[英]How do I list the files inside a JAR file?

I have this code which reads all the files from a directory.


    File textFolder = new File("text_directory");

    File [] texFiles = textFolder.listFiles( new FileFilter() {
           public boolean accept( File file ) {
               return file.getName().endsWith(".txt");

It works great. It fills the array with all the files that end with ".txt" from directory "text_directory".

它的工作原理。它将所有以“。”结尾的文件填充到数组中。txt text_directory“从目录。

How can I read the contents of a directory in a similar fashion within a JAR file?


So what I really want to do is, to list all the images inside my JAR file, so I can load them with:



(That one works because the "CompanyLogo" is "hardcoded" but the number of images inside the JAR file could be from 10 to 200 variable length.)




So I guess my main problem would be: How to know the name of the JAR file where my main class lives?


Granted I could read it using java.util.Zip.


My Structure is like this:


They are like:



Right now I'm able to load for instance "images/image01.png" using:



But only because I know the file name, for the rest I have to load them dynamically.


13 个解决方案



CodeSource src = MyClass.class.getProtectionDomain().getCodeSource();
if (src != null) {
  URL jar = src.getLocation();
  ZipInputStream zip = new ZipInputStream(jar.openStream());
  while(true) {
    ZipEntry e = zip.getNextEntry();
    if (e == null)
    String name = e.getName();
    if (name.startsWith("path/to/your/dir/")) {
      /* Do something with this entry. */
else {
  /* Fail... */

Note that in Java 7, you can create a FileSystem from the JAR (zip) file, and then use NIO's directory walking and filtering mechanisms to search through it. This would make it easier to write code that handles JARs and "exploded" directories.

注意,在Java 7中,您可以从JAR (zip)文件创建一个文件系统,然后使用NIO的目录移动和过滤机制来搜索它。这样可以更容易地编写处理jar和“爆炸”目录的代码。



Code that works for both IDE's and .jar files:


import java.io.*;
import java.net.*;
import java.nio.file.*;
import java.util.*;
import java.util.stream.*;

public class ResourceWalker {
    public static void main(String[] args) throws URISyntaxException, IOException {
        URI uri = ResourceWalker.class.getResource("/resources").toURI();
        Path myPath;
        if (uri.getScheme().equals("jar")) {
            FileSystem fileSystem = FileSystems.newFileSystem(uri, Collections.<String, Object>emptyMap());
            myPath = fileSystem.getPath("/resources");
        } else {
            myPath = Paths.get(uri);
        Stream<Path> walk = Files.walk(myPath, 1);
        for (Iterator<Path> it = walk.iterator(); it.hasNext();){



erickson's answer worked perfectly:


Here's the working code.


CodeSource src = MyClass.class.getProtectionDomain().getCodeSource();
List<String> list = new ArrayList<String>();

if( src != null ) {
    URL jar = src.getLocation();
    ZipInputStream zip = new ZipInputStream( jar.openStream());
    ZipEntry ze = null;

    while( ( ze = zip.getNextEntry() ) != null ) {
        String entryName = ze.getName();
        if( entryName.startsWith("images") &&  entryName.endsWith(".png") ) {
            list.add( entryName  );

 webimages = list.toArray( new String[ list.size() ] );

And I have just modify my load method from this:


File[] webimages = ... 
BufferedImage image = ImageIO.read(this.getClass().getResource(webimages[nextIndex].getName() ));

To this:


String  [] webimages = ...

BufferedImage image = ImageIO.read(this.getClass().getResource(webimages[nextIndex]));



So I guess my main problem would be, how to know the name of the jar where my main class lives.


Assuming that your project is packed in a Jar (not necessarily true!), you can use ClassLoader.getResource() or findResource() with the class name (followed by .class) to get the jar that contains a given class. You'll have to parse the jar name from the URL that gets returned (not that tough), which I will leave as an exercise for the reader :-)


Be sure to test for the case where the class is not part of a jar.




