採用Java Web所實現的MVC結構圖如下,其中控制器部分採用Servlet來實現,模型部分採用JavaBean來實現,而大部分的視圖採用Jsp頁面來實現。
思想基礎
JSP+JavaBean兩層結構工作原理應該是比較熟悉的,也比較好理解。
但是有一點必須要清楚就是用戶通過瀏覽器來發送網頁的請求,此請求到達服務器後在服務器端查找對應的網頁,如果是首次請求(第二次就不用解釋執行了),對於JSP來說要生成Servlet,然後通過Servlet引擎來執行Servlet,把調用JavaBean的結果嵌入到頁面中返回給用戶的瀏覽器。
JSP+JavaBean+Servlet三層結構的實質是多了一個Controller:Servlet來分發客戶端瀏覽器的請求。如果把起控制器作用的Servlet的作用理解為對客戶端的請求進行預處理對理解Servlet將有很大的幫助。通過web.xml配置文件可以找到用戶請求和特定的Servlet的對應關係,每個Servlet都有一個特定的Servlet對象與之對應,所以說處理用戶請求的就是一個繼承自HttpServlet的Servlet對象。
!-- JSPC servlet mappings start -- servlet servlet-namems1/servlet-name servlet-classnews.FirstAction/servlet-class /servlet servlet servlet-namems2/servlet-name servlet-classnews.DetailAction/servlet-class /servlet !-- JSPC servlet mappings end -- servlet-mapping servlet-namems1/servlet-name url-pattern/newsmain/url-pattern /servlet-mapping servlet-mapping servlet-namems2/servlet-name url-pattern/newsDetail/url-pattern /servlet-mapping
如上面所示的摘自web.xml的一段配置servlet,第一部分主要用來配置Servlet與具體的Servlet對象關聯,第二部分主要用來配置請求由哪個Servlet處理,Servlet名字的關聯,處理請求就與具體Servlet處理對象關聯起來,比如說,客戶端瀏覽器發來/newsmain的請求,它由ms1 servlet進行處理,通過ms1就能找到相對應的serlet對象news.FirstAction,即/newsmain-ms1-news.FirstAction,這也就是配置文件的意義所在。到現在懂得了用戶/newsmain請求會被news.FirstAction類的對象進行處理,所以說,要看懂程序就要看懂FirstAction的作用是什麼就行了。比如說下面是FirstAction的一個實現。
public final class FirstAction extends HttpServlet { protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { DB db = new DB(); HttpSession session = req.getSession(); try { session.setAttribute(Constants.NEWS_LIST_KEY, News .SearchNewsTitle(db)); } catch (Exception e) { e.printStackTrace(); } db.close(); String target = "/P43_News/newsMain.jsp"; resp.sendRedirect(target); } }通過這個實現可以看到,當服務器收到客戶端請求執行News.SearchNewsTitle(db)的操作,然後把返回值通過session.setAttribute放到session裡,然後通過resp.sendRedirect(target)間接轉移到newsMain.jsp,這樣在newsMain.jsp里通過session.getAttribute函數就可以得到在存儲在session裡的對應值。
回過頭來就容易看出JSP+JavaBean工作原理和JSP+JavaBean+Servlet工作原理的不同了,兩層結構必須把預處理放在JSP中進行,比如說News.SearchNewsTitle(db),三層結構先把預處理在Servlet裡進行了,然後相當於把這個處理結果通過Session返回給JSP,讓JSP更關注於界面的顯示。
登陸註冊模塊需求
1 註冊
1.1 用戶的註冊表單(用戶名,密碼,郵箱,暱稱,驗證碼)
1.2 提交註冊:要做(用戶名,密碼,郵箱,暱稱,驗證碼)的校驗。
1.2.1 用戶名,密碼,郵箱,暱稱是在客戶端瀏覽器完成的,通過JS來實現。
1.2.2 驗證碼的是要在服務器端的程序完成的。
2.如果註冊表單的校驗通過, 那麼就進行業務邏輯的判斷。
2.1 如果用戶已經存在, 告訴用戶錯誤信息。
2.2 如果郵箱已經存在, 告訴用戶錯誤信息。
2.3 如果都不存在.則進行第3步。
3. 將用戶的信息保存到數據庫中
4. 註冊成功, 跳轉到登錄頁面
5. 登陸
5.1 將用戶的登陸信息發送到後台進行驗證
5.2 如果驗證成功,則跳轉到首頁
5.3 如果跳轉失敗,則跳轉到登陸頁面,並提示錯誤信息。
項目目錄結構
項目的源碼分成四個包文件,分別用來存取模型,視圖,控制器和工具類,具體文件如下:
對於視圖,我們定義三個JSP頁面,如下所示:
定義視圖
login.jsp頁面
<%@ 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>登錄的表單</title> </head> <body> <font color="red">${message }</font> <a href="regist.jsp">註冊新賬號</a> <form action="${pageContext.request.contextPath }/login" method="post"> 用戶名:<input type="text" name="username"><br/> 密碼:<input type="password" name="password"><br/> <input type="submit" value="登錄"></form> </body> </html>index.jsp頁面
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <!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> <font color="red">${message }</font> <% if(request.getSession().getAttribute("username")==null) { response.sendRedirect("login.jsp"); } else{ %> <font color="red">"歡迎您:" <%=request.getSession().getAttribute("username").toString() %></font> <% } %></body> </html>regist.jsp頁面
