Use servlet to generate random numbers. The principle is to obtain graphics objects for plotting.

Public class resonperandomimgdemo extends httpservlet {

Int width = 100;

Int Height = 30;

Public void doget (httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {

Response. setcontenttype ("text/html; charset = UTF-8 ");

// Obtain the bufferedimage object and set the size and type of the canvas.

Bufferedimage IMG = new bufferedimage (width, height, bufferedimage. type_int_rgb );

// Obtain the Drawing Object

Graphics2d G = (graphics2d) IMG. getgraphics ();

// Set the background color

Setbackgroudcolor (g );

// Generate a random number

Getnum (g );

// Write the image to the browser

Response. setcontenttype ("image/JPEG ");

ImageIO. Write (IMG, "jpg", response. getoutputstream ());

}

Private void getnum (graphics2d g ){

String STR = "0123456789 qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnm ";

G. setcolor (color. Blue );

For (INT I = 0; I <4; I ++ ){

// Generate a random number. % 30 is also the rotation angle to generate a random number between-30-30.

Int degee = new random (). nextint () % 30;

// Rotate

G. Rotate (degee * Math. PI/180, 20 + (I * 12), 15 );

G. setfont (new font ("", Font. Bold, 20 ));

G. drawstring (Str. charat (new random (). nextint (Str. Length () + "", 20 + (I * 12), 15 );

// Rotate back

G. Rotate (-degee * Math. PI/180, 20 + (I * 12), 15 );

}

}

Private void setbackgroudcolor (graphics2d g ){

G. setbackground (color. White );

G. fillrect (0, 0, width, height );

}

Public void dopost (httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {

Doget (request, response );

}

}

 

// JSP page

// servlettest/servlet/resonperandomimgdemo obtain information on the servelt page