Question about the servlet Verification Code under LINUXG

For more information about the servlet Verification Code under LINUXG-Linux Enterprise Application-Linux server application, see the following. Our project uses struts1.2. I used sertlet to write a program to generate verification,

BufferedImage buffImg = new BufferedImage (width, height, BufferedImage. TYPE_INT_RGB );
Graphics2D g = buffImg. createGraphics ();

G. setColor (Color. WHITE );
G. fillRect (0, 0, width, height );

Font font = new Font ("Times New Roman", Font. PLAIN, 18 );
G. setFont (font );
G. setColor (Color. BLACK );
G. drawRect (0, 0, width-1, height-1 );

G. setColor (Color. GRAY );

Random random = new Random ();

For (int I = 0; I <40; I ++ ){
Int x1 = random. nextInt (width );
Int y1 = random. nextInt (height );

Int x2 = random. nextInt (10 );
Int y2 = random. nextInt (10 );

G. drawLine (x1, y1, x1 + x2, y1 + y2 );
}

StringBuffer randomCode = new StringBuffer ();

For (int I = 0; I <4; I ++ ){
String strRand = String. valueOf (random. nextInt (10 ));
G. setColor (Color. RED );
G. drawString (strRand, 13 * I + 6, 16 );
RandomCode. append (strRand );
}

// Put the verification code in the cookie
CookieHelper. setCookie (response, "random", randomCode. toString ());

ServletOutputStream out = response. getOutputStream ();
Required imageencoder encoder = required codec. createJPEGEncoder (out );
Encoder. encode (buffImg );
Out. close ();

If the code runs in linux for one or two days, the Verification Code cannot be displayed. the following error is reported:

Type Exception report

Message

Description The server encountered an internal error () that prevented it from fulfilling this request.

Exception

Javax. servlet. ServletException: Servlet execution threw an exception
Org. jboss. web. tomcat. filters. ReplyHeaderFilter. doFilter (ReplyHeaderFilter. java: 81)


Root cause

Java. lang. NoClassDefFoundError
Java. lang. Class. forName0 (Native Method)
Java. lang. Class. forName (Class. java: 164)
Java. awt. GraphicsEnvironment. getLocalGraphicsEnvironment (GraphicsEnvironment. java: 68)
Java. awt. image. BufferedImage. createGraphics (BufferedImage. java: 1141)
Com. suntoward. scihoo. web. servlet. ValidateCode. doGet (ValidateCode. java: 38)
Javax. servlet. http. HttpServlet. service (HttpServlet. java: 697)
Javax. servlet. http. HttpServlet. service (HttpServlet. java: 810)
Org. jboss. web. tomcat. filters. ReplyHeaderFilter. doFilter (ReplyHeaderFilter. java: 81)


Note The full stack trace of the root cause is available in the Apache Tomcat/5.5.9 logs.


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Apache Tomcat/5.5.9

I still don't know why this problem occurs after several methods are changed. Thank you!