JSP Verification Code

<% @ Page contenttype = "image/JPEG" Import = "Java. AWT. *, Java. AWT. image. *, Java. util. *, javax. imageIO. * "%>
<%!
Color getrandcolor (int fc, int BC)... {// obtain the random color in the specified range.
Random random = new random ();
If (FC> 255) fc = 255;
If (BC> 255) BC = 255;
Int r = FC + random. nextint (BC-Fc );
Int G = FC + random. nextint (BC-Fc );
Int B = FC + random. nextint (BC-Fc );
Return new color (R, G, B );
}
%>
<%
// Set the page not to cache
Response. setheader ("Pragma", "No-Cache ");
Response. setheader ("cache-control", "No-Cache ");
Response. setdateheader ("expires", 0 );

// Create an image in memory
Int width = 60, Height = 20;
Bufferedimage image = new bufferedimage (width, height, bufferedimage. type_int_rgb );

// Obtain the image Context
Graphics G = image. getgraphics ();

// Generate a random class
Random random = new random ();

// Set the background color
G. setcolor (getrandcolor (200,250 ));
G. fillrect (0, 0, width, height );

// Set the font
G. setfont (new font ("Times New Roman", Font. Plain, 18 ));

// Draw a border
// G. setcolor (new color ());
// G. drawrect (0, 0, width-1, height-1 );


// Generates 155 random interference lines, making the authentication code in the image hard to be detected by other programs.
G. setcolor (getrandcolor (160,200 ));
For (INT I = 0; I <155; I ++)
...{
Int x = random. nextint (width );
Int y = random. nextint (height );
Int XL = random. nextint (12 );
Int yl = random. nextint (12 );
G. drawline (X, Y, x + XL, Y + yl );
}

// Obtain the random ID code (4 digits)
String srand = "";
For (INT I = 0; I <4; I ++ )...{
String Rand = string. valueof (random. nextint (10 ));
Srand + = rand;
// Display the authentication code to the image
G. setcolor (new color (20 + random. nextint (110), 20 + random. nextint (110), 20 + random. nextint (110); // The color from the call function is the same, probably because the seed is too close, so it can only be generated directly.
G. drawstring (RAND, 13 * I + 6, 16 );
}

// Save the authentication code to the session
Session. setattribute ("RAND", srand );


// The image takes effect
G. Dispose ();

// Output the image to the page
ImageIO. Write (image, "Jpeg", response. getoutputstream ());
%>