JavaWeb(五)：MVC案例

MVC是Model-View-Controller的简称，即模型-视图-控制器。
MVC是一种设计模式，它把应用程序分成三个核心模块：模型、视图、控制器，它们各自处理自己的任务。模型是应用程序的主体部分，模型表示业务数据和业务逻辑。一个模型能为多个视图提供数据。由于应用于模型的代码只需写一次就可以被多个视图重用，所以提高了代码的可重用性。视图是用户看到并与之交互的界面，作用如下：视图向用户显示相关的数据，接受用户的输入，不进行任何实际的业务处理。控制器接受用户的输入并调用模型和视图去完成用户的需求。控制器接收请求并决定调用哪个模型组件去处理请求，然后决定调用哪个视图来显示模型处理返回的数据。

把逻辑部分、访问数据库的部分放在Servlet，显示部分放在JSP页面。
发请求到服务器，服务器调用Servlet，Servlet做一个控制器，根据请求的情况取去调用Java类，Java类完成业务逻辑和访问数据库的操作，根据POJO的返回结果转向JSP，JSP进行显示，显示的时候可以使用一些标准标签库。
POJO里包含处理逻辑、业务逻辑，并去访问数据库。
Servlet根据不同的返回结果转向不同的JSP页面，转向的方式包括重定向和转发。

model：

controller：Servlet

view：JSP

一、查询和删除

1.1 查询

需求

点击超链接后在页面显示所有学生考试信息

数据库

字段

flowId
type
idCard
examCard
studentName
location
grade

数据表截图

Bean

public class Student {

    private Integer flowId;

    private int type;

    private String idCard;

    private String examCard;

    private String studentName;

    private String location;

    private int grade;

    public Integer getFlowId() {

        return flowId;

    }

    public void setFlowId(Integer flowId) {

        this.flowId = flowId;

    }

    public int getType() {

        return type;

    }

    public void setType(int type) {

        this.type = type;

    }

    public String getIdCard() {

        return idCard;

    }

    public void setIdCard(String idCard) {

        this.idCard = idCard;

    }

    public String getExamCard() {

        return examCard;

    }

    public void setExamCard(String examCard) {

        this.examCard = examCard;

    }

    public String getStudentName() {

        return studentName;

    }

    public void setStudentName(String studentName) {

        this.studentName = studentName;

    }

    public String getLocation() {

        return location;

    }

    public void setLocation(String location) {

        this.location = location;

    }

    public int getGrade() {

        return grade;

    }

    public void setGrade(int grade) {

        this.grade = grade;

    }

    public Student(Integer flowId, int type, String idCard, String examCard, String studentName, String location, int grade) {

        this.flowId = flowId;

        this.type = type;

        this.idCard = idCard;

        this.examCard = examCard;

        this.studentName = studentName;

        this.location = location;

        this.grade = grade;

    }

    // 反射需要一个无参的构造器

    public Student(){

    }

}

流程

页面

超链接的页面 c.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

</head>

<body>

    <a href="listAllStudent">List All Student</a>

</body>

</html>

c.jsp截图

转发的页面 students.jsp

<%@ page import="java.util.List" %>

<%@ page import="com.satguigu.mvc.Student" %><%--

  Created by IntelliJ IDEA.

  User: JieZhao

  Date: 2019/8/13

  Time: 13:38

  To change this template use File | Settings | File Templates.

--%>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

</head>

<body>

<%= request.getAttribute("students") %>

<br>

<%

    List<Student> stus = (List<Student>)request.getAttribute("students");

%>

<table>

    <tr>

        <th>FlowId</th>

        <th>Type</th>

        <th>IdCard</th>

        <th>ExamCard</th>

        <th>StudentName</th>

        <th>Location</th>

        <th>Grade</th>

    </tr>

    <%

    for (Student student: stus){

    %>

        <tr>

            <td><%= student.getFlowId() %>  </td>

            <td><%= student.getType() %>  </td>

            <td><%= student.getIdCard() %>  </td>

            <td><%= student.getExamCard() %>  </td>

            <td><%= student.getStudentName() %>  </td>

            <td><%= student.getLocation() %>  </td>

            <td><%= student.getGrade() %>  </td>

        </tr>

   <% }%>

</table>

</body>

</html>

代码

Dao

public class StudentDao {

    public List<Student> getAll(){

        List<Student> students = new ArrayList<>();

        Connection connection = null;

        PreparedStatement preparedStatement = null;

        ResultSet resultSet = null;

        try{

            String driverClass = "com.mysql.jdbc.Driver";

            String url = "jdbc:mysql:///aidata";

            String user = "root";

            String passward = "root";

            Class.forName(driverClass);

            connection = DriverManager.getConnection(url, user, passward);

            String sql = "SELECT flow_id, type, id_card, exam_card, sutdent_name, Location, Grade FROM examstudent";

            preparedStatement = connection.prepareStatement(sql);

            resultSet = preparedStatement.executeQuery();

            while (resultSet.next()){

                int flowId = resultSet.getInt(1);

                int type = resultSet.getInt(2);

                String idCard = resultSet.getString(3);

                String examCard = resultSet.getString(4);

                String studentName = resultSet.getString(5);

                String location = resultSet.getString(6);

                int grade = resultSet.getInt(7);

                Student student = new Student(flowId, type, idCard, examCard, studentName, location, grade);

                students.add(student);

            }

        }catch (Exception e){

            e.printStackTrace();

        }finally {

            try{

                if(resultSet != null){

                resultSet.close();

                }

            }catch (SQLException e){

                e.printStackTrace();

            }

            try{

                if(preparedStatement != null){

                    preparedStatement.close();

                }

            }catch (SQLException e){

                e.printStackTrace();

            }

            try{

                if(connection != null){

                    connection.close();

                }

            }catch (SQLException e){

                e.printStackTrace();

            }

        }

        return students;

    }

}

Servlet

public class ListAllStudentsServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException,  ServletException {

        StudentDao studentDao = new StudentDao();

        List<Student> students = studentDao.getAll();

        request.setAttribute("students", students); //结果添加到students属性里，存到request里

        request.getRequestDispatcher("/students.jsp").forward(request, response);

       // 将request转发到students.jsp页面

     }

}

配置web.xml

<servlet>

    <servlet-name>listAllStudent</servlet-name>

    <servlet-class>com.aidata.mvc.ListAllStudentsServlet</servlet-class>

</servlet>

<servlet-mapping>

    <servlet-name>listAllStudent</servlet-name>

    <url-pattern>/listAllStudent</url-pattern>

</servlet-mapping>

1.2 删除

students.jsp里添加删除按钮

Dao里添加删除方法

public void deleteByFlowId(Integer flowId){

        List<Student> students = new ArrayList<>();

