java nio file Path for a classpath resource

Question

Is there an API to get a classpath resource  e g  what I d get from Class getResource String   as a java nio file Path   Ideally  I d like to use the fancy new Path APIs with classpath resources

User · Answer

It turns out you can do this  with the help of the built-in Zip File System provider   However  passing a resource URI directly to Paths get won t work   instead  one must first create a zip filesystem for the jar URI without the entry name  then refer to the entry in that filesystem   static Path resourceToPath URL resource  throws IOException         URISyntaxException        Objects requireNonNull resource   Resource URL cannot be null        URI uri   resource toURI         String scheme   uri getScheme        if  scheme equals  file              return Paths get uri              if   scheme equals  jar              throw new IllegalArgumentException  Cannot convert to Path      uri              String s   uri toString        int separator   s indexOf            String entryName   s substring separator   2       URI fileURI   URI create s substring 0  separator         FileSystem fs   FileSystems newFileSystem fileURI          Collections  lt String  Object gt emptyMap         return fs getPath entryName       Update   It   s been rightly pointed out that the above code contains a resource leak  since the code opens a new FileSystem object but never closes it   The best approach is to pass a Consumer-like worker object  much like how Holger   s answer does it   Open the ZipFS FileSystem just long enough for the worker to do whatever it needs to do with the Path  as long as the worker doesn   t try to store the Path object for later use   then close the FileSystem

User · Answer

This one works for me   return Paths get ClassLoader getSystemResource resourceName  toURI

User · Answer

You need to define the Filesystem to read resource from jar file as mentioned in https   docs oracle com javase 8 docs technotes guides io fsp zipfilesystemprovider html  I success to read resource from jar file with below codes   Map lt String  Object gt  env   new HashMap lt  gt     try  FileSystem fs   FileSystems newFileSystem uri  env              Path path   fs getPath   path myResource             try  Stream lt String gt  lines   Files lines path

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Read a File from resources folder using NIO  in java8  public static String read String fileName             Path path          StringBuilder data   new StringBuilder            Stream lt String gt  lines   null          try               path   Paths get Thread currentThread   getContextClassLoader   getResource fileName  toURI                 lines   Files lines path             catch  URISyntaxException   IOException e                logger error  Error in reading propertied file     e               throw new RuntimeException e                      lines forEach line - gt  data append line            lines close            return data toString

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You can not create URI from resources inside of the jar file  You can simply write it to the temp file and then use it  java8    Path path   File createTempFile  some    address   toPath    Files copy ClassLoader getSystemResourceAsStream   path to resource    path  StandardCopyOption REPLACE EXISTING

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I wrote a small helper method to read Paths from your class resources  It is quite handy to use as it only needs a reference of the class you have stored your resources as well as the name of the resource itself   public static Path getResourcePath Class lt   gt  resourceClass  String resourceName  throws URISyntaxException       URL url   resourceClass getResource resourceName       return Paths get url toURI

User · Answer

The most general solution is as follows   interface IOConsumer lt T gt        void accept T t  throws IOException    public static void processRessource URI uri  IOConsumer lt Path gt  action  throws IOException       try           Path p Paths get uri           action accept p             catch FileSystemNotFoundException ex            try FileSystem fs   FileSystems newFileSystem                  uri  Collections  lt String Object gt emptyMap                   Path p   fs provider   getPath uri               action accept p                       The main obstacle is to deal with the two possibilities  either  having an existing filesystem that we should use  but not close  like with file URIs or the Java  9   s module storage   or having to open and thus safely close the filesystem ourselves  like zip jar files    Therefore  the solution above encapsulates the actual action in an interface  handles both cases  safely closing afterwards in the second case  and works from Java  7 to Java  10  It probes whether there is already an open filesystem before opening a new one  so it also works in the case that another component of your application has already opened a filesystem for the same zip jar file   It can be used in all Java versions named above  e g  to listing the contents of a package  java lang in the example  as Paths  like this   processRessource Object class getResource  Object class   toURI    new IOConsumer lt Path gt          public void accept Path path  throws IOException           try DirectoryStream lt Path gt  ds   Files newDirectoryStream path getParent                   for Path p  ds                  System out println p                         With Java  8 or newer  you can use lambda expressions or method references to represent the actual action  e g   processRessource Object class getResource  Object class   toURI    path - gt        try Stream lt Path gt  stream   Files list path getParent               stream forEach System out  println               to do the same     The final release of Java  9   s module system has broken the above code example  The JRE inconsistently returns the path  java base java lang Object class for Object class getResource  Object class   whereas it should be  modules java base java lang Object class  This can be fixed by prepending the missing  modules  when the parent path is reported as non-existent   processRessource Object class getResource  Object class   toURI    path - gt        Path p   path getParent        if  Files exists p           p   p resolve   modules   resolve p getRoot   relativize p        try Stream lt Path gt  stream   Files list p             stream forEach System out  println               Then  it will again work with all versions and storage methods

User · Answer

Guessing that what you want to do  is call Files lines      on a resource that comes from the classpath - possibly from within a jar   Since Oracle convoluted the notion of when a Path is a Path by not making getResource return a usable path if it resides in a jar file  what you need to do is something like this   Stream lt String gt  stream   new BufferedReader new InputStreamReader ClassLoader getSystemResourceAsStream   filename txt     lines

[java] java.nio.file.Path for a classpath resource

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