<ul>
<li >验证码： </li>
<li >
<img id="img_validate" src="<%=basePath%>image/getImg_validate" onclick="reloadImg()">
<input type="text" name="yanzhengma" id="yanzhengma" placeholder="请输入验证码"/>
</li> 
</ul>


<script type="text/javascript">

function reloadImg() {

document.getElementById("img_validate").src="<%=basePath%>image/getImg_validate";
}

</script>

package com.svse.house.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

public class ImageUtil {

//1.定义变量保存生成后的验证码字符串
static String code = "";

//2.生成验证码
public static String createcode() {
code = "";
String a = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";//随机生成的字符范围(0-9,a-z,A-Z)

//生成验证码的位数(这里是4位)
for (int i = 0; i < 4; i++) {
int index = (int) (Math.random() * 62);//会产生一个[0,62)的数，不包含小数
char b = a.charAt(index);
code = code + b;
}
return code;
}

//查看已经生成的验证码
public static String getCode() {
return code;
}

//3.生成图片
public static BufferedImage createimage() {
// 前2个参数为：width, height.后面是图像类型
//创建一个不带透明色的BufferedImage对象,TYPE_INT_ARGB为带透明色
BufferedImage bi = new BufferedImage(130,50, BufferedImage.TYPE_INT_RGB);

//1.得到一个画布
Graphics g = bi.getGraphics();
//2.添加背景颜色
g.setColor(Color.WHITE);
g.fillRect(0, 0, 130, 50);

//3.添加干扰线
for (int i = 0; i < 10; i++) {
Random r = new Random();
int red = r.nextInt(256);
int green = r.nextInt(256);
int blue = r.nextInt(256);
Color c = new Color(red, green, blue);
g.setColor(c);
int x1 = r.nextInt(131);
int y1 = r.nextInt(51);
int x2 = r.nextInt(131);
int y2 = r.nextInt(51);
g.drawLine(x1,y1,x2,y2);//画线
//g.drawOval(x1, y1, x2, y2);//画曲线
}


//3.添加文字
g.setColor(Color.BLACK);
g.setFont(new Font("宋体", Font.BOLD, 50));

String str = getCode();
//4.将文字填充到画板中
g.drawString(str, 15, 40);

//5.关闭画布
g.dispose();
return bi;
}

}

package com.svse.house.controller;

import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import com.svse.house.util.ImageUtil;

@Controller
@RequestMapping("/image")
public class ImageController {
@RequestMapping("/getImg_validate")
public void yanzheng(HttpServletResponse response){
try {
ImageUtil.createcode();
BufferedImage image = ImageUtil.createimage();
//以流的方式返回给客户端
response.setContentType("image/jpeg");
//response.setContentType("image/bmp");
ByteArrayOutputStream bt = new ByteArrayOutputStream();
//将图片转换成字节流    
ImageIO.write(image,"jpeg",bt);
//ImageIO.write(image,"bmp",bt);
//得到输出流，返回客户端
ServletOutputStream outputStream = response.getOutputStream();
outputStream.write(bt.toByteArray());
} catch (IOException e) {
e.printStackTrace();
}
}
}