增删改查（简单版&连接数据库）

这个博客也是补充之前的学习内容:

项目总述：这个增删改查我以，选课名称，选课教室，选课教师基本信息，作为主要的信息来源。主要对这些信息最基本的增删改查

详细的分析与说明：

1.首先在src文件里定义四个包，com.bean(定义类），com.dao(对数据进行处理，书写增删改查的函数），com.db(用于连接数据库），com.servlet(用于接受jsp中传输的值，并对其进行判断处理）

                                                

 相关代码展示：

Bean.java:

package com.bean;

public class Bean {
    
    private String name;
    private String teacher;
    private String classroom;
    
    public Bean() {
        super();
    }
    
    public Bean(String name, String teacher, String classroom) {
        super();
        this.name = name;
        this.teacher = teacher;
        this.classroom = classroom;
    }
    
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getTeacher() {
        return teacher;
    }
    public void setTeacher(String teacher) {
        this.teacher = teacher;
    }
    public String getClassroom() {
        return classroom;
    }
    public void setClassroom(String classroom) {
        this.classroom = classroom;
    }

    @Override
    public String toString() {
        return "Bean [name=" + name + ", teacher=" + teacher + ", classroom=" + classroom + "]";
    }
    
}

Dao.java:

package com.dao;

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

import com.db.DB;
import com.servlet.selectNameServlet;
import com.servlet.updateServlet;
import com.db.DB;
import com.bean.Bean;

public class Dao {
    
    //增加
    @SuppressWarnings("static-access")
    public boolean add(Bean bean) {
        String tablename = "test";//表名
        DB db=new DB();
        Connection con = db.getCon();
        
        try {
            String sql="insert into "+tablename+"(name,teacher,classroom) values ('"+bean.getName()+"','"+bean.getTeacher()+"','"+bean.getClassroom()+"')";
            Statement stm = con.createStatement();
            System.out.println(sql);
            stm.execute(sql);
            db.close(stm, con);
        }catch(Exception e) {
            e.printStackTrace();
            System.out.println("add false");
            return false;
        }
        System.out.println("add true");
        return true;
    }

    //根据名称进行查询
    @SuppressWarnings("static-access")
    public static Bean selectName(String name) {
        String tablename = "test";
        System.out.println("select bean where name = "+name);
        Bean bean=null;
        DB db=new DB();
        Connection con = db.getCon();
        try {
            Statement stm = con.createStatement();
            ResultSet rs = stm.executeQuery("select * from "+tablename+" where name='" + name + "'");
            /*
             * ResultSet rs =stm.executeQuery("select value3 from "+tablename+" where value2="+i);
             */
            if(rs.next())
            {
                bean = new Bean();
                System.out.println("select the bean from mysql");
                bean.setName(rs.getString("name"));
                bean.setTeacher(rs.getString("teacher"));
                bean.setClassroom(rs.getString("classroom"));
                //bean.setValue2(Integer.parseInt(rs.getString("teacher")));
                //bean.setValue3(Boolean.parseBoolean(rs.getString("address")));
                System.out.println("name of the bean is "+rs.getString("name"));
            }
            db.close(rs,stm, con);
        }catch(Exception e) {
            e.printStackTrace();
        }
        return bean;
    }
    
