使用Java随机生成4位字母验证码
看了其他人写的验证码程序，于是自己写了个很小的，因为字母就是用ASCii码表示的，那么可以使用int值直接生成就可以了，这样程序很简单，执行效率也很高。
1 ImageOut.java 复则产生验证码
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.util.Random;
public class ImageOut {
private static final int WIDTH = 62;
private static final int HEIGHT = 20;
private static Color getRandomColor() {
Random random = new Random();
return new Color(50 + random.nextInt(100), 50 + random.nextInt(100),
50 + random.nextInt(100));
}
private static int getRandomBgInt() {
Random random = new Random();
return 180 + random.nextInt(60);
}
private static Font getRandomFont() {
Random random = new Random();
return new Font("Times New Roman", Font.PLAIN, 10 + random.nextInt(8));
}
public static char getRandomChar() {
Random random = new Random();
if (random.nextInt(5) < 3) {
return (char) (65 + random.nextInt(26));
}
return (char) (97 + random.nextInt(26));
}
public static Pair<String, BufferedImage> getImage() {
BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics2D g = image.createGraphics();
g.setColor(new Color(255, getRandomBgInt(), 255));
g.fillRect(0, 0, WIDTH, HEIGHT);
StringBuilder s = new StringBuilder();
for (int i = 0; i < 4; i++) {
String t = String.valueOf(getRandomChar());
s.append(t);
g.setColor(getRandomColor());
g.setFont(getRandomFont());
g.drawString(t, 3 + 16 * i, 18);
}
g.dispose();
return new Pair<String, BufferedImage>(s.toString(), image);
}
}
2 上面使用了Pair类，使用Map也可以的，只不过Java里的类都几千行代码的，自己写个可以节约些资源：
Pair.java
public class Pair<K, E> {
private K key;
private E value;
public Pair() {
}
public Pair(K key, E value) {
this.key = key;
this.value = value;
}
public K getKey() {
return key;
}
public void setKey(K key) {
this.key = key;
}
public E getValue() {
return value;
}
public void setValue(E value) {
this.value = value;
}
}
3 在jsp环境中使用上面的程序：
3.1 首先写个为当前用户生成验证码的jsp页面：
ValidateImage.jsp
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page import="java.awt.image.BufferedImage,javax.imageio.ImageIO" %>
<%@page import="com.bookshop.util.Pair,com.bookshop.util.ImageOut" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<%
response.setContentType("image/jpeg");
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
Pair<String, BufferedImage> p = ImageOut.getImage();
ImageIO.write(p.getValue(), "JPEG", response.getOutputStream());
session.setAttribute("valid", p.getKey());
%>
3.2 在登录注册的页面中调用：
比如login.jsp
<form id="form1" name="form1" method="post" action="<%=path%>/bookshop/login.jsp">
<input type="hidden" name="op" value="login" readonly="readonly" />
<label></label>
<p>
<label></label>
</p>
<p class="STYLE1">用户登录</p>
<table width="317">
<tr>
<td width="100"><span class="STYLE2">登录名称：</span></td>
<td width="200"><input class="field" type="text" name="username" /></td>
</tr>
<tr>
<td><span class="STYLE2">登陆密码：</span></td>
<td><input class="field" type="password" name="password" /></td>
</tr>
<tr>
<td rowspan="2"><span class="STYLE2">验证码：</span></td>
<td>
<input class="field" type="text" name="yanzhm" />
</td>
</tr>
<tr>
<td><img alt="看不清？单击更换！" src="<%=path%>/bookshop/ValidateImage.jsp" onclick="changeValidateCode(this)"/> </td>
</tr>
<tr>
<td>
<input class="tijiao" type="submit" name="Submit" value="登 录" />
</td>
<td style="text-align:right">
<input type="reset" name="Submit" value="重 置" />
</td>
</tr>
</table>
</form>
上面调用了一个能刷新验证码的js代码：如下
<script type="text/javascript">
function changeValidateCode(obj) {
var timenow = new Date().getTime();
obj.src="<%=path%>/bookshop/ValidateImage.jsp?d="+timenow;
}
</script>
在验证逻辑处只需获取验证就可以了：
String yanzhm = request.getParameter("yanzhm");
String valid = (String) session.getAttribute("valid");
if (!yanzhm.equalsIgnoreCase(valid)) {
request.setAttribute("info", "验证码输入错误，请重新输入！");
request.getRequestDispatcher("/bookshop/error.jsp").forward(request, response);
return;
}
4 在servlet中使用与此类似，此处省略！