Java实现登录界面的验证码总结

java实现验证码的步骤：

1.创建验证码的实体类，代码如下：

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 {
/**
*楠岃瘉鐮�
* @author 瑕冧匠鍗�
*/

private int w = 50;
private int h = 25;
private Random r = new Random();
private String[] fontNames = {"瀹嬩綋","鍗庢枃妤蜂綋","榛戜綋","寰蒋闆呴粦","妤蜂綋_GB2312"};
private String codes = "23456789abcdefghjkmnpqrstuvwxyzABCEFGHIJKLMNPQRSTUVWXYZ";
private Color bgColor = new Color(255,255,255);
private String text;

private Color randomColor(){
int red = r.nextInt(200);
int green = r.nextInt(200);
int blue = r.nextInt(200);
return new Color(red,green,blue);
}

private Font randomFont(){
int index = r.nextInt(fontNames.length);
String fontName = fontNames[index];
int style = r.nextInt(4);
int size = r.nextInt(6)+15;
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 = r.nextInt();
int y1 = r.nextInt();
int x2 = r.nextInt();
int y2 = r.nextInt();
g2.setStroke(new BasicStroke(1.5F));
g2.setColor(Color.BLUE);
g2.drawLine(x1,y1,x2,y2);
}
}
private char randomChar(){
int index = r.nextInt(codes.length());
return codes.charAt(index);
}
private BufferedImage createImage(){
BufferedImage image = new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = (Graphics2D)image.getGraphics();
g2.setColor(this.bgColor);
g2.fillRect(0, 0, w, 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*w/4;
g2.setFont(randomFont());
g2.setColor(randomColor());
g2.drawString(s, x, h-5);
}
this.text = sb.toString();
drawLine(image);
return image;
}
public String getText(){
return text;
}
public static void output (BufferedImage image,OutputStream out) throws IOException{
ImageIO.write(image, "JPEG", out);
}
}
2.创建验证码的servlet
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import util.VerifyCode;

@WebServlet("/VerifyCodeServlet")
public class VerifyCodeServlet extends HttpServlet {

/**
* 锟斤拷桑锟斤拷锟斤拷锟斤拷锟街わ拷锟斤拷Servlet
* @author weiqiang
*/

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

VerifyCode vc = new VerifyCode();
response.setHeader("Cache-Control", "no-cache");
response.setContentType("image/jpeg");
BufferedImage bim = vc.getImage();
ImageIO.write(bim, "JPEG", response.getOutputStream());
String verifycode = vc.getText();
request.getSession().setAttribute("verifyCode", verifycode);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
public void destroy(){
super.destroy();
}
public void init() throws ServletException{
}

}

3.在需要使用验证码的地方使用如下代码：
<!--这是看不清刷新一下的函数-->
<script>
function changeVerifyCode(){
document.getElementById("validateCodeImg").src="VerifyCodeServlet?t="+Math.random();

}
</script>
<!-- 这是输入验证码的输入框-->
<INPUT id=txtSN size=4 name=txtSN>
<!-- 这是显示的验证码，以图片显示-->
<!-- src的路劲为servlet的路劲 -->
<img src="<%=basePath%>VerifyCodeServlet" border=0 id="validateCodeImg" style="height: 25px; width: 57px"/><a href="#" onclick="changeVerifyCode()">看不清？换一张</a></TD>


4.实际效果如下