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>用戶註冊的表單</title> <script type="text/javascript"> function changeImage(){ document.getElementById("image").src="${pageContext.request.contextPath }/checkimage?" + new Date().getTime() } function validateForm(){ // 做用戶名, 密碼, 郵箱, 暱稱的校驗var username= document.getElementById("username").value; if(username==""){ alert("用戶名不能為空"); return false; } var password= document.getElementById("password").value; if(password==""){ alert("密碼不能為空"); return false; } var repassword= document.getElementById("repassword").value; if(password!=repassword){ alert("密碼必須一致"); return false; } var nickname= document.getElementById("nickname").value; if(nickname==""){ alert("暱稱不能為空"); return false; } // ^//s*//w+(?://.{0,1}[//w-]+)*@[a-zA-Z0-9]+(?:[-.][a-zA-Z0-9]+)*//.[a-zA-Z]+//s*$ var email= document.getElementById("email").value; if(email.match("^//s*//w+(?://.{0,1}[//w-]+)*@[a-zA-Z0-9]+(?:[-.][a-zA-Z0-9]+)*//.[a-zA-Z]+//s*$")==null){ alert("郵箱地址不正確"); return false; } }</script> </head> <body> <h3>用戶註冊的表</h3> <font color="red">${message }</font> <form action="${pageContext.request.contextPath }/regist" onsubmit="return validateForm();" method="post"> <table> <tr> <td>用戶名</td> <td> <input type="text" name="username" id="username1" v> </td> </tr> <tr> <td>密碼</td> <td> <input type="password" name="password" id="password"> </td> </tr> <tr> <td>請確認密碼</td> <td> <input type="password" name="repassword" id="repassword"> </td> </tr> <tr> <td>暱稱</td> <td> <input type="text" name="nickname" id="nickname"> </td> </tr> <tr> <td>郵箱</td> <td> <input type="text" name="email" id="email"> </td> </tr> <tr> <td>驗證碼</td> <td> <input type="text" name="checkcode"> <img src="${pageContext.request.contextPath }/checkimage" style="cursor: pointer;" id="image" onclick="changeImage();"> </td> </tr> <tr> <td></td> <td> <input type="submit" value="註冊"> </td> </tr> </table> </form></body> </html>定義模型
User模型:
package com.vs2022.model;public class User { private String username; private String password; private String nickname; private String email; // alt+shft+ s // 彈出覆蓋方法的對話框。 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; } public String getNickname() { return nickname; } public void setNickname(String nickname) { this.nickname = nickname; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; }}UserOperation模型
package com.vs2022.model;import com.vs2022.utils.DBUtil;public class UserOperation { public final static int USERNAMEEXIST=1; public final static int EMAILEXIST=2; public final static int SUCCESS=3; public final static int FAIL=4; public int regist(User user){ DBUtil db = new DBUtil(); if(db.serchUserName(user.getUsername())){ // 說明用戶名已經存在了return USERNAMEEXIST; } if(db.serchEmail(user.getEmail())){ // 說明郵箱已經存在return EMAILEXIST; } // 如果走到這裡, 則說明,郵箱用戶名都不存咋, 那麼就讓其註冊. 添加到數據庫中db.updateUser(user); return SUCCESS; } public int login(User user) { DBUtil db = new DBUtil(); if(db.loginSuccess(user.getUsername(), user.getPassword())){ // 說明找到了用戶名和密碼都正確的return SUCCESS; } return FAIL; }} CheckCode模型
