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by Goldy Lukka.
Original Post: 7 tips to improve Server Side Java Performance
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I found these 7 tips from one of the newsletters of javaperformancetuning.com and loved to blog here. These tips are authored by Jayson Falkner. He has also authored "Servlets and JSP the J2EE Web Tier" Book. http://www.jspbook.com
#1 Database Connection Pooling - This is a well-established technique. Instead of opening a new database connection each time a query is done, a pool of several connections is shared. Tomcat provides fantastic built-in support for this via the Jakarta Commons Database Connection Pool API, http://jakarta.apache.org/tomcat/tomcat-5.0-doc/jndi-datasource-examples-howto.html.
#2 Don't read flat files from the hard disk. Reading information from the hard drive is really slow. In the JSP world there is a trivial fix to this. We save content as a JSP page, properly translated and encoded in any language. Tomcat automatically converts the JSP to a in-memory servlet the first time someone tries to view the page's content. Any dynamic information the page relies on, say links to pages describing the day's news, is passed around using the popular Model 2 design pattern. The result is that flat files are rarely ever read more than once from the hard drive.
#3 Server-Side Caching. A servlet filter that automatically caches content for you is trivial to deploy, and it can save enormous amounts of time. Here is a full writeup I did on this, http://www.onjava.com/pub/a/onjava/2003/11/19/filters.html.
#4 Client-Side Caching. Set the HTTP response headers (i.e. Control-Cache) that tell a client what it can cache. That way users aren't downloading your header/footer images, style sheets, or javascript files multiple times. Here is a write up I did for this, http://www.jspbook.com/faq.jsp#1069699404218.
#5 Simplify everything. This is a trick taken from Google, but that some sites can't use. The technique is to trim down your content to the smallest amount of stuff you actually need. Ditch flashly DHTML in favor of plainly describing the content. Style things well using an external CSS file, don't embed styles. This results in your sever needing to send less information to a client, thus faster page download times.
#6 GZIP compress when possible. Most web browsers will accept GZIP compressed content (about 1/6th the size of normal content). Compress whenever possible and you will have to send less bytes to a user to convey the same information. Here is a writeup I did on this, http://www.onjava.com/pub/a/onjava/2003/11/19/filters.html.
#7 Know what you are keeping in memory. Far too often I've seen nicely optimized sites crash because someone is abusing either the session or application scopes. Java can have memory leak(ish) stuff. You can't reference a billion objects and expect your JVM to handle it. Whenever you can, use only the request scope for passing objects between resources in your web application. If you must use application or session scope, ensure you eventually clean up the resource.
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