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[[setting-session-characteristics]]
=== Setting Session Characteristics

Sessions are a concept within the Servlet api which allow requests to store and retrieve information across the time a user spends in an application.  
Choosing the correct session manager implementation is an important consideration for every application as each can fit and perform optimally in different situations.
If you need a simple in-memory session manager that can persist to disk then the `HashSessionManager` can be a good place to start.  
If you need a session manager that can work in a clustered scenario with multiple instances of Jetty, then the JDBC session manager can be an excellent option.
Jetty also offers more niche session managers that leverage backends such as MongoDB, Inifinispan, or even Google's Cloud Data Store.

To modify the session characteristics of a web application, you can use the following parameters, applying them as in one of the example configurations:

[[using-init-parameters]]
==== Using Init Parameters

Use these parameters to set session characteristics.

.Init Parameters
[cols=",,",options="header",]
|=======================================================================
|Context Parameter |Default Value |Description
|org.eclipse.jetty.servlet.SessionCookie |JSESSIONID |Session cookie
name defaults to JSESSIONID, but can be set for a particular webapp with
this context param.

|org.eclipse.jetty.servlet.SessionIdPathParameterName |jsessionid
|Session URL parameter name. Defaults to jsessionid, but can be set for
a particular webapp with this context param. Set to "none" to disable
URL rewriting.

|org.eclipse.jetty.servlet.SessionDomain |- |Session Domain. If this
property is set as a ServletContext param, then it is used as the domain
for session cookies.If it is not set, then no domain is specified for
the session cookie.

|org.eclipse.jetty.servlet.SessionPath |- |Session Path. If this
property is set as a ServletContext param, then it is used as the path
for the session cookie. If it is not set, then the context path is used
as the path for the cookie.

|org.eclipse.jetty.servlet.MaxAge |-1 |Session Max Age. If this property
is set as a ServletContext param, then it is used as the max age for the
session cookie. If it is not set, then a max age of -1 is used.

|org.eclipse.jetty.servlet.CheckingRemoteSessionIdEncoding |false |If
true, Jetty will add JSESSIONID parameter even when encoding external
urls with calls to encodeURL(). False by default.
|=======================================================================

[[applying-init-parameters]]
===== Applying Init Parameters

The following sections provide examples of how to apply the init parameters.

[[context-parameter-example]]
====== Context Parameter Example

You can set these parameters as context parameters in a web application's `WEB-INF/web.xml` file:

[source, xml, subs="{sub-order}"]
----

<?xml version="1.0" encoding="UTF-8"?>
<web-app
  xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
  version="2.5">
  ...
  <context-param>
    <param-name>org.eclipse.jetty.servlet.SessionCookie</param-name>
    <param-value>XSESSIONID</param-value>
  </context-param>
  <context-param>
    <param-name>org.eclipse.jetty.servlet.SessionIdPathParameterName</param-name>
    <param-value>xsessionid</param-value>
  </context-param>
  ...
</web-app>

        
----

[[web-application-examples]]
====== Web Application Examples

You can configure init parameters on a web application, either in code, or in a Jetty context xml file equivalent:

[source, xml, subs="{sub-order}"]
----

<Configure class="org.eclipse.jetty.webapp.WebAppContext">
  <Set name="contextPath">/test</Set>
  <Set name="war"><SystemProperty name="jetty.home" default="."/>/webapps/test</Set>
 
  ...
 
  <Call name="setInitParameter">
        <Arg>org.eclipse.jetty.servlet.SessionCookie</Arg>
        <Arg>XSESSIONID</Arg>
  </Call>
  <Call name="setInitParameter">
        <Arg>org.eclipse.jetty.servlet.SessionIdPathParameterName</Arg>
        <Arg>xsessionid</Arg>
  </Call>
</Configure>

        
----

[[init-parameter-examples]]
====== SessionManager Examples

You can configure init parameters directly on a `SessionManager` instance, either in code or the equivalent in xml:

[source, xml, subs="{sub-order}"]
----

<Configure class="org.eclipse.jetty.webapp.WebAppContext">
  <Set name="contextPath">/test</Set>
  <Set name="war"><SystemProperty name="jetty.home" default="."/>/webapps/test</Set>
 
   ...