    
    //删除
    @SuppressWarnings("static-access")
    public static boolean delete(String name)
    {
        //String tablename ="test";
        DB db=new DB();
        Connection con = db.getCon();
        //Connection con=null;
        PreparedStatement stm=null;
        try {
            con=DB.getCon();
            String sql="delete from test where name='"+name+"'";
            //String sql="delete from test where name='"+bean.getName()+"'";
            System.out.println(sql);
            stm=con.prepareStatement(sql);
            stm.executeUpdate();
            return true;
        }
        catch(SQLException e)
        {
            e.printStackTrace();
        }
        finally {
            db.close(stm, con);
        }
        return false;
    }
   //修改
    @SuppressWarnings("static-access")
    public boolean update(Bean bean) {
        Connection con=null;
        PreparedStatement stm=null;
        String tablename="test";
        DB db=new DB();
        try {
            con=DB.getCon();
            String sql="update "+tablename+" set teacher=?,classroom=? where name=?";
            //String sql="update "+tablename+"set teacher=?,classroom=? where name=?";
            stm=con.prepareStatement(sql);
            stm.setString(3,bean.getName());
            stm.setString(1, bean.getTeacher());
            stm.setString(2,bean.getClassroom());
            stm.executeUpdate();
        }
        catch(SQLException e)
        {
            e.printStackTrace();
            return false;
        }
        finally {
            db.close(stm, con);
            return true;
        }
    }
  //根据名字进行查找
     public  boolean findName(String name){
            boolean flag=false;
            Connection con=null;
            PreparedStatement psts=null;
            ResultSet rs=null;
            String tablename="test";
            DB db=new DB();
            try {
                con=db.getCon();
                String sql="select * from"+tablename+" where name=?";
                psts=con.prepareStatement(sql);
                psts.setString(1, name);
                rs=psts.executeQuery();
                while(rs.next()){
                    flag=true;
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
            
            return flag;
     }
    
    //
    @SuppressWarnings("static-access")
     public ArrayList<Bean> selectList(){
        Connection con=null;
        PreparedStatement stm=null;
        ResultSet rs=null;
        ArrayList<Bean> listbean=new ArrayList<Bean>();
        String tablename="test";
        DB db=new DB();
        try {
            con=db.getCon();
            String sql="select * from "+tablename;
            stm=con.prepareStatement(sql);
            rs=stm.executeQuery();
            while(rs.next()){
            
                String name=rs.getString("name");
                String teacher=rs.getString("teacher");
                String classroom=rs.getString("classroom");
                Bean bean=new Bean(name,teacher,classroom);
                listbean.add(bean);
                
            }
        } 
        catch(SQLException e)
        {
            e.printStackTrace();
        }
        finally
        {
            db.close(stm, con);
        }
        return listbean;
    }

}

    
    //
//    public Bean login(String name,String password) {
//        String tablename = null;
//        DB db=new DB();
//        Connection con = db.getCon();
//        Bean bean = null;
//        try {
//            Statement stm = con.createStatement();
//            ResultSet rs = stm.executeQuery("select * from "+tablename+" where value1='" + name + "'");
//            if(rs.next()) {
//                if (rs.getString("password").equals(password)) {
//                    
//                }
//            }
//        }catch(Exception e) {
//            
//        }
//    }
    

DB.java:

package com.db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;



public class DB {
    private static String mysqlname = "database";//数据库名
    private static Connection con;
    private static Statement stm;
    private static ResultSet rs;
    private static String coursename = "com.mysql.jdbc.Driver";
    private static String url = "jdbc:mysql://127.0.0.1:3306/"+mysqlname+"?useUnicode=true&characterEncoding=GB18030&useSSL=false&serverTimezone=GMT&allowPublicKeyRetrieval=true";
    
    public static Connection getCon() {
        try {
            Class.forName(coursename);
            System.out.println("注册驱动成功");
        }catch(ClassNotFoundException e) {
            e.printStackTrace();
        }
        try {
            con = DriverManager.getConnection(url,"root","20000604");
            System.out.println("建立连接成功");
        }catch(Exception e){
            e.printStackTrace();
            con = null;
        }
        return con;
    }
    
    public static void close(Statement stm,Connection connection) {
        if(stm!=null) {
            try {
                stm.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null) {
            try {
                connection.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
    }
        
    //关闭
    public static void close(ResultSet rs,Statement stm,Connection connection) {
        if(rs!=null) {
            try {
                rs.close();
            }catch(SQLException e) {
            e.printStackTrace();
            }
        }
        if(stm!=null) {
            try {
                stm.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
        if(connection!=null) {
            try {
                connection.close();
            }catch(SQLException e) {
                e.printStackTrace();
            }
        }
    }
    public static void main(String[] args)
    {
        getCon();
    }
}

addServlet.java:

package com.servlet;

import java.io.IOException;
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 com.bean.Bean;
import com.dao.Dao;

