URL*/public static boolean isUrl(@Nullable String resourceLocation) {if (resourceLocation == null) {return false;}if (resourceLocation.startsWith(CLASSPATH_URL_PREFIX)) {return true;}try {new URL(resourceLocation);return true;}catch (MalformedURLException ex) {return false;}}/*** Resolve the given resource location to a {@code java.net.URL}.* <p>Does not check whether the URL actually exists; simply returns* the URL that the given location would correspond to.* @param resourceLocation the resource location to resolve: either a* "classpath:" pseudo URL, a "file:" URL, or a plain file path* @return a corresponding URL object* @throws FileNotFoundException if the resource cannot be resolved to a URL*/public static URL getURL(String resourceLocation) throws FileNotFoundException {Assert.notNull(resourceLocation, "Resource location must not be null");if (resourceLocation.startsWith(CLASSPATH_URL_PREFIX)) {String path = resourceLocation.substring(CLASSPATH_URL_PREFIX.length());ClassLoader cl = ClassUtils.getDefaultClassLoader();URL url = (cl != null ? cl.getResource(path) : ClassLoader.getSystemResource(path));if (url == null) {String description = "class path resource [" + path + "]";throw new FileNotFoundException(description +" cannot be resolved to URL because it does not exist");}return url;}try {// try URLreturn new URL(resourceLocation);}catch (MalformedURLException ex) {// no URL -> treat as file pathtry {return new File(resourceLocation).toURI().toURL();}catch (MalformedURLException ex2) {throw new FileNotFoundException("Resource location [" + resourceLocation +"] is neither a URL not a well-formed file path");}}}/*** Resolve the given resource location to a {@code java.io.File},* i.e. to a file in the file system.* <p>Does not check whether the file actually exists; simply returns* the File that the given location would correspond to.* @param resourceLocation the resource location to resolve: either a* "classpath:" pseudo URL, a "file:" URL, or a plain file path* @return a corresponding File object* @throws FileNotFoundException if the resource cannot be resolved to* a file in the file system*/public static File getFile(String resourceLocation) throws FileNotFoundException {Assert.notNull(resourceLocation, "Resource location must not be null");if (resourceLocation.startsWith(CLASSPATH_URL_PREFIX)) {String path = resourceLocation.substring(CLASSPATH_URL_PREFIX.length());String description = "class path resource [" + path + "]";ClassLoader cl = ClassUtils.getDefaultClassLoader();URL url = (cl != null ? cl.getResource(path) : ClassLoader.getSystemResource(path));if (url == null) {throw new FileNotFoundException(description +" cannot be resolved to absolute file path because it does not exist");}return getFile(url, description);}try {// try URLreturn getFile(new URL(resourceLocation));}catch (MalformedURLException ex) {// no URL -> treat as file pathreturn new File(resourceLocation);}}/*** Resolve the given resource URL to a {@code java.io.File},* i.e. to a file in the file system.* @param resourceUrl the resource URL to resolve* @return a corresponding File object* @throws FileNotFoundException if the URL cannot be resolved to* a file in the file system*/public static File getFile(URL resourceUrl) throws FileNotFoundException {return getFile(resourceUrl, "URL");}/*** Resolve the given resource URL to a {@code java.io.File},* i.e. to a file in the file system.* @param resourceUrl the resource URL to resolve* @param description a description of the original resource that* the URL was created for (for example, a class path location)* @return a corresponding File object* @throws FileNotFoundException if the URL cannot be resolved to* a file in the file system*/public static File getFile(URL resourceUrl, String description) throws FileNotFoundException {Assert.notNull(resourceUrl, "Resource URL must not be null");if (!URL_PROTOCOL_FILE.equals(resourceUrl.getProtocol())) {throw new FileNotFoundException(description + " cannot be resolved to absolute file path " +"because it does not reside in the file system: " + resourceUrl);}try {return new File(toURI(resourceUrl).getSchemeSpecificPart());}catch (URISyntaxException ex) {// Fallback for URLs that are not valid URIs (should hardly ever happen).return new File(resourceUrl.getFile());}}/*** Resolve the given resource URI to a {@code java.io.File},* i.e. to a file in the file system.* @param resourceUri the resource URI to resolve* @return a corresponding File object* @throws FileNotFoundException if the URL cannot be resolved to* a file in the file system* @since 2.5*/public static File getFile(URI resourceUri) throws FileNotFoundException {return getFile(resourceUri, "URI");}/*** Resolve the given resource URI to a {@code java.io.File},* i.e. to a file in the file system.* @param resourceUri the resource URI to resolve* @param description a description of the original resource that* the URI was created for (for example, a class path location)* @return a corresponding File object* @throws FileNotFoundException if the URL cannot be resolved to* a file in the file system* @since 2.5*/public static File getFile(URI resourceUri, String description) throws FileNotFoundException {Assert.notNull(resourceUri, "Resource URI must not be null");if (!URL_PROTOCOL_FILE.equals(resourceUri.getScheme())) {throw new FileNotFoundException(description + " cannot be resolved to absolute file path " +"because it does not reside in the file system: " + resourceUri);}return new File(resourceUri.getSchemeSpecificPart());}/*** Determine whether the given URL points to a resource in the file system,* i.e. has protocol "file", "vfsfile" or "vfs".