项目结构如下,MyEclipse中新建一个Web Project,取名servlet
1、src下new一个servlet类
package com.servlet; import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random; import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder; public class IdentityServlet extends HttpServlet { public static final char[] chars={'','','','','','','','','A'};//自定义验证码池
public static Random random=new Random(); //随机数 public static String getRandomString(){ //获取6位随机数,放在图片里
StringBuffer buffer=new StringBuffer();
for(int i=;i<;i++){
buffer.append(chars[random.nextInt(chars.length)]);
}
return buffer.toString();
} public static Color getRandomColor(){ //获取随机的颜色
return new Color(random.nextInt(), random.nextInt(), random.nextInt());
} public static Color getReverseColor(Color c){ //返回某颜色的反色
return new Color( - c.getRed(), - c.getGreen(), - c.getBlue());
} /**
* Constructor of the object.
*/
public IdentityServlet() {
super();
} /**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
} /**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("image/jpeg"); //设置输出类型 String randomString = getRandomString(); //随机字符串
request.getSession(true).setAttribute("randomString", randomString);//放到session里 int width=; //图片宽度
int height=; //图片高度 Color color=getRandomColor(); //随机颜色,用于背景色
Color reverse=getReverseColor(color);//反色,用于前景色
//创建一个彩色图片
BufferedImage bi=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D g=bi.createGraphics(); //绘图对象
g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,));//设置字体
g.setColor(color);//设置颜色
g.fillRect(, , width, height);//绘制背景
g.setColor(reverse);
g.drawString(randomString, , );//绘制随机字符
for(int i=,n=random.nextInt();i<n;i++){ //画最多100个噪音点
g.drawRect(random.nextInt(width), random.nextInt(height), , );
}
ServletOutputStream out= response.getOutputStream();//转成JPEG格式
JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);//编码器
encoder.encode(bi); //对图片进行编码
out.flush(); //输出到客户端
} /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doGet(request, response);
} /**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
} }
2、web.xml,会自动生成servlet和servlet-mapping的配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<servlet>
<servlet-name>IdentityServlet</servlet-name>
<servlet-class>com.servlet.IdentityServlet</servlet-class>
</servlet> <servlet-mapping>
<servlet-name>IdentityServlet</servlet-name>
<url-pattern>/servlet/IdentityServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
3、WebRoot下新建一个html,展示验证码
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
function reloadImage(){
document.getElementById('btn').disabled=true;
document.getElementById('identity').src='servlet/IdentityServlet?ts='+new Date().getTime();
}
</script>
</head> <body> <img src="servlet/IdentityServlet" id="identity" onload="btn.disabled=false;" />
<input type=button value="换个图片" onclick="reloadImage()" id="btn">
</body>
</html>
启动Tomcat,输入网址:http://localhost:8080/servlet/identity.html,效果如下:
点击‘换个图片’,会生成新的验证码