High-performance, high-flexibility JSP and Servlet performance optimization (1)

Is your J2EE application running slowly? Can they withstand rising traffic volumes? This article describes how to develop high-performance and highly elastic JSP pages and Servlet performance optimization technologies. It means to build as fast as possible and adapt to the increasing number of users and their requests. In this article, I will lead you to learn the proven performance Adjustment Technology, which will greatly improve the performance of your servlet and jsp pages, and thus improve the performance of J2EE. These technologies are used in the development phase, such as the design and coding phase. Other technologies are related to configuration.

Method 1: cache data in the HttpServlet init () method

The server will call the servlet init () method after creating the servlet instance and before the servlet processes any request. This method is called only once in the servlet lifecycle. To improve performance, cache static data in init () or complete expensive operations to be completed during initialization. For example, a best practice is to use the JDBC connection pool that implements the javax. SQL. DataSource interface.

DataSource is obtained from the JNDI tree. Every time an SQL statement is called, it is very expensive to use JNDI to search for DataSource, which seriously affects the application performance. Servlet's init () method can be used to obtain DataSource and cache it for later reuse:

public class ControllerServlet extends HttpServlet { private javax.sql.DataSource testDS = null; public void init(ServletConfig config) throws ServletException { super.init(config); Context ctx　= null; try { ctx = new InitialContext(); testDS = (javax.sql.DataSource)ctx.lookup("jdbc/testDS"); } catch(NamingException ne) { ne.printStackTrace(); } catch(Exception e) { e.printStackTrace(); } } public javax.sql.DataSource getTestDS() { return testDS; } ... ... }

Method 2: Disable Automatic servlet and Jsp loading.

After modifying Servlet/JSP, You have to restart the server. Because the automatic loading function reduces development time, this function is considered very useful in the development stage. However, it is very expensive in the running stage; servlet/JSP causes poor performance due to unnecessary loading and increasing the load on the class loader. Similarly, this will cause a strange conflict between the classes loaded by a certain type of loader and the classes loaded by the current class loader. Therefore, in the runtime environment, disable the automatic loading function of servlet/JSP for better performance.

Method 3: Control HttpSession

Many applications need a series of client requests, so they can be associated with each other. Because the HTTP protocol is stateless, Web-based applications need to maintain such a session state. To support applications that require State maintenance, Java servlet technology provides APIs for managing sessions and allowing multiple mechanisms to implement sessions. The HttpSession object plays the role of the session, but the cost is required to use it. Whenever an HttpSession is used and overwritten, it is read by the servlet. You can use the following technologies to improve performance:

Do not create the default HttpSession on the JSP page: by default, the JSP page creates an HttpSession. If you do not need HttpSession on the JSP page, to save performance overhead, use the following page command to avoid automatically creating an HttpSession object:

＜ %@ page session="false"%＞

Do not store large object graphs in HttpSession: If you store data as a large object graph in HttpSession, the application server will have to process the entire HttpSession object each time. This will force Java serialization and increase computing overhead. Due to the serialization overhead, as the data objects stored in the HttpSession object increase, the system throughput will decrease.

Release HttpSession after use: When HttpSession is not used, use HttpSession. invalidate () to invalidate the sesion.

Set the timeout value: a servlet engine has a default timeout value. If you do not delete a session or keep using it for a long time, the servlet engine will delete the session from the memory. Due to the overhead of memory and garbage collection, the larger the session Timeout value, the greater the impact on system elasticity and performance. Try to set the session Timeout value as low as possible.