How do I set the timezone in Tomcat for a single web app?

EDIT: I was wrong about this. This edit corrects it.

The answer is that you cannot portably set the (default) timezone for a single webapp. But if you are using Java 6 (at least), the java.util.TimeZone class implements the default timezone methods getDefault(), setDefault() and setDefault(TimeZone) using an inheritable thread local. In other words, calling setDefault() only affects the current thread and future child threads.

The behaviour is not documented in the Sun Javadocs. It works for Java 6 and 5 (see above), but there are no guarantees it will work in older or newer Sun JREs. However, I would be very surprised if Sun decided to change/revert to a 'global' model for the default TimeZone. It would break too many existing applications, and besides globals are BAD.

In JDK 6, Sun/Oracle has changed the implementation of Timezone. In JDK 5.0 setDefault sets the timezone in a thread local variable always and not across the JVM and that caused a few issues. Sun acknowledged this as a bug and fixed in JDK 1.6.

In JDK 1.6 onwards ( I checked the source code for both JDK 1.6 and JDK 1.7) if the JVM is not started with a security manager ( or it's not set with System.SetsecurityManager()), setDefault method sets it globally across the JVM and not in a thread specific way. If you want to set it only for a given thread then you have to start JVM with a security manager.

When you start Tomcat JVM with a security manager you need to provide individual permissions which was a no starter for us as we were late in the release cycle. Hence in the security policy file we provided all permissions and we overrode the default JAVA security manager to selectively deny the timezone write access. Due to lazy initialization issue with Timezone class I needed to call Timezone.getDefault() in the static block that makes the Timezone class initialized before the securityManager comes into play.

Here is my test program.

--Policy file test.policy

grant {
        permission java.security.AllPermission;

};

-- Custom Security Manager

import java.security.Permission;
import java.util.TimeZone;


public class CustomSecurityManager extends SecurityManager {

static {
    TimeZone.getDefault().getDisplayName();
}



public CustomSecurityManager() {
    super();
}


public void checkPermission(Permission perm) throws SecurityException,NullPointerException
{

            String propertyName = perm.getName();
            String actionName = perm.getActions();
            if(propertyName != null && actionName != null)
            {
                if(propertyName.equalsIgnoreCase("user.timezone")
                        && actionName.equalsIgnoreCase("write"))
                {
                    throw new SecurityException("Timezone write is not permitted.");
                }

            }

}

}

-- JVM startup Parameters

-Djava.security.manager=CustomSecurityManager -Djava.security.policy=C:/workspace/test/src/test.policy

The only way I found is to setup a filter and change the timezone in the filter,

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
        throws IOException, ServletException {
    TimeZone savedZone = TimeZone.getDefault();
    TimeZone.setDefault(webappZone);
    chain.doFilter(request, response);
    TimeZone.setDefault(savedZone);
}

The setDefault() changes the zone for the thread. So everything running in the thread inside the filter will have a different default timezone. We have to change it back because the thread is shared by other apps. You also need to do the same for your init(), destroy() methods and any other thread you might start in your application.

I had to do this because a third-party library assumes default timezone and we don't have source code. It was a mess because this changes log timezone but we don't want log in different times. The correct way to handle this is to use a specific timezone in any time value exposed to end users.

Set the system variable to CATALINA_OPTS=-Duser.timezone=America/Denver

You can also specify the CATALINA_OPTS in the $TOMCAT_HOME/bin/catalina.sh or %TOMCAT_HOME%\bin\catalina.bat file as well.

Here's a list of acceptable timezones.

Source