jsp 简单把数据库数据，展示在网页

页面代码：

StudentDaoImpl

import com.mchange.v2.c3p0.ComboPooledDataSource;
import day13.dao.StudentDao;
import day13.entity.Student;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import javax.sql.DataSource;
import java.util.List;

public class StudentDaoImpl implements StudentDao {   //这两句一定记住 实现
    private DataSource ds =  new ComboPooledDataSource();
    private QueryRunner qr = new QueryRunner(ds);  //这两句一定记住

    public List selectAll(){
        List studentList = null;
        try {
            String sql ="select * from test1";
            studentList = qr.query(sql,new BeanListHandler(Student.class));  //小写 query  //这两句一定记住
        } catch (Exception e) {
            e.printStackTrace();
        }

        return studentList;
        
    }
}

 

StudentDao

import day13.entity.Student;

import java.util.List;

public interface StudentDao {
    List selectAll();  //仅定义类型（一定记住的）
}

 

StudentServiceImpl

import day13.dao.StudentDao;
import day13.dao.impl.StudentDaoImpl;
import day13.entity.Student;
import day13.service.StudentService;

import java.util.List;

public class StudentServiceImpl implements StudentService {  //这两句一定记住  实现
    private StudentDao studentDao = new StudentDaoImpl();  //这句一定记住  实例后，才能使用

    public List selectAll(){
        return studentDao.selectAll();
    }

}

 

StudentServlet

import day13.entity.Student;
import day13.service.ServiceImpl.StudentServiceImpl;
import day13.service.StudentService;

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.util.List;

@WebServlet(name = "studentServlet",urlPatterns = "/studentServlet")
public class StudentServlet extends HttpServlet {
    private StudentService studentService ;

    @Override
    public void init() throws ServletException {
        studentService = new StudentServiceImpl();  //接口
    }

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List studentList =studentService.selectAll();
        req.setAttribute("studentList",studentList);
        req.getRequestDispatcher("index.jsp").forward(req,resp);

    }
}

 

index.jsp

<%@ page import="java.util.List" %>
<%@ page import="day13.entity.Student" %><%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2020/8/12
  Time: 9:18
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>

  
    
  
  
  <%
      List studentList = null;
      if (request.getAttribute("studentList")==null){
          request.getRequestDispatcher("studentServlet").forward(request,response);
          return;
      }else {
          studentList = (List) request.getAttribute("studentList");
          System.out.println(111);
      }

      %>



<%
    for (int i = 0 ;i
      

                  <%
                      }
                  %>

              

  

      
编号
      
姓名
      
年龄
  

        
<%=studentList.get(i).getPid()%>
        
<%=studentList.get(i).getPname()%>
         
<%=studentList.get(i).getPage()%>
      
  

 

结果展示：

数据库：

网页