        Connection connection = null;

        PreparedStatement preparedStatement = null;

        try {

            String driverClass = "com.mysql.jdbc.Driver";

            String url = "jdbc:mysql:///aidata";

            String user = "root";

            String password = "root";

            Class.forName(driverClass);

            connection = DriverManager.getConnection(url, user, password);

            String sql = "DELETE FROM examstudent WHERE flow_id = ?";

            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setInt(1, flowId);

            preparedStatement.executeUpdate();

        }catch (Exception e){

            e.printStackTrace();

        }finally {

            try{

                if(preparedStatement != null){

                    preparedStatement.close();

                }

            }catch (SQLException e){

                e.printStackTrace();

            }

            try{

                if(connection != null){

                    connection.close();

                }

            }catch (SQLException e){

                e.printStackTrace();

            }

        }

    }

Servlet添加删除的Servlet

public class DeleteStudentServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws IOException, ServletException {

        String flowId = request.getParameter("flowId");

        StudentDao studentDao = new StudentDao();

        studentDao.deleteByFlowId(Integer.parseInt(flowId));

        List<Student> students = studentDao.getAll();

        request.setAttribute("students", students);

        request.getRequestDispatcher("/listAllStudent").forward(request, response); // 重定向到servlet

    }

}

配置web.xml

<servlet>

    <servlet-name>deleteStudent</servlet-name>

    <servlet-class>com.aidata.mvc.DeleteStudentServlet</servlet-class>

</servlet>

<servlet-mapping>

    <servlet-name>deleteStudent</servlet-name>

    <url-pattern>/deleteStudent</url-pattern>

</servlet-mapping>

二、案例

2.1 架构分析

下面开始做一个小案例：利用MVC模式对数据进行增删改查

没有业务层，直接由Servlet调用DAO，所以也没有事务操作，可以在DAO中直接获取Connection对象

采取MVC设计模式

使用到的技术：

MVC设计模式：JSP、Servlet
数据库使用MySQL
连接数据库使用C3P0数据库连接池
JDBC工具采用DBUtils
页面的提示操作采用jQuery

技术难点：

多个请求如何使用一个Servlet
模糊查询
在创建或修改的情况下，验证用户名已经被使用，并给出提示信息

2.2 DAO层

DAO 模式

DAO (DataAccessobjects 数据存取对象)是指位于业务逻辑和持久化数据之间实现对持久化数据的访问。通俗来讲，就是将数据库操作都封装起来。

对外提供相应的接口

在面向对象设计过程中，有一些"套路”用于解决特定问题称为模式。

DAO 模式提供了访问关系型数据库系统所需操作的接口，将数据访问和业务逻辑分离对上层提供面向对象的数据访问接口。

从以上 DAO 模式使用可以看出，DAO 模式的优势就在于它实现了两次隔离。

1、隔离了数据访问代码和业务逻辑代码。业务逻辑代码直接调用DAO方法即可，完全感觉不到数据库表的存在。分工明确，数据访问层代码变化不影响业务逻辑代码,这符合单一职能原则，降低了藕合性，提高了可复用性。

2、隔离了不同数据库实现。采用面向接口编程，如果底层数据库变化，如由 MySQL 变成 Oracle 只要增加 DAO 接口的新实现类即可，原有 MySQ 实现不用修改。这符合 "开-闭" 原则。该原则降低了代码的藕合性，提高了代码扩展性和系统的可移植性。

一个典型的DAO 模式主要由以下几部分组成。

1、DAO接口：把对数据库的所有操作定义成抽象方法，可以提供多种实现。

2、DAO 实现类：针对不同数据库给出DAO接口定义方法的具体实现。

3、实体类：用于存放与传输对象数据。

4、数据库连接和关闭工具类：避免了数据库连接和关闭代码的重复使用，方便修改。

数据库

建立数据表

Create table customers(

    id int primary key auto_increment,

    name varchar(30) not null unique,

    address varchar(30),

    phone varchar(30)

);

# 为 name 字段添加唯一约束

alter table customers add constraint name_uk unique(name);

数据表截图

C3P0数据源

论数据库连接池的必要性及c3p0的详解

使用eclipse

添加c3p0的jar包和mysql驱动的jar包到根目录的lib目录中

添加commons-dbutils-1.3.jar到根目录的lib目录中

添加c3p0的配置文件到src目录

c3p0-config.xml

<?xml version="1.0" encoding="UTF-8"?>

<c3p0-config>

    <named-config name="mvcapp">

        <!-- 指定连接数据源的基本属性 -->

        <property name="user">root</property>

        <property name="password">root</property>

        <property name="driverClass">com.mysql.jdbc.Driver</property>

        <property name="jdbcUrl">jdbc:mysql:///aidata</property>

        <!-- 若数据库中连接数不足时, 一次向数据库服务器申请多少个连接 -->

        <property name="acquireIncrement">5</property>

        <!-- 初始化数据库连接池时连接的数量 -->

        <property name="initialPoolSize">5</property>

        <!-- 数据库连接池中的最小的数据库连接数 -->

        <property name="minPoolSize">5</property>

        <!-- 数据库连接池中的最大的数据库连接数 -->

        <property name="maxPoolSize">10</property>

        <!-- C3P0 数据库连接池可以维护的 Statement 的个数 -->

        <property name="maxStatements">20</property>

        <!-- 每个连接同时可以使用的 Statement 对象的个数 -->

        <property name="maxStatementsPerConnection">5</property>

    </named-config>

</c3p0-config>

实体类

Customer.java

package com.aidata.mvcapp.domain;

public class Customer {

    private Integer id;

    private String name;

    private String address;

    private String phone;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getAddress() {

        return address;

    }

    public void setAddress(String address) {

        this.address = address;

    }

    public String getPhone() {

        return phone;

    }

    public void setPhone(String phone) {

        this.phone = phone;

    }

    @Override

    public String toString() {

        return "Customer [id=" + id + ", name=" + name + ", address=" + address + ", phone=" + phone + "]";

    }

}

数据库连接和关闭工具类

JdbcUtils.java

package com.aidata.mvcapp.db;

import java.sql.Connection;

import java.sql.SQLException;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.ComboPooledDataSource;

/**

 * @ClassName JdbcUtils

 * @Description JDBC操作的工具类

 * @author JZ

 * @Date

 * @version 1.0.0

 */

public class JdbcUtils {

    /**

     * @Description 释放连接

     * @param connection

     */

    public static void releaseConnection(Connection connection) {

        try {

            if (connection != null) {

                connection.close();

            }

        } catch (Exception e) {

            // TODO: handle exception

        }

    }

    private static DataSource dataSource = null;

