Servlet Tutorials

HttpSession interface
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HttpSession interface

HttpSession interface can be used a container creates a session id for each user and this id to identify the particular user.An object of HttpSession can be used to perform two tasks:

bind objects view and manipulate information about a session, such as the session identifier, creation time, and last accessed time.

HttpSession object

Getting the HttpSession object ?

The HttpServletRequest interface provides two methods to get the object of HttpSession:

  1. public HttpSession getSession():Returns the current session associated with this request, or if the request does not have a session, creates one.
  2. public HttpSession getSession(boolean create):Returns the current HttpSession associated with this request or, if there is no current session and create is true, returns a new session.

Commonly used methods of HttpSession interface

  1. public String getId():Returns a string containing the unique identifier value.
  2. public long getCreationTime():Returns the time when this session was created, measured in milliseconds since midnight January 1, 1970 GMT.
  3. public long getLastAccessedTime():Returns the last time the client sent a request associated with this session, as the number of milliseconds since midnight January 1, 1970 GMT.
  4. public void invalidate():Invalidates this session then unbinds any objects bound to it.

Example HttpSession

We are setting the attribute in the session scope and getting that value from the session scope in another servlet.

Then we can set the attribute in the session scope and used the setAttribute() method of HttpSession interface and to get the attribute, we have used the getAttribute method.

index.html
<form action="servlet1">
Name:<input type="text" name="userName"/><br/>
<input type="submit" value="go"/>
</form>
FirstServlet.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class FirstServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response){
		try{
		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		String n=request.getParameter("userName");
		out.print("Welcome "+n);
		HttpSession session=request.getSession();
		session.setAttribute("uname",n);
		out.print("<a href='servlet2'>visit</a>");
		out.close();
                }catch(Exception e){System.out.println(e);}
	}
}
SecondServlet.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class SecondServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
		try{
		response.setContentType("text/html");
		PrintWriter out = response.getWriter();
		HttpSession session=request.getSession(false);
		String n=(String)session.getAttribute("uname");
		out.print("Hello "+n);
		out.close();
                }catch(Exception e){System.out.println(e);}
	}
}
web.xml
<web-app>
<servlet>
<servlet-name>s1</servlet-name>
<servlet-class>FirstServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>s1</servlet-name>
<url-pattern>/servlet1</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>s2</servlet-name>
<servlet-class>SecondServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>s2</servlet-name>
<url-pattern>/servlet2</url-pattern>
</servlet-mapping>
</web-app>
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