java 验证码servlet怎么把图片传到jsp

Question

如题所述

Answer 1

在JSP上<img src="servlet.do"> ，然后这个servlet.do的servlet直接以图片方式输出随机生成的数字即可。与后台验证是通过session实现的。直接上代码了。

package system.servlet;

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.imageio.ImageIO;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import system.constant.BusinessConfigConst;

public class ServletAuthCode extends HttpServlet {

private static final long serialVersionUID = 1L;

private Font mFont = new Font("Arial Black", Font.PLAIN, 15); // 设置字体

private int lineWidth = 3; // 干扰线的长度=1.414*lineWidth

private int width = 46; // 定义图形大小

private int height = 21; // 定义图形大小

private int count = 200;

protected void doGet(HttpServletRequest request, HttpServletResponse response) {
doPost(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) {
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/gif");

request.getSession().removeAttribute(BusinessConfigConst.SESSION_AUTH_CODE);

// 在内存中创建图象
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// 获取图形上下文
Graphics2D g = (Graphics2D) image.getGraphics();
// 生成随机类
Random random = new Random();
// 设定背景色
g.setColor(getRandColor(200, 250)); // ---1
g.fillRect(0, 0, width, height);
// 设定字体
g.setFont(mFont);
// 画边框
g.setColor(getRandColor(0, 20)); // ---2
g.drawRect(0, 0, width - 1, height - 1);
// 随机产生干扰线
for (int i = 0; i < count; i++) { // g.setColor(Color.BLUE);
g.setColor(getRandColor(150, 200)); // ---3
int x = random.nextInt(width - lineWidth - 1) + 1; // 保证画在边框之内
int y = random.nextInt(height - lineWidth - 1) + 1;
int xl = random.nextInt(lineWidth);
int yl = random.nextInt(lineWidth);
g.drawLine(x, y, x + xl, y + yl);
}
// 取随机产生的认证码(4位数字)
String sRand = "";
for (int i = 0; i < 3; i++) {
String rand = String.valueOf(random.nextInt(10));
sRand += rand;
// 将认证码显示到图象中
g.setColor(new Color(20 + random.nextInt(130), 20 + random.nextInt(130), 20 + random.nextInt(130)));
g.drawString(rand, (13 * i) + 6, 16);
}

// System.out.println(sRand);
// 将认证码存入SESSION
request.getSession().setAttribute(BusinessConfigConst.SESSION_AUTH_CODE, sRand);
// 图象生效
g.dispose();
// 输出图象到页面

try {
ImageIO.write(image, "PNG", response.getOutputStream());
} catch (IOException e) {
e.printStackTrace();
}
}

private Color getRandColor(int fc, int bc) { // 取得给定范围随机颜色
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);
}
}

Answer 2

在JSP页面中的验证码：
<img alt="验证码" name="reqCode" id="reqCode" src="<%=request.getContextPath() %>/code"/>
code是一个servlet，它在web.xml中的配置是：
<servlet>
<servlet-name>Code</servlet-name>
<servlet-class>com.niit.servlet.Code</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Code</servlet-name>
<url-pattern>/code</url-pattern>
</servlet-mapping>本回答被网友采纳

Answer 3

验证码在前天的图片只是html的显示表达，实际上你是产生一张图片将它写入jsp的response输出流中

Answer 4

在jsp使用图片的src的属性,使他指向servlet