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CheckImgServlet.java

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package com . wlian . web . servlet ;

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 . FileReader ;

import java . io . IOException ;

import java . util . ArrayList ;

import java . util . List ;

import java . util . Random ;

import javax . imageio . ImageIO ;

import javax . servlet . ServletException ;

import javax . servlet . http . HttpServlet ;

import javax . servlet . http . HttpServletRequest ;

import javax . servlet . http . HttpServletResponse ;

/**

* 验证码生成程序

public class CheckImgServlet extends HttpServlet {

// 集合中保存所有成语

private List < String > words = new ArrayList < String >();

@ Override

public void init () throws ServletException {

// 初始化阶段，读取new_words.txt

// web工程中读取文件，必须使用绝对磁盘路径

String path = getServletContext (). getRealPath ( "/WEB-INF/new_words.txt" );

try {

BufferedReader reader = new BufferedReader ( new FileReader ( path ));

String line ;

while (( line = reader . readLine ()) != null ) {

words . add ( line );

}

reader . close ();

} catch ( IOException e ) {

e . printStackTrace ();

}

public void doGet ( HttpServletRequest request , HttpServletResponse response )

throws ServletException , IOException {

// 禁止缓存

// response.setHeader("Cache-Control", "no-cache");

// response.setHeader("Pragma", "no-cache");

// response.setDateHeader("Expires", -1);

int width = 120 ;

int height = 30 ;

// 步骤一绘制一张内存中图片

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 );

// 步骤三绘制边框

graphics . setColor ( Color . WHITE );

graphics . drawRect ( 0 , 0 , width - 1 , height - 1 );

// 步骤四四个随机数字

Graphics2D graphics2d = ( Graphics2D ) graphics ;

// 设置输出字体

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 --- 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 );

}

// 将上面图片输出到浏览器 ImageIO

graphics . dispose (); // 释放资源

ImageIO . write ( bufferedImage , "jpg" , response . getOutputStream ());

public void doPost ( HttpServletRequest request , HttpServletResponse response )

throws ServletException , IOException {

doGet ( request , response );

}

/**

* 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 ;

}

if ( bc > 255 ) {

bc = 255 ;

}

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 );

}

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