    // 数据源只能创建一次，所以用static

    static {

        dataSource = new ComboPooledDataSource("mvcapp");

    }

    /**

     * @Description 返回数据源的一个Connection对象

     * @return

     * @throws SQLException

     */

    public static Connection getConnection() throws SQLException {

        return dataSource.getConnection();

    }

}

DAO接口

CustomerDAO.java

该接口定义了和业务相关的功能，操作customer

package com.aidata.mvcapp.dao;

import java.util.List;

import com.aidata.mvcapp.domain.Customer;

public interface CustomerDAO {

    public List<Customer> getAll();

    public void save(Customer customer);

    public Customer get(Integer id);

    public void delete(Integer id);

    /**

     *

     * @Description 返回和name相等的记录数

     * @param name

     * @return

     */

    public long getCountWithName(String name);

}

DAO 实现类

DAO.java

该类不和业务相关，即和customer不相关，而是关注增删改查的功能

增删改都是update，查

package com.aidata.mvcapp.dao;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.sql.Connection;

import java.util.List;

import org.apache.commons.dbutils.QueryRunner;

import org.apache.commons.dbutils.handlers.BeanHandler;

import org.apache.commons.dbutils.handlers.BeanListHandler;

import org.apache.commons.dbutils.handlers.ScalarHandler;

import com.aidata.mvcapp.db.JdbcUtils;

/**

 * @ClassName DAO

 * @Description 封装了CRUD的方法，以供子类继承使用 当前DAO没有事务，直接在方法中获取数据库连接 整个DAO采取DBUtils解决方案

 * @author JZ

 * @Date

 * @version 1.0.0

 * @param <T>

 *            所处理的实体类的类型

 */

public class DAO<T> {

    private QueryRunner queryRunner = new QueryRunner();

    private Class<T> clazz;

    public DAO() {

        Type superClass = getClass().getGenericSuperclass();

        if (superClass instanceof ParameterizedType) {

            ParameterizedType parameterizedType = (ParameterizedType) superClass;

            Type[] typeArgs = parameterizedType.getActualTypeArguments();

            if (typeArgs != null && typeArgs.length > 0) {

                clazz = (Class<T>) typeArgs[0];

            }

        }

    }

    /**

     * @Description 返回某一个字段的值，例如某一天记录的customerName或 返回数据表中由多少条记录等

     * @param sql

     * @param args

     * @return

     */

    public <E> E getForValue(String sql, Object... args) {

        Connection connection = null;

        try {

            connection = JdbcUtils.getConnection();

            return (E) queryRunner.query(connection, sql, new ScalarHandler(), args);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            JdbcUtils.releaseConnection(connection);

        }

        return null;

    }

    /**

     * @Description 返回 T 所对应的List

     * @param sql

     * @param args

     * @return

     */

    public List<T> getForList(String sql, Object... args) {

        Connection connection = null;

        try {

            connection = JdbcUtils.getConnection();

            return queryRunner.query(connection, sql, new BeanListHandler<>(clazz), args);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            JdbcUtils.releaseConnection(connection);

        }

        return null;

    }

    /**

     * @Description 返回对应T的一个实例类对象

     * @param sql

     * @param args

     * @return

     */

    public T get(String sql, Object... args) {

        Connection connection = null;

        try {

            connection = JdbcUtils.getConnection();

            return queryRunner.query(connection, sql, new BeanHandler<>(clazz), args);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            JdbcUtils.releaseConnection(connection);

        }

        return null;

    }

    /**

     * @Description 封装了INSERT、DELETE、UPDATE操作

     * @param sql

     *            SQL语句

     * @param args

     *            填充SQL语句的占位符

     */

    public void update(String sql, Object... args) {

        Connection connection = null;

        try {

            connection = JdbcUtils.getConnection();

            queryRunner.update(connection, sql, args);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            JdbcUtils.releaseConnection(connection);

        }

    }

}

CustomerDAOJdbcImpl.java

将业务和功能结合起来，实现了业务操作

package com.aidata.mvcapp.dao.impl;

import java.util.List;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.DAO;

import com.aidata.mvcapp.domain.Customer;

public class CustomerDAOJdbcImpl extends DAO<Customer> implements CustomerDAO {

    @Override

    public List<Customer> getAll() {

        String sql = "SELECT id, name, address, phone From customers";

        return getForList(sql);

    }

    @Override

    public void save(Customer customer) {

        String sql = "INSERT INTO customers(name, address, phone) VALUES(?,?,?)";

        update(sql, customer.getName(), customer.getAddress(), customer.getPhone());

    }

    @Override

    public Customer get(Integer id) {

        String sql = "SELECT id, name, address, phone FROM customers WHERE id = ?";

        return get(sql, id);

    }

    @Override

    public void delete(Integer id) {

        String sql = "DELETE FROM customers WHERE id = ?";

        update(sql, id);

    }

    @Override

    public long getCountWithName(String name) {

        String sql = "SELECT count(id) FROM customers WHERE name = ?";

        return getForValue(sql, name);

    }

}

2.3 多个请求对应一个Servlet

第一种方式：url添加参数

jsp

<body>

    <a href="customerServlet?method=add">Add</a>

    <br><br>

    <a href="customerServlet?method=query">Query</a>

    <br><br>

    <a href="customerServlet?method=delete">Delete</a>

    <br><br>

</body>

定义Servlet

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class CustomerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public CustomerServlet() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String method = request.getParameter("method");

        switch (method) {

        case "add":

            add(request, response);

            break;

        case "query":

            query(request, response);

            break;

        case "delete":

            delete(request, response);

            break;

        }

    }

    private void add(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("add");

    }

    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("query");

    }

    private void delete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("delete");

    }

}

web.xml

  <servlet>

    <servlet-name>customerServlet</servlet-name>

    <servlet-class>com.aidata.mvcapp.servlet.CustomerServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>customerServlet</servlet-name>

    <url-pattern>/customerServlet</url-pattern>

  </servlet-mapping>

缺点：当添加一个请求时，需要在 Servlet 中修改两处代码：switch、添加方法；url 中使用 method=xxx 暴漏了要调用的方法，不私密，有安全隐患。

第二种方式：反射

jsp

<body>

    <a href="addCustomer.do">Add</a>

    <br><br>

    <a href="query.do">Query</a>

    <br><br>

    <a href="deleteCustomer.do">Delete</a>

    <br><br>

</body>

web.xml

  <servlet>

    <servlet-name>customerServlet</servlet-name>

    <servlet-class>com.aidata.mvcapp.servlet.CustomerServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>customerServlet</servlet-name>

