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https://issues.apache.org/jira/browse/IO-250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17803978#comment-17803978
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Elliotte Rusty Harold commented on IO-250:
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Interesting. Would be careful about testing and handling links.
> Add FileUtils.pathTo(File aFile, File fromAnotherFile)
> ------------------------------------------------------
>
> Key: IO-250
> URL: https://issues.apache.org/jira/browse/IO-250
> Project: Commons IO
> Issue Type: New Feature
> Environment: n/a
> Reporter: Jasper Blues
> Priority: Minor
> Fix For: 3.x
>
> Original Estimate: 3h
> Remaining Estimate: 3h
>
> Please consider adding the following method to
> org.apache.commons.io.FileUtils. I've submitted the method, with test cases
> below (rather than create a patch file). As a single method, it should prove
> very simple to integrate.
> The method returns the path to a file, from another file, as described in the
> Javadoc method header below:
> {code}
> /**
> * Returns the path of a aFile relative to another aFile, for example the
> location of a file:
> * <code>resources/language/english/foobar.properties</code> relative to
> * <code>resources/language/japanese/foobar.properties</code> is
> * <code>../../english/foobar.properties</code>
> *
> * @param aFile the aFile to check relative location
> * @param fromAnotherFile the base location
> * @return the relative location path
> * @throws java.io.IOException on IO error
> */
> public static String pathTo(File aFile, File fromAnotherFile) throws
> IOException {
> LOGGER.debug("Find path to file: " + aFile.toString() + " from file:
> " + fromAnotherFile.toString());
> Stack<File> fileToDirectories = directoriesFor(aFile);
> Stack<File> fileFromDirectories = directoriesFor(fromAnotherFile);
> while (fileToDirectories.peek().equals(fileFromDirectories.peek())) {
> fileToDirectories.pop();
> fileFromDirectories.pop();
> if (fileToDirectories.isEmpty() || fileFromDirectories.isEmpty())
> {
> break;
> }
> }
> StringBuilder pathToCommonParentDirectory = new StringBuilder();
> while (!fileFromDirectories.isEmpty()) {
> pathToCommonParentDirectory.append("../");
> fileFromDirectories.pop();
> }
> StringBuilder pathToFileFromCommonParentDirectory = new
> StringBuilder();
> while (!fileToDirectories.isEmpty()) {
>
> pathToFileFromCommonParentDirectory.append(fileToDirectories.pop().getName());
> if (!fileToDirectories.isEmpty()) {
> pathToFileFromCommonParentDirectory.append("/");
> }
> }
> return pathToCommonParentDirectory.toString() +
> pathToFileFromCommonParentDirectory.toString();
> }
> private static Stack<File> directoriesFor(File file) throws IOException {
> Stack<File> pathElements = new Stack<File>();
> for (File element = file.getCanonicalFile(); element != null; element
> = element.getParentFile()) {
> pathElements.push(element);
> }
> return pathElements;
> }
> {code}
> . . . this is useful for batch processing, web applications, etc.
> Test Cases:
> {code}
> @Test
> public void pathTo() throws IOException {
> //Setup
> File file1 = new File("configs/js/en/a.xml");
> File file2 = new File("configs/js/ja/a.xml");
> Assert.assertNotNull(file1);
> Assert.assertNotNull(file2);
> //Test
> Assert.assertEquals("../../en/a.xml", FileUtils.pathTo(file1, file2));
> }
> @Test
> public void pathTo_windowsStyleOnUnixMachine() throws IOException {
> File file1 = new File("c:/fred/foobar/dude.properties");
> File file2 = new File("c:/data/zz.txt");
> Assert.assertEquals("../../fred/foobar/dude.properties",
> FileUtils.pathTo(file1, file2));
> Assert.assertEquals("../../../data/zz.txt", FileUtils.pathTo(file2,
> file1));
> }
> @Test
> public void pathTo_fromParentDirectory() throws IOException {
> File file1 = new
> File("ui-performance-enhancer/out/test/ui-performance-enhancer/configs/css/imported.xml");
> File file2 = new
> File("ui-performance-enhancer/out/test/ui-performance-enhancer/configs/css");
> Assert.assertEquals("imported.xml", FileUtils.pathTo(file1, file2));
> }
> {code}
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