结构图如下：
Java的action层下创建一个Servlet，名字：checkImg_Servlet
package com.liaoyuanping.action;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.imageio.ImageIO;
//import java.io.IOException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/checkImg_Servlet")
public class checkImg_Servlet extends HttpServlet {
private List<String> words = new ArrayList<String>();
public void init(ServletConfig config) throws ServletException {
words.add("廖远平帅");
words.add("廖远平酷");
words.add("廖远平棒");
words.add("人才济济");
words.add("千钧一发");
//由于试过多个读取文件的方式都出现错误，暂时使用手动加进数组，
//以后是使用配置文件进行操作的
/*
* //初始化阶段，读取new_words.txt文件 //Web工程读取文件，必须使用绝对磁盘路径
* System.out.println("初始化1");
*
* System.out.println("contextPath："+this.getServletContext());
*
* try { InputStreamReader reader22 = new InputStreamReader(new
* FileInputStream("..."),"UTF-8"); } catch
* (UnsupportedEncodingException e1) { // TODO Auto-generated catch
* block e1.printStackTrace(); } catch (FileNotFoundException e1) { //
* TODO Auto-generated catch block e1.printStackTrace(); }
* //System.out.println("contextPath："+this.getServletContext().
* getContextPath()); //InputStreamReader reader = new
* InputStreamReader(new FileInputStream(realPath),"UTF-8");
*
* String path = getServletContext().getRealPath("");
* System.out.println("初始化2"); System.out.println(path); path +=
* "new_words.txt";
*
*
*
* try { BufferedReader reader = new BufferedReader( null );
* //BufferedReader reader = new BufferedReader(new FileReader(path));
* String line; while((line = reader.readLine()) != null){
* words.add(line); } reader.close(); } catch (IOException e) {
* System.out.println("初始化发生异常："+e.getMessage()); e.printStackTrace(); }
* System.out.println("初始化关键字。。。。完成");
*/
}
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 禁止缓存
int width = 120;
int height = 30;
System.out.println("开始执行");
// 步骤一：绘制一张内存中的图片
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// 步骤二：图片绘制背景颜色 --通过绘图对象
Graphics graphics = bufferedImage.getGraphics(); // 得到画图对象，画笔
// 绘制任何图形之前都必须指定一个颜色
graphics.setColor(getRandColor(200, 250));
graphics.fillRect(0, 0, width, height);
// 绘制边框
graphics.setColor(Color.WHITE);
graphics.drawRect(0, 0, width - 1, height - 1);
// 步骤四：设置四个随机数字
Graphics2D graphics2d = (Graphics2D) graphics;
// 设置输出的字体
graphics2d.setFont(new Font("宋体", Font.BOLD, 18));
Random random = new Random(); // 生成随机数
int index = random.nextInt(words.size());
String word = words.get(index); // 获得成语
// 定义x的坐标
int x = 10;
for (int i = 0; i < word.length(); i++) {
// 随机颜色
graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
// 旋转 -30度--正30度
int jiaodu = random.nextInt(60) - 30;
// 换算弧度
double theta = jiaodu * Math.PI / 180;
// 获得字母数字
char c = word.charAt(i);
// 将 c 输出到图片
graphics2d.rotate(theta, x, 20);
graphics2d.drawString(String.valueOf(c), x, 20);
graphics2d.rotate(-theta, x, 20);
x += 30;
}
// 将验证码内容保存到session
request.getSession().setAttribute("checkcode_session", word);
// 步骤五：绘制干扰线
graphics.setColor(getRandColor(160, 200));
int x1;
int x2;
int y1;
int y2;
for (int i = 0; i < 30; i++) {
x1 = random.nextInt(width);
x2 = random.nextInt(12);
y1 = random.nextInt(height);
y2 = random.nextInt(12);
graphics.drawLine(x1, y1, x1 + x2, x2 + y2);
}
// 将上面的图片加载到浏览器ImageIo
graphics.dispose(); // 释放资源
// 将图片写到response.getOutputStream()中
ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
}
/*
* 取其某一范围的color
*
* @param fc int 范围参数1
*
* @param bc int 范围参数2
*
* @return Color
*/
private Color getRandColor(int fc, int bc) {
// 取其随机颜色
Random random = new Random();
if (fc > 255) {
fc = 255; // 限定最大值
}
if (bc > 255) {
bc = 255; // 也是限定最大值
}
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
HTML代码如下：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>首页</title>
<script type="text/javascript">
window.onload = function(){
}
function changeImg (obj){
obj.src ="checkImg?time="+new Date().getTime(); //设置有效期
//document.getElementById("validateCodeImg").src="${pageContext.request.contextPath}/servlet/DrawImage?"+Math.random();
}
</script>
</head>
<body>
<form action="/WEB13/login" method="post">
用户名：<input type="text" name="username"><br>
密码：<input type="password" name="password"><br>
验证码：<input type="text" name="username"><img onclick="changeImg(this)" src="checkImg_Servlet"><br/>
<input type="button" name="btnLogin" value="登录"><br/>
</form>
</body>
</html>
不过这个案例还有一些问题，也正在解决当中，还请各位大佬指点