/**
 * Servlet implementation class addServlet
 */
@WebServlet("/addServlet")
public class addServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("UTF-8");
        
        Bean bean = new Bean();
        bean.setName(request.getParameter("name"));
        bean.setTeacher(request.getParameter("teacher"));
        bean.setClassroom(request.getParameter("classroom"));
        Dao dao = new Dao();
        if(dao.add(bean)) {
            
            request.setAttribute("message", "添加成功");
            request.getRequestDispatcher("add.jsp").forward(request,response);
            //response.sendRedirect("index.jsp");
        }
        else {
            request.setAttribute("message","添加失败");
            request.getRequestDispatcher("add.jsp").forward(request,response);
            //response.sendRedirect("add.jsp");
        }
    }

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        doGet(request, response);
    }

}

deleteServlet.java:

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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 com.bean.Bean;
import com.dao.Dao;

/**
 * Servlet implementation class deleteServlet
 */
@WebServlet("/deleteServlet")
public class deleteServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");

        Dao dao=new Dao();
        if(dao.delete(request.getParameter("delete"))) {//response.sendRedirect("index.jsp");
            request.setAttribute("message", "删除成功");
            request.getRequestDispatcher("delete.jsp").forward(request,response);
            //response.sendRedirect("index.jsp");
        }
        else {
            request.setAttribute("message", "删除失败");
            request.getRequestDispatcher("delete.jsp").forward(request,response);
            //response.sendRedirect("index.jsp");//response.sendRedirect("delete.jsp");
        }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

selectNameServlet.java:

package com.servlet;

import java.io.IOException;
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 com.bean.Bean;
import com.dao.Dao;

/**
 * Servlet implementation class selectNameServlet
 */
@WebServlet("/selectNameServlet")
public class selectNameServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
  
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        Bean bean=new Bean();
        bean.setName(request.getParameter("selectname"));
        Dao dao=new Dao();
        bean = dao.selectName(bean.getName());
        if(bean!=null)
        {
            request.setAttribute("Bean",bean);
            request.getRequestDispatcher("select_show.jsp").forward(request,response);
        }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

showAllServlet.java:

package com.servlet;

import java.io.IOException;
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 com.bean.Bean;
import com.dao.Dao;

/**
 * Servlet implementation class selectNameServlet
 */
@WebServlet("/selectNameServlet")
public class selectNameServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
  
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        Bean bean=new Bean();
        bean.setName(request.getParameter("selectname"));
        Dao dao=new Dao();
        bean = dao.selectName(bean.getName());
        if(bean!=null)
        {
            request.setAttribute("Bean",bean);
            request.getRequestDispatcher("select_show.jsp").forward(request,response);
        }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

updatenewServlet.java:

package com.servlet;

import java.io.IOException;
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 com.bean.Bean;
import com.dao.Dao;

/**
 * Servlet implementation class updatenewServlet
 */
@WebServlet("/updatenewServlet")
public class updatenewServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //response.getWriter().append("Served at: ").append(request.getContextPath());
        request.setCharacterEncoding("UTF-8");
        Bean beannew=new Bean();
        Dao dao=new Dao();
        beannew.setName(request.getParameter("updatename"));
        beannew.setTeacher(request.getParameter("updateteacher"));
        beannew.setClassroom(request.getParameter("updateclassroom"));
        //System.out.println("接受成功");
        //System.out.println(request.getParameter("updatename"));
        //bean.setValue2(Integer.parseInt(request.getParameter("value2")));
        //bean.setValue3(Boolean.parseBoolean(request.getParameter("value3")));
          if(dao.update(beannew)) {
             response.sendRedirect("index.jsp");
        }
        else {
            response.sendRedirect("update_show.jsp");
        }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

updateServlet:

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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 com.bean.Bean;
import com.dao.Dao;

/**
 * Servlet implementation class updateServlet
 */
@WebServlet("/updateServlet")
public class updateServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
        request.setCharacterEncoding("UTF-8");
        Bean bean=new Bean();
        Bean beanform=new Bean();
        Dao dao=new Dao();
        bean = dao.selectName(request.getParameter("selectname"));
         System.out.println(request.getParameter("selectname"));
        if(bean!=null)
        {
            request.setAttribute("Bean",bean);
            request.getRequestDispatcher("update_show.jsp").forward(request,response);
        }
        
