Where is System.out.println() printed in Servlets?

Question

I have seen in some servlet programs, System.out.println() statements. Do they work? If so where are they printed? I have checked the Web console in the browser. But I couldn't see it?

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class MyServlet extends HttpServlet
{
    public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException
    {
        System.out.println("This is in System.out.println()");
    }
}

Because this program is not executed in command prompt, where will the output be printed? Is there any console in the browser that can print this?

This will depend on the server you're running the servlet on. In Websphere, I believe it would wind up in stdout.log. — keshlam, Feb 01 '14 at 21:03
@MartinDinov Thank you very much for the replies. I am sleepy and haven't noticed the duplicate. — JavaTechnical, Feb 01 '14 at 21:07

score 1 · Answer 1 · answered Feb 01 '14 at 21:02

1

I think this is a duplicate question, but, you typically only use System.out.println() in servlets for debugging purposes and what not. Try outputting everything to the logs, by using

log.info("some message")

or

log.error("some error message")

answered Feb 01 '14 at 21:02

Thanks. yeah! but System.out is also outputting in the logs only! :) – JavaTechnical Feb 01 '14 at 21:15
1

Yeah I figured - this is a bit more direct to see if it will work as well. :) – Feb 01 '14 at 23:06
Sure I'll check it! +Ivan – JavaTechnical Feb 02 '14 at 12:31

score 1 · Accepted Answer · answered Feb 01 '14 at 21:05

1

It is in tomcat7-stdout-<date>.txt file. I am using Tomcat.

answered Feb 01 '14 at 21:05

JavaTechnical

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Note that it is configurable. – Sotirios Delimanolis Feb 01 '14 at 21:15

score 0 · Answer 3 · answered Feb 01 '14 at 21:00

0

It is printed on the standard output or wherever it is redirected.

Usually logs/catalina.out (if we speak about Tomcat).

answered Feb 01 '14 at 21:00

peter.petrov

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Yes, right. Just thought the same. – peter.petrov Feb 01 '14 at 21:02
Unfortunately, I couldn't see it there. – JavaTechnical Feb 01 '14 at 21:03
Interesting. How can it be redirected to the text file? – JavaTechnical Feb 01 '14 at 21:09
Type "java MainProgram > out.txt" in a Windows command prompt. It is similar here, I guess. – peter.petrov Feb 01 '14 at 21:11
Yes, you are right. That redirects to out.txt. But how is it implemented programatically? – JavaTechnical Feb 01 '14 at 21:12
1

Not that hard, it seems. See here: http://www.avajava.com/tutorials/lessons/how-do-i-redirect-standard-output-to-a-file.html – peter.petrov Feb 01 '14 at 21:12
1

Simple, `System.setOut(..)`. – Sotirios Delimanolis Feb 01 '14 at 21:14
SUPERB @peter.petrov Great catch!! – JavaTechnical Feb 01 '14 at 21:14

Where is System.out.println() printed in Servlets?

3 Answers3