严重: useBean类属性[shl.test1.jsp.JspUserDao]的值无效
严重: 在路径为/201909250329的上下文中，Servlet[jsp]的Servlet.service（）引发了具有根本原因的异常/301/login_act.jsp (行.: [4], 列: [1]) useBean类属性[shl.test1.jsp.JspUserDao]的值无效。 应该怎么解决
jsp代码
<%@ 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>Insert title here</title>
</head>
<body>
<h1 align="center">系统登陆</h1>
<form action="login_act.jsp" method="get">
<table align="center">
<tr>
<td>用户名:</td>
<td><input type="text" name="name"></td>
</tr>
<tr>
<td>密码:</td>
<td><input type="text" name="pwd"></td>
</tr>
<tr>
<td><input type="submit" value="提交"></td>
</tr>
</table>
</form>
<%
String info = (String) request.getAttribute("info");
%>
<%=info == null ? "" : info%>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<jsp:useBean id="user" class="shl.test1.jsp.JspUser"></jsp:useBean>
<jsp:useBean id="dao" class="shl.test1.jsp.JspUserDao"></jsp:useBean>
<!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>Insert title here</title>
</head>
<body>
<% request.setCharacterEncoding("utf-8");
String name = request.getParameter("name");
String pwd =request.getParameter("pwd");
if(name.equals("")||pwd.equals(""))
{
//name="";pwd="";
request.setAttribute("info", "请输入用户名！");
%>
<jsp:forward page="login.jsp"></jsp:forward>
<%
}
user.setUsername(name);
user.setPassword(pwd);
if(!dao.login(user))
{
request.setAttribute("info", "用户名或密码错误！");
%>
<jsp:forward page="login.jsp"></jsp:forward>
<%
}
else {
session.setAttribute("user", user);
response.sendRedirect("main.jsp");
}
%>
</body>
</html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@page import="shl.test1.jsp.JspUser"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<jsp:useBean id="user" class="shl.test1.jsp.JspUser"></jsp:useBean>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
user = (JspUser)session.getAttribute("user");
if(user== null){
request.setAttribute("info", "请登录！");
%>
<jsp:forward page="login.jsp"></jsp:forward>
<% }
%>
<input type="button" value="注销" onclick="window.location.href('outlogin.jsp')" />
</body>
</html>
package shl.test1.jsp;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class DbConnection {
String url = "jdbc:mysql://localhost:3306/jsptest?"+"useUnicode=true&characterEncoding=UTF8";
String user = "root";
String password = "";
static Connection conn ;
public static Connection getConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("Not find Driver!");
}
try {
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jsptest","root","");
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("Not getConnection!");
}
System.out.println("Connection is success!");
return conn;
}
}
package shl.test1.jsp;
public class JspUser {
private int id;
private String username;
private String email;
private String password;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
package shl.test1.jsp;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
public class JspUserDao {
Connection conn = DbConnection.getConnection();
Statement sta;
ResultSet rst;
public boolean login(JspUser user) {
String name = user.getUsername();
String pwd = user.getPassword();
String sql = "select * from jspuser where username='" + name + "' and Password = '" + pwd + "' ";
try {
sta = conn.createStatement();
} catch (SQLException e) {
e.printStackTrace();
System.out.println("sta is not correct ");
}
try {
rst = sta.executeQuery(sql);
} catch (SQLException e) {
e.printStackTrace();
System.out.println("rst is not correct ");
}
try {
if (rst.next()) {
System.out.println("-------login is success ! ");
sta.close();
rst.close();
conn.close();
return true;
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return false;
}
}
这个user没看到创建或者声明啊