    <url-pattern>*.do</url-pattern>

  </servlet-mapping>

Servlet

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class CustomerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public CustomerServlet() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String servletPath = request.getServletPath();

        String methodName = servletPath.substring(1);

        methodName = methodName.substring(0, methodName.length() - 3);

        System.out.println(methodName);

        Method method;

        try {

            method = getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);

            method.invoke(this, request, response);

        } catch (NoSuchMethodException | SecurityException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalArgumentException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    private void addCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        System.out.println("add");

    }

    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("query");

    }

    private void deleteCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        System.out.println("delete");

    }

    private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("edit");

    }

}

流程：

2.4 模糊查询

非模糊查询

JSP

<%@page import="java.util.List"%>

<%@page import="com.aidata.mvcapp.domain.Customer"%>

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

<form action="query.do" method="post">

    <table>

        <tr>

            <td>CustomerName:</td>

            <td><input type="text" name="name"></td>

        </tr>

        <tr>

            <td>Address:</td>

            <td><input type="text" name="address"></td>

        </tr>

        <tr>

            <td>Phone:</td>

            <td><input type="text" name="phone"></td>

        </tr>

        <tr>

            <td><input type="submit" name="Query"></td>

            <td><a href="">Add New Customer</a></td>

        </tr>

    </table>

</form>

    <br><br>

    <%

       List<Customer> customers = (List)request.getAttribute("customers");

       if(customers != null && customers.size() > 0){

    %>

    <hr>

    <br><br>

        <table border="1" cellpadding="0" cellspacing="10">

          <tr>

            <th>ID</th>

            <th>CustomerName</th>

            <th>Address</th>

            <th>Phone</th>

            <th>UPDATE\DELETE</th>

           </tr>

        <%

            for(Customer customer: customers){

        %>

        <tr>

            <td><%= customer.getId() %></td>

            <td><%= customer.getName() %></td>

            <td><%= customer.getAddress() %></td>

            <td><%= customer.getPhone() %></td>

            <td>

                <a href="">UPDATE</a>

                <a href="">DELETE</a>

            </td>

        </tr>

        <%

       }

        %>

     </table>

    <%

       }

    %>

</body>

</html>

Servlet

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.impl.CustomerDAOJdbcImpl;

import com.aidata.mvcapp.domain.Customer;

public class CustomerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();

    public CustomerServlet() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String servletPath = request.getServletPath();

        String methodName = servletPath.substring(1);

        methodName = methodName.substring(0, methodName.length() - 3);

        System.out.println(methodName);

        Method method;

        try {

            method = getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);

            method.invoke(this, request, response);

        } catch (NoSuchMethodException | SecurityException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalArgumentException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    private void addCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        System.out.println("add");

    }

    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 1.调用CustomerDAO的getAll()方法，得到Customer的集合

        List<Customer> customers = customerDAO.getAll();

        // 2.把customer集合放入request中

        request.setAttribute("customers", customers);

        // 3.转发页面到index.jsp，不能用重定向

        request.getRequestDispatcher("/index.jsp").forward(request, response);

    }

    private void deleteCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        System.out.println("delete");

    }

    private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("edit");

    }

}

模糊查询

接口添加方法，定义用于查询的类

需要在 CustomerDAO 接口中定义一个 getForListWithCriteriaCustomer(CriteriaCustomer cc)。其中 CriteriaCustomer 用于封装查询条件：name, address, phone。因为查询条件很多时候和 domain 类并不相同，所以要做成一个单独的类

package com.aidata.mvcapp.dao;

import java.util.List;

import com.aidata.mvcapp.domain.Customer;

public interface CustomerDAO {

    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc);

    public List<Customer> getAll();

    public void save(Customer customer);

    public Customer get(Integer id);

    public void delete(Integer id);

    /**

     * @Description 返回和name相等的记录数

     * @param name

     * @return

     */

    public long getCountWithName(String name);

}

CriteriaCustomer

package com.aidata.mvcapp.dao;

public class CriteriaCustomer {

    private String name;

    private String address;

    private String phone;

    public CriteriaCustomer(String name, String address, String phone) {

        super();

        this.name = name;

        this.address = address;

        this.phone = phone;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getAddress() {

        return address;

    }

    public void setAddress(String address) {

        this.address = address;

    }

    public String getPhone() {

        return phone;

    }

    public void setPhone(String phone) {

        this.phone = phone;

    }

}

拼 SQL
SQL: "SELECT id, name, address, phone FROM customers WHERE " +
"name LIKE ? AND address LIKE ? ANDphone LIKE ?";

package com.aidata.mvcapp.dao.impl;

import java.util.List;

import com.aidata.mvcapp.dao.CriteriaCustomer;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.DAO;

import com.aidata.mvcapp.domain.Customer;

public class CustomerDAOJdbcImpl extends DAO<Customer> implements CustomerDAO {

    @Override

    public List<Customer> getAll() {

        String sql = "SELECT id, name, address, phone From customers";

        return getForList(sql);

    }

    @Override

    public void save(Customer customer) {

        String sql = "INSERT INTO customers(name, address, phone) VALUES(?,?,?)";

        update(sql, customer.getName(), customer.getAddress(), customer.getPhone());

    }

    @Override

    public Customer get(Integer id) {

        String sql = "SELECT id, name, address, phone FROM customers WHERE id = ?";

        return get(sql, id);

    }

    @Override

    public void delete(Integer id) {

        String sql = "DELETE FROM customers WHERE id = ?";

        update(sql, id);

    }

    @Override

    public long getCountWithName(String name) {

        String sql = "SELECT count(id) FROM customers WHERE name = ?";

        return getForValue(sql, name);

    }

    @Override

    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc) {

        String sql = "SELECT id, name, address, phone FROM customers WHERE "

                + "name LIKE ? AND address LIKE ? AND phone LIKE ?";

        return getForList(sql, cc.getName(), cc.getAddress(), cc.getPhone());

    }

}

为了正确的填充占位符时，重写了 CriteriaCustomer 的 getter：

package com.aidata.mvcapp.dao;

public class CriteriaCustomer {

    private String name;

    private String address;

    private String phone;

    public CriteriaCustomer(String name, String address, String phone) {

        super();

        this.name = name;

        this.address = address;

        this.phone = phone;

    }

    public String getName() {

        if (name == null) {

            name = "%%";

        } else {

            name = "%" + name + "%";

        }

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getAddress() {

        if (address == null) {

            address = "%%";

        } else {

            address = "%" + address + "%";

        }

        return address;

    }

    public void setAddress(String address) {

        this.address = address;

    }

    public String getPhone() {

        if (phone == null) {

            phone = "%%";

        } else {

            phone = "%" + phone + "%";

        }

        return phone;

