This section provides some tips on coding practices that improve servlet and JSP application performance.
Follow these general guidelines to increase performance of the presentation tier:
Minimize Java synchronization in servlets.
Do not use the single thread model for servlets.
Use the servlet's init() method to perform expensive one-time initialization.
Avoid using System.out.println() calls.
In the servlet multithread model which is the default, a single instance of a servlet is created for each application server instance. All requests for a servlet on that application instance share the same servlet instance. This can lead to thread contention if there are synchronization blocks in the servlet code. So, avoid using shared modified class variables, since they create the need for synchronization.
Follow these guidelines when using HTTP sessions:
Create sessions sparingly. Session creation is not free. If a session is not required, do not create one.
Use javax.servlet.http.HttpSession.invalidate() to release sessions when they are no longer needed.
Keep session size small, to reduce response times. If possible, keep session size below seven KB.
Use the directive <%page session="false"%> in JSP files to prevent the Server from automatically creating sessions when they are not necessary.
Avoid large object graphs in an HttpSession. They force serialization and add computational overhead. Generally, do not store large objects as HttpSession variables.
Do not cache transaction data in HttpSession. Access to data in an HttpSession is not transactional. Do not use it as a cache of transactional data, which is better kept in the database.