servlet--get session,application built-in objects

In the previous blog, using the servlet to obtain the Request,response,config object, in fact, through the servlet program can also get session,application and other built-in objects.

1, obtained httpsession through HttpServletRequest

<span style= "White-space:pre" ></span>//returns the current Sessionpublic abstract HttpSession getsession ();// Returns the current session, and if not, creates a new session object that returns public abstract HttpSession getsession (Boolean Paramboolean);

package linkin;import java.io.ioexception;import javax.servlet.ServletException; Import Javax.servlet.http.httpservlet;import Javax.servlet.http.httpservletrequest;import Javax.servlet.http.httpservletresponse;import Javax.servlet.http.httpsession;public class LinkinServlet extends Httpservlet{private static final Long serialversionuid = 1L; @Overrideprotected void Doget (HttpServletRequest req, HttpServletResponse resp) throws Servletexception, ioexception{httpsession session = Req.getsession (); System.out.println (Session.getid ());//4214f4ce399e02730c3219cf0bd83623session.setattribute ("Age", 25); System.out.println (Session.getattribute ("Age"));//25} @Overrideprotected void DoPost (HttpServletRequest req, HttpServletResponse resp) throws Servletexception, Ioexception{this.doget (req, resp);}} 

<?xml version= "1.0" encoding= "UTF-8"? ><web-app version= "2.5" xmlns= "Http://java.sun.com/xml/ns/javaee" Xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation= "Http://java.sun.com/xml/ns/javaee http ://java.sun.com/xml/ns/javaee/web-app_2_5.xsd "><servlet><servlet-name>linkinservlet</ Servlet-name><servlet-class>linkin. Linkinservlet</servlet-class><init-param><param-name>name</param-name><param-value >LinkinPark...</param-value></init-param></servlet><servlet-mapping>< servlet-name>linkinservlet</servlet-name><url-pattern>/linkinservlet</url-pattern></ Servlet-mapping></web-app>

2, using Genericservlet to obtain ServletContext instance

Public ServletContext Getservletcontext ()  {    return Getservletconfig (). Getservletcontext ();  

Package Linkin;import Java.io.ioexception;import Javax.servlet.servletcontext;import Javax.servlet.servletexception;import Javax.servlet.http.httpservlet;import Javax.servlet.http.httpservletrequest;import Javax.servlet.http.httpservletresponse;public class LinkinServlet Extends httpservlet{private static final long serialversionuid = 1L; @Overrideprotected void Doget (HttpServletRequest req , HttpServletResponse resp) throws Servletexception, Ioexception{servletcontext context = Getservletcontext ();//Get "/", That is, the actual physical location of the project on the server System.out.println (Context.getrealpath ("/"));//e:\workserver\apache-tomcat-6.0.37\webapps\ Linkin} @Overrideprotected void DoPost (HttpServletRequest req, HttpServletResponse resp) throws Servletexception, Ioexception{this.doget (req, resp);}}

<?xml version= "1.0" encoding= "UTF-8"? ><web-app version= "2.5" xmlns= "Http://java.sun.com/xml/ns/javaee" Xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation= "Http://java.sun.com/xml/ns/javaee http ://java.sun.com/xml/ns/javaee/web-app_2_5.xsd "><servlet><servlet-name>linkinservlet</ Servlet-name><servlet-class>linkin. Linkinservlet</servlet-class><init-param><param-name>name</param-name><param-value >LinkinPark...</param-value></init-param></servlet><servlet-mapping>< servlet-name>linkinservlet</servlet-name><url-pattern>/linkinservlet</url-pattern></ Servlet-mapping></web-app>

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servlet--get session,application built-in objects