    }

    public void setPhone(String phone) {

        this.phone = phone;

    }

}

修改 Servlet

获取请求参数，把请求参数封装为CriteriaCustomer 对象，再调用 getForListWithCriteriaCustomer(CriteriaCustomer cc) 方法

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.aidata.mvcapp.dao.CriteriaCustomer;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.impl.CustomerDAOJdbcImpl;

import com.aidata.mvcapp.domain.Customer;

public class CustomerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();

    public CustomerServlet() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String servletPath = request.getServletPath();

        String methodName = servletPath.substring(1);

        methodName = methodName.substring(0, methodName.length() - 3);

        System.out.println(methodName);

        Method method;

        try {

            method = getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);

            method.invoke(this, request, response);

        } catch (NoSuchMethodException | SecurityException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalArgumentException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    private void addCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        System.out.println("add");

    }

    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String name = request.getParameter("name");

        String phone = request.getParameter("phone");

        String address = request.getParameter("address");

        CriteriaCustomer cc = new CriteriaCustomer(name, address, phone);

        // 1.调用CustomerDAO的getAll()方法，得到Customer的集合

        List<Customer> customers = customerDAO.getForListWithCriteriaCustomer(cc);

        // 2.把customer集合放入request中

        request.setAttribute("customers", customers);

        // 3.转发页面到index.jsp，不能用重定向

        request.getRequestDispatcher("/index.jsp").forward(request, response);

    }

    private void deleteCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        System.out.println("delete");

    }

    private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("edit");

    }

}

2.5 删除操作

Servlet

超链接：delete.do?id=<%=customer.getId()%>
Servlet 的 delete 方法
获取 id
调用 DAO 执行删除
重定向到 query.do（若目标页面不需要读取当前请求的 request 属性，就可以使用重定向），将显示删除后的 Customer 的 List

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.aidata.mvcapp.dao.CriteriaCustomer;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.impl.CustomerDAOJdbcImpl;

import com.aidata.mvcapp.domain.Customer;

public class CustomerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();

    public CustomerServlet() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String servletPath = request.getServletPath();

        String methodName = servletPath.substring(1);

        methodName = methodName.substring(0, methodName.length() - 3);

        System.out.println(methodName);

        Method method;

        try {

            method = getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);

            method.invoke(this, request, response);

        } catch (NoSuchMethodException | SecurityException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalArgumentException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    private void addCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        System.out.println("add");

    }

    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String name = request.getParameter("name");

        String phone = request.getParameter("phone");

        String address = request.getParameter("address");

        CriteriaCustomer cc = new CriteriaCustomer(name, address, phone);

        // 1.调用CustomerDAO的getAll()方法，得到Customer的集合

        List<Customer> customers = customerDAO.getForListWithCriteriaCustomer(cc);

        // 2.把customer集合放入request中

        request.setAttribute("customers", customers);

        // 3.转发页面到index.jsp，不能用重定向

        request.getRequestDispatcher("/index.jsp").forward(request, response);

    }

    private void deleteCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String idStri = request.getParameter("id");

        int id = 0;

        // try...catch... 防止idStri不能转为int类型，若不能转，id=0，不进行任何删除操作

        try {

            id = Integer.parseInt(idStri);

            customerDAO.delete(id);

        } catch (Exception e) {

        }

        response.sendRedirect("query.do");

        System.out.println("delete");

    }

    private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("edit");

    }

}

JSP

jQuery 提示：
确定要删除 xx 的信息吗？

<%@page import="java.util.List"%>

<%@page import="com.aidata.mvcapp.domain.Customer"%>

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

<script type="text/javascript" src="scripts/jquery-1.11.3.min.js"></script>

<script type="text/javascript">

    $(function () {

        $(".delete").click(function() {

            var content = $(this).parent().parent().find("td:eq(1)").text();

            var flag = confirm("确定要删除"+content+"的信息吗？");

            return flag;

        });

    });

</script>

</head>

<body>

<form action="query.do" method="post">

    <table>

        <tr>

            <td>CustomerName:</td>

            <td><input type="text" name="name"></td>

        </tr>

        <tr>

            <td>Address:</td>

            <td><input type="text" name="address"></td>

        </tr>

        <tr>

            <td>Phone:</td>

            <td><input type="text" name="phone"></td>

        </tr>

        <tr>

            <td><input type="submit" name="Query"></td>

            <td><a href="">Add New Customer</a></td>

        </tr>

    </table>

</form>

    <br><br>

    <%

       List<Customer> customers = (List)request.getAttribute("customers");

       if(customers != null && customers.size() > 0){

    %>

    <hr>

    <br><br>

        <table border="1" cellpadding="0" cellspacing="10">

          <tr>

            <th>ID</th>

            <th>CustomerName</th>

            <th>Address</th>

            <th>Phone</th>

            <th>UPDATE\DELETE</th>

           </tr>

        <%

            for(Customer customer: customers){

        %>

        <tr>

            <td><%= customer.getId() %></td>

            <td><%= customer.getName() %></td>

            <td><%= customer.getAddress() %></td>

            <td><%= customer.getPhone() %></td>

            <td>

                <a href="">UPDATE</a>

                <a href="deleteCustomer.do?id=<%= customer.getId() %>" class="delete">DELETE</a>

            </td>

        </tr>

        <%

       }

        %>

     </table>

    <%

       }

    %>

</body>

</html>

request的getParameter(String name)方法获取表单里面的name信息

只有设置了 name 属性的表单元素才能在提交表单时传递它们的值，因为服务端获取表单提交的数据是通过表单元素的 name 属性的值而得到的，没有 name 属性就无法得到表单元素提交给服务端的值

2.6 新增

流程

效果：点击Add New Customer 超链接，连接到 newcustomer.jsp

创建newcustomer.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

<form action="addCustomer.do" method="post">

    <table>

        <tr>

            <td>CustomerName:</td>

            <td><input type="text" name="name" value="<%= request.getParameter("name") == null?"": request.getParameter("name") %>"></td>

        </tr>

        <tr>

            <td>Address:</td>

            <td><input type="text" name="address"></td>

        </tr>

        <tr>

            <td>Phone:</td>

            <td><input type="text" name="phone"></td>

        </tr>

        <tr>

            <td colspan="2"><input type="submit" name="Submit"></td>

        </tr>

    </table>

</form>

</body>

</html>

success.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

    <h4>操作成功！</h4>

    <h4><a href="index.jsp">Return...</a></h4>

</body>

</html>

修改addCustomer 方法
CustomerServlet 的 addCustomer 方法

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.aidata.mvcapp.dao.CriteriaCustomer;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.impl.CustomerDAOJdbcImpl;

import com.aidata.mvcapp.domain.Customer;

public class CustomerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();

    public CustomerServlet() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String servletPath = request.getServletPath();

