I am trying to detect which class inside a jar contains main or a supplied method name (if possible).
At the moment I have the following code
public static void getFromJars(String pathToAppJar) throws IOException{
FileInputStream jar = new FileInputStream(pathToAppJar);
ZipInputStream zipSteam = new ZipInputStream(jar);
ZipEntry ze;
while ((ze = zipSteam.getNextEntry()) != null) {
System.out.println(ze.toString());
}
zipSteam.close();
}
This will allow me to get packages and classes under these packages, but I do not know if it is possible to even get methods inside classes.
Further, I do not know if this approach is even good for a case of several pkgs inside the jar, since each package can have a class with main in it.
I would appreciate any ideas.
Thanks to fvu's comments, I ended up with the following code.
public static void getFromJars(String pathToAppJar) throws IOException, ClassNotFoundException
{
FileInputStream jar = new FileInputStream(pathToAppJar);
ZipInputStream zipSteam = new ZipInputStream(jar);
ZipEntry ze;
URL[] urls = { new URL("jar:file:" + pathToAppJar+"!/") };
URLClassLoader cl = URLClassLoader.newInstance(urls);
while ((ze = zipSteam.getNextEntry()) != null) {
// Is this a class?
if (ze.getName().endsWith(".class")) {
// Relative path of file into the jar.
String className = ze.getName();
// Complete class name
className = className.replace(".class", "").replace("/", ".");
Class<?> klazz = cl.loadClass(className);
Method[] methodsArray = klazz.getMethods();
}
}
zipSteam.close();
}
I removed the code that uses the methods found, since it is not important for this answer
I created a javafx project using Netbeans, the project itself works just fine.
I'm now trying to implement a custom light-weight plugin system, the plugins are external JARs located inside the plugins/ directory of the main project. I'm using javax.security package to sandbox the plugins.
Here's the main project's structure:
MainProject
|
|---plugins/
| |---MyPlugin.jar
|
|---src/
| |---main.app.plugin
| |---Plugin.java
| |---PluginSecurityPolicy.java
| |---PluginClassLoader.java
| |---PluginContainer.java
....
And the plugin's one:
Plugin
|
|---src/
| |---my.plugin
| | |---MyPlugin.java
| |--settings.xml
|
|---dist/
|---MyPlugin.jar
|---META-INF/
| |---MANIFEST.MF
|---my.plugin
| |---MyPlugin.class
|---settings.xml
To load the plugins into the program i've made a PluginContainer class that gets all the jar files from the plugins directory, lists all file inside the jar and lookup for the plugin file and the settings file.
I can load and make an instance of the plugin class, but when it comes to the XML there's no way i can even list it among the jar contents.
Here's the code, maybe someone can see where i did it wrong.
PluginSecurityPolicy.java
import java.security.AllPermission;
import java.security.PermissionCollection;
import java.security.Permissions;
import java.security.Policy;
import java.security.ProtectionDomain;
public class PluginSecurityPolicy extends Policy {
#Override
public PermissionCollection getPermissions(ProtectionDomain domain) {
if (isPlugin(domain)) {
return pluginPermissions();
} else {
return applicationPermissions();
}
}
private boolean isPlugin(ProtectionDomain domain) {
return domain.getClassLoader() instanceof PluginClassLoader;
}
private PermissionCollection pluginPermissions() {
Permissions permissions = new Permissions();
//
return permissions;
}
private PermissionCollection applicationPermissions() {
Permissions permissions = new Permissions();
permissions.add(new AllPermission());
return permissions;
}
}
PluginClassLoader.java
import java.net.URL;
import java.net.URLClassLoader;
public class PluginClassLoader extends URLClassLoader {
public PluginClassLoader(URL jarFileUrl) {
super(new URL[] {jarFileUrl});
}
}
PluginContainer.java, the #load method is the one
import main.app.plugin.PluginClassLoader;
import main.app.plugin.PluginSecurityPolicy;
import java.io.File;
import java.net.URL;
import java.security.Policy;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
public class PluginContainer {
private ArrayList<Plugin> plugins;
private ManifestParser parser;
public PluginContainer() {
Policy.setPolicy(new PluginSecurityPolicy());
System.setSecurityManager(new SecurityManager());
plugins = new ArrayList<>();
parser = new ManifestParser();
}
public void init() {
File[] dir = new File(System.getProperty("user.dir") + "/plugins").listFiles();
for (File pluginJarFile : dir) {
try {
Plugin plugin = load(pluginJarFile.getCanonicalPath());
plugins.add(plugin);
} catch (Exception e) {
