Session sharing in Apache Tomcat 6
Sometimes when you want to create large portal-like application which consists of a few smaller applications, or you want to create your own SSO (Single Sign On) domain, you must share session and session data between all interested applications.
This article will show you how you can share session and data across applications in Apache Tomcat 6.
Enabling session sharing
Open $CATALINA_HOME/conf/server.xml, find the 8080 connector definition:
<connector port="8080" protocol="HTTP/1.1" connectiontimeout="20000" redirectport="8443" />
and simply add emptySessionPath="true" attribute to it so that it looks something like this:
<Connector port="8080" protocol="HTTP/1.1" emptySessionPath="true" connectionTimeout="20000" redirectPort="8443" />
Test projects
There are two simple applications called session1 and session2.
session1 increments the counter:
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>++</title>
</head>
<body>
<h1>I'm incrementing the counter!</h1>
<c:set var="counter" value="${sessionScope.counter + 1}" scope="session" />
<h1>Current counter value is ${sessionScope.counter}</h1>
</body>
</html>
session2 decrements the counter:
Deploying
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>--</title>
</head>
<body>
<h1>I'm decrementing the counter!</h1>
<c:set var="counter" value="${sessionScope.counter - 1}" scope="session" />
<h1>Current counter value is ${sessionScope.counter}</h1>
</body>
</html>
Deploy both applications and refreshed a few times their index pages:
http://localhost:8080/session1/
http://localhost:8080/session2/
although the JSESSIONID cookie was the same:
counters were independent. The first one showed +4, the second one showed -4.
The problem and the solution
Problem: even though the session id is the same in both applications you cannot share data directly using HttpSession object.
Solution: you have to use session-aware cross contexts in order to share data between applications.
Cross contexts in Apache Tomcat
First you have to allow applications to access each others' contexts.
Open $CATALINA_HOME/conf/context.xml and add crossContext="true" attribute to the root element:
<?xml version='1.0' encoding='utf-8'?>Re-start the server.
<Context crossContext="true">
<WatchedResource>WEB-INF/web.xml</WatchedResource>
<Manager pathname="" />
</Context>
Resources: jee-bpel-soa
