案例練習：聯繫人CURD 連接數據庫

技術選型：Servlet+JSP+MySQL+JDBCTempleat+Duird+BeanUtilS+tomcat

1.導入必須用到的jar包

2.先實現查詢所有條目的功能（查詢功能），真個代碼邏輯思路如下圖：

3層結構，第一層是servlet（對客戶端請求作出響應），第二層是service層（調用和組合dao層的一些基本操作），第三層是dao層（封裝一些數據庫基本操作）。

3.因爲聯繫人存在各種屬性，編寫一個User類

package domain;

public class User {
//    id INT PRIMARY KEY AUTO_INCREMENT,
//    NAME VARCHAR(20) NOT NULL,
//    gender VARCHAR(5),
//    age INT,
//    address VARCHAR(32),
//    qq VARCHAR(20),
//    email VARCHAR(50)
    private int id;
    private String name;
    private String gender;
    private int age;
    private String address;
    private String qq;
    private String email;
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getQq() {
        return qq;
    }

    public void setQq(String qq) {
        this.qq = qq;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", age=" + age +
                ", address='" + address + '\'' +
                ", qq='" + qq + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

4.創新兩個接口,一個是Userservice,另一個是Userdao。在這兩個接口中都寫一個findAll抽象方法，返回值就是一個List，裏面泛型是User類。然後再寫一下這兩個接口的實現類，首先是UserdaoImpl：

new一個JdbcTemplate類對象，傳進去JDBCUtils工具類中getDataSource方法返回值（JDBCUtils類功能是配置和使用Durid連接池）。

package dao;

import domain.User;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import util.JDBCUtils;

import java.util.List;

public class UserDaoImpl implements UserDao {
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    @Override
    public List<User> findAll() {
        //使用JDBC來操作數據庫
        String sql = "select * from user";
        List<User> users = template.query(sql, new BeanPropertyRowMapper<User>(User.class));
        return users;
    }
}

另一個是Userservice實現類UserserviceImpl：

package service;

import dao.UserDao;
import dao.UserDaoImpl;
import domain.User;

import java.util.List;

public class UserServiceImpl implements UserService{
    private UserDao dao = new UserDaoImpl();
    @Override
    public List<User> findAll() {
        return dao.findAll();
    }
}

5.寫一下UserListServlet的功能：

新建一個UserService實現類對象，調用findAll得到裝有User類的List容器。將獲取到的信息，存入request域中，然後轉發給list.jsp。

package web.servlet;

import domain.User;
import service.UserService;
import service.UserServiceImpl;

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 java.io.IOException;
import java.util.List;

@WebServlet("/userListServlet")
public class UserListServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.調用Userservice完成查詢操作
        UserService service = new UserServiceImpl();
        List<User> users = service.findAll();
        //2.將list存入request域
        request.setAttribute("users",users);
        //3.轉發
        request.getRequestDispatcher("/list.jsp").forward(request,response);

    }

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

6.配置list.jsp（用於顯示查詢到的結果）：

前面導入Jstl配置語句，<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

使用Jstl語句，編寫一個foreach循環，依次獲取每一條User類中屬性值。

<c:forEach items="${users}" var="user" varStatus="s">

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<!-- 網頁使用的語言 -->
<html lang="zh-CN">
<head>
    <!-- 指定字符集 -->
    <meta charset="utf-8">
    <!-- 使用Edge最新的瀏覽器的渲染方式 -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <!-- viewport視口：網頁可以根據設置的寬度自動進行適配，在瀏覽器的內部虛擬一個容器，容器的寬度與設備的寬度相同。
    width: 默認寬度與設備的寬度相同
    initial-scale: 初始的縮放比，爲1:1 -->
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- 上述3個meta標籤*必須*放在最前面，任何其他內容都*必須*跟隨其後！ -->
    <title>用戶信息管理系統</title>

