Application of 20110607-DAY06 session domain object

The default condition for setmaxage in a cookie is a session level, where the browser shutdown disappears, and SetPath defaults to the directory where the current program resides (the valid directory where the cookie is saved) is actually based on a cookie. If after a browser is closed, the corresponding session in the server generally will be 30 minutes after the destruction, if you want to manage the browser can also obtain the content of the previous session, you need to manually rewrite the contents of the cookie, is to manually set the cookie MaxAge

HttpSession session = Request.getsession (); Cookie cookie = new Cookie ("Jsessionid", Session.getid ()); Cookie.setmaxage (30*60),//cookie effective time, does not recommend setting too long Cookie.setpath ("/*web Resource Path * *"); Response.addcookie (cookie);

When cookies are disabled, the session ID is followed by the URL above all Web sites.

You can rewrite the URL bar using the Response.encodeurl in the Java API, he will follow the current session ID, or use Response.encoderedirecturl to override the redirected URL

Note the difference between request.getsession (create) and Request.getsession (), request.getsession () is equivalent to Request.getsession (true), When the browser checks to see if you have a session, a new session object is created, and Request.getsession (false) returns the current session object and returns null if there is one.

Use session to perform a one-time check code

Import Java.awt.Color; Import Java.awt.Font; Import Java.awt.Graphics; Import Java.awt.Graphics2D; Import Java.awt.image.BufferedImage; Import java.io.IOException; Import Java.io.OutputStream; Import Java.util.Random; Import Javax.imageio.ImageIO; Import javax.servlet.ServletException; Import Javax.servlet.http.HttpServlet; Import Javax.servlet.http.HttpServletRequest; Import Javax.servlet.http.HttpServletResponse; public class Imageservlet extends HttpServlet {private static final int WIDTH = 130; private static final int HEIGHT = 30 ; public void doget (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException { BufferedImage image = new BufferedImage (WIDTH,HEIGHT,BUFFEREDIMAGE.TYPE_INT_RGB); Graphics g = image.getgraphics (); SetBackground (g); SetBorder (g); Drawrandomline (g); String random = Drawrandomnum ((graphics2d) g); Request.getsession (). setattribute ("Checkcode", random); Response.setheader ("Content-type", "image/jpeg"); Expires:-1//cachE-control:no-cache//pragma:no-cache//The following code must not be less response.setdateheader ("Expires",-1); Response.setheader ("Cache-control", "No-cache"); Response.setheader ("Pragma", "No-cache"); Response.setcontenttype ("Image/jpeg"); OutputStream out = Response.getoutputstream (); Imageio.write (image, "JPG", out); } private void SetBackground (Graphics g) {G.setcolor (color.white); g.fillrect (0, 0, WIDTH, HEIGHT);} private void Setbor Der (Graphics g) {G.setcolor (Color.Blue); G.drawrect (1, 1, WIDTH-2, HEIGHT-2);} private void Drawrandomline (Graphics g) { G.setcolor (Color.green); for (int i=0;i<5;i++) {int x1 = new Random (). Nextint (WIDTH); int y1 = new Random (). Nextint (HEIGHT); int x2 = new Random ( ). Nextint (WIDTH); int y2 = new Random (). Nextint (HEIGHT); G.drawline (x1, y1, x2, y2); }//[/u4e00-/u9fa5] 30*3.14/180 private String drawrandomnum (graphics2d g) {G.setcolor (color.red); G.setfont (New Font ( "Song Body", font.bold,20)); Common Font Library String base = "/u7684/u4e00/u4e86/u662f/u6211/u4e0d/u5728/u4eba/u4eec/u6709/u6765/u4ed6/u8fd9/u4e0a/u7740/u4e2a/u5730/u5230/u5927/u91cc/u8bf4/u5c31/u53bb/u5b50/u5f97/u4e5f/u548c/ u90a3/u8981/u4e0b/u770b/u5929/u65f6/u8fc7/u51fa/u5c0f/u4e48/u8d77/u4f60/u90fd/u628a/u597d/u8fd8/u591a/u6ca1/ u4e3a/u53c8/u53ef/u5bb6/u5b66/u53ea/u4ee5/u4e3b/u4f1a/u6837/u5e74/u60f3/u751f/u540c/u8001/u4e2d/u5341/u4ece/ u81ea/u9762/u524d/u5934/u9053/u5b83/u540e/u7136/u8d70/u5f88/u50cf/u89c1/u4e24/u7528/u5979/u56fd/u52a8/u8fdb/ u6210/u56de/u4ec0/u8fb9/u4f5c/u5bf9/u5f00/u800c/u5df1/u4e9b/u73b0/u5c71/u6c11/u5019/u7ecf/u53d1/u5de5/u5411/ u4e8b/u547d/u7ed9/u957f/u6c34/u51e0/u4e49/u4e09/u58f0/u4e8e/u9ad8/u624b/u77e5/u7406/u773c/u5fd7/u70b9/u5fc3/ u6218/u4e8c/u95ee/u4f46/u8eab/u65b9/u5b9e/u5403/u505a/u53eb/u5f53/u4f4f/u542c/u9769/u6253/u5462/u771f/u5168/ u624d/u56db/u5df2/u6240/u654c/u4e4b/u6700/u5149/u4ea7/u60c5/u8def/u5206/u603b/u6761/u767d/u8bdd/u4e1c/u5e2d/ u6b21/u4eb2/u5982/u88ab/u82b1/u53e3/u653e/u513f/u5e38/u6c14/u4e94/u7b2c/u4f7f/u5199/u519b/u5427/u6587/u8fd0/ U518d/u679c/u600e/u5b9a/u8bb8/u5feb/u660e/u884c/u56e0/u522b/u98de/u5916/u6811/u7269/u6d3b/u90e8/u95e8/u65e0/u5f80/u8239/u671b/u65b0/u5e26/ u961f/u5148/u529b/u5b8c/u5374/u7ad9/u4ee3/u5458/u673a/u66f4/u4e5d/u60a8/u6bcf/u98ce/u7ea7/u8ddf/u7b11/u554a/ u5b69/u4e07/u5c11/u76f4/u610f/u591c/u6bd4/u9636/u8fde/u8f66/u91cd/u4fbf/u6597/u9a6c/u54ea/u5316/u592a/u6307/ u53d8/u793e/u4f3c/u58eb/u8005/u5e72/u77f3/u6ee1/u65e5/u51b3/u767e/u539f/u62ff/u7fa4/u7a76/u5404/u516d/u672c/ u601d/u89e3/u7acb/u6cb3/u6751/u516b/u96be/u65e9/u8bba/u5417/u6839/u5171/u8ba9/u76f8/u7814/u4eca/u5176/u4e66/ u5750/u63a5/u5e94/u5173/u4fe1/u89c9/u6b65/u53cd/u5904/u8bb0/u5c06/u5343/u627e/u4e89/u9886/u6216/u5e08/u7ed3/ u5757/u8dd1/u8c01/u8349/u8d8a/u5b57/u52a0/u811a/u7d27/u7231/u7b49/u4e60/u9635/u6015/u6708/u9752/u534a/u706b/ u6cd5/u9898/u5efa/u8d76/u4f4d/u5531/u6d77/u4e03/u5973/u4efb/u4ef6/u611f/u51c6/u5f20/u56e2/u5c4b/u79bb/u8272/ u8138/u7247/u79d1/u5012/u775b/u5229/u4e16/u521a/u4e14/u7531/u9001/u5207/u661f/u5bfc/u665a/u8868/u591f/u6574/ u8ba4/u54cd/u96ea/u6d41/u672a/u573a/u8be5/u5e76/u5e95/u6df1/u523b/u5e73/u4f1f/u5fd9/u63d0/u786e/u8fd1/u4eae/u8f7b/u8bb2/u519c/u53e4/u9ed1 /u544a/u754c/u62c9/u540d/u5440/u571f/u6e05/u9633/u7167/u529e/u53f2/u6539/u5386/u8f6c/u753b/u9020/u5634/u6b64/ u6cbb/u5317/u5fc5/u670d/u96e8/u7a7f/u5185/u8bc6/u9a8c/u4f20/u4e1a/u83dc/u722c/u7761/u5174/u5f62/u91cf/u54b1/ u89c2/u82e6/u4f53/u4f17/u901a/u51b2/u5408/u7834/u53cb/u5ea6/u672f/u996d/u516c/u65c1/u623f/u6781/u5357/u67aa/ u8bfb/u6c99/u5c81/u7ebf/u91ce/u575a/u7a7a/u6536/u7b97/u81f3/u653f/u57ce/u52b3/u843d/u94b1/u7279/u56f4/u5f1f/ u80dc/u6559/u70ed/u5c55/u5305/u6b4c/u7c7b/u6e10/u5f3a/u6570/u4e61/u547c/u6027/u97f3/u7b54/u54e5/u9645/u65e7/ u795e/u5ea7/u7ae0/u5e2e/u5566/u53d7/u7cfb/u4ee4/u8df3/u975e/u4f55/u725b/u53d6/u5165/u5cb8/u6562/u6389/u5ffd/ U79cd/u88c5/u9876/u6025/u6797/u505c/u606f/u53e5/u533a/u8863/u822c/u62a5/u53f6/u538b/u6162/u53d4/u80cc/u7ec6 "; StringBuffer sb = new StringBuffer (); int x = 10; for (int i=0;i<4;i++) {String ch = base.charat (new Random (). Nextint (Base.length()))+""; Sb.append (CH); Before writing the word, set the rotation int degree = new Random (). Nextint ()%30; G.rotate (degree*math.pi/180, X, 20); g.DrawString (CH, x, 20); G.rotate (-degree*math.pi/180, X, 20); x = x+30; return sb.tostring (); public void DoPost (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException {DoG ET (request, response); } }

Import java.io.IOException; Import javax.servlet.ServletException; Import Javax.servlet.http.HttpServlet; Import Javax.servlet.http.HttpServletRequest; Import Javax.servlet.http.HttpServletResponse; public class Registerservlet extends HttpServlet {public void doget (HttpServletRequest request, HttpServletResponse resp Onse) throws Servletexception, IOException {request.setcharacterencoding ("UTF-8"); Verify that the authentication code is valid before processing the registration request String C_ Checkcode = Request.getparameter ("Checkcode"); String s_checkcode = (string) request.getsession (). getattribute ("Checkcode"); if (c_checkcode!=null && s_checkcode!=null && c_checkcode.equals (S_checkcode)) {System.out.println (" Process Registration Requests ... "); } else{System.out.println ("Authentication code error.") "); } } public void DoPost (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException { Doget (request, response); } }

PS: In development, if there is the need to retrieve data, it is best to use a two-chain collection.