Java - Servlet - Mazenet Solution
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This document discusses servlets, servlet configuration, servlet context, session tracking techniques, and servlet filters in Java web applications. It explains that servletconfig is used to configure individual servlets while servletcontext is used for global application configuration. Session tracking can be done via cookies, hidden form fields, URL rewriting, or HTTP session. Filters provide preprocessing and postprocessing of requests and have initialization, processing, and destruction lifecycle methods.
Java - Servlet - Mazenet Solution
- 1. Servlets By Sharmilee J Java Trainer Mazenet Solution
- 3. Servlet config Interface • An object of ServletConfig is created by the web container for each servlet. • This object can be used to get configuration information from web.xml file Advantage: • No need to update in web.xml if any changes occurs. Method: getServletConfig()
- 4. Syntax: public ServletConfig getServletConfig(); <web-app> <servlet> <init-param> <param-name>parametername</param-name> <param-value>parametervalue</param-value> </init-param> </servlet> </web-app>
- 6. ServletContext Interface • An object of ServletContext is created by the web container at time of deploying the project • <context-param>element is used Method: getServletContext() method of ServletConfig interface returns the object of ServletContext. Syntax: public ServletContext getServletContext()
- 8. Diff between ServletConfig & ServletContext ServletConfig ServletContext ServletConfig available in javax.servlet.*; package ServletContext available in javax.servlet.*; package ServletConfig object is one per servlet class ServletContext object is global to entire web application Object of ServletConfig will be created during initialization process of the servlet Object of ServletContext will be created at the time of web application deployment Scope: As long as a servlet is executing, ServletConfig object will be available, it will be destroyed once the servlet execution is completed. Scope: As long as web application is executing, ServletContext object will be available, and it will be destroyed once the application is removed from the server. We should give request explicitly, in order to create ServletConfig object for the first time ServletContext object will be available even before giving the first request In web.xml – <init-param> tag will be appear under <servlet-class> tag In web.xml – <context-param> tag will be appear under <web-app> tag
- 10. Session Tracking • Session refers a particular interval of time. • Session tracking is used to maintain the state of an user. It is known as session management.
- 11. Session Tracking Techniques: There are four techniques used in Session tracking: • Cookies • Hidden Form Field • URL Rewriting • HttpSession
- 12. 1. cookies
- 13. Cookies • It is a piece of information. • In cookies, request from same client is not considered as the new request.
- 14. Types of cookies. 1. Non-Persistent cookie. Valid for single session 2.Persistent cookie. Valid for multiple session. Advantage of Cookies: • State maintenance Disadvantages: • Cookie can be disabled from the browser. • Only textual information can be set.
- 15. Cookie creation: • Cookie ck=new Cookie("user","sonoo jaiswal"); //creating cookie object • response.addCookie(ck); //adding cookie in the response Cookie deletion: • Cookie ck=new Cookie("user",""); //deleting value of cookie • ck.setMaxAge(0); //changing the maximum age to 0 seconds • response.addCookie(ck); //adding cookie in the response
- 16. 2. Hidden Form Field
- 17. Hidden Form field • We store the information in the hidden field and get it from another servlet. <input type="hidden" name="uname" value=“java"> Advantage: • Work when the cookie is disabled. Disadvantages: • Only textual information can be sent. • Maintained at server side.
- 18. 3. URL Rewriting
- 19. URL Rewriting • Appending session ID to the url is known as url Rewriting. • We implement url rewriting by caling, response.encodeURL(String url); Advantage: • Work when the cookie is disabled. • No form submission is not required as in case of hidden form field.
- 20. 4. HTTP Session
- 21. Http Session • Used to view and manipulate information about a session, such as the session identifier, creation time, and last accessed time. • HttpSession session=request.getSession();
- 22. Servlet Filters
- 23. Servlet Filters • A filter is an object that is invoked at the preprocessing and postprocessing of a request. • servlet filter is pluggable, i.e if we remove filter in web.xml, filter is automatically removed. Advantage • Encryption and decryption • Input validation • Recording all incoming requests
- 24. Filter API Three interfaces: • Filter • FilterChain • FilterConfig Filter interface life cycle methods: 1.init(filterConfig) 2.doFilter(ServletRequest,ServletResponse,FilterChain) 3.destroy()
- 25. FilterConfig interface life cycle methods: 1.getInitParameter() 2.getInitParameterNames() 3.getServletContext() 4.getFilterName() FilterChain interface life cycle method: 1.doFilter(ServletRequest,ServletResponse)