Web---java生成验证码

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/qq_34928644/article/details/82109269

技术入口：

java.awt.image包中的BufferedImage类

过程：

先new一个BufferedImage类的实例（对象）：BufferedImage bufImg = new BufferedImage(width,height,type);

再获取java.awt.Graphics类的实例（对象）： Graphics g = bufImg.getGraphics();

然后进行验证码的设计： ......

最后通过 javax.imageio.ImageIO类的静态方法write把图片输出

代码演示：

生成验证码的工具类

package cn.hncu.checkCode.utils;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;

public class CheckCodeGenerator {
	private static Random random = new Random( System.currentTimeMillis() );
	private static String[] codes = {"0","1","2","3","4","5",
									 "6","7","8","9","A","B",
									 "C","D","E","F","G","H",
									 "I","J","K","L","M","N",
									 "O","P","Q","R","S","T",
									 "U","V","W","X","Y","Z" };
	/**
	 * 产生一个图片验证码，并且返回以字符串表示的验证码
	 * @param height 图片的高度
	 * @param out 把验证码图片通过out对象输出
	 * @return 字符串的验证码
	 * @throws IOException
	 */
	public static String CheckCodeOfImgCanRotate( int height,OutputStream out) throws IOException {
		//用来校验的验证码
		String checkCode = "";
		//计算宽度
		int width = 3*height;
		
		//1. 先创建一个BufferedImage对象
		BufferedImage bufImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		
		//2. 获取Graphics对象
		Graphics g = bufImg.getGraphics();
		//3. 把Graphics对象强转成Graphics2D,用到旋转与缩放
		Graphics2D g2d = (Graphics2D) g;
		
		//设置验证码字体
		int size = height>>1; //字体大小位高度的1/2	
		Font font = new Font("微软雅黑", Font.BOLD, size);
		g2d.setFont(font);
		
		int offset = size; //第一个字符的偏移量
		
		//以白色填充背景
		g2d.setColor( Color.WHITE );
		g2d.fillRect(0, 0, width, height);
		
		//生成4位验证码
		for(int i = 0; i < 4; i++ ) {
			String str = codes[random.nextInt( codes.length )];
			checkCode += str;
			//产生随机颜色
			Color c = new Color( random.nextInt(200),random.nextInt(200), random.nextInt(200) );
			g2d.setColor(c);
			//创建变换对象
			AffineTransform aff = new AffineTransform();
			//设置好变化规则
			aff.rotate(Math.random()*Math.PI, offset+ (i+0.5)*size, height/2);
			g2d.setTransform( aff );
			
			g2d.drawString(str, offset + i*size, height );
		}
		//清空变化
		g2d.setTransform( new AffineTransform() );
		//产生干扰线
		for (int i = 0; i < 3; i++) {
			//产生随机颜色
			Color c = new Color( random.nextInt(200),random.nextInt(200), random.nextInt(200) );
			g2d.setColor(c);
			//画干扰线
			g2d.drawLine(random.nextInt(height), random.nextInt(height),(height<<1) + random.nextInt(height),random.nextInt(height));
		}
		
		g2d.dispose();
		
		ImageIO.write(bufImg, "JPEG", out);
		
		return checkCode;
	}
	/**
	 * 通过 height 生成一张验证码图片，验证码具有上下浮动特性，最后通过out输出
	 * @param height 图片高度
	 * @param out 字节输出流
	 * @return 验证码的码值
	 * @throws IOException
	 */
	public static String CheckCodeOfImgCanFolat( int height,OutputStream out) throws IOException {
		//用来校验的验证码
		String checkCode = "";
		//计算宽度
		int width = height<<1; //宽度为高度的2倍
		
		int offset = height>>2; //第一个字符的偏移量
		
		//1. 先创建一个BufferedImage对象
		BufferedImage bufImg = new BufferedImage(width+offset, height, BufferedImage.TYPE_INT_RGB);
		
		//2. 获取Graphics对象
		Graphics g = bufImg.getGraphics();
		
		//设置验证码字体
		int size = height>>1;	
		Font font = new Font("微软雅黑", Font.BOLD, size);
		g.setFont(font);
		
		//以白色填充背景
		g.setColor( Color.WHITE );
		g.fillRect(0, 0, width+offset, height);
		
		//生成4位验证码
		for(int i = 0; i < 4; i++ ) {
			String str = codes[random.nextInt( codes.length )];
			checkCode += str;
			//产生随机颜色
			Color c = new Color( random.nextInt(200),random.nextInt(200), random.nextInt(200) );
			g.setColor(c);
			
			g.drawString(str, offset + i*size, size+random.nextInt(size) );
		}
		//产生干扰线
		for (int i = 0; i < 3; i++) {
			//产生随机颜色
			Color c = new Color( random.nextInt(200),random.nextInt(200), random.nextInt(200) );
			g.setColor(c);
			//画干扰线
			g.drawLine(random.nextInt(height), random.nextInt(height),(height<<1) + random.nextInt(height),random.nextInt(height));
		}
		
		g.dispose(); //销毁g对象，该方法内部会调用把内存中的数据全部刷到bufImg对象中
		
		ImageIO.write(bufImg, "JPEG", out);
		
		return checkCode;
	}
	/**
	 * 产生一个高度为32px的验证码图片（默认选取上下浮动类型），并且通过out流输出
	 * @param out 字节输出流
	 * @return 验证码的码值
	 * @throws IOException
	 */
	public static String CheckCodeOfImg(OutputStream out) throws IOException {
		return CheckCodeOfImgCanFolat(32, out);
	}
}

servlet类：

package cn.hncu.checkCode.servlets;

import java.io.IOException;

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 cn.hncu.checkCode.utils.CheckCodeGenerator;

/**
 * Servlet implementation class CheckCodeServlet
 */
@WebServlet("/code") //url路径
public class CheckCodeServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		String code = CheckCodeGenerator.CheckCodeOfImg( resp.getOutputStream() );
		System.out.println(code);
	}
}

前端（JSP）页面：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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>测试验证码</title>
		<style type="text/css">
			*{
				margin: 0px;
				padding: 0px;
			}
			
			.codeDiv{
				margin:5px;
				height: 32px;
				vertical-align:middle;
			}
			.codeDiv input {
				height:30px;
				width:80px;
				font-size:14pt;
				box-sizing: border-box;
			}
			.codeDiv span {
				display: inline-block;
				line-height: 32px;
			}
			.codeDiv img {
				cursor:pointer;
				vertical-align: middle;
			}
		</style>
	</head>
	<body>
		<form action=""></form>
		<div class="codeDiv">
			<span>验证码：</span><input type="text" name="checkCode"/>
			<img alt="验证码" src="code" onclick="changeCheckCode(this);"/>
		</div>
		
		
	</body>
	<script type="text/javascript">
		function changeCheckCode(oImg) {
			oImg.src = "code?time="+new Date();
		}
	</script>
</html>

效果：

------