简单实现Java验证码功能

今晚看到网上有关验证码的实现的代码，很早就想写一个了，感觉验证码挺有意思的，于是就写了一个，然而后来一直加载不出图片。尝试了很多方法，后来终于解决了，原来是我项目里面的 web.xml中没有部署servlet的映射，web.xml如下图：

运行效果如下：

代码如下：

package model; 

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random; 

/**
 * Created by Petty on 2017/5/4.
 */
public class VCode { 

 private int w; //图片宽
 private int h;//图片高
 private Color bgColor = new Color(240,240,240);//背景色
 private Random random = new Random();//随机对象
 //设置字体范围
 private String[] fontNames = {"宋体","华文楷体","黑体","华文新魏","华文隶书","微软雅黑","楷体"};
 //设置字体样式范围
 private int[] fontstyle = {0,1,2,3};
 //设置字号范围
 private int[] fontSizes = {24,25,26,27,28};
 //设置所有字符串范围
 private String codes="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; 

 //无参数构造函数
 public VCode(){ 

 } 

 //带宽和高的构造函数
 public VCode(int w,int h){
  this.w = w;
  this.h = h;
 } 

 //返回一张背景图片
 private BufferedImage createImage(){
  /**
   * 1.创建图片 2.设置背景色
   */
  //创建图片
  BufferedImage img = new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
  //设置背景色
  Graphics g = img.getGraphics();
  g.setColor(bgColor);
  g.fillRect(0,0,w,h);
  return img;
 } 

 // 随机返回字体颜色
 private Color randomColor() {
     int r = random.nextInt(256);
     int g = random.nextInt(256);
     int b = random.nextInt(256);
   return new Color(r, g, b);
   } 

 //随机返回字体样式
 private Font randomFont(){
  //随机生成字体下标，随机从给定的范围内获取一个字体
  int index = random.nextInt(fontNames.length);
  String name = fontNames[index]; 

  //随机生成字体样式下标，随即从给定的范围内获取一个字体样式
  index = random.nextInt(fontstyle.length);
  int style = fontstyle[index]; 

  //随机生成字体大小下标，随机从给定的范围内获取一个字体大小
  index = random.nextInt(fontSizes.length);
  int size = fontSizes[index]; 

  return new Font(name,style,size);
 } 

 //随机返回字体内容
 private String randomChar(){
  int index = random.nextInt(codes.length()); 

  return codes.charAt(index)+"";
 } 

 //随机返回几条干扰线
 private void getLine(BufferedImage img){
  //设置干扰线的宽度为1.5倍宽，随机画五条
  Graphics2D g =(Graphics2D) img.getGraphics();
  g.setColor(Color.BLACK);
  g.setStroke(new BasicStroke(1.5f));
  for(int i=0;i<5;i++){
   int x1 = random.nextInt(w);
   int y1 = random.nextInt(h);
   int x2 = random.nextInt(w);
   int y2 = random.nextInt(h);
   g.drawLine(x1,y1,x2,y2);
  }
 } 

 //用户调用该方法获取图片
 public BufferedImage getImage(){
  /**
   * 随机生成字符0-9A-Za-z,设置字体，字号，是否粗体，字符颜色，都是随机的
   */
  BufferedImage img = createImage(); 

  this.getLine(img); 

  //获取画笔
  Graphics g = img.getGraphics(); 

  //画内容
  for(int i=0;i<4;i++){
   g.setColor(this.randomColor());//获取随机颜色
   g.setFont(this.randomFont());//获取随机字体
   g.drawString(this.randomChar(),w/4*i,h-5);//获取字符串随机内容
  }
  return img;
 } 

 //用户调用该方法保存图片到本地
 public void saveImage(BufferedImage img, OutputStream ous){ 

  try {
   ImageIO.write(img,"JPEG",ous);
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
}

package model; 

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 java.awt.image.BufferedImage;
import java.io.IOException; 

/**
 * Created by Petty on 2017/5/4.
 */
@WebServlet(name = "BServlet")
public class BServlet extends HttpServlet {
 public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  VCode v = new VCode(70,35);
  BufferedImage img = v.getImage();
  v.saveImage(img,response.getOutputStream());
 } 

 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  VCode v = new VCode(70,35 );
  BufferedImage img = v.getImage();
  v.saveImage(img,response.getOutputStream());
 }
}

<%--
 Created by IntelliJ IDEA.
 User: Petty
 Date: 2017/5/4
 Time: 22:28
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
 <head>
 <title>一次性验证码</title>
 </head>
 <body>
 <form action="" method="get">
  <table align="center">
   <tr>
    <td><img id="img" alt="" src="servlet/BServlet" onclick="changeNext()"></td>
   </tr>
  </table>
 </form>
 </body>
</html>
<script type="text/javascript">
 function changeNext(){
  var a=document.getElementById("img");
  a.src="servlet/BServlet?a="+new Date().getTime();
 }
</script>

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