来个java大佬带一下我这个小白。。。我接收不到book表里面的数据，有人教我一下吗？

weixin_44571835 2019-10-13 09:55:34

首页

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录</title>
</head>
<body>
图书管理系统
<form action="user?action=login" method="post">
用户名: <input type="text" name="username"/>
密码: <input type="text" name="userpassword"/>
<input type="submit" value="登录"/>
<input type="reset" value="重置"/>
</form>
</body>
</html>

loginservlet页
package com.lsx.servlet;

import java.io.IOException;
import java.util.List;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.lsx.bean.User;
import com.lsx.dao.UserDao;

public class LoginServlet extends HttpServlet{

UserDao userdao =new UserDao();
List<User> listUser = userdao.findAll();

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub

doPost(request, response);

}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//登录
//获取前台数据

String userid = request.getParameter("userid");
String username = request.getParameter("username");
String userpassword = request.getParameter("userpassword");
String bookid = request.getParameter("bookid");
String bookname= request.getParameter("bookname");
String booktype= request.getParameter("booktype");
String bookauth= request.getParameter("bookauth");

//获取action的值
String action =request.getParameter("action");
System.out.println(action);
System.out.println(username);
System.out.println(userpassword);

//下面的值获取不到。
System.out.println(bookname);
System.out.println(bookid);
System.out.println(userid);

if(action.equals("login")) {

int mmm = userdao.checkNameAnd(username, userpassword);

if(mmm ==1) {
request.setAttribute("listUser", listUser);
RequestDispatcher rd =request.getRequestDispatcher("/user/list.jsp");
rd.forward(request, response);

} else {
RequestDispatcher rd= request.getRequestDispatcher("/login1.jsp");
rd.forward(request, response);

}
userdao页

package com.lsx.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.lsx.util.DbUtil;
import com.sun.org.apache.xpath.internal.operations.And;
import com.lsx.bean.User;

public class UserDao {

public int checkNameAnd( String username, String userpassword) {
//获取连接

Connection conn = DbUtil.getConn();
//select * from users where name='admin' and password='123456'

String sql="select * from users where username='" +username + "' and userpassword='" + userpassword + "'" ;

try {
PreparedStatement pre = conn.prepareStatement(sql);

//ResultSet rs = pre.executeQuery();
ResultSet rs =pre.executeQuery();
while(rs.next()){

return 1;

}
} catch (SQLException e) {
// TODO Auto-generated catch block
System.out.println("sql 语句错误");
e.printStackTrace();
}

return 0;

}

public List<User> findAll() {
// TODO Auto-generated method stub
//连接数据库
Connection conn = DbUtil.getConn();
String sql = "select * from book ,users";

List<User> list =new ArrayList<User>();

try {
//编译sql
PreparedStatement per = conn.prepareStatement(sql);
ResultSet rs = per.executeQuery();
while(rs.next()){
User user = new User();
user.setUserid(rs.getInt("userid"));
user.setUsername(rs.getString("username"));
user.setUserpassword(rs.getString("userpassword"));
user.setBookid(rs.getInt("bookid"));
user.setBookname(rs.getString("bookname"));
user.setBookauth(rs.getString("bookauth"));
user.setBooktype(rs.getString("booktype"));
list.add(user);

}
return list;

} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

return null;
}