Where does system.out.println print from a JSP?

Question

Where does tomcat put the System.out.println output ?

I'm not interested in out.println. I'm using a system that uses system.out to log issues, like login success/fail, and I need to look to that generated "log".

Piecework

Answer 1

It usually prints to catalina.out.

It is highly unrecommended to log using system.out.println() from several reasons:

• you cannot control which messages are logged and which aren't unless you change the code
• catalina.out just grow all the time, and you cannot move it so that tomcat will create another one.

A better solution is to use one of the popular (and mature) logging frameworks:

• java.util.logging (actually used by tomcat itself and you have no third party dependencies)
• Log4j
• Logback

A good solution which is backed by log4j, is to use Jakarta's log tag library, where you can have your logging messages in any of this forms

<log:info message="this is a message"/>

<log:info category="foo.bar" message="this is a message"/>

<log:info category="foo.bar">
  this is a message
</log:info>

Leeuwarden

The author of Log4J left the project and is working on logback (for some time already) which works in combination of slf4j. Both should be the preferred logging frameworks. – Dierdre

@Brice I agree, SLF4J is my preference these days as well. It also has a JSP tag library, documented at slf4j.org/taglib – Leeuwarden

Answer 2

CATALINA_HOME/logs/stdout_YYYYMMDD.log

is the default, where CATALINA_HOME is your base Tomcat directory. There are various ways to change this programatically and via configuration.

Centra

$ ls /usr/local/tomcat/logs admin.2009-10-06.log catalina.2009-10-06.log catalina.out host-manager.2009-10-06.log localhost.2009-10-06.log manager.2009-10-06.log tomcat.log in none of this files i notice any change with a system.out.println, where should this configuration be ? tnx! – Piecework

What version of Tomcat are you running? – Centra