Sun Microsystems 820434310 Suggested Coding Practices, General Guidelines, Http Session Handling

Java Server Page and Servlet Tuning

Suggested Coding Practices

This section provides some tips on coding practices that improve servlet and JSP application performance.

General Guidelines

Follow these general guidelines to increase performance of the presentation tier:

■Minimize Java synchronization in servlets.

■Don’t 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.

Avoid Shared Modified Class Variables

In the servlet multithread model (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.

HTTP Session Handling

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 Enterprise 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.

■Don’t 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 and accessed using entity beans. Transactions will rollback upon failures to their original state. However, stale and inaccurate data may remain in HttpSession objects. The Enterprise Server provides “read-only” bean-managed persistence entity beans for cached access to read-only data.

30 Sun GlassFish Enterprise Server 2.1 Performance Tuning Guide • January 2009