Error: Could not find or load main class ?jar

Question

Something strange happens when I try running a java -jar command programatically on Windows.

When running the command like this:

Process p = Runtime.getRuntime().exec(cmd); //cmd string is ok
p.waitFor();

I get the error

Error: Could not find or load main class �jar

The cmd var is constructed like this:

cmd = String.format("java –jar %s –o win -i %s -n %s -d %s -s %s", jarLocation, param1, param2, tgtFilePath, srcFilePath);

I tried debugging this issue so I copy pasted the command to CMD and got the same error. However, when I typed it manually and not copy pasted, everything just worked fine.

When getting the bytes of each String I got:

bytes of generated string:

[106, 97, 118, 97, 32, -30, -128, -109, 106, 97, 114, 32, 110, 112, 116, 95, 108, 105, 99, 101, 110, 115, 101, 46, 106, 97, 114, 32, -30, -128, -109, 111, 32, 119, 105, 110, 32, 45, 105, 32, 104, 111, 115, 116, 105, 100, 55, 56, 57, 48, 49, 32, 45, 110, 32, 104, 111, 115, 116, 110, 97, 109, 101, 32, 45, 100, 32, 108, 105, 99, 101, 110, 99, 101, 70, 105, 108, 101, 45, 105, 110, 112, 117, 116, 76, 105, 99, 101, 110, 99, 101, 45, 114, 101, 115, 117, 108, 116, 46, 100, 97, 116, 32, 45, 115, 32, 108, 105, 99, 101, 110, 99, 101, 70, 105, 108, 101, 45, 105, 110, 112, 117, 116, 76, 105, 99, 101, 110, 99, 101]

bytes of hard coded string:

[106, 97, 118, 97, 32, 45, 106, 97, 114, 32, 110, 112, 116, 95, 108, 105, 99, 101, 110, 115, 101, 46, 106, 97, 114, 32, 45, 111, 32, 119, 105, 110, 32, 45, 105, 32, 104, 111, 115, 116, 105, 100, 55, 56, 57, 48, 49, 32, 45, 110, 32, 104, 111, 115, 116, 110, 97, 109, 101, 32, 45, 100, 32, 108, 105, 99, 101, 110, 99, 101, 70, 105, 108, 101, 45, 105, 110, 112, 117, 116, 76, 105, 99, 101, 110, 99, 101, 45, 114, 101, 115, 117, 108, 116, 46, 100, 97, 116, 32, 45, 115, 32, 108, 105, 99, 101, 110, 99, 101, 70, 105, 108, 101, 45, 105, 110, 112, 117, 116, 76, 105, 99, 101, 110, 99, 101]

The jarLocation is the one parameter that is already hard coded and not received as a web service parameter.

What can cause an issue like that?

when I typed it manually and not copy pasted, everything just worked fine means? — Naman Gala
What I'm running that is causing this issue is a Spring web service. So do you mean the pom.xml? What is supposed to be there? — Yonatan Nir
@NamanGala it means just that. I tried typing the command like I'm typing these words right now and that made it work. — Yonatan Nir

SubOptimal SubOptimal · Accepted Answer · 2015-10-09T06:00:26

Ok to make it more clear what I proposed you should do.

Amend you code like this

// this will be the command which produces �jar
cmd = String.format("java –jar %s –o win -i %s -n %s -d %s -s %s", jarLocation,
          param1, param2, tgtFilePath, srcFilePath);
System.out.println(Arrays.toString(cmd.getBytes(charsetLatin1)));

// this will be the working command, as you wrote
cmd = "here you type the same command";
System.out.println(Arrays.toString(cmd.getBytes(charsetLatin1)));

Then you compare the bytes and have at least the difference. Based on this you can investigate further.

update
Find a short example code for visualising few different dashes, which look quite similar on some fonts.

import java.nio.charset.StandardCharsets;

public class Dashes {

    public static void main(String[] args) {
        // see: https://en.wikipedia.org/wiki/Dash
        byte[] enDash = {-30, -128, -109};
        byte[] minusSign = {45};
        byte[] emDash = {-30, -128, -108};

        byte[][] charBytes = new byte[3][];
        charBytes[0] = enDash;
        charBytes[1] = minusSign;
        charBytes[2] = emDash;

        for (byte[] bytes : charBytes) {
            String s = new String(bytes, StandardCharsets.UTF_8);
            char c = s.charAt(0);
            System.out.printf("%d  %s  %s%n", s.length(), c, Character.getName(c));
        }
    }
}

You need to check the code which generates the value for jarLocation. As the option -jar and -o contain a EN DASH instead of the HYPHEN-MINUS.

the pattern from your code, via copy'n'paste

byte[] b = "java –jar %s –o win -i %s -n %s -d %s -s %s".getBytes();
System.out.println(Arrays.toString(b));

output

[106, 97, 118, 97, 32, -30, -128, -109, 106, 97, 114, 32, 37, 115, 32, -30, -128, -109, 111, 32, 119, 105, 110, 32, 45, 105, 32, 37, 115, 32, 45, 110, 32, 37, 115, 32, 45, 100, 32, 37, 115, 32, 45, 115, 32, 37, 115]

Which shows the dash before jar and o is not a HYPHEN-MINUS

solution

Remove the – (EN DASH) in front of the jar and o option and type it again (as HYPHEN-MINUS).

Error: Could not find or load main class ?jar

1 Answers