Read a file from inside of an external Jar file?

Question

I'm trying to read a file from inside an external jar using java.. For example, I have two jar files. One is "foo.jar" the other is "bar.jar". Inside of "bar.jar" is the file "foo-bar.txt". How do i read the file "foo-bar.txt" from inside of "bar.jar" using code in "foo.jar"...? Is this even possible..? I know that i can read a file from iside of foo.jar using

this.getClass().getClassLoader().getResourceAsStream("foo-bar.txt");

But I don't know how to do it from an external jar.. can someone help me?

does `bar` provide a way to access this file? if so, add it to the build path of `foo` and use the appropriate objects. — mre, Nov 08 '12 at 17:40

Roman C · Accepted Answer · 2012-11-08T17:49:13.137

7

Use jar url to open connection the example code

InputStream in = null;
String inputFile = "jar:file:/c:/path/to/my.jar!/myfile.txt";
if (inputFile.startsWith("jar:")){
  try {
    inputURL = new URL(inputFile);
    JarURLConnection conn = (JarURLConnection)inputURL.openConnection();
    in = conn.getInputStream();
  } catch (MalformedURLException e1) {
    System.err.println("Malformed input URL: "+inputURL);
    return;
  } catch (IOException e1) {
    System.err.println("IO error open connection");
    return;
  }
}

edited Nov 08 '12 at 17:49

answered Nov 08 '12 at 17:43

Roman C

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[This](http://stackoverflow.com/questions/13208999/how-can-i-retrieve-information-from-text-file-using-java-streams/13209144#13209144) information could be helpful for file IO. – Roman C Nov 10 '12 at 11:20

score 5 · Answer 2 · answered Nov 08 '12 at 17:42

5

If the jar is in your classpath then getResourceAsStream will work, but note that it will find the first instance in your classpath. If foo.jar and bar.jar both contain this file then it will return whichever jar is first in classpath.

To read it from the jar use JarFile.getEntry and JarFile.getInputStream

answered Nov 08 '12 at 17:42

Miserable Variable

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Would I do that like this? `JarFile j = new JarFile("bar.jar");` `j.getClass().getResourceAsStream("foo-bar.txt");` – Nathan F. Nov 08 '12 at 18:01
No. You would need `j.getEntry` and `j.getInputStream` – Miserable Variable Nov 08 '12 at 18:07
Could you show me some code? (I learn best from code snippets) – Nathan F. Nov 09 '12 at 00:59
@Roman's (answer)[http://stackoverflow.com/a/13294687/18573] is better and has example, but I confess I believe there is enough information in my answer to not need actual code. Have you done any programming before? – Miserable Variable Nov 09 '12 at 01:29
Quite a bit. But very little java. – Nathan F. Nov 12 '12 at 14:36

Read a file from inside of an external Jar file?

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