solve the problem of 'java web project cannot display verification code'
my java code of the function:
package com.util; import java.awt.Color; import java.awt.Font; import java.awt.Graphics2D; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.sun.image.codec.jpeg.JPEGCodec; import com.sun.image.codec.jpeg.JPEGImageEncoder; /** * @ClassName: CaptchaUtil * @Description: 关于验证码的工具类 * @author 无名 * @date 2016-5-7 上午8:33:08 * @version 1.0 */ public final class CaptchaUtil { private CaptchaUtil(){} /* * 随机字符字典 */ private static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' }; /* * 随机数 */ private static Random random = new Random(); /* * 获取6位随机数 */ private static String getRandomString() { StringBuffer buffer = new StringBuffer(); for(int i = 0; i < 6; i++) { buffer.append(CHARS[random.nextInt(CHARS.length)]); } return buffer.toString(); } /* * 获取随机数颜色 */ private static Color getRandomColor() { return new Color(random.nextInt(255),random.nextInt(255), random.nextInt(255)); } /* * 返回某颜色的反色 */ private static Color getReverseColor(Color c) { return new Color(255 - c.getRed(), 255 - c.getGreen(), - c.getBlue()); } public static void outputCaptcha(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("image/jpeg"); String randomString = getRandomString(); request.getSession(true).setAttribute("randomString", randomString); int width = 100; int height = 30; Color color = getRandomColor(); Color reverse = getReverseColor(color); BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics2D g = bi.createGraphics(); g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16)); g.setColor(color); g.fillRect(0, 0, width, height); g.setColor(reverse); g.drawString(randomString, 18, 20); for (int i = 0, n = random.nextInt(100); i < n; i++) { g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1); } // 转成JPEG格式 ServletOutputStream out = response.getOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); encoder.encode(bi); out.flush(); } }
First, I found that the awt library of java cannot be used on Linux.
So, must add parameters of jvm to run it.
-Djava.awt.headless=true \
As for the tomcat environment, u should add this line '-Djava.awt.headless=true \' to the file of 'catalina.sh' for 8 times.
If it not works. u can try these commands:
yum install libXp.so.6 yum install dejagnu.noarch 1:1.4.4-17.el6 yum install dejavu-sans-mono-fonts.noarch 2.33-1.el6 yum install dejavu-serif-fonts.noarch 2.33-1.el6
Just try, I donot know why~
After doing these things, I still can't solve the problem,
the error log is:
It's the problem of this java class.
then I found that the 1.8 jdk has abandoned the class of com.sun.image.codec.jpeg.JPEGCodec & com.sun.image.codec.jpeg.JPEGImageEncoder
So I change the code from
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); ........... // 转成JPEG格式 ServletOutputStream out = response.getOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); encoder.encode(bi);
to
// 转成JPEG格式 ServletOutputStream out = response.getOutputStream(); ImageIO.write(bi, "JPEG", out);
And it worked: