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Axis2 Session Management

  • July 18, 2006
  • By Deepal Jayasinghe
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Transport session scope

In the case of a Transport session, Axis2 uses transport-related session management techniques to manage session. As an example, in the case of HTTP, it uses HTTP cookies to manage the session. The lifetime of the session is controlled by the transport, not by Axis2; Axis2 stores the service context and serviceGroupContext in the transport session object so that the service can access those contexts as long as the session lives.

One of the key advantages of the Transport session over other sessions is that you can talk to multiple service groups within one transport session. In a SOAP session, you don't have a way to communicate between two service groups, but with the transport session you have that capability. In this case, the number of service instances created depends on the number of transport sessions created.

Deploying a service in a transport session requires you to change services.xml as follows:

<service name="foo" scope=" transportsession">
</service>

If you are using Axis2 nightly builds or planning to use them the next version, deploying a service in a transport session requires additional changes to axis2.xml. That is mainly to improve the memory usage; otherwise, whether you deploy the service in a transport session or not Axis2 tries to create a session object at the transport level; with these changes, it will not create unnecessary objects. To manage the transport-level session, you need to set the manageTransportSession parameter value to true in axis2.xml:

<parameter name="manageTransportSession"
   locked="false">true</parameter>

Application scope

Application scope has the longest lifetime compared to others; the lifetime of the application session is equal to the lifetime of the system. If you deploy a service in application scope, there will be only one instance of that service and obviously there will be only one service context for that service. In the Axis2 world, if you consider the memory footprint and if you don't want to manage the session, the good candidate is to deploy the service in application scope.

When you deploy a service in application scope, a client does not need to send any additional data to use the same session. To deploy a service in application scope, you need to change axis2.xml as shown below:

<service name="foo" scope=" application">
</service>

Managing the session using the service client

Managing the session on the client side involves bit of a work. As mentioned above, both in a SOAP session and Transport session a client has to send the session-related data if he wants to live in the same session. Maybe he can do that for a SOAP session by coping with required reference parameters, but with a Transport session a user must get access to the transport to copy and send cookies.

To make life easier, Axis2 has the built-in capability of managing sessions in the client session by just setting a flag. Then, depending on the service side session, it will send the corresponding data as long as you use the same service client. So, the main requirement is to use the same service client to invoke the service if you want to live in the same session.

If you want to live in the same session, you can create service client as shown below and re-use the created service client object to invoke the service.

Options options = new Options();
options.setManageSession(true);
ServiceClient sender = new ServiceClient();
sender.setOptions(options);

Once you create the service client as shown above, if the service deploys in a SOAP session it will copy the serviceGroupId and send that from the second invocation onwards. If the server sends the session id, such as HTTP cookies, it will copy that to the service context (on the client side) and send it back to the server when the client invokes the service for a second time.

Summary

The stateless nature is one of the main characteristics of Web services, but it is a limitation for advanced Web services developers. Developing an enterprise-level application using Web services is not easy unless you have a session management layer. Axis2 has four levels of sessions to address enterprises-level Web service development issues.





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