        String methodName = servletPath.substring(1);

        methodName = methodName.substring(0, methodName.length() - 3);

        System.out.println(methodName);

        Method method;

        try {

            method = getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);

            method.invoke(this, request, response);

        } catch (NoSuchMethodException | SecurityException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalArgumentException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    private void addCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // 1. 获取表单参数：name,address,phone

        String name = request.getParameter("name");

        String address = request.getParameter("address");

        String phone = request.getParameter("phone");

        // 2. 检验name是否已经被占用

        // 2.1 调用customerDAO的getCountWithName方法获取name是否在数据库中存在

        long count = customerDAO.getCountWithName(name);

        // 2.2 若返回值大于0，则响应newcustomer.jsp页面：

        // 通过转发的方式响应newcustomer.jsp

        if (count > 0) {

            // 2.2.1 要求在newcustomer.jsp页面显示一个错误消息：用户名name已经被占用，请重新选择！

            // 在request中放入一个属性，比如message：用户名name已经被占用，请重新选择！，

            // 在页面上通过request.getAttribute("message")的方式显示

            request.setAttribute("message", "用户名" + name + "已经被占用，请重新选择！");

            // 2.2.2 newcustomer.jsp的表单值可以回显

            // jsp中，value="<%= request.getParameter("name") == null?"": request.getParameter("name") %>

            // 2.2.3 结束方法：return

            request.getRequestDispatcher("/newcustomer.jsp").forward(request, response);

            return;

        }

        // 3. 若验证通过，则把表单参数封装为一个Customer对象customer

        Customer customer = new Customer(name, address, phone);

        // 4. 调用CustomerDAO的save方法，执行保存操作

        customerDAO.save(customer);

        // 5. 重定向到success.jsp页面

        response.sendRedirect("success.jsp");

    }

    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String name = request.getParameter("name");

        String phone = request.getParameter("phone");

        String address = request.getParameter("address");

        CriteriaCustomer cc = new CriteriaCustomer(name, address, phone);

        // 1.调用CustomerDAO的getAll()方法，得到Customer的集合

        List<Customer> customers = customerDAO.getForListWithCriteriaCustomer(cc);

        // 2.把customer集合放入request中

        request.setAttribute("customers", customers);

        // 3.转发页面到index.jsp，不能用重定向

        request.getRequestDispatcher("/index.jsp").forward(request, response);

    }

    private void deleteCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String idStri = request.getParameter("id");

        int id = 0;

        // try...catch... 防止idStri不能转为int类型，若不能转，id=0，不进行任何删除操作

        try {

            id = Integer.parseInt(idStri);

            customerDAO.delete(id);

        } catch (Exception e) {

        }

        response.sendRedirect("query.do");

    }

    private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("edit");

    }

}

执行流程图

2.7 修改

先显示（SELECT 操作）修改的页面，再进行修改（update）
显示修改页面
Update 的超链接：<a href="edit.do?id=<%= customer.getId() %>">UPDATE</a>

index.jsp

<%@page import="java.util.List"%>

<%@page import="com.aidata.mvcapp.domain.Customer"%>

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

<script type="text/javascript" src="scripts/jquery-1.11.3.min.js"></script>

<script type="text/javascript">

    $(function () {

        $(".delete").click(function() {

            var content = $(this).parent().parent().find("td:eq(1)").text();

            var flag = confirm("确定要删除"+content+"的信息吗？");

            return flag;

        });

    });

</script>

</head>

<body>

<form action="query.do" method="post">

    <table>

        <tr>

            <td>CustomerName:</td>

            <td><input type="text" name="name"></td>

        </tr>

        <tr>

            <td>Address:</td>

            <td><input type="text" name="address"></td>

        </tr>

        <tr>

            <td>Phone:</td>

            <td><input type="text" name="phone"></td>

        </tr>

        <tr>

            <td><input type="submit" name="Query"></td>

            <td><a href="newcustomer.jsp">Add New Customer</a></td>

        </tr>

    </table>

</form>

    <br><br>

    <%

       List<Customer> customers = (List)request.getAttribute("customers");

       if(customers != null && customers.size() > 0){

    %>

    <hr>

    <br><br>

        <table border="1" cellpadding="0" cellspacing="10">

          <tr>

            <th>ID</th>

            <th>CustomerName</th>

            <th>Address</th>

            <th>Phone</th>

            <th>UPDATE\DELETE</th>

           </tr>

        <%

            for(Customer customer: customers){

        %>

        <tr>

            <td><%= customer.getId() %></td>

            <td><%= customer.getName() %></td>

            <td><%= customer.getAddress() %></td>

            <td><%= customer.getPhone() %></td>

            <td>

                <a href="edit.do?id=<%= customer.getId() %>">UPDATE</a>

                <a href="deleteCustomer.do?id=<%= customer.getId() %>" class="delete">DELETE</a>

            </td>

        </tr>

        <%

       }

        %>

     </table>

    <%

       }

    %>

</body>

</html>

edit 方法：

private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String forwardPath = "/error.jsp";

        // 1. 获取请求参数id

        String idStr = request.getParameter("id");

        // 2.调用customerDAO的customerDAO.get(id)获取和id对应的Customer对象

        try {

            Customer customer = customerDAO.get(Integer.parseInt(idStr));

            if (customer != null) {

                forwardPath = "updatecustomer.jsp";

                // 3.将customer放入request中

                request.setAttribute("customer", customer);

            }

        } catch (Exception e) {

        }

        // 4.响应updatecustomer.jsp页面：转发

        request.getRequestDispatcher(forwardPath).forward(request, response);

    }

JSP 页面
获取请求域中的 Customer 对象，调用对应的字段的 get 方法来显示值。
使用隐藏域来保存要修改的 Customer 对象的 id：<input type="hidden" name="id" value=“<%= customer.getId() %>"/>。虽然没有修改id，当然也不能改，但依然少不了，id用来判断到底是哪个customer。

使用隐藏域来保存 oldName：<input type="hidden" name=“oldName" value=“<%= customer.getName() %>"/>，oldName保存修改前的名字，name会更新为提交的名字。

关于隐藏域：和其他的表单域一样可以被提交到服务器，只不过在页面上不显示
提交到 update.do

updatecustomer.jsp：

<%@page import="com.aidata.mvcapp.domain.Customer"%>

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

<%

    Object msg = request.getAttribute("message");

    if(msg != null){

%>

    <br>

    <font color="red"><%= msg %></font>

    <br>

    <br>

<%

}

    String id = null;

    String oldName = null;

    String name = null;

    String address = null;

    String phone = null;