I would like to expand on acheron55's answer, since it is a very non-safe solution, for several reasons:


  1. It doesn't close the FileSystem object.
  2. 它没有关闭文件系统对象。
  3. It doesn't check if the FileSystem object already exists.
  4. 它不检查文件系统对象是否已经存在。
  5. It isn't thread-safe.
  6. 它不是线程安全的。

This is somewhat a safer solution:


private static ConcurrentMap<String, Object> locks = new ConcurrentHashMap<>();

public void walk(String path) throws Exception {

    URI uri = getClass().getResource(path).toURI();
    if ("jar".equals(uri.getScheme()) {
        safeWalkJar(path, uri);
    } else {

private void safeWalkJar(String path, URI uri) throws Exception {

    synchronized (getLock(uri)) {    
        // this'll close the FileSystem object at the end
        try (FileSystem fs = getFileSystem(uri)) {

private Object getLock(URI uri) {

    String fileName = parseFileName(uri);  
    locks.computeIfAbsent(fileName, s -> new Object());
    return locks.get(fileName);

private String parseFileName(URI uri) {

    String schemeSpecificPart = uri.getSchemeSpecificPart();
    return schemeSpecificPart.substring(0, schemeSpecificPart.indexOf("!"));

private FileSystem getFileSystem(URI uri) throws IOException {

    try {
        return FileSystems.getFileSystem(uri);
    } catch (FileSystemNotFoundException e) {
        return FileSystems.newFileSystem(uri, Collections.<String, String>emptyMap());

There's no real need to synchronize over the file name; one could simply synchronize on the same object every time (or make the method synchronized), it's purely an optimization.


I would say that this is still a problematic solution, since there might be other parts in the code that use the FileSystem interface over the same files, and it could interfere with them (even in a single threaded application).
Also, it doesn't check for nulls (for instance, on getClass().getResource().

我认为这仍然是一个有问题的解决方案,因为在代码中可能会有其他部分使用文件系统接口而不是相同的文件,并且它可能会干扰它们(即使是在单线程应用程序中)。另外,它不检查null(例如,在getClass(). getresource()中。

This particular Java NIO interface is kind of horrible, since it introduces a global/singleton non thread-safe resource, and its documentation is extremely vague (a lot of unknowns due to provider specific implementations). Results may vary for other FileSystem providers (not JAR). Maybe there's a good reason for it being that way; I don't know, I haven't researched the implementations.

这个特定的Java NIO接口有点可怕,因为它引入了一个全局/单例非线程安全的资源,而且它的文档非常模糊(由于提供者特定的实现,很多未知因素)。结果可能因其他文件系统提供者(而不是JAR)而异。也许这是有原因的;我不知道,我没有研究过这些实现。



Here's a method I wrote for a "run all JUnits under a package". You should be able to adapt it to your needs.


private static void findClassesInJar(List<String> classFiles, String path) throws IOException {
    final String[] parts = path.split("\\Q.jar\\\\E");
    if (parts.length == 2) {
        String jarFilename = parts[0] + ".jar";
        String relativePath = parts[1].replace(File.separatorChar, '/');
        JarFile jarFile = new JarFile(jarFilename);
        final Enumeration<JarEntry> entries = jarFile.entries();
        while (entries.hasMoreElements()) {
            final JarEntry entry = entries.nextElement();
            final String entryName = entry.getName();
            if (entryName.startsWith(relativePath)) {
                classFiles.add(entryName.replace('/', File.separatorChar));

Edit: Ah, in that case, you might want this snippet as well (same use case :) )


private static File findClassesDir(Class<?> clazz) {
    try {
        String path = clazz.getProtectionDomain().getCodeSource().getLocation().getFile();
        final String codeSourcePath = URLDecoder.decode(path, "UTF-8");
        final String thisClassPath = new File(codeSourcePath, clazz.getPackage().getName().repalce('.', File.separatorChar));
    } catch (UnsupportedEncodingException e) {
        throw new AssertionError("impossible", e);



A jar file is just a zip file with a structured manifest. You can open the jar file with the usual java zip tools and scan the file contents that way, inflate streams, etc. Then use that in a getResourceAsStream call, and it should be all hunky dory.

jar文件只是一个带有结构化清单的zip文件。您可以使用常用的java zip工具打开jar文件,并通过这样的方式扫描文件内容,然后在getresour流调用中使用它,并且它应该都是很健壮的dory。

EDIT / after clarification


It took me a minute to remember all the bits and pieces and I'm sure there are cleaner ways to do it, but I wanted to see that I wasn't crazy. In my project image.jpg is a file in some part of the main jar file. I get the class loader of the main class (SomeClass is the entry point) and use it to discover the image.jpg resource. Then some stream magic to get it into this ImageInputStream thing and everything is fine.


