JavaWeb筆記3、MVC 設計模式

時間 2019-11-30

標籤 javaweb 筆記 mvc 設計模式欄目 Java 简体版

原文原文鏈接

1、經過 MVC 進行查詢和刪除操做

1. 準備一個數據表（examstudent）

2. 建立一個查詢頁面（test.jsp）

　　經過鏈接進入 Servlet（listAllStudents.java）

 1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2  pageEncoding="UTF-8"%> 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 4 <html> 5 <head> 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 7 <title>Insert title here</title> 8 </head> 9 <body> 10 <a href="listAllStudents">List All Students</a> 11 </body> 12 </html>

3. 建立一個 Servlet（listAllStudents.java）

　　建立一個 StudentDao 對象，調用 StudentDao 中的 getAll() 方法，獲得 Student 的 List 集合，並設置給 request 對象， request 經過轉發把信息傳遞到 students.jsp 頁面

 1 package com.panku.mvc;
 2 
 3 import java.io.IOException; 4 import java.util.List; 5 6 import javax.servlet.ServletException; 7 import javax.servlet.annotation.WebServlet; 8 import javax.servlet.http.HttpServlet; 9 import javax.servlet.http.HttpServletRequest; 10 import javax.servlet.http.HttpServletResponse; 11 12 @WebServlet("/listAllStudents") 13 public class ListAllStudents extends HttpServlet { 14 private static final long serialVersionUID = 1L; 15 16 protected void doGet(HttpServletRequest request, HttpServletResponse response) 17 throws ServletException, IOException { 18 19 StudentDao studentDao = new StudentDao(); 20 List<Student> students = studentDao.getAll(); 21 request.setAttribute("students", students); 22 23 request.getRequestDispatcher("/students.jsp").forward(request, response); 24 25  } 26 }

4. 建立 StudentDao.java 文件

　　在 StudentDao,java 中建立 getAll()、 deleteByFlowId(Integer flowId) 兩個方法分別實現查詢所有數據和刪除一條數據的操做

  1 package com.panku.mvc;
  2 
  3 import java.sql.Connection; 4 import java.sql.DriverManager; 5 import java.sql.PreparedStatement; 6 import java.sql.ResultSet; 7 import java.sql.SQLException; 8 import java.util.ArrayList; 9 import java.util.List; 10 11 public class StudentDao { 12 13 public void deleteByFlowId(Integer flowId) { 14 15 Connection connection = null; 16 PreparedStatement preparedStatement = null; 17 18 try { 19 String driverClass = "com.mysql.jdbc.Driver"; 20 String url = "jdbc:mysql:///java_jdbc"; 21 String user = "root"; 22 String password = "123456"; 23 24  Class.forName(driverClass); 25 connection = DriverManager.getConnection(url, user, password); 26 27 String sql = "DELETE FROM examstudent WHERE flow_id = ?"; 28 preparedStatement = connection.prepareStatement(sql); 29 30 preparedStatement.setInt(1, flowId); 31  preparedStatement.executeUpdate(); 32 33 } catch (Exception e) { 34  e.printStackTrace(); 35 } finally { 36 try { 37 if (preparedStatement != null) { 38  preparedStatement.close(); 39  } 40 } catch (SQLException e) { 41  e.printStackTrace(); 42  } 43 try { 44 if (connection != null) { 45  connection.close(); 46  } 47 } catch (SQLException e) { 48  e.printStackTrace(); 49  } 50  } 51 52  } 53 54 public List<Student> getAll() { 55 56 List<Student> students = new ArrayList<>(); 57 58 Connection connection = null; 59 PreparedStatement preparedStatement = null; 60 ResultSet resultSet = null; 61 62 try { 63 String driverClass = "com.mysql.jdbc.Driver"; 64 String url = "jdbc:mysql:///java_jdbc"; 65 String user = "root"; 66 String password = "123456"; 67 68  Class.forName(driverClass); 69 connection = DriverManager.getConnection(url, user, password); 70 71 String sql = "SELECT flow_id, type, id_card, exam_card, student_name, location, " 72 + "grade FROM examstudent"; 73 preparedStatement = connection.prepareStatement(sql); 74 resultSet = preparedStatement.executeQuery(); 75 76 while (resultSet.next()) { 77 int flowId = resultSet.getInt(1); 78 int type = resultSet.getInt(2); 79 String idCard = resultSet.getString(3); 80 String examCard = resultSet.getString(4); 81 String studentName = resultSet.getString(5); 82 String location = resultSet.getString(6); 83 int grade = resultSet.getInt(7); 84 85 Student student = new Student(flowId, type, idCard, examCard, studentName, location, grade); 86  students.add(student); 87  } 88 89 } catch (Exception e) { 90  e.printStackTrace(); 91 } finally { 92 try { 93 if (resultSet != null) { 94  resultSet.close(); 95  } 96 } catch (SQLException e) { 97  e.printStackTrace(); 98  } 99 try { 100 if (preparedStatement != null) { 101  preparedStatement.close(); 102  } 103 } catch (SQLException e) { 104  e.printStackTrace(); 105  } 106 try { 107 if (connection != null) { 108  connection.close(); 109  } 110 } catch (SQLException e) { 111  e.printStackTrace(); 112  } 113  } 114 115 return students; 116  } 117 118 }