//        else if(bean==null) {
//            request.setAttribute("Bean",bean);
//            request.getRequestDispatcher("delete.jsp").forward(request,response);
//            return ;
//        }
            
        
    
//        beanform.setName(request.getParameter("updatename"));
//        beanform.setTeacher(request.getParameter("updateteacher"));
//        beanform.setClassroom(request.getParameter("updateclassroom"));
//         //bean.setValue2(Integer.parseInt(request.getParameter("value2")));
//         //bean.setValue3(Boolean.parseBoolean(request.getParameter("value3")));
//          if(dao.update(beanform)) {//             response.sendRedirect("index.jsp");
//        }
//        else {//            response.sendRedirect("update.jsp");
//        }
    }

}

2.然后继续完成前端页面：

                                  

 代码展示：

index.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>首界面</title>
</head>
<body>

           <div>
            <h1 align="center" color="blue"> 增删改查的主页面</h1>
            <hr/>
            <a href="add.jsp"><h2 align="center">添加课程信息</a></h2>
            <a href="delete.jsp"><h2 align="center">删除课程信息</a></h2>
            <a href="update.jsp"><h2 align="center">修改课程信息</h2></a>
            <a href="select.jsp"><h2 align="center">查询课程信息</h2></a>
            <a href="showAllServlet"  ><h2 align="center">浏览课程全部信息</h2></a>
           </div>
        
</body>
</html>

add.jsp:

<%@page import="java.util.jar.Attributes.Name"%>
<%@page import="com.servlet.addServlet" %> 
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>添加课程</title>
</head>
<body>
<%
  String mess=(String)request.getAttribute("message");
     if(mess!=null&&!"".equals(mess)){
         %>
         <script type="text/javascript">
         alert("<%=mess%>");
         </script>
         <% 
     }
%>
<div align="center">
 <form action="addServlet" method="post">
   <a href="index.jsp"><h2>返回主界面</h2></a>
    <div >
    <table>
      <tr>
             <td>添加课程:</td>
             <td><input type="text" id="name" name="name"></td>
      </tr>
      <tr>
             <td>添加教师：</td>
             <td><input type="text" id="teacher" name="teacher"></td>
      </tr>
      <tr>
               <td>添加地点：</td>
               <td><input type="text" id="classroom" name="classroom"></td>
      </tr>
      <tr>
             <td><input align="center" type="submit" value="添加"></td>
      </tr>
          </table>
    </div>
   </form>
</div>
</body>
</html>

delete.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>删除课程</title>
</head>
<body>

<%
  String mess=(String)request.getAttribute("message");
     if(mess!=null&&!"".equals(mess)){
         %>
         <script type="text/javascript">
         alert("<%=mess%>");
         </script>
         <% 
     }
%>

    <form align="center" action="deleteServlet" method="post">
      <div>
      <h4><a href="index.jsp">返回主界面</a></h4>
       <table>
          <tr>
            <td>根据名字进行删除：</td>
          </tr>
          <tr>
              <td>请输入需要删除课程的名字：</td>
              <td><input type="text" name="delete" value=""></td>
          </tr>
          <tr>
            <input type="submit" value="确定" id="">
          </tr>
       </table>
      </div>
    </form>
</body>
</html>

select.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>查询课程信息</title>
</head>
<body>

<%
  String mess=(String)request.getAttribute("message");
     if(mess!=null&&!"".equals(mess)){
         %>
         <script type="text/javascript">
         alert("<%=mess%>");
         </script>
         <% 
     }
%>

 <h2 align="cneter">课程查询</h2>
 <hr/>
    <form align="center" action="selectNameServlet" method="post">
      <div>
       <table>
          <tr>
            <td>根据名字进行查询：</td>
          </tr>
          <tr>
              <td>请输入需要查询课程的名字：</td>
              <td><input type="text" name="selectname" value=""></td>
          </tr>
          <tr>
            <input type="submit" value="确定" id="">
          </tr>
          <a href="index.jsp">返回主页面</a>
       </table>
      </div>
    </form>
</body>
</html>

select_show.jsp:

<%@page import="com.bean.Bean"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>查询显示</title>
</head>
<body>
<%
 Bean b2=(Bean)request.getAttribute("Bean");

%>
  <form action="selectServlet" method="post">

  <table>
      <tr>
          <td>显示课程名字：</td>
          <td><input type="text" name="" value="<%=b2.getName()%>"></td>
      </tr>
      <tr>
          <td>显示课程教师：</td>
          <td><input type="text" name="" value="<%=b2.getTeacher()%>"></td>
      </tr>
      <tr>
          <td>显示课程地点：</td>
          <td><input type="text" naem="" value="<%= b2.getClassroom()%>"></td>
      </tr>
          
  </table>
 <a href="index.jsp">返回主界面</a>
 
 </form>
</body>
</html>

update.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>显示所要修改的课程</title>
</head>
<body>
 <form action="updateServlet" method="post">
          <tr>
               <td>请输入所要修改的课程的名字：</td>
               <td><input type="text" name="selectname" value=""></td>
          </tr>
          <tr>
              <input type="submit" value="确定" id="">
          </tr>
 </form>
</body>
</html>

update_show.jsp:

<%@page import="com.bean.Bean"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>修改课程信息</title>
</head>
   <%
      Bean b2=(Bean)request.getAttribute("Bean");
   %>
   
 
<body>
 
     <form action="updatenewServlet"  method="post">    
  <table>
  <h4>修改前的课程信息：</h4>
      <tr>
          <td>课程名字：</td>
          <td><input type="text" name="" value="<%=b2.getName()%>"></td>
      </tr>
      <tr>
          <td>课程教师：</td>
          <td><input type="text" name="" value="<%=b2.getTeacher()%>"></td>
      </tr>
      <tr>
          <td>课程地点：</td>
          <td><input type="text" name="" value="<%= b2.getClassroom()%>"></td>
      </tr>
     
  </table>
  <hr/>
  <h4>修改后的课程信息</h4>
  <table>
    <tr>
        <td>请输入所要修改的课程名称：</td>
        <td><input type="text" name="updatename" value=""></td>
    </tr>
    <tr>
        <td>请输入修改后的课程教师：</td>
        <td><input type="text" name="updateteacher" value=""></td>
    <tr>
        <td>请输入修改后的上课地点：</td>
        <td><input type="text" name="updateclassroom" value=""></td>
    </tr>
     <tr>
            <input type="submit" value="确定" id="">
          </tr>
  </table>
  <a href="index.jsp">返回主页面</a>
  </form>
</body>
</html>

showall.jsp:

<%@page import="com.dao.Dao"%>
<%@page import="com.bean.Bean"%>
<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%-- <%@ page isELIgnored="false" %> --%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>显示全部信息</title>
</head>
<body>
<!-- <form  action="showAllServlet" method="post"> -->
 <tr><h3>所有课程信息：</h3></tr>
 <hr/>
   <table>
           <tr>
               <td>课程名称</td>
               <td>课程教师</td>
               <td>课程地点</td>
           </tr>
           <c:forEach items="${listbean}" var="item">
           <tr>
              <td>${item.name}</td>
              <td>${item.teacher}</td>
              <td>${item.classroom}</td>
           </tr>
             </c:forEach> 
   </table>
        <a href="index.jsp">返回主界面</a>
        </form>
</html>

所遇到的问题：

1.在update_show.jsp的显示页面中，他的组成部分为两部分，一是显示需要修改之前的全部信息，二是输入修改之后的信息。界面如下所示

 所遇问题是保存不成功修改后的信息，原因：在updatenewServlet.java没有接收到update_show.jsp所要传输的信息

2.在显示全部信息的时，不能全部的显示：

界面如下：

 理应如下：

 原因：自己对于forEach语句的不熟练照成，需要多多学习，多多练习。