MVC模式（Model View Controller）：
Model:DAO模型
View:JSP 在頁面上填寫java代碼實現顯示
Controller：Servlet
重定向和請求的轉發：
若目標的相應頁面不需要從request里面讀取任何信息，則可以使用重定向，可以防止表單重復提交；
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Student.java類。里面封裝了許多屬性的信息；
package com.lanqiao.javatest;
public class Student {
private Integer id;
private String username;
private String password;
public Student() {
super();
}
public Student(Integer id, String username, String password) {
super();
this.id = id;
this.username = username;
this.password = password;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "Student [id=" + id + ", username=" + username + ", password=" + password + "]";
}
}
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StudentDAO.java類。里面實現數據庫的連接，和實現了對數據的查詢和刪除，可以修改一下實現增刪的功能
public class StudentDAO {
//連接數據庫並實現刪除的方法
public void deleteId(Integer id){
Connection connection=null;
PreparedStatement preparedStatement=null;
String sql="delete from person where id=?";
try {
String driverClass="com.mysql.jdbc.Driver";
String url="jdbc:mysql:///test";
String user="root";
String password="lxn123";
Class.forName(driverClass);
connection=DriverManager.getConnection(url, user, password);
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setInt(1, id);
preparedStatement.executeUpdate();
} catch (Exception e) {
}finally {
if (preparedStatement!=null) {
try {
preparedStatement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (connection!=null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
//連接數據庫並且實現查詢的方法
public List<Student> getAll(){
List<Student> list=new ArrayList<Student>();
//該方法獲取連接數據庫的方法
Connection connection=null;
PreparedStatement preparedStatement=null;
ResultSet resultSet=null;
String sql="select id,username,password from person";
try {
String driverClass="com.mysql.jdbc.Driver";
String url="jdbc:mysql:///test";
String user="root";
String password="lxn123";
Class.forName(driverClass);
connection=DriverManager.getConnection(url, user, password);
preparedStatement=connection.prepareStatement(sql);
resultSet=preparedStatement.executeQuery();
while(resultSet.next()){
int id=resultSet.getInt(1);
String username=resultSet.getString(2);
String password1=resultSet.getString(3);
Student student=new Student(id,username,password1);
list.add(student);
}
} catch (Exception e) {
e.printStackTrace();
}
finally {
if (resultSet!=null) {
try {
resultSet.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (preparedStatement!=null) {
try {
preparedStatement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (connection!=null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return list;
}
}
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ListAllStudent.servlet類。實現了，調用上邊的StudentDAO類里面的查詢方法，設置屬性的屬性名字，和屬性的值：request.setAttribute("student", students);再請求的轉發到student.jsp頁面，並超鏈接到test.jsp頁面，student.jsp頁面中插入java代碼，實現查詢的功能
public class ListAllStudent extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
StudentDAO studentDAO=new StudentDAO();
List<Student> students=studentDAO.getAll();
request.setAttribute("student", students);
//請求的轉發
request.getRequestDispatcher("/students.jsp").forward(request, response);
}
}
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student.jsp頁面實現數據庫數據在頁面上顯示：
<%@page import="com.lanqiao.javatest.Student"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
List<Student> list=(List<Student>)request.getAttribute("student");
%>
<table border="1" cellspacing="0" cellpadding="10">
<tr>
<th>Id</th>
<th>userName</th>
<th>password</th>
<th>Delete</th>
</tr>
<%for(Student student:list){%>
<tr>
<td><%=student.getId()%></td>
<td><%=student.getUsername()%></td>
<td><%=student.getPassword()%></td>
<td><a href="deleteStudent?id=<%=student.getId()%>">delete</a></td>
<tr>
<%}%>
</table>
</body>
</html>
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DeleteStudent.servlet類。通過student.jsp頁面的超鏈接獲取查詢到的屬性的id值，//String id=request.getParameter("id");調用StudentDAO類里面的刪除的方法，已經實現的功能，在請求的轉發到delete.jsp頁面實現刪除后的頁面顯示
public class DeleteStudent extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//獲取超鏈接<a href="deleteStudent?id=<%=student.getId()%>">delete</a>里面id的值
String id=request.getParameter("id");
StudentDAO studentDAO=new StudentDAO();
//Integer.parseInt(id)將String類型的轉化為Integer類型
studentDAO.deleteId(Integer.parseInt(id));
//請求的轉發
request.getRequestDispatcher("/delete.jsp").forward(request, response);
}
}
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delete.jsp頁面實現刪除后顯示的頁面，並且超鏈接到開始查詢的頁面，查看刪除后的數據
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h2>操作成功</h2>
<br><br>
<a href="listAllStudent">List All Student Page</a>
</body>
</html>
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test.jsp頁面實現查詢的功能：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="listAllStudent">List All Student Page</a>
</body>
</html>
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實現功能過程的截圖：
頁面實現一個鏈接：
點擊鏈接后顯示，查詢到的數據庫數據：
點擊每一個表格后面的刪除，實現刪除的功能：
點擊鏈接后，查出刪除后，剩余的數據
數據庫中數據未刪除的數據時：
實現功能后是：
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在lib下面的web.xml文件，里面有兩個配置和映射。通過配置和映射，可實現servlet類和jsp之間的關聯
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<servlet>
<description></description>
<display-name>ListAllStudent</display-name>
<servlet-name>ListAllStudent</servlet-name>
<servlet-class>com.lanqiao.javatest.ListAllStudent</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ListAllStudent</servlet-name>
<url-pattern>/listAllStudent</url-pattern>
</servlet-mapping>
<servlet>
<description></description>
<display-name>DeleteStudent</display-name>
<servlet-name>DeleteStudent</servlet-name>
<servlet-class>com.lanqiao.javatest.DeleteStudent</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DeleteStudent</servlet-name>
<url-pattern>/deleteStudent</url-pattern>
</servlet-mapping>
</web-app>