Generate verification code in Servlet
Package login;
Import java. AWT. color;
Import java. AWT. graphics;
Import java. AWT. image. bufferedimage;
Import java. Io. ioexception;
Import java. Io. outputstream;
Import java. Io. printwriter;
Import java. util. Random;
Import javax. servlet. servletexception;
Import javax. servlet. http. httpservlet;
Import javax. servlet. http. httpservletrequest;
Import javax. servlet. http. httpservletresponse;
Import javax. servlet. http. httpsession;
Import com.sun.image.codec.jpeg. Unzip codec;
Import com.sun.image.codec.jpeg. encode imageencoder;
/**
* Generate a verification code Servlet
* @ Author Administrator
*
*/
Public class checkcodeservlet extends httpservlet {
Public void Service (httpservletrequest request, httpservletresponse response)
Throws servletexception, ioexception {
System. Out. println ("service called ");
/** 1. Set the server response type to JPG */
Response. setcontenttype ("image/JPEG ");
/** 2. Drawing **/
// 1. Create a space to store images in the memory
Bufferedimage image = new bufferedimage (60, 25, bufferedimage. type_int_rgb );
// 2. Get the paint brush
Graphics G = image. getgraphics ();
// 3. Prepare a random number object
Random r = new random ();
// 4. Set the background color of the image
G. setcolor (new color (R. nextint (255), R. nextint (255), R. nextint (255 )));
// 5. Fill
G. fillrect (0, 0, 60, 25 );
// 6. Set the foreground color of the paint brush (set the font color)
G. setcolor (new color (0, 0 ));
// 7. Generate a random number
String number = string. valueof (R. nextint (99999) + 1000 );
/** Store the verification code in the session */
Httpsession session = request. getsession ();
Session. setattribute ("checkcode", number );
// 8. Digital Image
G. drawstring (number, 15, 15 );
G. drawline (R. nextint (20), R. nextint (20), R. nextint (50), R. nextint (50 ));
G. drawline (R. nextint (20), R. nextint (20), R. nextint (50), R. nextint (50 ));
G. drawline (R. nextint (20), R. nextint (20), R. nextint (50), R. nextint (50 ));
G. drawline (R. nextint (20), R. nextint (20), R. nextint (50), R. nextint (50 ));
/** 3. Use a specific format to compress the image and output it */
// 1. Create a file output stream
Outputstream OS = response. getoutputstream ();
// 2. Use the specified format
Required imageencoder encoder = required codec. createjpegencoder (OS );
Encoder. encode (image );
}
}
Use the verification code generated by Java on the JSP page:
<TD style = "width: 80px">
Verification Code:
</TD>
<TD valign = "Middle">
<Input name = "validatecode" size = "7px"/>
<! -- Equivalent to "#" -->
<A href = "javascript:;" onclick = "document. getelementbyid ('img ').
Src = 'checkcode? '+ New date (). gettime (); "> <span style =" font-size: 12px; "> can't see clearly, change one </span> </a>
<Br/>
<Span style = "color: red;">
<%
String check_error = (string) request. getattribute ("check_error ");
%>
<% = Check_error = NULL? "": Check_error %>
</Span>
</TD>
Configuration in the xmd File
<Servlet>
<Servlet-Name> check </servlet-Name>
<Servlet-class> login. checkcodeservlet </servlet-class>
</Servlet>
<Servlet-mapping>
<Servlet-Name> check </servlet-Name>
<URL-pattern>/checkcode </url-pattern>
</Servlet-mapping>
Some code for verification and judgment:
String validatecode = request. getparameter ("validatecode"); // Verification Code
String checkcode = (string) Session. getattribute ("checkcode ");
Compare In Servlet
