java生成一次性验证码

1.编写生成验证码的工具类：

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;

public class VerifyCode
{
private int w = 70;
private int h = 35;
private Random r = new Random();

private String[] fontNames = { "宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312" };
private String codes = "23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
private Color bgColor = new Color(255, 255, 255);
private String text;

private Color randomColor()
{
int red = this.r.nextInt(150);
int green = this.r.nextInt(150);
int blue = this.r.nextInt(150);
return new Color(red, green, blue);
}

private Font randomFont() {
int index = this.r.nextInt(this.fontNames.length);
String fontName = this.fontNames[index];
int style = this.r.nextInt(4);
int size = this.r.nextInt(5) + 24;
return new Font(fontName, style, size);
}

private void drawLine(BufferedImage image) {
int num = 3;
Graphics2D g2 = (Graphics2D)image.getGraphics();
for (int i = 0; i < num; ++i) {
int x1 = this.r.nextInt(this.w);
int y1 = this.r.nextInt(this.h);
int x2 = this.r.nextInt(this.w);
int y2 = this.r.nextInt(this.h);
g2.setStroke(new BasicStroke(1.5F));
g2.setColor(Color.BLUE);
g2.drawLine(x1, y1, x2, y2);
}
}

private char randomChar() {
int index = this.r.nextInt(this.codes.length());
return this.codes.charAt(index);
}

private BufferedImage createImage() {
BufferedImage image = new BufferedImage(this.w, this.h, 1);
Graphics2D g2 = (Graphics2D)image.getGraphics();
g2.setColor(this.bgColor);
g2.fillRect(0, 0, this.w, this.h);
return image;
}

public BufferedImage getImage() {
BufferedImage image = createImage();
Graphics2D g2 = (Graphics2D)image.getGraphics();
StringBuilder sb = new StringBuilder();

for (int i = 0; i < 4; ++i) {
String s = randomChar();
sb.append(s);
float x = i * 1.0F * this.w / 4.0F;
g2.setFont(randomFont());
g2.setColor(randomColor());
g2.drawString(s, x, this.h - 5);
}
this.text = sb.toString();
drawLine(image);
return image;
}

public String getText() {
return this.text;
}

public static void output(BufferedImage image, OutputStream out) throws IOException
{
ImageIO.write(image, "JPEG", out);
}
}

2.调用 验证码的工具类，创建Servlet保存验证码到Session中：

import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class VerifyCodeServlet extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
VerifyCode vc = new VerifyCode();
BufferedImage image = vc.getImage();

VerifyCode.output(image, response.getOutputStream());

request.getSession().setAttribute("vCode", vc.getText());
}
}

3.jsp中需要产生验证码：

<img src="/VerifyCodeServlet " id="yzm" />

<a href="" onclick="javascript:hyz()"></a>

function hyz(){

$("yzm").src="/VerifyCodeServlet ? a = " +new Date.getTime();    //加上时间戳解决IE浏览器的缓存

}