* @param url the URL to check* @return whether the URL has been identified as a file system URL*/public static boolean isFileURL(URL url) {String protocol = url.getProtocol();return (URL_PROTOCOL_FILE.equals(protocol) || URL_PROTOCOL_VFSFILE.equals(protocol) ||URL_PROTOCOL_VFS.equals(protocol));}/*** Determine whether the given URL points to a resource in a jar file.* i.e. has protocol "jar", "war, ""zip", "vfszip" or "wsjar".* @param url the URL to check* @return whether the URL has been identified as a JAR URL*/public static boolean isJarURL(URL url) {String protocol = url.getProtocol();return (URL_PROTOCOL_JAR.equals(protocol) || URL_PROTOCOL_WAR.equals(protocol) ||URL_PROTOCOL_ZIP.equals(protocol) || URL_PROTOCOL_VFSZIP.equals(protocol) ||URL_PROTOCOL_WSJAR.equals(protocol));}/*** Determine whether the given URL points to a jar file itself,* that is, has protocol "file" and ends with the ".jar" extension.* @param url the URL to check* @return whether the URL has been identified as a JAR file URL* @since 4.1*/public static boolean isJarFileURL(URL url) {return (URL_PROTOCOL_FILE.equals(url.getProtocol()) &&url.getPath().toLowerCase().endsWith(JAR_FILE_EXTENSION));}/*** Extract the URL for the actual jar file from the given URL* (which may point to a resource in a jar file or to a jar file itself).* @param jarUrl the original URL* @return the URL for the actual jar file* @throws MalformedURLException if no valid jar file URL could be extracted*/public static URL extractJarFileURL(URL jarUrl) throws MalformedURLException {String urlFile = jarUrl.getFile();int separatorIndex = urlFile.indexOf(JAR_URL_SEPARATOR);if (separatorIndex != -1) {String jarFile = urlFile.substring(0, separatorIndex);try {return new URL(jarFile);}catch (MalformedURLException ex) {// Probably no protocol in original jar URL, like "jar:C:/mypath/myjar.jar".// This usually indicates that the jar file resides in the file system.if (!jarFile.startsWith("/")) {jarFile = "/" + jarFile;}return new URL(FILE_URL_PREFIX + jarFile);}}else {return jarUrl;}}/*** Extract the URL for the outermost archive from the given jar/war URL* (which may point to a resource in a jar file or to a jar file itself).* <p>In the case of a jar file nested within a war file, this will return* a URL to the war file since that is the one resolvable in the file system.* @param jarUrl the original URL* @return the URL for the actual jar file* @throws MalformedURLException if no valid jar file URL could be extracted* @since 4.1.8* @see #extractJarFileURL(URL)*/public static URL extractArchiveURL(URL jarUrl) throws MalformedURLException {String urlFile = jarUrl.getFile();int endIndex = urlFile.indexOf(WAR_URL_SEPARATOR);if (endIndex != -1) {// Tomcat's "war:file:...mywar.war*/WEB-INF/lib/myjar.jar!/myentry.txt"String warFile = urlFile.substring(0, endIndex);if (URL_PROTOCOL_WAR.equals(jarUrl.getProtocol())) {return new URL(warFile);}int startIndex = warFile.indexOf(WAR_URL_PREFIX);if (startIndex != -1) {return new URL(warFile.substring(startIndex + WAR_URL_PREFIX.length()));}}// Regular "jar:file:...myjar.jar!/myentry.txt"return extractJarFileURL(jarUrl);}/*** Create a URI instance for the given URL,* replacing spaces with "%20" URI encoding first.* @param url the URL to convert into a URI instance* @return the URI instance* @throws URISyntaxException if the URL wasn't a valid URI* @see java.net.URL#toURI()*/public static URI toURI(URL url) throws URISyntaxException {return toURI(url.toString());}/*** Create a URI instance for the given location String,* replacing spaces with "%20" URI encoding first.* @param location the location String to convert into a URI instance* @return the URI instance* @throws URISyntaxException if the location wasn't a valid URI*/public static URI toURI(String location) throws URISyntaxException {return new URI(StringUtils.replace(location, " ", "%20"));}/*** Set the {@link URLConnection#setUseCaches "useCaches"} flag on the* given connection, preferring {@code false} but leaving the* flag at {@code true} for JNLP based resources.* @param con the URLConnection to set the flag on*/public static void useCachesIfNecessary(URLConnection con) {con.setUseCaches(con.getClass().getSimpleName().startsWith("JNLP"));}}2.2 常用方法
2.2.1 extractJarFileURL
public static URL extractJarFileURL(URL jarUrl)
从给定的URL (URL可以指向jar文件中的资源或jar文件本身)中提取实际jar文件的URL
2.2.2 getFile
- getFile(String resourceLocation)：将给定的资源位置解析为java.io.file
- getFile(URI resourceUri) ：将给定的资源位置解析为java.io.file
- getFile(String resourceLocation) ：将给定的资源位置解析为java.io.file
- getFile(URL resourceUrl, String description) ：将给定的资源位置解析为java.io.file
- getFile(URL resourceUrl, String description) ：将给定的资源位置解析为java.io.file
2.2.3 getURL
getURL(String resourceLocation)
将给定的资源位置解析为java.net.URL
2.2.4 isJarURL
isJarURL(URL url)
确定给定的URL是否指向jar文件中的资源，即具有协议“jar”、“zip”、“wsjar”或“代码源”
2.2.5 isUrl
返回给定资源位置是否是URL:一个特殊的“classpath”伪URL还是一个标准URL。
2.2.6 toURI
- toURI(String location) ：为给定的URL创建一个URI实例，首先用“%20”引号替换空格。
- toURI(URL url) ：为给定的URL创建一个URI实例，首先用“%20”引号替换空格。
3. 常见问题
3.1 打成jar后获取不到文件
Resource下的文件是存在于jar这个文件里面，在磁盘上是没有真实路径存在的，它是位于jar内部的一个路径。所以通过ResourceUtils.getFile或者this.getClass().getResource("")方法无法正确获取文件。
解决方案：
BufferedReader in = new BufferedReader(new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream(path)));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = in.readLine()) != null){buffer.append(line);
}
String input = buffer.toString();
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