JavaWeb登录实现：UserDAO与JSPServlet交互-优快云博客

准备User数据。

user类

package bean;
 
public class User {
    private int id;
    private String name;
    private String password;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

userDAO

package dao;
 
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
 
import bean.User;
 
public class UserDAO {
 
    public static void main(String[] args) {
 
        System.out.println(new UserDAO().getUser("tom", "123").getId());
 
    }
 
    public User getUser(String name, String password) {
        User result = null;
 
        try {
            Class.forName("com.mysql.jdbc.Driver");
 
            Connection c = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/cart?characterEncoding=UTF-8",
                    "root", "admin");
 
            String sql = "select * from user where name = ? and password = ?";
 
            PreparedStatement ps = c.prepareStatement(sql);
 
            ps.setString(1, name);
            ps.setString(2, password);
            ResultSet rs = ps.executeQuery();
 
            if (rs.next()){
                result = new User();
                result.setId(rs.getInt(1));
                result.setPassword(password);
                result.setName(name);
            }
 
            ps.close();
 
            c.close();
 
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return result;
    }
}

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import="java.util.*"%>
 
<!DOCTYPE html>
 
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 
<form action="login" method="post">
    账号： <input type="text" name="name"> <br>
    密码： <input type="password" name="password"> <br>
    <input type="submit" value="登录">
</form>

package servlet;
 
import java.io.IOException;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import bean.User;
import dao.UserDAO;
 
public class UserLoginServlet extends HttpServlet {
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
 
        String name = request.getParameter("name");
        String password = request.getParameter("password");
        User user = new UserDAO().getUser(name, password);
        if (null != user) {
            request.getSession().setAttribute("user", user);
            response.sendRedirect("/listProduct");
        } else
            response.sendRedirect("/login.jsp");
 
    }
}

在web.xml中为路径/login加上相关配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
  
    <servlet>
        <servlet-name>ProductListServlet</servlet-name>
        <servlet-class>servlet.ProductListServlet</servlet-class>
    </servlet>
  
    <servlet-mapping>
        <servlet-name>ProductListServlet</servlet-name>
        <url-pattern>/listProduct</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>servlet.UserLoginServlet</servlet-class>
    </servlet>
  
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
  
</web-app>

修改listProduct.jsp，如果用户登陆了，就显示用户的名字

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import="java.util.*" isELIgnored="false"%>
 
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
 
<c:if test="${!empty user}">
  <div align="center">
    当前用户: ${user.name}
  </div>
</c:if>
 
<table align='center' border='1' cellspacing='0'>
    <tr>
        <td>id</td>
        <td>名称</td>
        <td>价格</td>
        <td>购买</td>
    </tr>
    <c:forEach items="${products}" var="product" varStatus="st">
        <tr>
            <td>${product.id}</td>
            <td>${product.name}</td>
            <td>${product.price}</td>
            <td>
             
            <form action="addOrderItem" method="post">
             
            数量<input type="text" value="1" name="num">
            <input type="hidden" name="pid" value="${product.id}">
            <input type="submit" value="购买">
            </form>
              
        </tr>
    </c:forEach>
</table>

该部分运行后还是无法完全显示出来，暂时没有找到错误之处