Chapter 5 Web Application Tuning

Using the servlet Java cache

The servlet Java cache stores servlet output in Java core memory, which offers a faster response than page caching for servlets that can run under these limitations:

The output does not change during the cache timeout period, and does not depend on request method, parameters, or headers.
The servlet runs with exact path mappings. Responses are not cached if the servlet uses prefix mappings, default mappings, or extension mappings.
Cached content is returned without modification.
Cached response headers are returned without modification, except for:
- The Set-Cookie header, which depends on the com.sybase.jaguar.servlet.javacache.session property described below.
- The Connection header, which depends on the request Connection header.
Return code 200 is used for all cached replies. If the original response uses any other return code, it is not cached.
Chunked replies are not cached.
Only responses to GET requests are cached.

Servlets that cannot run under these limitations may still use the page cache.

To enable and configure the servlet Java cache, configure the following servlet properties for each servlet to be cached, using the Advanced tab in the Servlet Properties window:

com.sybase.jaguar.servlet.javacache.enabled enables the Java cache for the servlet. A value of true enables the Java cache. The default value of false disables the cache. If the Java cache and the page cache are both enabled, the Java cache takes precedence.

com.sybase.jaguar.servlet.javacache.session specifies how session cookie settings are treated by checking Set-Cookie headers in the request and response headers. Allowable values for this property are:

Value	To indicate
`no` (the default)	No session support. EAServer does not check request Set-Cookie headers or return response Set-Cookie headers.
`keep`	Attempt to preserve valid sessions. If the request includes a session identifier, EAServer checks if the session is valid. If it is not, the response Set-Cookie header is set to indicate an invalid session. Otherwise, no Set-Cookie header is returned.
`create`	Preserve valid session and create a new session if the previous session is invalid. If the request includes a session identifier, EAServer checks if the session is valid. If it is not, the response Set-Cookie header is set to indicate a new session. Otherwise, no Set-Cookie header is returned.

com.sybase.jaguar.servlet.javacache.maxsize specifies the size, in kilobytes, of the largest reply that can be cached. Responses larger than this are not cached. The default is 8. The hard upper limit is 100. If you set a value greater than 100, the effective cache size is 100K.
com.sybase.jaguar.servlet.javacache.timeout specifies the time, in seconds, that cached responses remain valid. The default is 60. A negative value specifies an infinite timeout, that is, cached responses do not expire.