将JAR资源作为FileStream打开

Question

I have a project where I want to access a resource in a JAR from another project. It's not on my classpath, so ClassLoader is not an option. I tried:

new FileInputStream("C:\\mydir\\my.jar!\\myresource.txt");

and received a FileNotFoundException.

JarInputStream might be a possibility, but I want the flexibility of the input filename being a jar resource or just a file on the system (user decides). Is there a class that can do this or do I have to build one myself?

Answer 1

URLs are your friend

URL.openStream .

Answer 2

Fortunately, the desicion with the "!" symbol doesn't work.

Have a look here:

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4730642

Answer 3

Try using a URLClassLoader . I've done something similar to this before, and it seems to work (though you may need to muck around with your security policy file, if you're in a secure JVM).

Answer 4

try using java.net.JarURLConnection

URL url = new URL("jar:file:C:\\mydir\\my.jar!\\myresource.txt");

JarURLConnection jarConnection = (JarURLConnection)url.openConnection();

Answer 5

  private InputStream twistLid(File jar, String resource) throws IOException {
    return new URL("jar:" + jar.toURI() + "!" + resource).openStream();
  }

Answer 6

Building on the work of many above, here's an example in groovy, listing the text contained in 'resource.txt' inside a folder named 'reources' at the root level of a jar file

import java.io.*
import java.util.*
import java.util.jar.*

def getJarResourceAsStream(String jarName, String resource) throws IOException {
    def resourceStr = 'jar:' + (new File(jarName)).toURI() + '!' + resource
    return new URL(resourceStr).openStream()
}

def inputStream = getJarResourceAsStream('/some/file/path/myJar.jar', '/resources/resource.txt')

def reader = new InputStreamReader(inputStream)
BufferedReader buffer = new BufferedReader(reader)
String line
while((line = buffer.readLine()) != null) {
    System.out.println(line)
}