package com.vs2022.model;import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.IOException; import java.io.OutputStream; import java.util.Hashtable;import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;public class CheckCode {private String getRandomString() { int ranNum = (int) (Math.random() * 9000) + 1000; return ranNum + "";}public void getCode(int width, int height, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{ // 在內存中創建圖像BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g=image.getGraphics(); //創建Graphics對象,其作用相當於畫筆g.setColor(Color.getColor("F8F8F8")); g.fillRect(0, 0, width, height); //繪製背景Font mfont=new Font("楷體",Font.BOLD,16); //定義字體樣式g.setFont(mfont); //設置字體g.setColor(Color.RED); //生成隨機數String rans=getRandomString(); //將隨機數寫入會話HttpSession session = request.getSession(); session.setAttribute("check", rans); //將隨機數寫入圖片g.drawString(rans, 5, 20); // 圖像生效g.dispose(); //輸出圖像ImageIO.write(image, "JPEG", response.getOutputStream());}}定義控制器
LoginServlet類
package com.vs2022.controller;import java.io.IOException; import java.io.PrintWriter;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import com.vs2022.model.User; import com.vs2022.model.UserOperation;public class LoginServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 完成登錄的邏輯String username = request.getParameter("username"); String password = request.getParameter("password"); User user = new User(); user.setUsername(username); user.setPassword(password); // 調用業務功能javabean 類去實現登錄的具體業務邏輯UserOperation us = new UserOperation(); // 返回值? int i = us.login(user); if(i==4){ // 說明登錄失敗,用戶名或密碼錯誤request.setAttribute("message", "用戶名或密碼錯誤"); request.getRequestDispatcher("login.jsp").forward(request, response); }else{ // 登錄成功, 跳轉到網站的首頁, 用重定向// 將username 存入到session 域中request.getSession().setAttribute("username", username); response.sendRedirect("index.jsp"); //request.getRequestDispatcher("index.jsp").forward(request, response); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}RegistServlet類
package com.vs2022.controller;import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import com.sun.org.apache.commons.beanutils.BeanUtils;import com.vs2022.model.User; import com.vs2022.model.UserOperation;public class RegistServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 解決post 方式的亂碼request.setCharacterEncoding("UTF-8"); // 完成驗證碼的校驗String checkcode = request.getParameter("checkcode"); String check_code_session = (String) request.getSession().getAttribute("check"); if(checkcode==null||!checkcode.equals(check_code_session)){ // 說明驗證碼輸入不正確request.setAttribute("message", "驗證碼輸入不正確"); request.getRequestDispatcher("regist.jsp").forward(request, response); return; } // 如果走到了這裡, 則說明所有的校驗都通過,就要調用涉及到處理業務邏輯了User user = new User(); // beanUtils 完成數據的封裝到java bean 對像中,apache 基金會的一個開源的jar的實現。 try { // 前提: javabean的字段名必須要與表單中提交過來的值的key 一致, 否則不能完成封裝. BeanUtils.populate(user, request.getParameterMap()); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException("對不起, 封裝數據失敗"); } // 所以又會設計一個新的java bean 類來實現業務邏輯UserOperation us = new UserOperation(); try { int feedBack = us.regist(user); if(feedBack==UserOperation.EMAILEXIST){ // 說明郵箱已經存在request.setAttribute("message", "郵箱已經存在"); request.getRequestDispatcher("regist.jsp").forward(request, response); }else if(feedBack==UserOperation.USERNAMEEXIST){ // 說明用戶名已經存在request.setAttribute("message", "用戶名已經存在"); request.getRequestDispatcher("regist.jsp").forward(request, response); }else{ // 說明註冊成功, 跳轉到登錄頁面. 要用重定向response.sendRedirect("login.jsp" ); } } catch (Exception e) { e.printStackTrace(); throw new RuntimeException("添加失敗"); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}CheckImageServlet類
