Add verification code to the Java Web login interface __web

Introduction: Add validation code to the Java Web login interface

1, the front-end HTML page part

<form onsubmit= "return FormCheck ()" method= "POST" class= "Form-horizontal" id= "BaseForm" role= "form" name= " BaseForm "enctype=" Multipart/form-data "> <div style=" margin:0px auto;width:400px; > <div class= "Panel Panel-default" style= "opacity:0.8" > <div class= "panel-heading" > <span CLA ss= "Glyphicon glyphicon-lock" ></span> login </div> <div class= "Panel-body" > <div class= " Form-group "> <label for=" username "class=" col-sm-3 Control-label "> Username:</label> <di  V class= "col-sm-9" > <input class= "Form-control" name= "username" value= "${username!"
	       Id= "username" placeholder= "username"/> </div> </div> <div class= "Form-group" > <label for= "Loginpass" class= "Col-sm-3 Control-label" > Secret     code:</label> <div clas s= "col-sm-9" > <input class= "form-control" name= "password" type= "password"placeholder= "Password" id= "Loginpass"/> </div> </div> <div class= "Form-group" > <lab El class= "col-sm-3 control-label" > Authenticode:</label> <div class= "col-sm-9" > <input class= "Form-con" Trol "style=" width:163px "name= checkcode" type= "text" id= "Checkcode"/> <!--Internal automatic Send request, load verification code--> </div> </div> <div class= "Form-group Last" > <div class = "Col-sm-offset-3 col-sm-9" > <button type= "Submit" class= "btn btn-success btn-sm" > Login </button> <butt  On type= "reset" class= "btn btn-success btn-sm" > Reset </button> </div> </div> </div> <div class= "Panel-footer" > < #if context.hasmessage??
		> < #list context.errors as error> ${error} </#list > < #list context.infos as info> ${info} </#list > </#if; </div> </div> </div> </form>

2, back-end controller code

public void Check (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException {
		        Long Time=system.currenttimemillis ();  
				Notifies the browser not to cache Response.setheader ("Content-type", "text/html;charset=utf-8");
				Response.setheader ("Expires", "-1");
				Response.setheader ("Cache-control", "No-cache");
				Response.setheader ("Pragma", "-1");
				Response.setdateheader ("last-modified", time);
				Response.setdateheader ("Date", time);
			Response.setdateheader ("Expires", 0);  
				Response.getwriter (). Write (///"Congratulations on your login success, will be in 3 seconds to jump to the home page, if not jump, please click <a href= ' > Hyperlink </a>");
				int height=33;
				int width=90;
				Get a memory image bufferedimage BufferedImage img=new bufferedimage (width, height, bufferedimage.type_int_rgb);
				Get a brush Graphics g=img.getgraphics ();
				Draws a border drawrect the border of the specified rectangle.
				G.drawrect (0, 0, width, height);
				Fill Color G.setcolor (color.gray);
	G.fillrect (1, 1, width-2, height-2);			Draw disturbing line G.setcolor (Color.Black);
				Random r=new Random ();
				for (int i=0;i<20;i++) G.drawline (r.nextint (width), r.nextint (height), r.nextint (width), r.nextint (height));
				Generating random digital G.setcolor (color.red); G.setfont (New Font ("Microsoft Ya Hei", font.bold|
				Font.Italic);//bold bold, italic italic int d=15;
					StringBuffer sb=new StringBuffer ();//The use of the variable string for (int j=0;j<4;j++) {String Code=r.nextint (10) + "";
					Sb.append (code);
					g.DrawString (code+ "", D, 20);
				d+=20;
				//Enter the validation code into the session to verify the Request.getsession (). setattribute ("Checkcode", sb.tostring ());
	Output hits the Web page Imageio.write (img, "JPG", Response.getoutputstream ()); }

Show results