JSP实现生成验证码

话不多说上代码Jsp，具体验证码图片可以在发挥

<%@ page language="java" pageEncoding="UTF-8"%>
<%@ page contentType="image/jpeg"  import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
    <%--该页面主要生成验证码 --%>
<%! 
//定义静态常量，表示验证码可以显示的字符
static ArrayList<Character> codeMembers;
static {
//初始化
        codeMembers=new ArrayList<Character>();
for(int i='A';i<='Z';i++){
            codeMembers.add((char)i);
        }
for(int i='0';i<='9';i++){
            codeMembers.add((char)i);
        }
    }
%>
<%!
//生成随机颜色
public Color getColor(){
        Random random=new Random();
int r=random.nextInt(256);//生成0-255随机数
int g=random.nextInt(256);
int b=random.nextInt(256);
return new Color(r,g,b);

    }
//生成4为随机验证码
public String getCode(){
        Random random=new Random();
        String res="";
//得到4为的验证码，且只包含字母和数字
for(int i=0;i<4;i++){
int index=random.nextInt(codeMembers.size());//
char c=codeMembers.get(index);
            res+=c;
        }
return res;
    }

%>
<%
    response.setHeader("pragma", "mo-cache");
    response.setHeader("cache-control", "no-cache");
    response.setDateHeader("expires", 0);

    BufferedImage image=new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB);
    Graphics g=image.getGraphics();
    g.setColor(new Color(200,200,200));
    g.fillRect(0,0,80,30);

//画干扰背景
for(int i=0;i<30;i++){
        Random random=new Random();
//起点坐标
int x1=random.nextInt(80);
int y1=random.nextInt(30);
//终点
int x2=random.nextInt(x1+10);
int y2=random.nextInt(y1+10);
        g.setColor(getColor());
        g.drawLine(x1,y1,x1+x2,y1+y2);
    }

//验证码信息
    g.setFont(new Font("serif",Font.BOLD,16));
    g.setColor(Color.BLACK);
//得到验证码字符串
    String code=getCode();
//处理字符串，加空格
    StringBuffer sb=new StringBuffer();
for(int i=0;i<code.length();i++){
        sb.append(code.charAt(i)+" ");
    }
//画
    g.drawString(sb.toString().toUpperCase(),15,20);
//重点：将验证码信息加入Session域
    session.setAttribute("CHECKCODE",code);

    ImageIO.write(image,"jpeg",response.getOutputStream());
out.clear();
out=pageContext.pushBody();
    System.out.println(session.getAttribute("CHECKCODE"));

%>