5. 建立一個Student.java 實體類

　　用來實例數據庫的數據

 1 package com.panku.mvc;
 2 
 3 public class Student { 4 5 private Integer flowId; 6 private Integer type; 7 private String idCard; 8 private String examCard; 9 private String studentName; 10 private String location; 11 private Integer grade; 12 13 public Integer getFlowId() { 14 return flowId; 15  } 16 17 public void setFlowId(Integer flowId) { 18 this.flowId = flowId; 19  } 20 21 public Integer getType() { 22 return type; 23  } 24 25 public void setType(Integer type) { 26 this.type = type; 27  } 28 29 public String getIdCard() { 30 return idCard; 31  } 32 33 public void setIdCard(String idCard) { 34 this.idCard = idCard; 35  } 36 37 public String getExamCard() { 38 return examCard; 39  } 40 41 public void setExamCard(String examCard) { 42 this.examCard = examCard; 43  } 44 45 public String getStudentName() { 46 return studentName; 47  } 48 49 public void setStudentName(String studentName) { 50 this.studentName = studentName; 51  } 52 53 public String getLocation() { 54 return location; 55  } 56 57 public void setLocation(String location) { 58 this.location = location; 59  } 60 61 public Integer getGrade() { 62 return grade; 63  } 64 65 public void setGrade(Integer grade) { 66 this.grade = grade; 67  } 68 69 public Student(Integer flowId, Integer type, String idCard, String examCard, String studentName, String location, 70  Integer grade) { 71 super(); 72 this.flowId = flowId; 73 this.type = type; 74 this.idCard = idCard; 75 this.examCard = examCard; 76 this.studentName = studentName; 77 this.location = location; 78 this.grade = grade; 79  } 80 81 public Student() { 82 super(); 83  } 84 85 }

6. 建立一個 Student.jsp 頁面經過表格方式顯示查詢結果

　　顯示查詢的結果，添加一個刪除操做

 1 <%@page import="com.panku.mvc.Student"%> 2 <%@page import="java.util.List"%> 3 <%@ page language="java" contentType="text/html; charset=UTF-8" 4  pageEncoding="UTF-8"%> 5 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 6 <html> 7 <head> 8 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 9 <title>Insert title here</title> 10 </head> 11 <body> 12 13 <% 14  List<Student> stus = (List) request.getAttribute("students"); 15 %> 16 17 <table border="1" cellpadding="10" cellspacing="0"> 18 <tr> 19 <th>FlowId</th> 20 <th>Type</th> 21 <th>IdCard</th> 22 <th>ExamCard</th> 23 <th>StudentName</th> 24 <th>Location</th> 25 <th>Grade</th> 26 <th>Delete</th> 27 </tr> 28 29 <% 30 for (Student student : stus) { 31 %> 32 <tr> 33 <td><%=student.getFlowId()%></td> 34 <td><%=student.getType()%></td> 35 <td><%=student.getIdCard()%></td> 36 <td><%=student.getExamCard()%></td> 37 <td><%=student.getStudentName()%></td> 38 <td><%=student.getLocation()%></td> 39 <td><%=student.getGrade()%></td> 40 <td><a href="deleteStudent?flowId=<%=student.getFlowId()%>">Delete</a></td> 41 </tr> 42 <% 43  } 44 %> 45 46 </table> 47 48 </body> 49 </html>

7. 建立一個 Servlet (DeleteStudent.java )

　　獲取 Student.jsp 頁面傳過來的參數，建立 StudentDAO 對象，調用 StudentDAO中刪除方法（deleteByFlowId() 方法），並把 request 轉發給 success.jsp 頁面

 1 package com.panku.mvc;
 2 
 3 import java.io.IOException; 4 import javax.servlet.ServletException; 5 import javax.servlet.annotation.WebServlet; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 10 @WebServlet("/deleteStudent") 11 public class DeleteStudent extends HttpServlet { 12 private static final long serialVersionUID = 1L; 13 14 protected void doGet(HttpServletRequest request, HttpServletResponse response) 15 throws ServletException, IOException { 16 String flowId = request.getParameter("flowId"); 17 18 StudentDao studentDao = new StudentDao(); 19  studentDao.deleteByFlowId(Integer.parseInt(flowId)); 20 21 request.getRequestDispatcher("/success.jsp").forward(request, response); 22  } 23 24 }

8. 建立一個 success.jsp 頁面

　　顯示刪除成功，並能夠點擊連接查看刪除以後的數據

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     刪除成功!!!
11     <br>
12     <br>
13     <a href="listAllStudents">List All Students</a>
14 </body>
15 </html>