Java验证码图片生成代码

public class VerifyCode {


private int w=70;
private int h=35;
private Random r=new Random();
//宋体，华文楷书，黑体，华文新魏，华文隶书，微软雅黑，楷体_GB2312,Times New Roman
private String [] fontNames={"宋体","华文楷书","黑体","华文新魏","微软雅黑","华文隶书","楷体_GB2312","Times New Roman"};
//可选的字符
private String codes="23456789abcdefghijkmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";
//背景色
private Color bgColor=new Color(255,255,255);
//验证码上的文本
private String text;

//生成随机颜色
private Color randomColor(){
 int red=r.nextInt(150);
 int green=r.nextInt(150);
 int blue=r.nextInt(150);
 return new Color(red,green,blue);
}

//生成随机字体
private Font randomFont(){
int index=r.nextInt(fontNames.length);//获取下标
String fontName=fontNames[index];//生成随机的字体名称
int style=r.nextInt(4);//获取随机样式，0表示无样式，1表示粗体，2表示斜体，3表示粗体加斜体
int size=r.nextInt(5)+24;//生成随机字号，24~28
return new Font(fontName,style,size);
}

//画干扰线
private void drawLine(BufferedImage image){
int num=3;//一共画3条
Graphics2D g2=(Graphics2D) image.getGraphics();
for(int i=0;i<num;i++){//随机生成坐标，即4个值
int x1=r.nextInt(w);
int y1=r.nextInt(h);
int x2=r.nextInt(w);
int y2=r.nextInt(h);
g2.setStroke(new BasicStroke(1.5F));//设置笔画的宽度
  g2.setColor(Color.blue);//干扰线颜色
  g2.drawLine(x1, y1, x2, y2);//画线
}
}

//随机生成一个字符
private char randomChar(){
int index=r.nextInt(codes.length());
return codes.charAt(index);
}

//创建BufferedImage
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;
}

//外界调用这个方法得到验证码
public BufferedImage getImage(){
BufferedImage image=createImage();//创建图片缓冲区
Graphics2D g2=(Graphics2D)image.getGraphics();//得到绘制环境
StringBuilder sb=new StringBuilder();//用来装载生成的验证码文本
//向图中画4个字符
for(int i=0;i<4;i++){//循环4次
String s=randomChar()+"";//随机生成一个字符
sb.append(s);//把字母添加到sb中
double x=i*1.0*w/4;//设置当前字符的x轴坐标
g2.setFont(randomFont());//设置随机字体
g2.setColor(randomColor());//设置随机颜色
g2.drawString(s, (int)x, h-5);
}
this.text=sb.toString();//把生成的字符串赋给了this.text
drawLine(image);//添加干扰线
return image;
}

//返回验证码图片上面的文本
public String getText(){
return text;
}

//保存图片到指定的输出流
public static void output(BufferedImage image,OutputStream out) throws IOException{
ImageIO.write(image, "JPEG", out);
}
}

<form action="/test/LoginServlet" method="post">
   用户名：<input type="text" name="username" value="<%=uname %>"><br>
   密 码：<input type="password" name="password"><br>
   验证码：<input type="text" name="verifyCode">
  <img id="img" src="/test/VerifyCodeServlet">
  <a href="JavaScript:_change()" rel="external nofollow" >看不清换一张</a><br>
  <input type="submit" value="登录">
 </form>

   <script type="text/javascript">
      function _change(){
        /**
        *1.得到image图片
        *2.修改其src为/test/VerifyCodeServlet 
        */
        var imgEle=document.getElementById("img");
        imgEle.src="/test/VerifyCodeServlet?a="+new Date().getTime();

      }
  </script>

public class VerifyCodeServlet extends HttpServlet {


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


/*
* 1.生成图片
* 2.保存图片上的文本到session域中
* 3.把图片响应给客户端
*/
VerifyCode vc=new VerifyCode();
BufferedImage image=vc.getImage();
//保存图片上的文本到session域
request.getSession().setAttribute("session_code", vc.getText());

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

  }
}

public class LoginServlet extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {


/*
* 校验验证码
* 1.从session中获取正取的验证码
* 2.从表单中获取用户填写的验证码
* 3.进行比较
* 4.如果相同，向下运行，否则保存错误信息到request域，转发到login.jsp
*/
String sessionCode=(String)                    

 request.getSession().getAttribute("session_code");//获得的验证码里面对应的文本内容
String paramCode=request.getParameter("verifyCode");//用户输入文本框里面的内容
if(!paramCode.equalsIgnoreCase(sessionCode)){
request.setAttribute("msg", "验证码错误！");
request.getRequestDispatcher("/login.jsp").forward(request, response);//打回到登录界面。
return;//返回，不继续执行下面的语句。
}
}
}