InputStream inputStream = SomeClass.class.getClassLoader().getResourceAsStream("image.jpg");
JPEGImageReaderSpi imageReaderSpi = new JPEGImageReaderSpi();
ImageReader ir = imageReaderSpi.createReaderInstance();
ImageInputStream iis = new MemoryCacheImageInputStream(inputStream);
ir.read(0); //will hand us a buffered image



Some time ago I made a function that gets classess from inside JAR:


public static Class[] getClasses(String packageName) 
throws ClassNotFoundException{
    ArrayList<Class> classes = new ArrayList<Class> ();

    packageName = packageName.replaceAll("\\." , "/");
    File f = new File(jarName);
            JarInputStream jarFile = new JarInputStream(
                    new FileInputStream (jarName));
            JarEntry jarEntry;

            while(true) {
                jarEntry=jarFile.getNextJarEntry ();
                if(jarEntry == null){
                if((jarEntry.getName ().startsWith (packageName)) &&
                        (jarEntry.getName ().endsWith (".class")) ) {
                            replaceAll("/", "\\.").
                            substring(0, jarEntry.getName().length() - 6)));
        catch( Exception e){
            e.printStackTrace ();
        Class[] classesA = new Class[classes.size()];
        return classesA;
        return null;



Here is an example of using Reflections library to recursively scan classpath by regex name pattern augmented with a couple of Guava perks to to fetch resources contents:


Reflections reflections = new Reflections("com.example.package", new ResourcesScanner());
Set<String> paths = reflections.getResources(Pattern.compile(".*\\.template$"));

Map<String, String> templates = new LinkedHashMap<>();
for (String path : paths) {
    log.info("Found " + path);
    String templateName = Files.getNameWithoutExtension(path);
    URL resource = getClass().getClassLoader().getResource(path);
    String text = Resources.toString(resource, StandardCharsets.UTF_8);
    templates.put(templateName, text);

This works with both jars and exploded classes.




Given an actual JAR file, you can list the contents using JarFile.entries(). You will need to know the location of the JAR file though - you can't just ask the classloader to list everything it could get at.


You should be able to work out the location of the JAR file based on the URL returned from ThisClassName.class.getResource("ThisClassName.class"), but it may be a tiny bit fiddly.




There are two very useful utilities both called JarScan:


  1. www.inetfeedback.com/jarscan


  2. jarscan.dev.java.net


See also this question: JarScan, scan all JAR files in all subfolders for specific class




Just a different way of listing/reading files from a jar URL and it does it recursively for nested jars

只是从一个jar URL中列出/读取文件的另一种方式,它会递归地用于嵌套的jar。



URL urlResource = Thead.currentThread().getContextClassLoader().getResource("foo");
JarReader.read(urlResource, new InputStreamCallback() {
    public void onFile(String name, InputStream is) throws IOException {
        // got file name and content stream 



I've ported acheron55's answer to Java 7 and closed the FileSystem object. This code works in IDE's, in jar files and in a jar inside a war on Tomcat 7; but note that it does not work in a jar inside a war on JBoss 7 (it gives FileSystemNotFoundException: Provider "vfs" not installed, see also this post). Furthermore, like the original code, it is not thread safe, as suggested by errr. For these reasons I have abandoned this solution; however, if you can accept these issues, here is my ready-made code:

我已经将acheron55的答案移植到Java 7并关闭了文件系统对象。这个代码在IDE中工作,在jar文件中工作,在Tomcat 7的战争中,在一个jar中工作;但是请注意,在JBoss 7的war中,它并不是在jar中工作(它提供了文件系统notfoundexception:没有安装的提供者“vfs”,也可以看到这个帖子)。而且,与原始代码一样,它不是线程安全的,正如errr所建议的那样。由于这些原因,我放弃了这个解决方案;但是,如果你能接受这些问题,这是我的现成代码:

import java.io.IOException;
import java.net.*;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Collections;

public class ResourceWalker {

    public static void main(String[] args) throws URISyntaxException, IOException {
        URI uri = ResourceWalker.class.getResource("/resources").toURI();
        System.out.println("Starting from: " + uri);
        try (FileSystem fileSystem = (uri.getScheme().equals("jar") ? FileSystems.newFileSystem(uri, Collections.<String, Object>emptyMap()) : null)) {
            Path myPath = Paths.get(uri);
            Files.walkFileTree(myPath, new SimpleFileVisitor<Path>() { 
                public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                    return FileVisitResult.CONTINUE;



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