JSP Build Verification Code

<%@ page contenttype= "image/jpeg" import= "java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%!
Color getrandcolor (int fc,int BC) {//random color for a given 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 Page Not Cached
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);

Get Graphics context
Graphics g = image.getgraphics ();

Generate Random Class
Random Random = new Random ();

Set Background color
G.setcolor (Getrandcolor (200,250));
G.fillrect (0, 0, width, height);

Set 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);


Randomly generated 155 lines of interference, so that the image of the authentication code is not easily 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);
}

Take a randomly generated authentication 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 in the image
G.setcolor (new color (20+random.nextint, 20+random.nextint (), 20+random.nextint (110));//Call function out of the same color, May be because the seed is too close, so can only be directly generated
g.DrawString (rand,13*i+6,16);
}

Save authentication Code in session
Session.setattribute ("Rand", SRand);


Image entry into force
G.dispose ();

Output image to Page
Imageio.write (Image, "JPEG", Response.getoutputstream ());


%>


When Linux is not displayed, you can modify it in the following ways

1. Upgrade the JDK to jdk1.4 and then add the run parameters after the Java command
–djava.awt.headless=true.
Tomcat is modifying catalina.sh.
Example:
"$_runjava" $JAVA _opts $CATALINA _opts/
-djava.endorsed.dirs= "$JAVA _endorsed_dirs"-classpath "$CLASSPATH"
-dcatalina.base= "$CATALINA _base"/
-dcatalina.home= "$CATALINA _home"/
-djava.io.tmpdir= "$CATALINA _tmpdir"/
-djava.awt.headless=true/
Org.apache.catalina.startup.Bootstrap "$@" Start/
>> "$CATALINA _base"/logs/catalina.out 2>&1 &

2. Use a Third-party toolkit. such as Pja package, download address http://www.eteks.com/pja/en/#Download