package com.vs2022.controller;import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import com.vs2022.model.CheckCode;public class CheckImageServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //禁用緩存,每次訪問此頁面,都重新生成response.setHeader("Pragma","No-cache"); response.setHeader("Cache-Control","no-cache"); response.setDateHeader("Expires", 0); response.setContentType("image/jpeg"); int width=40; int height=30; //生成驗證碼的匿名對象,並生成驗證碼new CheckCode().getCode(width,height,request,response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}定義工具類
DBUtil類
package com.vs2022.utils;import java.sql.*; import com.vs2022.model.User;public class DBUtil { boolean bInited = false; // 加載驅動public void initJDBC() throws ClassNotFoundException { // 加載MYSQL JDBC驅動程序Class.forName("com.mysql.jdbc.Driver"); bInited = true; System.out.println("Success loading Mysql Driver!"); } public Connection getConnection() throws ClassNotFoundException, SQLException { if (!bInited) { initJDBC(); } // 連接URL為jdbc:mysql//服務器地址/數據庫名// 後面的2個參數分別是登陸用戶名和密碼Connection conn = DriverManager.getConnection( "jdbc:mysql://localhost:3306/數據庫", "用戶名", "密碼"); return conn; } public boolean loginSuccess(String userName, String password) { boolean returnValue = false; String sql = "SELECT * FROM user where username=? and password=?"; Connection conn = null; PreparedStatement ps=null; int i=0; try { conn = getConnection(); ps=conn.prepareStatement(sql); ps.setString(1, userName); ps.setString(2, password); ResultSet rs=ps.executeQuery(); if(rs.next()){ returnValue=true; } } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } return returnValue; } public boolean updateUser(User user) { boolean flag=false; int i=0; Connection conn=null; PreparedStatement ps=null; String sql= "insert into user (username,password,nickname,email) values(?,?,?,?)"; try { conn = getConnection(); ps=conn.prepareStatement(sql); ps.setString(1, user.getUsername()); //對占位符設置值,佔位符順序從1開始,第一個參數是佔位符的位置,第二個參數是佔位符的值。 ps.setString(2, user.getPassword()); ps.setString(3, user.getNickname()); ps.setString(4, user.getEmail()); i=ps.executeUpdate(); if(i>0){ flag=true; } } catch (ClassNotFoundException e) { e.printStackTrace(); }catch (SQLException e) { e.printStackTrace(); } return flag; } public boolean serchUserName(String userName){ boolean returnValue = false; String sql = "SELECT * FROM user where username=?"; Connection conn = null; PreparedStatement ps=null; try { conn = getConnection(); ps=conn.prepareStatement(sql); ps.setString(1, userName); ResultSet rs=ps.executeQuery(); if(rs.next()){ returnValue=true; } } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } return returnValue; } public boolean serchEmail(String email){ boolean returnValue = false; String sql = "SELECT * FROM user where email=?"; Connection conn = null; PreparedStatement ps=null; int i=0; try { conn = getConnection(); ps=conn.prepareStatement(sql); ps.setString(1, email); ResultSet rs=ps.executeQuery(); if(rs.next()){ returnValue=true; } } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } return returnValue; }}