    Customer customer = (Customer)request.getAttribute("customer");

    if(customer != null){

        // 如果没有出错，从edit方法过来的，customer不为空

        id = customer.getId() + "";

        // 这里name和oldName一样，但是后面提交的时候，name会提交，即更新，而oldName保持不变，从而可以比较

        oldName = customer.getName();

        name = customer.getName();

        address = customer.getAddress();

        phone = customer.getPhone();

    }else{

        // 如果出错，即提交了重复的名字，会出现提示信息，会停留在本页面，没有edit方法了，也就没有customer属性了

        // 只能从之前提交的request中得到id等

        id = request.getParameter("id");

        oldName = request.getParameter("oldName");

        //

        name = request.getParameter("oldname");

        address = request.getParameter("address");

        phone = request.getParameter("phone");

    }

%>

<form action="update.do" method="post">

    <input type="hidden" name="id" value="<%= id %>" />

    <input type="hidden" name="oldName" value="<%= oldName %>" />

    <table>

        <tr>

            <td>CustomerName:</td>

            <td><input type="text" name="name" value="<%= name %>" /></td>

        </tr>

        <tr>

            <td>Address:</td>

            <td><input type="text" name="address" value="<%= address %>" /></td>

        </tr>

        <tr>

            <td>Phone:</td>

            <td><input type="text" name="phone"value="<%= phone %>" /></td>

        </tr>

        <tr>

            <td colspan="2"><input type="submit" name="Submit"></td>

        </tr>

    </table>

</form>

</body>

</html>

隐藏域的问题
回显的问题
Newcustomer.jsp 和 updateCustomer.jsp 能汇总到一个页面吗 ?

修改操作
Update 方法：

 private void update(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 1. 获取表单参数：name,address,phone

        String id = request.getParameter("id");

        String name = request.getParameter("name");

        String phone = request.getParameter("phone");

        String address = request.getParameter("address");

        String oldName = request.getParameter("oldName");

        // 2. 检验name是否已经被占用

        // 2.1 比较name和oldName是否相同，若相同说明name可用

        // 2.1 若不相同，调用customerDAO的getCountWithName方法获取name是否在数据库中存在

        if (!oldName.equalsIgnoreCase(name)) {

            // 如你输入了A，以前已经有了a，java的equals会认为两者不同，于是进入该if

            // 但是mysql认为A和a相同，于是返回了1，即已经存在了，从而引发message

            // 忽略大小写，不进入if，直接进行后面的update

            long count = customerDAO.getCountWithName(name);

            // 2.2 若返回值大于0，则响应updatecustomer.jsp

            if (count > 0) {

                // 2.2.1 在updatecustomer.jsp页面显示一个错误信息：用户名name已经被占用，请重新选择！

                // 在request中放入一个属性，比如message：用户名name已经被占用，请重新选择！，

                // 在页面上通过request.getAttribute("message")的方式显示

                request.setAttribute("message", "用户名" + name + "已经被占用，请重新选择！");

                // 2.2.2 updatecustomer.jsp的表单值可以回显

                // address，phone显示提交表单的新的值，而name显示oldName，而不是新提交的name

                // 2.2.3 结束方法：return

                return;

            }

        }

        // 3. 若验证通过，则把表单参数封装为一个Customer对象customer

        Customer customer = new Customer(name, address, phone);

        customer.setId(Integer.parseInt(id));

        // 4. 调用CustomerDAO的update(Customer customer)执行更新操作

        customerDAO.update(customer);

        // 5. 重定向到query.do

        response.sendRedirect("query.do");

    }

}

完整Servlet

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.aidata.mvcapp.dao.CriteriaCustomer;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.impl.CustomerDAOJdbcImpl;

import com.aidata.mvcapp.domain.Customer;

public class CustomerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();

    public CustomerServlet() {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String servletPath = request.getServletPath();

        String methodName = servletPath.substring(1);

        methodName = methodName.substring(0, methodName.length() - 3);

        System.out.println(methodName);

        Method method;

        try {

            method = getClass().getDeclaredMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);

            method.invoke(this, request, response);

        } catch (NoSuchMethodException | SecurityException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (IllegalArgumentException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

    private void addCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // 1. 获取表单参数：name,address,phone

        String name = request.getParameter("name");

        String address = request.getParameter("address");

        String phone = request.getParameter("phone");

        // 2. 检验name是否已经被占用

        // 2.1 调用customerDAO的getCountWithName方法获取name是否在数据库中存在

        long count = customerDAO.getCountWithName(name);

        // 2.2 若返回值大于0，则响应newcustomer.jsp页面：

        // 通过转发的方式响应newcustomer.jsp

        if (count > 0) {

            // 2.2.1 要求在newcustomer.jsp页面显示一个错误消息：用户名name已经被占用，请重新选择！

            // 在request中放入一个属性，比如message：用户名name已经被占用，请重新选择！，

            // 在页面上通过request.getAttribute("message")的方式显示

            request.setAttribute("message", "用户名" + name + "已经被占用，请重新选择！");

            // 2.2.2 newcustomer.jsp的表单值可以回显

            // jsp中，value="<%= request.getParameter("name") == null?"": request.getParameter("name") %>

            // 2.2.3 结束方法：return

            request.getRequestDispatcher("/newcustomer.jsp").forward(request, response);

            return;

        }

        // 3. 若验证通过，则把表单参数封装为一个Customer对象customer

        Customer customer = new Customer(name, address, phone);

        // 4. 调用CustomerDAO的save方法，执行保存操作

        customerDAO.save(customer);

        // 5. 重定向到success.jsp页面

        response.sendRedirect("success.jsp");

    }

    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String name = request.getParameter("name");

        String phone = request.getParameter("phone");

        String address = request.getParameter("address");

        CriteriaCustomer cc = new CriteriaCustomer(name, address, phone);

        // 1.调用CustomerDAO的getAll()方法，得到Customer的集合

        List<Customer> customers = customerDAO.getForListWithCriteriaCustomer(cc);

        // 2.把customer集合放入request中

        request.setAttribute("customers", customers);

        // 3.转发页面到index.jsp，不能用重定向

        request.getRequestDispatcher("/index.jsp").forward(request, response);

    }

    private void deleteCustomer(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String idStri = request.getParameter("id");

        int id = 0;

        // try...catch... 防止idStri不能转为int类型，若不能转，id=0，不进行任何删除操作

        try {

            id = Integer.parseInt(idStri);

            customerDAO.delete(id);

        } catch (Exception e) {

        }

        response.sendRedirect("query.do");

    }

    private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String forwardPath = "/error.jsp";

        // 1. 获取请求参数id

        String idStr = request.getParameter("id");

