📄 sessionservlet.java
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import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.util.*;/** * This servlet demonstrates how to manipulate and use sessions. */public class SessionServlet extends HttpServlet { /** * Process the HTTP Get request. */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); if (session.isNew()) { // This is a new session, ask the user for his data askForIdentification(request, response); } else { // This session is not new, // respond with the data associated with the session clientAlreadyKnown(request, response); } } /** * Send a form to the client asking for the user's name and favorite color. */ private void askForIdentification(HttpServletRequest request, HttpServletResponse response) throws IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<head><title>SessionServlet</title></head>"); out.println("<body>"); // Print a form asking for a name and a favorite color. // Notice the use of encodeURL() to make sure the session tracking works String my_url = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + request.getContextPath() + request.getServletPath(); out.println("<FORM METHOD=\"post\" ACTION=\"" + response.encodeURL(my_url) + "\">"); out.println("<br>"); out.println("What is your name: <INPUT TYPE=\"text\" NAME=\"name\" >"); out.println("<br>"); out .println("What is your favorite color: <INPUT TYPE=\"text\" NAME=\"color\" >"); out.println("<br>"); out.println("<INPUT TYPE=\"submit\" >"); out.println("<br>"); out.println("</FORM>"); out.println("</body></html>"); } /** * Handle the case where we already know the user's name * and favorite color. Respond with the name and color. */ private void clientAlreadyKnown(HttpServletRequest request, HttpServletResponse response) throws javax.servlet.ServletException, java.io.IOException { // inspect the session to get the client's name and favorite color HttpSession session = request.getSession(); String name = (String) session.getAttribute("name"); String color = (String) session.getAttribute("color"); response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<head><title>SessionServlet</title></head>"); out.println("<body>"); out.println("I know you, " + name + ", your favorite color is " + color); out.println("</body></html>"); } /** * Process the HTTP POST request. * Extract the form data from the request and store it * as session attributes for later use. */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws javax.servlet.ServletException, java.io.IOException { // have to get the session before writing any output HttpSession session = request.getSession(); response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<head><title>SessonServlet</title></head>"); out.println("<body>"); // Get the user's name and favorite color from the form String name = request.getParameter("name"); String color = request.getParameter("color"); // Set two attributes in the session to hold them. session.setAttribute("name", name); session.setAttribute("color", color); out.println("Thanks " + name + ", I like " + color + " too!<br>"); out.println("</body></html>"); } }⌨️ 快捷键说明
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