throw new RuntimeException(e.getMessage(), e);
}
}
}
public <T extends Plugin> T getPlugin(Class<T> plugin) {
for (Plugin p : plugins) {
if (p.getClass().equals(plugin)) {
return (T)p;
}
}
return null;
}
private Plugin load(String pluginJarFile) throws Exception {
PluginManifest manifest = null;
Plugin plugin = null;
// Load the jar file
ZipFile jarFile = new ZipFile(pluginJarFile);
// Get all jar entries
Enumeration allEntries = jarFile.entries();
String pluginClassName = null;
while (allEntries.hasMoreElements()) {
// Get single file
ZipEntry entry = (ZipEntry) allEntries.nextElement();
String file = entry.getName();
// Look for classfiles
if (file.endsWith(".class")) {
// Set class name
String classname = file.replace('/', '.').substring(0, file.length() - 6);
// Look for plugin class
if (classname.endsWith("Plugin")) {
// Set the class name and exit loop
pluginClassName = classname;
break;
}
}
}
// Load the class
ClassLoader pluginLoader = new PluginClassLoader(new URL("file:///" + pluginJarFile));
Class<?> pluginClass = pluginLoader.loadClass(pluginClassName);
// Edit as suggested by KDM, still null
URL settingsUrl = pluginClass.getResource("/settings.xml");
manifest = parser.load(settingsUrl);
// Check if manifest has been created
if (null == manifest) {
throw new RuntimeException("Manifest file not found in " + pluginJarFile);
}
// Create the plugin
plugin = (Plugin) pluginClass.newInstance();
plugin.load(manifest);
return plugin;
}
}
And the autogenerated MANIFEST.MF
Manifest-Version: 1.0
Ant-Version: Apache Ant 1.9.4
Created-By: 1.8.0_25-b18 (Oracle Corporation)
The Class-Path directive is missing, but if i force it to . or ./settings.xml or settings.xml (by manually editing the MANIFEST.MF file) it won't work either.
This is all I can think of, Thanks in advance for any help
[EDIT] I've created an images/monitor-16.png into the plugin jar root, added the #load2 method into the PluginContainer.
Since the method is called within a loop I left the Policy.setPolicy(new PluginSecurityPolicy()); and System.setSecurityManager(new SecurityManager()); inside the constructor.
Here's the new plugn jar structure:
TestPlugin.jar
|
|---META-INF/
| |---MANIFEST.MF
|
|---dev.jimbo
| |---TestPlugin.class
|
|---images
| |---monitor-16.png
|
|---settings.xml
The new method code:
private Plugin load2(String pluginJarFile) throws MalformedURLException, ClassNotFoundException {
PluginClassLoader urlCL = new PluginClassLoader(new File(pluginJarFile).toURL());
Class<?> loadClass = urlCL.loadClass("dev.jimbo.TestPlugin");
System.out.println(loadClass);
System.out.println("Loading the class using the class loader object. Resource = " + urlCL.getResource("images/monitor-16.png"));
System.out.println("Loading the class using the class loader object with absolute path. Resource = " + urlCL.getResource("/images/monitor-16.png"));
System.out.println("Loading the class using the class object. Resource = " + loadClass.getResource("images/monitor-16.png"));
System.out.println();
return null;
}
Here's the output
class dev.jimbo.TestPlugin
Loading the class using the class loader object. Resource = null
Loading the class using the class loader object with absolute path. Resource = null
Loading the class using the class object. Resource = null
The following program:
public static void main(String[] args) throws MalformedURLException, ClassNotFoundException {
Policy.setPolicy(new PluginSecurityPolicy());
System.setSecurityManager(new SecurityManager());
PluginClassLoader urlCL = new PluginClassLoader(new File(
"A Jar containing images/load.gif and SampleApp class").toURL());
Class<?> loadClass = urlCL.loadClass("net.sourceforge.marathon.examples.SampleApp");
System.out.println(loadClass);
System.out.println("Loading the class using the class loader object. Resource = " + urlCL.getResource("images/load.gif"));
System.out.println("Loading the class using the class loader object with absolute path. Resource = " + urlCL.getResource("/images/load.gif"));
System.out.println("Loading the class using the class object. Resource = " + loadClass.getResource("images/load.gif"));
}
Produces the following output:
class net.sourceforge.marathon.examples.SampleApp
Loading the class using the class loader object. Resource = jar:file:/Users/dakshinamurthykarra/Projects/install/marathon/sampleapp.jar!/images/load.gif
Loading the class using the class loader object with absolute path. Resource = null
Loading the class using the class object. Resource = null
So I do not think any problem with your class loader. Putting this as an answer so that the code can be formatted properly.
