验证码图片生成及无法显示问题的解决

IntelliJ IDEA实现网页生成验证码相关模块：

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;

public final class ImageUtil {
    
    private static final char[] chars = { '0', '1', '2', '3', '4', '5', '6',
            '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I' };
    private static final int SIZE = 4;
    private static final int LINES = 5;
    private static final int WIDTH = 80;
    private static final int HEIGHT = 40;
    private static final int FONT_SIZE = 30;

    public static Map<String, BufferedImage> createImage() {
        StringBuffer sb = new StringBuffer();
        BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
                BufferedImage.TYPE_INT_RGB);
        Graphics graphic = image.getGraphics();
        graphic.setColor(Color.LIGHT_GRAY);
        graphic.fillRect(0, 0, WIDTH, HEIGHT);
        Random ran = new Random();
        
        for (int i = 1; i <= SIZE; i++) {
            int r = ran.nextInt(chars.length);
            graphic.setColor(getRandomColor());
            graphic.setFont(new Font(null, Font.BOLD + Font.ITALIC, FONT_SIZE));
            graphic.drawString(chars[r] + "", (i - 1) * WIDTH / SIZE,
                    HEIGHT / 2);
            sb.append(chars[r]);
        }
        
        for (int i = 1; i <= LINES; i++) {
            graphic.setColor(getRandomColor());
            graphic.drawLine(ran.nextInt(WIDTH), ran.nextInt(HEIGHT),
                    ran.nextInt(WIDTH), ran.nextInt(HEIGHT));
        }
        Map<String, BufferedImage> map = new HashMap<String, BufferedImage>();
        map.put(sb.toString(), image);
        return map;
    }

    public static Color getRandomColor() {
        Random ran = new Random();
        Color color = new Color(ran.nextInt(256), ran.nextInt(256),
                ran.nextInt(256));
        return color;
    }

    public static InputStream getInputStream(BufferedImage image)
            throws IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);
        encoder.encode(image);
        byte[] imageBts = bos.toByteArray();
        InputStream in = new ByteArrayInputStream(imageBts);
        return in;
    }

}

生成验证码ImageUtill类

    /**
     * 产生登录页面验证码
     */
    @RequestMapping("/createImage.do")
    public void createImage(
            HttpServletResponse response, HttpSession session)
            throws Exception {
        Map<String, BufferedImage> imageMap = ImageUtil.createImage();
        String code = imageMap.keySet().iterator().next();
        session.setAttribute("imageCode", code);
        
        BufferedImage image = imageMap.get(code);
        
        response.setContentType("image/jpeg");
        OutputStream ops = response.getOutputStream();
        ImageIO.write(image, "jpeg", ops);
        ops.close();
    }

JSP网页调用（片段，将上面的ceateImage.do放入src中）：

<tr>
    <td class="login_info">验证码：</td>
    <td class="width70"><input name="code" type="text" class="width70" id="code" onfocus="set_msg('code_msg','');"/></td>
    <td><img src="createImage.do" alt="验证码" title="点击更换" id="code_image" onclick="change();"/></td>  
    <td><span class="required" id="code_msg"></span></td>
</tr>

程序确定是无误的！

可以写成Java程序进行验证图片的生成：









但是：在网页中无法显示验证码图片。错误信息是无法写入Tomcat的temp目录，但temp目录肯定是存在的，原因是写入temp目录必须要管理员权限。
解决方法：
进入tomcat安装目录：C:\Program Files\Apache Software Foundation\Tomcat 8.5
右击temp属性：

对所有用户勾选所有权限，问题解决！！！