Get a list of resources from classpath directory

Question

I am looking for a way to get a list of all resource names from a given classpath directory  something like a method List lt String gt  getResourceNames  String directoryName    For example  given a classpath directory x y z containing files a html  b html  c html and a subdirectory d  getResourceNames  x y z   should return a List lt String gt  containing the following strings   a html    b html    c html    d     It should work both for resources in filesystem and jars   I know that I can write a quick snippet with Files  JarFiles and URLs  but I do not want to reinvent the wheel  My question is  given existing publicly available libraries  what is the quickest way to implement getResourceNames  Spring and Apache Commons stacks are both feasible

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This should work  if spring is not an option    public static List lt String gt  getFilenamesForDirnameFromCP String directoryName  throws URISyntaxException  UnsupportedEncodingException  IOException       List lt String gt  filenames   new ArrayList lt  gt          URL url   Thread currentThread   getContextClassLoader   getResource directoryName       if  url    null            if  url getProtocol   equals  file                  File file   Paths get url toURI    toFile                if  file    null                    File   files   file listFiles                    if  files    null                        for  File filename   files                            filenames add filename toString                                                                     else if  url getProtocol   equals  jar                  String dirname   directoryName                    String path   url getPath                String jarPath   path substring 5  path indexOf                    try  JarFile jar   new JarFile URLDecoder decode jarPath  StandardCharsets UTF 8 name                        Enumeration lt JarEntry gt  entries   jar entries                    while  entries hasMoreElements                          JarEntry entry   entries nextElement                        String name   entry getName                        if  name startsWith dirname   amp  amp   dirname equals name                             URL resource   Thread currentThread   getContextClassLoader   getResource name                           filenames add resource toString                                                                               return filenames

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Used a combination of Rob s response    final String resourceDir    resourceDirectory    List lt String gt  files   IOUtils readLines Thread currentThread   getClass   getClassLoader   getResourceAsStream resourceDir   Charsets UTF 8    for String f   files     String data  IOUtils toString Thread currentThread   getClass   getClassLoader   getResourceAsStream resourceDir   f          process data

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I think you can leverage the  Zip File System Provider  1  to achieve this  When using FileSystems newFileSystem it looks like you can treat the objects in that ZIP as a  regular  file   In the linked documentation above      Specify the configuration options for the zip file system in the java util Map object passed to the FileSystems newFileSystem method  See the  Zip File System Properties  2  topic for information about the provider-specific configuration properties for the zip file system       Once you have an instance of a zip file system  you can invoke the methods of the  java nio file FileSystem  3  and  java nio file Path  4  classes to perform operations such as copying  moving  and renaming files  as well as modifying file attributes    The documentation for the jdk zipfs module in  Java 11 states  5       The zip file system provider treats a zip or JAR file as a file system and provides the ability to manipulate the contents of the file  The zip file system provider can be created by  FileSystems newFileSystem  6  if installed    Here is a contrived example I did using your example resources  Note that a  zip is a  jar  but you could adapt your code to instead use classpath resources   Setup  cd  tmp mkdir -p x y z touch x y z  a b c  html echo  hello world   gt  x y z d zip -r example zip x   Java  import java io IOException  import java net URI  import java nio file FileSystem  import java nio file FileSystems  import java nio file Files  import java util Collections  import java util stream Collectors   public class MkobitZipRead      public static void main String   args  throws IOException       final URI uri   URI create  jar file  tmp example zip        try           final FileSystem zipfs   FileSystems newFileSystem uri  Collections emptyMap                   Files walk zipfs getPath       forEach path - gt  System out println  Files in zip     path          System out println  -----          final String manifest   Files readAllLines            zipfs getPath  x    y    z   resolve  d           stream   collect Collectors joining System lineSeparator            System out println manifest                  Output  Files in zip   Files in zip  x  Files in zip  x y  Files in zip  x y z  Files in zip  x y z c html Files in zip  x y z b html Files in zip  x y z a html Files in zip  x y z d ----- hello world

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Here is the code Source  forums devx com showthread php t 153784  import java io File  import java io IOException  import java util ArrayList  import java util Collection  import java util Enumeration  import java util regex Pattern  import java util zip ZipEntry  import java util zip ZipException  import java util zip ZipFile          list resources available from the classpath         public class ResourceList                  for all elements of java class path get a Collection of resources Pattern        pattern   Pattern compile        gets all resources                 param pattern                   the pattern to match         return the resources in the order they are found             public static Collection lt String gt  getResources          final Pattern pattern           final ArrayList lt String gt  retval   new ArrayList lt String gt             final String classPath   System getProperty  java class path                 final String   classPathElements   classPath split System getProperty  path separator             for final String element   classPathElements               retval addAll getResources element  pattern                      return retval             private static Collection lt String gt  getResources          final String element          final Pattern pattern           final ArrayList lt String gt  retval   new ArrayList lt String gt             final File file   new File element           if file isDirectory                 retval addAll getResourcesFromDirectory file  pattern              else              retval addAll getResourcesFromJarFile file  pattern                      return retval             private static Collection lt String gt  getResourcesFromJarFile          final File file          final Pattern pattern           final ArrayList lt String gt  retval   new ArrayList lt String gt             ZipFile zf          try              zf   new ZipFile file             catch final ZipException e               throw new Error e             catch final IOException e               throw new Error e                     final Enumeration e   zf entries            while e hasMoreElements                 final ZipEntry ze    ZipEntry  e nextElement                final String fileName   ze getName                final boolean accept   pattern matcher fileName  matches                if accept                   retval add fileName                                   try              zf close              catch final IOException e1               throw new Error e1                     return retval             private static Collection lt String gt  getResourcesFromDirectory          final File directory          final Pattern pattern           final ArrayList lt String gt  retval   new ArrayList lt String gt             final File   fileList   directory listFiles            for final File file   fileList               if file isDirectory                     retval addAll getResourcesFromDirectory file  pattern                  else                  try                      final String fileName   file getCanonicalPath                        final boolean accept   pattern matcher fileName  matches                        if accept                           retval add fileName                                           catch final IOException e                       throw new Error e                                                     return retval                        list the resources that match args 0                  param args                   args 0  is the pattern to match  or list all resources if                   there are no args             public static void main final String   args           Pattern pattern          if args length  lt  1               pattern   Pattern compile                  else              pattern   Pattern compile args 0                      final Collection lt String gt  list   ResourceList getResources pattern           for final String name   list               System out println name                         If you are using Spring Have a look at PathMatchingResourcePatternResolver

