JavaWeb实现登录验证码示例

一、页面部分

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二、登录Servlet

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package
cn.wj.servlet;

import
java.io.IOException;

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
Login
extends
HttpServlet {


public

void
doGet(HttpServletRequest request, HttpServletResponse response)

throws
ServletException, IOException {
        doPost(request, response);
    }


public

void
doPost(HttpServletRequest request, HttpServletResponse response)

throws
ServletException, IOException {
        request.setCharacterEncoding(
“utf-8”
);
        response.setContentType(
“text/html;charset=utf-8”
);

String
username=request.getParameter(
“username”
);

String
password=request.getParameter(
“password”
);

String
v_code=request.getParameter(
“verificode”
);
        HttpSession session=request.getSession();

String
v_code2=(
String
) session.getAttribute(
“session_code”
);

if
(!v_code.equalsIgnoreCase(v_code2)){
            request.setAttribute(
“msg”
,
“验证码错误”
);
            request.getRequestDispatcher(
“/index.jsp”
).forward(request, response);

return
;
        }
else
{
            request.getRequestDispatcher(
“success.jsp”
).forward(request, response);
        }
    }

}

三、验证码生成工具类

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package
cn.wj.servlet;

import
java.awt.BasicStroke;

import
java.awt.Color;

import
java.awt.Font;

import
java.awt.Graphics2D;

import
java.awt.image.BufferedImage;

import
java.io.IOException;

import
java.io.OutputStream;

import
java.util.Random;

import
javax.imageio.ImageIO;

public

class
VerifyCode {

private

int
w =
70
;

private

int
h =
35
;

private
Random r =
new
Random();

// {“宋体”, ”华文楷体”, ”黑体”, ”华文新魏”, ”华文隶书”, ”微软雅黑”, ”楷体_GB2312”}


private

String
[] fontNames  = {
“宋体”
,
“华文楷体”
,
“黑体”
,
“微软雅黑”
,
“楷体_GB2312”
};

// 可选字符


private

String
codes  =
“23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ”
;

// 背景色


private
Color bgColor  =
new
Color(
255
,
255
,
255
);

// 验证码上的文本


private

String
text ;


// 生成随机的颜色


private
Color randomColor () {

int
red = r.nextInt(
150
);

int
green = r.nextInt(
150
);

int
blue = r.nextInt(
150
);

return

new
Color(red, green, blue);
    }


// 生成随机的字体


private
Font randomFont () {

int
index = r.nextInt(fontNames.length);

String
fontName = fontNames[index];
//生成随机的字体名称


int
style = r.nextInt(
4
);
//生成随机的样式, 0(无样式), 1(粗体), 2(斜体), 3(粗体+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++) {
//生成两个点的坐标，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));
            g2.setColor(Color.BLUE);
//干扰线是蓝色

            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;
    }


// 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


// 向图片中画4个字符


for
(
int
i =
0
; i <
4
; i++)  {
//循环四次，每次生成一个字符


String
s = randomChar() +
“”
;
//随机生成一个字母

            sb.append(s);
//把字母添加到sb中


float
x = i
1
.0F  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, x, h-
5
);
//画图

        }

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);
    }
}

四、验证码Servlet

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package
cn.wj.servlet;

import
java.awt.image.BufferedImage;

import
java.io.IOException;

import
javax.servlet.ServletException;

import
javax.servlet.http.HttpServlet;

import
javax.servlet.http.HttpServletRequest;

import
javax.servlet.http.HttpServletResponse;

public

class
VerifyCodeServlet
extends
HttpServlet {


public

void
doGet(HttpServletRequest request, HttpServletResponse response)

throws
ServletException, IOException {
        doPost(request, response);
    }

public

void
doPost(HttpServletRequest request, HttpServletResponse response)

throws
ServletException, IOException {
        request.setCharacterEncoding(
“utf-8”
);
        response.setContentType(
“text/html;charset=utf-8”
);

        VerifyCode vc=
new
VerifyCode();
        BufferedImage img=vc.getImage();
        request.getSession().setAttribute(
“session_code”
, vc.getText());
        VerifyCode.output(img, response.getOutputStream());
    }

}