Nailed it! Seems that my previous Netbeans (8.0) was deleting the plugin directory from the added Jar/Folder Libraries references on Clean and Build action. I've downloaded and installed Netbeans 8.0.2 and the problem was solved. Couldn't find any related bug for that version on their tracker though..
Anyways Thanks for the help :)
Does the Java Compiler API support manifest-only jar files with Class-Path entries in the classpath arguments?
I am trying to use the Java Compiler API in Maven Surefire tests, but it seems that the Java Compiler API, or more precisely the ToolProvider.getSystemJavaCompiler(), does not handle manifest-only jars of Surefire properly.
Here is a code snippet that shows a failing test
new File("target/out").mkdir();
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
URLClassLoader classLoader = (URLClassLoader)Thread.currentThread().getContextClassLoader();
// create classpath
StringBuilder path = new StringBuilder();
for (URL url : ((URLClassLoader) classLoader).getURLs()) {
if (path.length() > 0) {
path.append(File.pathSeparator);
}
String decodedPath = URLDecoder.decode(url.getPath(), "UTF-8");
path.append(new File(decodedPath).getAbsolutePath());
}
System.err.println(path);
// compile
List<String> options = Arrays.asList(
"-classpath", path.toString(),
"-s", "target/out",
"src/test/java/com/mysema/codegen/SimpleCompilerTest.java");
int compilationResult = compiler.run(null, null, null,
options.toArray(new String[options.size()]));
if (compilationResult != 0) {
Assert.fail("Compilation Failed");
}
I ran into a similar issue running embedded jetty with jsp compilation inside of surefire unit tests. The easier solution was to configure the surefire plugin to not use the manifest-only jar
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<configuration>
<useManifestOnlyJar>false</useManifestOnlyJar>
</configuration>
</plugin>
The harder solution was to expand the class path to include jar files referenced from manifest class-path fields
static List<String> getClassPathForJspCompiler() throws IOException {
List<String> classPath = Lists.newArrayList(System.getProperty("java.class.path")
.split(File.pathSeparator));
return expandManifestClassPathElements(classPath);
}
private static List<String> expandManifestClassPathElements(List<String> classPath)
throws IOException {
for (int i = 0; i < classPath.size(); i++) {
String element = classPath.get(i);
if (element.endsWith(".jar")) {
for (String manifestElement : getManifestClassPath(element)) {
// add to the end of the class path so it will get processed
if (!classPath.contains(manifestElement)) {
// only add if not already present to prevent cyclic loop
classPath.add(manifestElement);
}
}
}
}
return classPath;
}
private static List<String> getManifestClassPath(String jarFilePath) throws IOException {
File jarFile = new File(jarFilePath);
if (!jarFile.isFile()) {
return ImmutableList.of();
}
Manifest manifest = new JarFile(jarFile).getManifest();
if (manifest == null) {
return ImmutableList.of();
}
String manifestClassPath = manifest.getMainAttributes().getValue(
Attributes.Name.CLASS_PATH);
if (manifestClassPath == null) {
return ImmutableList.of();
}
// split at all spaces that are not preceded by a backslash
return Lists.newArrayList(manifestClassPath.split("(?<!\\\\) "));
}
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".
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:
ImageIO.read(this.getClass().getResource("CompanyLogo.png"));
(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.)
EDIT
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:
my.jar!/Main.class
my.jar!/Aux.class
my.jar!/Other.class
my.jar!/images/image01.png
my.jar!/images/image02a.png
my.jar!/images/imwge034.png
my.jar!/images/imagAe01q.png
my.jar!/META-INF/manifest
Right now I'm able to load for instance "images/image01.png" using:
ImageIO.read(this.getClass().getResource("images/image01.png));
But only because I know the file name, for the rest I have to load them dynamically.
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)
break;
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.
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();){
System.out.println(it.next());
}
}
}
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]));
I would like to expand on acheron55's answer, since it is a very non-safe solution, for several reasons:
It doesn't close the FileSystem object.
It doesn't check if the FileSystem object already exists.
It isn't thread-safe.
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 {
Files.walk(Paths.get(path));
}
}
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)) {
Files.walk(fs.getPath(path));
}
}
}
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().
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.
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'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:
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>() {
#Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
System.out.println(file);
return FileVisitResult.CONTINUE;
}
});
}
}
}
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.
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);
}
}
Just to mention that if you are already using Spring, you can take advantage of the PathMatchingResourcePatternResolver.