    <!-- 1. 導入CSS的全局樣式 -->
    <link href="css/bootstrap.min.css" rel="stylesheet">
    <!-- 2. jQuery導入，建議使用1.9以上的版本 -->
    <script src="js/jquery-2.1.0.min.js"></script>
    <!-- 3. 導入bootstrap的js文件 -->
    <script src="js/bootstrap.min.js"></script>
    <style type="text/css">
        td, th {
            text-align: center;
        }
    </style>
</head>
<body>
<div class="container">
    <h3 style="text-align: center">用戶信息列表</h3>
    <table border="1" class="table table-bordered table-hover">
        <tr class="success">
            <th>編號</th>
            <th>姓名</th>
            <th>性別</th>
            <th>年齡</th>
            <th>籍貫</th>
            <th>QQ</th>
            <th>郵箱</th>
            <th>操作</th>
        </tr>
        <c:forEach items="${users}" var="user" varStatus="s">
            <tr>
                <td>${s.count}</td>
                <td>${user.name}</td>
                <td>${user.gender}</td>
                <td>${user.age}</td>
                <td>${user.address}</td>
                <td>${user.qq}</td>
                <td>${user.email}</td>
                <td><a class="btn btn-default btn-sm" href="update.html">修改</a>&nbsp;<a class="btn btn-default btn-sm" href="">刪除</a></td>
            </tr>
        </c:forEach>

        <tr>
            <td colspan="8" align="center"><a class="btn btn-primary" href="add.html">添加聯繫人</a></td>
        </tr>
    </table>
</div>
</body>
</html>

由上基本完成了一個查詢聯繫人的功能，是最基本的查詢。

*********************************************************************************************************************************************

加入登錄功能。（前面案例現成的）

1.修改了login.jsp的內容：

修改了表單提交後跳轉的servlet： <form action="${pageContext.request.contextPath}/loginservlet" method="post">

添加點擊圖片換驗證碼的功能，即點擊事件綁定和修改驗證碼圖片url路徑。使用EL表達式，動態表示

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="utf-8"/>
    <meta http-equiv="X-UA-Compatible" content="IE=edge"/>
    <meta name="viewport" content="width=device-width, initial-scale=1"/>
    <title>管理員登錄</title>

    <!-- 1. 導入CSS的全局樣式 -->
    <link href="css/bootstrap.min.css" rel="stylesheet">
    <!-- 2. jQuery導入，建議使用1.9以上的版本 -->
    <script src="js/jquery-2.1.0.min.js"></script>
    <!-- 3. 導入bootstrap的js文件 -->
    <script src="js/bootstrap.min.js"></script>
    <script type="text/javascript">
		function refreshCode() {
			var vcode = document.getElementById("vcode");
			vcode.src = "${pageContext.request.contextPath}/checkCodeServlet?time="+new Date().getTime();
		}
    </script>

  </head>
  <body>
  	<div class="container" style="width: 400px;">
  		<h3 style="text-align: center;">管理員登錄</h3>
        <form action="${pageContext.request.contextPath}/loginservlet" method="post">
	      <div class="form-group">
	        <label for="user">用戶名：</label>
	        <input type="text" name="username" class="form-control" id="user" placeholder="請輸入用戶名"/>
	      </div>
	      
	      <div class="form-group">
	        <label for="password">密碼：</label>
	        <input type="password" name="password" class="form-control" id="password" placeholder="請輸入密碼"/>
	      </div>
	      
	      <div class="form-inline">
	        <label for="vcode">驗證碼：</label>
	        <input type="text" name="verifycode" class="form-control" id="verifycode" placeholder="請輸入驗證碼" style="width: 120px;"/>
	        <a href="javascript:refreshCode()">
				<img src="${pageContext.request.contextPath}/checkCodeServlet" title="看不清點擊刷新" id="vcode"/>
			</a>
	      </div>
	      <hr/>
	      <div class="form-group" style="text-align: center;">
	        <input class="btn btn btn-primary" type="submit" value="登錄">
	       </div>
	  	</form>
		<!-- 出錯顯示的信息框 -->
	  	<div class="alert alert-warning alert-dismissible" role="alert">
		  <button type="button" class="close" data-dismiss="alert" >
		  	<span>&times;</span></button>
		   <strong>${login_msg}</strong>
		</div>
  	</div>
  </body>
</html>

