[英]Getting null values in the browser from jsp page?
JSP page JSP页面
<%@ page import="Student.*"%>
<html>
<body>
<%
String id =request.getParameter("ID1");
StudentDAO std=new StudentDAO();
Student st=std.searchinfo("id");
%>
<h1> <%=st.showStudent()%> </h1>
</body>
</html>
Student.java 学生.java
import java.io.*;
public class Student implements Serializable {
String name;
String id1,phone,clas;
public Student()
{
}
public String showStudent()
{
return "Name: "+name+" Address: "+clas+" Phone: "+phone+" ID: "+id1;
}
public void Student1(String id,String n,String c,String ph)
{
name=n;
id1=id;
phone=ph;
clas=c;
}
}
StudentDAO.java StudentDAO.java
import java.sql.*;
import java.io.*;
public class StudentDAO implements Serializable
{
static String i,id,nam,clas,ph;
Student studentinfo=new Student();
public Student searchinfo(String id2)
{
id=id2;
try{
String url="jdbc:ucanaccess://C:\\Users\\Asim Iqbal\\Documents\\IT.accdb";
Connection conn = DriverManager.getConnection(url);
String sql= "SELECT * FROM Student WHERE ID=?";
PreparedStatement stmt = conn.prepareStatement(sql);
stmt.setString(1,id);
ResultSet rs=stmt.executeQuery();
if (rs.next())
{
i=rs.getString("ID");
nam=rs.getString("Name");
clas=rs.getString("Class");
ph=rs.getString("Phone");
studentinfo.Student1(i, nam, clas, ph);
}
} catch (SQLException e) {
}
return studentinfo;
}
}
This is the error.. But StudentDAO.java connect DB properly and give output as individually.. But in the browser it give null values as follows.. 这是错误。.但是StudentDAO.java正确连接DB并单独提供输出。.但是在浏览器中,它给出了空值,如下所示。
Name: null Address: null Phone: null ID: null 名称:null地址:null电话:null ID:null
<html>
<body>
<%
String id =request.getParameter("ID1");
StudentDAO std=new StudentDAO();
Student st=std.searchinfo(id); 学生st = std.searchinfo(id);
%>
<h1> <%=st.showStudent()%> </h1>
</body>
</html>
Change you jsp page code as above, you should pass the id value as an argument to a DAO method, What your passing now is a string "id". 如上更改您的jsp页面代码,您应该将id值作为参数传递给DAO方法,现在传递的是字符串“ id”。
Remember writing a java code inside a jsp is a bad practise 记住在jsp内编写Java代码是一种不好的做法
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