For instance to get all the PNG files from a images folder in resources
ClassLoader cl = this.getClass().getClassLoader();
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(cl);
Resource[] resources = resolver.getResources("images/*.png");
for (Resource r: resources){
logger.info(r.getFilename());
// From your example
// ImageIO.read(cl.getResource("images/" + r.getFilename()));
}
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.
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.setInput(iis);
....
ir.read(0); //will hand us a buffered image
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.
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);
if(f.exists()){
try{
JarInputStream jarFile = new JarInputStream(
new FileInputStream (jarName));
JarEntry jarEntry;
while(true) {
jarEntry=jarFile.getNextJarEntry ();
if(jarEntry == null){
break;
}
if((jarEntry.getName ().startsWith (packageName)) &&
(jarEntry.getName ().endsWith (".class")) ) {
classes.add(Class.forName(jarEntry.getName().
replaceAll("/", "\\.").
substring(0, jarEntry.getName().length() - 6)));
}
}
}
catch( Exception e){
e.printStackTrace ();
}
Class[] classesA = new Class[classes.size()];
classes.toArray(classesA);
return classesA;
}else
return null;
}
public static ArrayList<String> listItems(String path) throws Exception{
InputStream in = ClassLoader.getSystemClassLoader().getResourceAsStream(path);
byte[] b = new byte[in.available()];
in.read(b);
String data = new String(b);
String[] s = data.split("\n");
List<String> a = Arrays.asList(s);
ArrayList<String> m = new ArrayList<>(a);
return m;
}
There are two very useful utilities both called JarScan:
www.inetfeedback.com/jarscan
jarscan.dev.java.net
See also this question: JarScan, scan all JAR files in all subfolders for specific class
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.)
How to know the name of the JAR file where my main class lives?
URI mainClasspathElementURI;
try (ScanResult scanResult = new ClassGraph().whitelistPackages("x.y.z")
.enableClassInfo().scan()) {
mainClasspathElementURI =
scanResult.getClassInfo("x.y.z.MainClass").getClasspathElementURI();
}
How can I read the contents of a directory in a similar fashion within a JAR file?
List<String> classpathElementResourcePaths;
try (ScanResult scanResult = new ClassGraph().overrideClasspath(mainClasspathElementURI)
.scan()) {
classpathElementResourcePaths = scanResult.getAllResources().getPaths();
}
There are lots of other ways to deal with resources too.
One more for the road that's a bit more flexible for matching specific filenames because it uses wildcard globbing. In a functional style this could resemble:
import java.io.IOException;
import java.net.URISyntaxException;
import java.nio.file.FileSystem;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.function.Consumer;
import static java.nio.file.FileSystems.getDefault;
import static java.nio.file.FileSystems.newFileSystem;
import static java.util.Collections.emptyMap;
/**
* Responsible for finding file resources.
*/
public class ResourceWalker {
/**
* Globbing pattern to match font names.
*/
public static final String GLOB_FONTS = "**.{ttf,otf}";
/**
* #param directory The root directory to scan for files matching the glob.
* #param c The consumer function to call for each matching path
* found.
* #throws URISyntaxException Could not convert the resource to a URI.
* #throws IOException Could not walk the tree.
*/
public static void walk(
final String directory, final String glob, final Consumer<Path> c )
throws URISyntaxException, IOException {
final var resource = ResourceWalker.class.getResource( directory );
final var matcher = getDefault().getPathMatcher( "glob:" + glob );
if( resource != null ) {
final var uri = resource.toURI();
final Path path;
FileSystem fs = null;
if( "jar".equals( uri.getScheme() ) ) {
fs = newFileSystem( uri, emptyMap() );
path = fs.getPath( directory );
}
else {
path = Paths.get( uri );
}
try( final var walk = Files.walk( path, 10 ) ) {
for( final var it = walk.iterator(); it.hasNext(); ) {
final Path p = it.next();
if( matcher.matches( p ) ) {
c.accept( p );
}
}
} finally {
if( fs != null ) { fs.close(); }
}
}
}
}
Consider parameterizing the file extensions, left an exercise for the reader.
Be careful with Files.walk. According to the documentation:
This method must be used within a try-with-resources statement or similar control structure to ensure that the stream's open directories are closed promptly after the stream's operations have completed.
Likewise, newFileSystem must be closed, but not before the walker has had a chance to visit the file system paths.
Just a different way of listing/reading files from a jar URL and it does it recursively for nested jars
https://gist.github.com/trung/2cd90faab7f75b3bcbaa
URL urlResource = Thead.currentThread().getContextClassLoader().getResource("foo");
JarReader.read(urlResource, new InputStreamCallback() {
#Override
public void onFile(String name, InputStream is) throws IOException {
// got file name and content stream
}
});