2.添加一個生成驗證碼的CheckCodeServlet：

package web.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 驗證碼
 */
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
		
		//服務器通知瀏覽器不要緩存
		response.setHeader("pragma","no-cache");
		response.setHeader("cache-control","no-cache");
		response.setHeader("expires","0");
		
		//在內存中創建一個長80，寬30的圖片，默認黑色背景
		//參數一：長
		//參數二：寬
		//參數三：顏色
		int width = 80;
		int height = 30;
		BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
		
		//獲取畫筆
		Graphics g = image.getGraphics();
		//設置畫筆顏色爲灰色
		g.setColor(Color.GRAY);
		//填充圖片
		g.fillRect(0,0, width,height);
		
		//產生4個隨機驗證碼，12Ey
		String checkCode = getCheckCode();
		//將驗證碼放入HttpSession中
		request.getSession().setAttribute("CHECKCODE_SERVER",checkCode);
		
		//設置畫筆顏色爲黃色
		g.setColor(Color.YELLOW);
		//設置字體的小大
		g.setFont(new Font("黑體",Font.BOLD,24));
		//向圖片上寫入驗證碼
		g.drawString(checkCode,15,25);
		
		//將內存中的圖片輸出到瀏覽器
		//參數一：圖片對象
		//參數二：圖片的格式，如PNG,JPG,GIF
		//參數三：圖片輸出到哪裏去
		ImageIO.write(image,"PNG",response.getOutputStream());
	}
	/**
	 * 產生4位隨機字符串 
	 */
	private String getCheckCode() {
		String base = "0123456789ABCDEFGabcdefg";
		int size = base.length();
		Random r = new Random();
		StringBuffer sb = new StringBuffer();
		for(int i=1;i<=4;i++){
			//產生0到size-1的隨機值
			int index = r.nextInt(size);
			//在base字符串中獲取下標爲index的字符
			char c = base.charAt(index);
			//將c放入到StringBuffer中去
			sb.append(c);
		}
		return sb.toString();
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		this.doGet(request,response);
	}
}

3.在UserDao實現類中添加新方法：用於來校驗客戶端輸入的用戶名和密碼是否在數據庫中。

同理在UserService實現類中也要添加新方法，來調用UserDaoImpl的新方法。

package dao;

import domain.User;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import util.JDBCUtils;

import java.util.List;

public class UserDaoImpl implements UserDao {
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    @Override
    public List<User> findAll() {
        //使用JDBC來操作數據庫
        String sql = "select * from user";
        List<User> users = template.query(sql, new BeanPropertyRowMapper<User>(User.class));
        return users;
    }

    @Override
    public User findUserByUsernameAndPassword(String username, String password) {
        try {
            String sql = "select * from user where username = ? and password = ?";
            User user = template.queryForObject(sql,new BeanPropertyRowMapper<User>(User.class),username,password);
            return user;
        }catch (Exception e){
            e.printStackTrace();
            return null;
        }

    }
    
}

package service;

import dao.UserDao;
import dao.UserDaoImpl;
import domain.User;

import java.util.List;

public class UserServiceImpl implements UserService{
    private UserDao dao = new UserDaoImpl();
    @Override
    public List<User> findAll() {
        return dao.findAll();
    }

    @Override
    public User login(User user) {
        return dao.findUserByUsernameAndPassword(user.getUsername(),user.getPassword());
    }
}

