數據庫的修改功能，主要是通過查詢，保留之前的數據，得到當前想要修改的頁面，並進行修改。
一.dao層
在dao層需要添加兩個fangfa，一個查詢，一個修改（這是整個dao層，包括之前的增刪、瀏覽）
package 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.mysql.cj.protocol.ResultBuilder; import Bean.Course; import util.DBUtil; public class daoCourse { public boolean add(Course n) { boolean f=false; int a=0; String sql="insert submitcourse(classname,teachername,place) values(?,?,?)"; try { Connection conn=DBUtil.getConnection(); PreparedStatement pstmt=conn.prepareStatement(sql); pstmt.setString(1,n.getClassname()); pstmt.setString(2,n.getTeachername()); pstmt.setString(3,n.getPlace()); a=pstmt.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } if(a>0) f=true; return f; } public boolean delete(Course n) { boolean f=false; int a=0; String sql="delete from submitcourse where teachername=?"; try { Connection conn=DBUtil.getConnection(); PreparedStatement pstmt=conn.prepareStatement(sql); pstmt.setString(1,n.getTeachername()); a=pstmt.executeUpdate(); System.out.println("fuck you"); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } if(a>0) f=true; return f; }public List<Course> list(){ String sql="select * from submitcourse"; List<Course> list=new ArrayList<>(); ResultSet rs=null; Course ns=new Course(); try { Connection conn=DBUtil.getConnection(); PreparedStatement pstmt=conn.prepareStatement(sql); // pstmt.setString(1,n.getTeachername()); rs=pstmt.executeQuery(); while(rs.next()) { ns=new Course(rs.getString(1),rs.getString(2),rs.getString(3)); list.add(ns); } //System.out.println(rs); System.out.println(rs); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return list; } public boolean update(Course n,String old_teachername){//修改信息 boolean f=false; int a=0; String sql = "update submitcourse set classname='"+n.getClassname()+"',teachername='"+n.getTeachername()+"',place='"+n.getPlace()+"' where teachername='"+old_teachername+"'"; try { Connection conn=DBUtil.getConnection(); PreparedStatement pstmt=conn.prepareStatement(sql); a=pstmt.executeUpdate(); System.out.println(a); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } if(a>0) f=true; return f; } public Course queryByTeachername(String teachername) {//查詢信息 String sql="select * from submitcourse where teachername=?"; Course n=new Course(); try { ResultSet rs=null; Connection conn=DBUtil.getConnection(); PreparedStatement pstmt=conn.prepareStatement(sql); pstmt.setString(1,teachername); rs=pstmt.executeQuery(); while(rs.next()) { n=new Course(rs.getString(1), rs.getString(2),rs.getString(3)); } System.out.println("fuck you"); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return n ; } }
二。servlert層
servlet里面主要也是兩個方法，用來傳參交互。（這是整個servlet層，包括增刪、瀏覽）
package servlet; import java.io.IOException; import java.util.ArrayList; import java.util.List; 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 Bean.Course; import dao.daoCourse; /** * Servlet implementation class course_servlet */ @WebServlet("/course_servlet") public class course_servlet extends HttpServlet { private static final long serialVersionUID = 1L; daoCourse gooddao=new daoCourse(); /** * @see HttpServlet#HttpServlet() */ public course_servlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doPost(request, response); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub request.setCharacterEncoding("utf-8"); response.setCharacterEncoding("utf-8"); String method=request.getParameter("method"); if("add".equals(method)) { String teachername=request.getParameter("teachername"); String classname=request.getParameter("classname"); String place=request.getParameter("place"); Course n=new Course(classname,teachername,place); gooddao.add(n); request.setAttribute("message", "添加成功"); request.getRequestDispatcher("NewFile2.jsp").forward(request, response); } else if("delete".equals(method)) { String teachername=request.getParameter("teachername"); Course n=new Course(); n.setTeachername(teachername); gooddao.delete(n); request.setAttribute("message", "刪除成功"); request.getRequestDispatcher("course_servlet?method=looklist").forward(request, response); } else if("looklist".equals(method)) { List<Course> nt= gooddao.list(); request.setAttribute("nt", nt); System.out.println("王建民"); request.getRequestDispatcher("NewFile3.jsp").forward(request, response); } else if("queryByTeachername".equals(method)) { String teachername=request.getParameter("teachername"); Course n=new Course(); System.out.println("8888"); n.setTeachername(teachername); n= gooddao.queryByTeachername(teachername); request.setAttribute("n", n); request.getRequestDispatcher("update.jsp").forward(request, response); } else if("update".equals(method)) { String teachername=request.getParameter("teachername"); String classname=request.getParameter("classname"); String place=request.getParameter("place"); String old_teachername=request.getParameter("old_teachername"); Course n=new Course(classname,teachername,place); gooddao.update(n,old_teachername); request.setAttribute("message", "添加成功"); request.getRequestDispatcher("course_servlet?method=looklist").forward(request, response); } } }
三.寫jap
在之前文章的原有的基礎上，再加入一個update.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" import="Bean.*"%> <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Insert title here</title> </head> <body> <% Course n=(Course)request.getAttribute("n"); %> <form action="course_servlet?method=update" method="post"> <input type="hidden" name="old_teachername" value="<%=n.getTeachername()%>"/> 課程名稱:<input type="text" name="classname" id="classname" value="<%=n.getClassname()%>"><br> 教師姓名:<input type="text" name="teachername" id="teachername" value="<%=n.getTeachername()%>"><br> 教學地點:<input type="text" name="place" id="place" value="<%=n.getPlace()%>"> <input type="submit" value="修改"> </form> </body> </html>
四.運行結果
點擊修改進入修改頁面
點擊修改
修改成功
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