  <Get name="sessionHandler">
     <Set name="sessionManager">
         <New class="org.eclipse.jetty.server.session.HashSessionManager">
            <Set name="sessionCookie">XSESSIONID</Set>
            <Set name="sessionIdPathParameterName">xsessionid</Set>
         </New>
     </Set>
  </Get>
</Configure>

        
----

==== Using Servlet 3.0 Session Configuration

With the advent of http://jcp.org/en/jsr/detail?id=315[Servlet Specification 3.0] there are new APIs for configuring session handling characteristics. 
What was achievable before only via Jetty-specific link:#session-init-params[init-parameters] can now be achieved in a container-agnostic manner either in code, or via `web.xml`.

[[session-cookie-configuration]]
===== SessionCookieConfiguration

The http://docs.oracle.com/javaee/6/api/javax/servlet/SessionCookieConfig.html[javax.servlet.SessionCookieConfig] class can be used to set up session handling characteristics. 
For full details, consult the http://docs.oracle.com/javaee/6/api/javax/servlet/SessionCookieConfig.html[javadoc].

Below is an example of this implementation: a `ServletContextListener` retrieves the `SessionCookieConfig` and sets up some new values when the context is being initialized:

[source, java, subs="{sub-order}"]
----
import javax.servlet.SessionCookieConfig;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class TestListener implements ServletContextListener 
{

    public void contextInitialized(ServletContextEvent sce) 
    {
        String comment = "This is my special cookie configuration";
        String domain = "foo.com";
        String path = "/my/special/path";
        boolean isSecure = true;
        boolean httpOnly = false;
        int maxAge = 30000;
        String cookieName = "FOO_SESSION";


        SessionCookieConfig scf = sce.getServletContext().getSessionCookieConfig();

        scf.setComment(comment);
        scf.setDomain(domain);
        scf.setHttpOnly(httpOnly);
        scf.setMaxAge(maxAge);
        scf.setPath(path);
        scf.setSecure(isSecure);
        scf.setName(cookieName);
    }

    public void contextDestroyed(ServletContextEvent sce) 
    {

    }
}
----

You can also use `web.xml` to configure the session handling characteristics instead: here's an example doing exactly the same as above instead of using code:

[source, xml, subs="{sub-order}"]
----
<?xml version="1.0" encoding="UTF-8"?>
<web-app
   xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
   metadata-complete="true"
   version="3.0">

   <session-config>
      <cookie-config>
         <comment>This is my special cookie configuration</comment>
         <domain>foo.com</domain>
         <http-only>false</http-only>
         <max-age>30000</max-age>
         <path>/my/special/path</path>
         <secure>true</secure>
         <name>FOO_SESSION</name>
      </cookie-config>
   </session-config>
</web-app>
----

[[session-tracking-modes]]
===== SessionTrackingModes

In addition to the configuration of link:#session-cookie-configuration[session cookies], since Servlet 3.0 you can also use the http://docs.oracle.com/javaee/6/api/javax/servlet/SessionTrackingMode.html[javax.servlet.SessionTrackingMode] to configure session tracking.

To determine what are the _default_ session tracking characteristics used by the container, call:

[source, java, subs="{sub-order}"]
----
javax.servlet.SessionContext.getDefaultSessionTrackingModes();
----

This returns a java.util.Set of javax.servlet.SessionTrackingMode. The
_default_ session tracking modes for Jetty are:

* http://docs.oracle.com/javaee/6/api/javax/servlet/SessionTrackingMode.html#COOKIE[SessionTrackingMode.COOKIE]
* http://docs.oracle.com/javaee/6/api/javax/servlet/SessionTrackingMode.html#URL[SessionTrackingMode.URL]

To see which session tracking modes are actually in effect for this Context, the following call returns a `java.util.Set` of `javax.servlet.SessionTrackingMode`:

[source, java, subs="{sub-order}"]
----
javax.servlet.SessionContext.getEffectiveSessionTrackingModes();
----

To change the session tracking modes, call:

[source, java, subs="{sub-order}"]
----
javax.servlet.SessionContext.setSessionTrackingModes(Set<SessionTrackingMode>);
----

You may also set the tracking mode in `web.xml`, e.g.:

[source, xml, subs="{sub-order}"]
----
<?xml version="1.0" encoding="UTF-8"?>
<web-app
   xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
   metadata-complete="true"
   version="3.0">

   <session-config>
      <tracking-mode>URL</tracking-mode>
      <tracking-mode>COOKIE</tracking-mode>
   </session-config>
</web-app>
----