com.oreilly.servlet

Class CacheHttpServlet

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

com.oreilly.servlet.CacheHttpServlet

All Implemented Interfaces:

java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public abstract class CacheHttpServlet
extends javax.servlet.http.HttpServlet

A superclass for HTTP servlets that wish to have their output cached and automatically resent as appropriate according to the servlet's getLastModified() method. To take advantage of this class, a servlet must:

• Extend CacheHttpServlet instead of HttpServlet
• Implement a getLastModified(HttpServletRequest) method as usual

This class uses the value returned by getLastModified() to manage an internal cache of the servlet's output. Before handling a request, this class checks the value of getLastModified(), and if the output cache is at least as current as the servlet's last modified time, the cached output is sent without calling the servlet's doGet() method.

In order to be safe, if this class detects that the servlet's query string, extra path info, or servlet path has changed, the cache is invalidated and recreated. However, this class does not invalidate the cache based on differing request headers or cookies; for servlets that vary their output based on these values (i.e. a session tracking servlet) this class should probably not be used.

No caching is performed for POST requests.

CacheHttpServletResponse and CacheServletOutputStream are helper classes to this class and should not be used directly.

This class has been built against Servlet API 2.2. Using it with previous Servlet API versions should work; using it with future API versions likely won't work.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
CacheHttpServlet()

Method Summary

Modifier and Type	Method and Description
protected void	service(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse res)

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doGet, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CacheHttpServlet

public CacheHttpServlet()

Method Detail

service

protected void service(javax.servlet.http.HttpServletRequest req,
                       javax.servlet.http.HttpServletResponse res)
                throws javax.servlet.ServletException,
                       java.io.IOException

Overrides:

service in class javax.servlet.http.HttpServlet

Throws:

javax.servlet.ServletException

java.io.IOException