本次案例为Servlet+JDBC实现登陆功能的小例子的进阶版本，关于与数据库交互部分，这里不再赘述
案例需求：
- 访问带有验证码的登录页面login.jsp
- 用户输入用户名，密码以及验证码。
- 如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误
- 如果验证码输入有误，跳转登录页面，提示：验证码错误
- 如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您
分析
步骤
文件树展示
1.配置文件和jar包在上个案例均有配置过，需要改的有：User类新增验证码成员变量，数据库增加了一个验证码字段（无用，只是为了UserDao包把查找到的数据值导入到User类不出错）。
2.登陆界面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>login</title>
<script>
window.onload = function(){
document.getElementById("img").onclick = function(){
this.src="/CaS/checkCodepic?time="+new Date().getTime();
}
}
</script>
<style>
div{
color: red;
}
</style>
</head>
<body>
<form action="/CaS/loginServlet" method="post">
<table>
<tr>
<td>用户名</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>密码</td>
<td><input type="password" name="password"></td>
</tr>
<tr>
<td>验证码</td>
<td><input type="text" name="checkCode"></td>
</tr>
<tr>
<td colspan="2"><img id="img" src="/CaS/checkCodepic"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登录"></td>
</tr>
</table>
</form>
<div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div>
<div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div>
</body>
</html>
3.验证码，画了个验证码，每次都把随机数加入session中以便进行对比
package Test;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet("/checkCodepic")
public class CheckCodepic extends HttpServlet {
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
int width=100;
int height=50;
//创建图片对象
BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//美化图片
//创建画笔
Graphics g = image.getGraphics();
//画笔颜色
g.setColor(Color.pink);
//画个矩形，填充为粉红色
g.fillRect(0,0,width,height);
//给矩形加边框
g.setColor(Color.blue);
g.drawRect(0,0,width-1,height-1);
//写字母或数字
g.setColor(Color.green);
String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
Random rd=new Random();
StringBuilder sb=new StringBuilder();
for(int i=1;i<=4;i++){
int index = rd.nextInt(str.length());
char c = str.charAt(index);
sb.append(c);
g.drawString(c+"",width/5*i,height/2);
}
String checkCode_session = sb.toString();
//将验证码存入session
req.getSession().setAttribute("checkCode_session",checkCode_session);
//加干扰线
g.setColor(Color.blue);
for(int i=1;i<=10;i++){
int x1 = rd.nextInt(width);
int x2 = rd.nextInt(width);
int y1 = rd.nextInt(height);
int y2 = rd.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
//输出展示
ImageIO.write(image,"jpg",resp.getOutputStream());
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req,resp);
}
}
4.loginServlet类，用来判断验证码和用户名密码是否正确，注意先判断验证码；注意重定向和请求转发的不同，还有session的应用。
package Test;
import Test.dao.UserDao;
import Test.userclass.User;
import org.apache.commons.beanutils.BeanUtils;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;
@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置request编码
request.setCharacterEncoding("utf-8");
//获取参数
// String username = request.getParameter("username");
// String password = request.getParameter("password");
// String checkCode = request.getParameter("checkCode");
// User user=new User();
// user.setUsername(username);
// user.setPassword(password);
// user.setCheckCode(checkCode);
Map<String, String[]> parameterMap = request.getParameterMap();
User user=new User();
try {
BeanUtils.populate(user,parameterMap);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
UserDao userDao=new UserDao();
//先判断验证码是否正确
String checkCode_session = (String)request.getSession().getAttribute("checkCode_session");
request.getSession().removeAttribute("checkCode_session");
if(checkCode_session!=null && checkCode_session.equalsIgnoreCase(user.getCheckCode())){//忽略大小写
//如果正确，判断用户名密码是否正确
User login = userDao.login(user);
if(login!=null){
//登陆成功，存储用户信息
request.getSession().setAttribute("username",login.getUsername());
//重定向到success.jsp
response.sendRedirect(request.getContextPath()+"/success.jsp");
}else{//登陆失败，转发到登陆界面
request.setAttribute("login_error","用户名或密码不正确");
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}else{ //如果不正确，转发到登陆界面
request.setAttribute("cc_error","验证码不正确");
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
5.成功登陆界面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h1><%=request.getSession().getAttribute("username")%>,欢迎您</h1>
</body>
</html>
结果
登陆界面
验证码错误情况
用户名或密码不正确情况
成功登陆