4.新建一個loginservlet，用於處理客戶端輸入驗證碼，用戶名和密碼後，對客戶端提交信息的響應。處理邏輯：先校驗驗證碼輸入是否正確，若不正確直接返回驗證碼不正確。若正確，再校驗輸入的用戶名和密碼是否存在於數據庫之中。

package web.servlet;
import domain.User;
import org.apache.commons.beanutils.BeanUtils;
import service.UserService;
import service.UserServiceImpl;
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 javax.servlet.http.HttpSession;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;
@WebServlet("/loginservlet")
//HttpServlet：對http協議的一種封裝，簡化操作
public class Loginservlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        String verifycode = request.getParameter("verifycode");//獲取用戶輸入的驗證碼
        HttpSession session = request.getSession();//獲取Session對象
        String checkCode_session = (String) session.getAttribute("CHECKCODE_SERVER");//從session獲取系統儲存的正確的驗證碼
        //優化返回後，驗證碼圖片不刷新的情況
        session.removeAttribute("CHECKCODE_SERVER");//獲取session後，刪除session來確保驗證碼的一次性
        //先判斷checkcode是否爲null
        if(checkCode_session !=null &&checkCode_session.equalsIgnoreCase(verifycode)){
            //驗證碼正確
            Map<String, String[]> map = request.getParameterMap();//將獲取的屬性變成map集合
            User loginuser = new User();
            try {
                BeanUtils.populate(loginuser,map);
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }
            UserService service = new UserServiceImpl();
            User user = service.login(loginuser);
            //5.登錄是否成功，關鍵就是這個user對象
            if(user != null){
                //都正確
                //存儲數據
                session.setAttribute("user",user);
                response.sendRedirect(request.getContextPath()+"/index.jsp");
            }else {
                //用戶名或者密碼錯誤
                request.setAttribute("login_msg","用戶名或者密碼錯誤");
                request.getRequestDispatcher("/login.jsp").forward(request,response);//跳轉到登錄界面
            }
        }else {
            //驗證碼不正確
            //儲存信息到request
            request.setAttribute("login_msg","驗證碼錯誤");
            request.getRequestDispatcher("/login.jsp").forward(request,response);//跳轉到登錄界面
            return;
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

*********************************************************************************************************************************************

添加功能實現：實現邏輯如下圖所示

1.新建一個add.jsp，在其中主要是構建一個添加頁面。

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<!-- 網頁使用的語言 -->
<html lang="zh-CN">
<head>
    <!-- 指定字符集 -->
    <meta charset="utf-8">
    <!-- 使用Edge最新的瀏覽器的渲染方式 -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <!-- viewport視口：網頁可以根據設置的寬度自動進行適配，在瀏覽器的內部虛擬一個容器，容器的寬度與設備的寬度相同。
    width: 默認寬度與設備的寬度相同
    initial-scale: 初始的縮放比，爲1:1 -->
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- 上述3個meta標籤*必須*放在最前面，任何其他內容都*必須*跟隨其後！ -->
    <title>添加用戶</title>

    <!-- 1. 導入CSS的全局樣式 -->
    <link href="css/bootstrap.min.css" rel="stylesheet">
    <!-- 2. jQuery導入，建議使用1.9以上的版本 -->
    <script src="js/jquery-2.1.0.min.js"></script>
    <!-- 3. 導入bootstrap的js文件 -->
    <script src="js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
    <center><h3>添加聯繫人頁面</h3></center>
    <form action="${pageContext.request.contextPath}/addUserServlet" method="post">
        <div class="form-group">
            <label for="name">姓名：</label>
            <input type="text" class="form-control" id="name" name="name" placeholder="請輸入姓名">
        </div>

        <div class="form-group">
            <label>性別：</label>
            <input type="radio" name="gender" value="男" checked="checked"/>男
            <input type="radio" name="gender" value="女"/>女
        </div>

        <div class="form-group">
            <label for="age">年齡：</label>
            <input type="text" class="form-control" id="age" name="age" placeholder="請輸入年齡">
        </div>

        <div class="form-group">
            <label for="address">籍貫：</label>
            <select name="address" class="form-control" id="jiguan">
                <option value="廣東">廣東</option>
                <option value="廣西">廣西</option>
                <option value="湖南">湖南</option>
            </select>
        </div>

        <div class="form-group">
            <label for="qq">QQ：</label>
            <input type="text" class="form-control" name="qq" placeholder="請輸入QQ號碼"/>
        </div>

        <div class="form-group">
            <label for="email">Email：</label>
            <input type="text" class="form-control" name="email" placeholder="請輸入郵箱地址"/>
        </div>

