java实现验证码
java验证码的实现(一)
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1.ImageServlet类的实现:
package com.mobile.control;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
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;
public class ImageServlet extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
// 生成数字和字母的验证码
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
BufferedImage img = new BufferedImage(68, 22,
BufferedImage.TYPE_INT_RGB);
// 得到该图片的绘图对象
Graphics g = img.getGraphics();
Random r = new Random();
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某知名门户网站的一道笔试题
public class Test {
public static void stringUpd(String str) {
str = str.replace("j", "l");
System.out.println(str);
}
public static void stringBufferUpd(StringBuffer bf) {
bf.append("c");
System.out.println(bf);
}
......
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet. ......
java.util
类 Random
java.lang.Object
java.util.Random
所有已实现的接口:
Serializable
直接已知子类:
SecureRandom
public class Random
extends Object
implements Serializable
此类的实例用于生成伪随机数流。此类使用 48 位的种子,使用线性同余公式对其进行修改(请参阅 Donald Knuth 的 ......
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