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Based on  rob  s information above  I created the implementation which I am releasing to the public domain   private static List lt String gt  getClasspathEntriesByPath String path  throws IOException       InputStream is   Main class getClassLoader   getResourceAsStream path        StringBuilder sb   new StringBuilder        while  is available   gt 0            byte   buffer   new byte 1024           sb append new String buffer  Charset defaultCharset                 return Arrays              asList sb toString   split   n                Convert StringBuilder to individual lines              stream                                        Stream the list              filter line - gt  line trim   length   gt 0         Filter out empty lines              collect Collectors toList                     Collect remaining lines into a List again     While I would not have expected getResourcesAsStream to work like that on a directory  it really does and it works well

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My way  no Spring  used during a unit test   URI uri   TestClass class getResource   resources   toURI    Path myPath   Paths get uri   Stream lt Path gt  walk   Files walk myPath  1   for  Iterator lt Path gt  it   walk iterator    it hasNext            Path filename   it next           System out println filename

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The Spring framework s PathMatchingResourcePatternResolver is really awesome for these things   private Resource   getXMLResources   throws IOException       ClassLoader classLoader   MethodHandles lookup   getClass   getClassLoader        PathMatchingResourcePatternResolver resolver   new PathMatchingResourcePatternResolver classLoader        return resolver getResources  classpath x y z   xml        Maven dependency    lt dependency gt       lt groupId gt org springframework lt  groupId gt       lt artifactId gt spring-core lt  artifactId gt       lt version gt LATEST lt  version gt   lt  dependency gt

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With Spring it s easy  Be it a file  or folder  or even multiple files  there are chances  you can do it via injection   This example demonstrates the injection of multiple files located in x y z folder   import org springframework beans factory annotation Value  import org springframework core io Resource  import org springframework stereotype Service    Service public class StackoverflowService        Value  classpath x y z         private Resource   resources       public List lt String gt  getResourceNames             return Arrays stream resources                   map Resource  getFilename                   collect Collectors toList               It does work for resources in the filesystem as well as in JARs

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Using Reflections  Get everything on the classpath   Reflections reflections   new Reflections null  new ResourcesScanner     Set lt String gt  resourceList   reflections getResources x - gt  true     Another example - get all files with extension  csv from some package   Reflections reflections   new Reflections  some package   new ResourcesScanner     Set lt String gt  fileNames   reflections getResources Pattern compile       csv

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Custom Scanner Implement your own scanner  For example   limitations of this solution are mentioned in the comments  private List lt String gt  getResourceFiles String path  throws IOException       List lt String gt  filenames   new ArrayList lt  gt          try               InputStream in   getResourceAsStream path               BufferedReader br   new BufferedReader new InputStreamReader in              String resource           while   resource   br readLine       null                filenames add resource                        return filenames     private InputStream getResourceAsStream String resource        final InputStream in               getContextClassLoader   getResourceAsStream resource        return in    null   getClass   getResourceAsStream resource    in     private ClassLoader getContextClassLoader         return Thread currentThread   getContextClassLoader       Spring Framework Use PathMatchingResourcePatternResolver from Spring Framework  Ronmamo Reflections The other techniques might be slow at runtime for huge CLASSPATH values  A faster solution is to use ronmamo s Reflections API  which precompiles the search at compile time

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If you use apache commonsIO you can use for the filesystem  optionally with extension filter     Collection lt File gt  files   FileUtils listFiles new File  directory     null  false     and for resources classpath   List lt String gt  files   IOUtils readLines MyClass class getClassLoader   getResourceAsStream  directory     Charsets UTF 8     If you don t know if  directoy   is in the filesystem or in resources you may add a   if  new File  directory    isDirectory      or  if  MyClass class getClassLoader   getResource  directory       null    before the calls and use both in combination

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Neither of answers worked for me even though I had my resources put in resources folders  and followed the above answers  What did make a trick was    Value  file      resources    schema   json   private Resource   resources

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So in terms of the PathMatchingResourcePatternResolver this is what is needed in the code    Autowired ResourcePatternResolver resourceResolver   public void getResources       resourceResolver getResources  classpath config   xml

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The most robust mechanism for listing all resources in the classpath is currently to use this pattern with ClassGraph  because it handles the widest possible array of classpath specification mechanisms  including the new JPMS module system   I am the author of ClassGraph    List lt String gt  resourceNames  try  ScanResult scanResult   new ClassGraph   whitelistPaths  x y z   scan          resourceNames   scanResult getAllResources   getNames

[java] Get a list of resources from classpath directory

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