工具類——驗證碼

servlet端

package web;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.OutputStream;

import java.util.Random;

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 CheckcodeServlet extends HttpServlet {

 

 public void service(HttpServletRequest request, HttpServletResponse response)

   throws ServletException, IOException {

  /*

   * 繪圖

   */

  //step1,創建內存映像對象(畫板)

  BufferedImage image =

    new BufferedImage(80,30,

      BufferedImage.TYPE_INT_RGB);

  //step2,獲得畫筆

  Graphics g = image.getGraphics();

  //step3,給筆設置顏色

  g.setColor(new Color(255,255,255));

  //step4,設置畫板的背景顏色

  g.fillRect(0, 0, 80, 30);

  //step5,給筆設置顏色

  Random r = new Random();

  g.setColor(new Color(r.nextInt(255),

    r.nextInt(255),r.nextInt(255)));

  //Font(字體,風格,大小)

  g.setFont(new Font(null,Font.ITALIC,24));

  //step6,生成一個隨機數

  String number = getNumber(5);

  HttpSession session = request.getSession();

  session.setAttribute("number", number);

  //step7,繪製字符串

  g.drawString(number, 2, 25);

  //step8,加一些干擾線

  for(int i = 0; i < 8; i ++){

   g.setColor(new Color(r.nextInt(255),

     r.nextInt(255),r.nextInt(255)));

   g.drawLine(r.nextInt(80), r.nextInt(30),

     r.nextInt(80), r.nextInt(30));

  }

  /*

   * 將圖片壓縮,發送給瀏覽器

   */

  //step1,設置content-type消息頭，告訴

  //瀏覽器，服務器返回的是一張圖片

  response.setContentType("image/jpeg");

  //step2,獲得字節輸出流

  OutputStream ops = response.getOutputStream();

  //step3,將原始圖片按照指定的壓縮格式

  //進行壓縮，然後發送給瀏覽器。

  javax.imageio.ImageIO.write(

    image, "jpeg", ops);

  ops.close();

 }

 //返回長度爲size,隨機從A~Z,0~9中選取

 //的字符組成的字符串

 private String getNumber(int size) {

  String number = "";

  String strs = "ABCDEFGHIJKLMNOPQRST" +

    "UVWXYZ0123456789";

  Random r = new Random();

  for(int i = 0; i < size; i ++){

   number += strs.charAt(r.nextInt(strs.length()));

  }

  return number;

 }

}

JSP端

驗證碼:<input name="number"/>

    <%

     String msg2 =

     (String)request.getAttribute("number_error");

     %>

     <span style="color:red;"><%=(msg2 == null ? "" : msg2)%></span>

    <br/>

    <img id="img1" src="checkcode" border="1"

  οnclick="this.src='checkcode?' + Math.random();"/>

  <a href="javascript:;"  

  οnclick="document.getElementById('img1').src='checkcode?' + Math.random();">看不清，換一個</a>

web.xml

<servlet>

    <servlet-name>CheckcodeServlet</servlet-name>

    <servlet-class>web.CheckcodeServlet</servlet-class>

  </servlet>

 <servlet-mapping>

    <servlet-name>CheckcodeServlet</servlet-name>

    <url-pattern>/checkcode</url-pattern>