how to list resources in a package?

[stoughto]

I have a set of files (a.txt, b.txt, c.txt, ....) in a java package along with code. I can access one of these using the getResourceAsStream method. However, I want to get a list of these resources, using a regular expression to find all resources that satisfy *.txt

This needs to work whether the .class and *.txt files are on disk or in a jar file.

Seems like something the reflection api or the Package api should do, but I can't find a way.

Suggestions??

Thanks

[sjalle]

You could scan the jar file(s) using the methods available in java.util.jar/java.util.zip, and, for the case of plain files, directory scanning using the methods in the File class. Both cases would use regex to identify the desired files.

[stoughto]

Thanks. Here is what I came up with. I was hoping that there was a class or method that already did this.

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
* @author stoughto
*
*/
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<String> getResources(Pattern pattern) {
ArrayList<String> retval = new ArrayList<String>();
String classPath = System.getProperty("java.class.path",".");
String[] classPathElements = classPath.split(":");
for (String element : classPathElements) {
retval.addAll(getResources(element, pattern));
}
return retval;
}

private static Collection<String> getResources(String element, Pattern pattern) {
ArrayList<String> retval = new ArrayList<String>();
File file = new File(element);
if (file.isDirectory()) {
retval.addAll(getResourcesFromDirectory(file, pattern));
} else {
retval.addAll(getResourcesFromJarFile(file, pattern));
}
return retval;
}

private static Collection<String> getResourcesFromJarFile(File file, Pattern pattern) {
ArrayList<String> retval = new ArrayList<String>();
ZipFile zf;
try {
zf = new ZipFile(file);
} catch (ZipException e) {
throw new Error(e);
} catch (IOException e) {
throw new Error(e);
}
Enumeration e = zf.entries();
while (e.hasMoreElements()) {
ZipEntry ze = (ZipEntry) e.nextElement();
String fileName = ze.getName();
boolean accept = pattern.matcher(fileName).matches();
if (accept) {
retval.add(fileName);
}
}
try {
zf.close();
} catch (IOException e1) {
throw new Error(e1);
}
return retval;
}

private static Collection<String> getResourcesFromDirectory(File directory, Pattern pattern) {
ArrayList<String> retval = new ArrayList<String>();
File[] fileList = directory.listFiles();
for (File file : fileList) {
if (file.isDirectory()) {
retval.addAll(getResourcesFromDirectory(file, pattern));
} else {
try {
String fileName = file.getCanonicalPath();
boolean accept = pattern.matcher(fileName).matches();
if (accept) {
retval.add(fileName);
}
} catch (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(String[] args) {
Pattern pattern;
if (args.length < 1) {
pattern = Pattern.compile(".*");
} else {
pattern = Pattern.compile(args[0]);
}
Collection<String> list = ResourceList.getResources(pattern);
for (String name : list) {
System.out.println(name);
}

}
}