Unable to execute java program from jsp using Runtime.getRuntime().exec

Question

I am trying to run a jar file through jsp. I use the command Runtime.getRuntime().exec("java -jar file.jar"); I get the error Unable to access jarfile file.jar when I print the error stream.

I tried running with the classpath set to the current directory as Runtime.getRuntime().exec("java -cp . -jar file.jar"); but still get the same error. I also tried giving the entire path to the jar file. When I do this, the jsp file hangs after execuing the exec statement.

This is the line I use in windows:

process = Runtime.getRuntime().exec("java -jar C:\\Users\\Jeff\\Documents\\NetBeansProjects\\WebApplication1\\file.jar");

I use the streamgobbler thing given in the article but still have the same problem (hangs). Can someone help?

Instead of doing Runtime.exec, can't you include the jar file in your web application and call the appropriate class/function directly? — Manish
– Manish, Commented Jan 16, 2012 at 8:35

aviad · Accepted Answer · 2012-01-16 08:47:29Z

3

It will never work. Otherwise it would be security breach. Imagine that you could run any executable from web browser... You should put your classes on server, make them accessible to your jsp and then run some method from jsp.

answered Jan 16, 2012 at 8:47

aviad

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9 Comments

Avil Over a year ago

agreed.. client's jar/executable can not be accessible through JSP.. not sure about Java Applet

yatskevich Over a year ago

JSP is executed on a server, not on a client. JSP do not have access to client's executables.

aviad Over a year ago

@Yatskevitch, of course that the corresponding servlet page executes on server that is not what was said.

bestsss Over a year ago

the answer is incorrect. most of the time it should work, it wont work only if security manager is present... and that's not very often

user1151450 Over a year ago

the jar file is on the server. I have a html form that's displayed in the client side. When a submit button is clicked, the jsp is executed on the server and as a first step I want the jar to be executed on the server machine(currently localhost) and as a next step, execute the jar on a remote machine using ssh.

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yatskevich · Accepted Answer · 2012-01-16 10:29:00Z

Though it's better to add a jar to WEB-INF/lib and execute needed functionality using method call or at least move scriptlet code to a servlet, it's perfectly legal to use any functionality provided by Java in JSP scriptlets.

test.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>Test</title>
  </head>
  <body>
  <%
    try {
      Runtime runtime = Runtime.getRuntime();
      Process exec = runtime.exec(new String[]{"java", "-cp", "/home/test/test.jar", "Main"});
      int i = exec.waitFor();
      System.out.println(i);
    } catch (InterruptedException e) {
      throw new RuntimeException(e);
    }
  %>
  hi
  </body>
</html>

test.jar contains the following class:

Main.java

public class Main {

  public static void main(String[] args) {
    System.out.println('hello');
  }

}

This example runs fine. JSP prints 0 in a server output stream which means that no error has happened.

While you're developing webapp locally your machine is a server and a client at the same time. This thing can confuse you, so you have to understand that the code from jar file you are trying to run will be executed on a _server.

In your case the problem is caused by the code in jar file itself. Try to create a simple class and see if it works.

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