        // 2.调用customerDAO的customerDAO.get(id)获取和id对应的Customer对象

        try {

            Customer customer = customerDAO.get(Integer.parseInt(idStr));

            if (customer != null) {

                forwardPath = "updatecustomer.jsp";

                // 3.将customer放入request中

                request.setAttribute("customer", customer);

            }

        } catch (Exception e) {

        }

        // 4.响应updatecustomer.jsp页面：转发

        request.getRequestDispatcher(forwardPath).forward(request, response);

    }

    private void update(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 1. 获取表单参数：name,address,phone

        String id = request.getParameter("id");

        String name = request.getParameter("name");

        String phone = request.getParameter("phone");

        String address = request.getParameter("address");

        String oldName = request.getParameter("oldName");

        // 2. 检验name是否已经被占用

        // 2.1 比较name和oldName是否相同，若相同说明name可用

        // 2.1 若不相同，调用customerDAO的getCountWithName方法获取name是否在数据库中存在

        if (!oldName.equalsIgnoreCase(name)) {

            // 如你输入了A，以前已经有了a，java的equals会认为两者不同，于是进入该if

            // 但是mysql认为A和a相同，于是返回了1，即已经存在了，从而引发message

            // 忽略大小写，不进入if，直接进行后面的update

            long count = customerDAO.getCountWithName(name);

            // 2.2 若返回值大于0，则响应updatecustomer.jsp

            if (count > 0) {

                // 2.2.1 在updatecustomer.jsp页面显示一个错误信息：用户名name已经被占用，请重新选择！

                // 在request中放入一个属性，比如message：用户名name已经被占用，请重新选择！，

                // 在页面上通过request.getAttribute("message")的方式显示

                request.setAttribute("message", "用户名" + name + "已经被占用，请重新选择！");

                // 2.2.2 updatecustomer.jsp的表单值可以回显

                // address，phone显示提交表单的新的值，而name显示oldName，而不是新提交的name

request.getRequestDispatcher("update.jsp").forward(request, response);
// 2.2.3 结束方法：return
return; // 重定向跳转后必须加上return，要不然页面虽然跳转了，但是还会执行跳转后面的语句

            }

        }

        // 3. 若验证通过，则把表单参数封装为一个Customer对象customer

        Customer customer = new Customer(name, address, phone);

        customer.setId(Integer.parseInt(id));

        // 4. 调用CustomerDAO的update(Customer customer)执行更新操作

        customerDAO.update(customer);

        // 5. 重定向到query.do

        response.sendRedirect("query.do");

    }

}

2.8 更换底层存储源

深入理解面向接口编程：在类中调用接口的方法，而不必关心具体的实现。这将有利于代码的解耦，使程序有更好的可移植性和可扩展性。

需要修改源码

src下新建customes.xml

<?xml version="1.0" encoding="UTF-8"?>

<customers>

    <customer id="1001">

        <name>Tom</name>

        <address>Beijing</address>

        <phone>123</phone>

    </customer>

</customers>

新建实现类，功能暂时省略

package com.aidata.mvcapp.dao.impl;

import java.util.List;

import com.aidata.mvcapp.dao.CriteriaCustomer;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.domain.Customer;

public class CustomerDAOXMLImpl implements CustomerDAO {

    @Override

    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc) {

        // TODO Auto-generated method stub

        return null;

    }

    @Override

    public List<Customer> getAll() {

        // TODO Auto-generated method stub

        return null;

    }

    @Override

    public void save(Customer customer) {

        // TODO Auto-generated method stub

    }

    @Override

    public Customer get(Integer id) {

        // TODO Auto-generated method stub

        return null;

    }

    @Override

    public void delete(Integer id) {

        // TODO Auto-generated method stub

    }

    @Override

    public void update(Customer customer) {

        // TODO Auto-generated method stub

    }

    @Override

    public long getCountWithName(String name) {

        // TODO Auto-generated method stub

        return 0;

    }

}

只需要在CustomerServlet中修改一行语句

private CustomerDAO customerDAO = new CustomerDAOXMLImpl();

使用工厂模式，不修改源码

如果一行语句也不用修改怎么做？

使用属性文件

动态修改 Customer 的存储方式：通过修改类路径下的 switch.properties 文件的方式来实现

src下创建switch.properties

#type=xml

type=jdbc

创建Servlet读取配置文件

当Web 应用在启动的时候，InitServlet 被创建，并由 Servlet 容器调用其 init() 方法：

  <servlet>

    <servlet-name>InitServlet</servlet-name>

    <servlet-class>com.aidata.mvcapp.servlet.InitServlet</servlet-class>

    <load-on-startup>1</load-on-startup>

  </servlet>

读取类路径下的 switch.properties 文件，获取 switch.properties 的 type 属性值，赋给了 CustomerDAOFactory 的 type 属性值

package com.aidata.mvcapp.servlet;

import java.io.IOException;

import java.io.InputStream;

import java.util.Properties;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.aidata.mvcapp.dao.factory.CustomerDAOFactory;

public class InitServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    @Override

    public void init() throws ServletException {

        CustomerDAOFactory.getInstance().setType("jdbc");

        InputStream in = getServletContext().getResourceAsStream("/WEB-INF/classes/switch.properties");

        Properties properties = new Properties();

        try {

            properties.load(in);

            String type = properties.getProperty("type");

            CustomerDAOFactory.getInstance().setType(type);

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

}

需要通过一个类的一个方法来获取具体的实现类的对象：

package com.aidata.mvcapp.dao.factory;

import java.util.HashMap;

import java.util.Map;

import com.aidata.mvcapp.dao.CustomerDAO;

import com.aidata.mvcapp.dao.impl.CustomerDAOJdbcImpl;

import com.aidata.mvcapp.dao.impl.CustomerDAOXMLImpl;

public class CustomerDAOFactory {

    private Map<String, CustomerDAO> daos = new HashMap<String, CustomerDAO>();

    private CustomerDAOFactory() {

        daos.put("jdbc", new CustomerDAOJdbcImpl());

        daos.put("xml", new CustomerDAOXMLImpl());

    }

    private static CustomerDAOFactory instance = new CustomerDAOFactory();

    public static CustomerDAOFactory getInstance() {

        return instance;

    }

    private static String type = null;

    public void setType(String type) {

        this.type = type;

    }

    public CustomerDAO getCustomerDAO() {

        return daos.get(type);

    }

}

创建 CustomerServlet 时，为 customerDAO 属性赋值是通过 CustomerDAOFactory 的 getCustomerDAO() 方法完成的。此时的 type 已经在 InitServlet 中被赋值了。

private CustomerDAO customerDAO = CustomerDAOFactory.getInstance().getCustomerDAO();