        <div class="form-group" style="text-align: center">
            <input class="btn btn-primary" type="submit" value="提交" />
            <input class="btn btn-default" type="reset" value="重置" />
            <input class="btn btn-default" type="button" value="返回" />
        </div>
    </form>
</div>
</body>
</html>

2.在Userservice和Userdao里加入添加功能的方法，接口和實現類都要加入。

    @Override
    public void add(User user) {
        String sql = "insert into user values(null,?,?,?,?,?,?,null,null)";
        template.update(sql,user.getName(),user.getGender(),user.getAge(),user.getAddress(),user.getQq(),user.getEmail());

    }

    @Override
    public void add(User user) {
        dao.add(user);
    }

3.新建一個addUserservlet。

package web.servlet;

import domain.User;
import org.apache.commons.beanutils.BeanUtils;
import service.UserService;
import service.UserServiceImpl;

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 java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

@WebServlet("/addUserServlet")
public class addUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        Map<String, String[]> map = request.getParameterMap();
        User user = new User();
        try {
            BeanUtils.populate(user,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        UserService service = new UserServiceImpl();
        service.add(user);
        response.sendRedirect(request.getContextPath()+"/userListServlet");
    }

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

*********************************************************************************************************************************************

刪除功能：

1.分別在Userservice和UserDao加入刪除功能

    @Override
    public void delUser(int id) {
        String sql = "delete from user where id = ?";
        template.update(sql,id);
    }

    @Override
    public void delUser(String id) {
        dao.delUser(Integer.parseInt(id));
    }

2.新建一個DeleteUserServlet

package web.servlet;

import service.UserService;
import service.UserServiceImpl;

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 java.io.IOException;

@WebServlet("/deleteUserServlet")
public class DeleteUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String id = request.getParameter("id");
        UserService service = new UserServiceImpl();
        service.delUser(id);
        response.sendRedirect(request.getContextPath()+"/userListServlet");
    }

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

3.刪除前，應該先詢問一下是否確定刪除：

在list.jsp中修改：

在刪除超鏈接中添加href地址，但不直接寫出地址而是javascript語句寫成一個函數，將id傳入進去。如下：

然後再在script中，編寫函數來實現確認。

<script>
        function deleteUser(id) {
            if(confirm("確定刪除嗎？")){
                location.href = "${pageContext.request.contextPath}/deleteUserServlet?id="+id;
            }
        }
</script>

*********************************************************************************************************************************************

修改功能：

實現邏輯如下：首先根據id值來獲取該用戶的信息，然後再將信息回顯在update.jsp頁面上，這個工作是由findUserServlet來完成的，然後在update.jsp將回顯後的信息修改後，點擊提交按鈕後，會跳轉到UpdateUserServlet這個界面上，然後 UpdateUserServlet會獲取到你修改後的各項屬性，封裝成User對象，然後調用Service和dao層的方法去update數據庫。這個在數據庫中的操作和添加功能很像，區別在於修改功能需要隱藏地傳過去id，讓後續的數據庫操作指導對哪一條數據進行修改。

1.在list.jsp界面上進行修改：

<td><a class="btn btn-default btn-sm" href="${pageContext.request.contextPath}/findUserServlet?id=${user.id}">修改</a>

2.新建一個findUserServlet，來實現回顯功能。同時在service和dao層也要添加方法

package web.servlet;

import domain.User;
import service.UserService;
import service.UserServiceImpl;

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 java.io.IOException;

@WebServlet("/findUserServlet")
public class FindUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String id = request.getParameter("id");
        UserService service = new UserServiceImpl();
        User user = service.findUserByid(id);
        request.setAttribute("user",user);
        request.getRequestDispatcher("/update.jsp").forward(request,response);
    }

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

dao:

@Override
    public User findByid(int id) {
        String sql = "select * from user where id = ?";
        return template.queryForObject(sql,new BeanPropertyRowMapper<User>(User.class),id);
    }

service:

public User findUserByid(String id) {
        return dao.findByid(Integer.parseInt(id));
    }

