Some Notes on Coding

some of the points you should note while doing development

1. on java

• Use primitive data types instead of objects as instance variables.
• Use the final modifier on instance-variable definitions to create immutable internally accessible objects
• Eliminate unnecessary casts (use jdk1.5 feature)
• String.equals() is expensive if you are only testing for an empty string. It is quicker to test if the length of the string is 0.
• When using Vector, ensure that elementAt() is not used inside a loop.
• Modify java.lang.String to cache the hashCode if you are using many string keys in hash tables [note Sun added this optimization to the String class in SDK 1.3]
• Reorder CLASSPATH so that the most used libraries occur first
• Compile java files with the optimizer on.

 

2. On JDBC

• Turn off autocommit, but don't leave transactions open for too long.
• Cache any required metadata and use metadata methods as rarely as possible as they are quite slow. Use Connection.setReadOnly(true) to optimize read-only
• Choose the optimal cursor: forward-only for sequential reads; insensitive for two-way scrolling. Avoid insenstive cursors for queries that only return one row.
• Use a parametrized remote procedure call (RPC) rather than passing parameters as part of the RPC call, e.g. use Connection.prepareCall("Call getCustName (?)").setLong (1,12345) rather than Connection.prepareCall("Call getCustName (12345)")
• CachedRowSet provides cached result sets that do not require continuous connection to the database, allowing connections to be reused more efficiently.
• Use PreparedStatements to batch statements for optimal performance.

 

3. On JSP/Servlet

• Avoid using the SingleThreadModel interface for servlets: write thread-safe code instead.
• ServletRequest.getRemoteHost() is very inefficient, and can take seconds to complete the reverse DNS lookup it performs.
• OutputStream can be faster than PrintWriter. JSPs are only generally slower than servlets when returning binary data, since JSPs always use a PrintWriter, whereas servlets can take advantage of a faster OutputStream.
• Do not store large object graphs in javax.servlet.http.HttpSession. Servlets may need to serialize and deserialize HttpSession objects for persistent sessions, and making them large produces a large serialization overhead.
• Call HttpSession.invalidate() to clean up a session when you no longer need to use it.
• For Web pages that don't require session tracking, save resources by turning off automatic session creation using: <%@ page session="false"%>
• Timeout sessions more quickly by setting the timeout or using session.setMaxInactiveInterval().
• Use the include directive <%@ include file="copyleft.html" %>where possible, as this is a compile-time directive (include action is a runtime directive).
• Use the jspInit() method to cache static data, and release them in the jspDestroy() method.