3.寫一個update.jsp界面，用於填寫修改信息。這裏主要關注 1.隱藏域傳參 2.類似gender和address這樣的多選框怎麼回顯

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<!-- 網頁使用的語言 -->
<html lang="zh-CN">
    <head>
        <!-- 指定字符集 -->
         <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <title>修改用戶</title>

        <link href="css/bootstrap.min.css" rel="stylesheet">
        <script src="js/jquery-2.1.0.min.js"></script>
        <script src="js/bootstrap.min.js"></script>
        
    </head>
    <body>
        <div class="container" style="width: 400px;">
        <h3 style="text-align: center;">修改聯繫人</h3>
        <form action="${pageContext.request.contextPath}/updateUserServlet" method="post">
            <input type="hidden" name="id" value="${user.id}">
          <div class="form-group">
            <label for="name">姓名：</label>
            <input type="text" class="form-control" id="name" name="name" value="${user.name}" readonly="readonly" placeholder="請輸入姓名" />
          </div>

          <div class="form-group">
            <label>性別：</label>
              <c:if test="${user.gender == '男'}" >
                  <input type="radio" name="gender" value="男" checked />男
                  <input type="radio" name="gender" value="女"  />女
              </c:if>
              <c:if test="${user.gender == '女'}" >
                  <input type="radio" name="gender" value="男"  />男
                  <input type="radio" name="gender" value="女" checked />女
              </c:if>

          </div>

          <div class="form-group">
            <label for="age">年齡：</label>
            <input type="text" class="form-control" id="age" value="${user.age}" name="age" placeholder="請輸入年齡" />
          </div>

          <div class="form-group">
            <label for="address">籍貫：</label>
             <select name="address" class="form-control" >
                 <c:if test="${user.address == '廣東'}" >
                     <option value="廣東" selected>廣東</option>
                     <option value="廣西">廣西</option>
                     <option value="湖南">湖南</option>
                 </c:if>
                 <c:if test="${user.address == '廣西'}" >
                     <option value="廣東" >廣東</option>
                     <option value="廣西"selected>廣西</option>
                     <option value="湖南">湖南</option>
                 </c:if>
                 <c:if test="${user.address == '湖南'}" >
                     <option value="廣東" >廣東</option>
                     <option value="廣西">廣西</option>
                     <option value="湖南"selected>湖南</option>
                 </c:if>

            </select>
          </div>

          <div class="form-group">
            <label for="qq">QQ：</label>
            <input type="text" class="form-control" name="qq" value="${user.qq}" placeholder="請輸入QQ號碼"/>
          </div>

          <div class="form-group">
            <label for="email">Email：</label>
            <input type="text" class="form-control" name="email" value="${user.email}" placeholder="請輸入郵箱地址"/>
          </div>

             <div class="form-group" style="text-align: center">
                <input class="btn btn-primary" type="submit" value="提交" />
                <input class="btn btn-default" type="reset" value="重置" />
                <input class="btn btn-default" type="button" value="返回"/>
             </div>
        </form>
        </div>
    </body>
</html>

4.新建一個UpdateUserServlet實現修改功能，在service和dao層也要相應加方法

package web.servlet;

import domain.User;
import org.apache.commons.beanutils.BeanUtils;
import service.UserService;
import service.UserServiceImpl;

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 java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

@WebServlet("/updateUserServlet")
public class UpdateUserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        Map<String, String[]> map = request.getParameterMap();
        User user = new User();
        try {
            BeanUtils.populate(user,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        UserService service = new UserServiceImpl();
        service.update(user);
        response.sendRedirect(request.getContextPath()+"/userListServlet");

    }

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

service:

 @Override
    public void update(User user) {
        dao.update(user);
    }

dao:

    @Override
    public void update(User user) {
        String sql = "update user set name=?,gender=?,age=?,address=?,qq=?,email=? where id = ?";
        template.update(sql,user.getName(),user.getGender(),user.getAge(),user.getAddress(),user.getQq(),user.getEmail(),user.getId());
    }

以上就是增刪改查的全部實現。

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