一、JSP和Servlet的简单介绍

1、Servlet和JSP简介：

Java开发Web应用程序时用到的技术主要有两种，即Servlet和JSP，Servlet是在服务器端执行的Java程序，一个被称为Servlet容器的程序（其实就是服务器） 负责执行Java程序，而JSP(Java Server Page)则是一个页面， 由JSP容器负责执行.

2、Servlet和JSP的区别：

Servlet以Java程序为主， 输出HTML代码时需要使用out.println函数，也就是说Java中内嵌HTML； 而JSP则以HTML页面为主，需要写Java代码时则在页面中直接插入Java代码， 即HTML中内嵌Java.

3、MVC模型

MVC模型就是将数据、逻辑处理、用户界面分离的一种方法

1）、M(Model, 模型)：用于数据处理、逻辑处理

2）、V(View，视图)：用于显示用户界面

3）、C(Controller，控制器)：根据客户端的请求控制逻辑走向和画面

而在Java中，MVC这三个部分则分别对应于 JavaBeans、JSP和Servlet

1）、M = JavaBeans：用于传递数据，拥有与数据相关的逻辑处理

2）、V = JSP：从Model接收数据并生成HTML

3）、C = Servlet：接收HTTP请求并控制Model和View

4、jdbc连接，可参考文章：点击打开链接

二、代码演示，实现了book的添加删除和修改功能

1、环境的配置

myeclipse+tomcat+MySQL

2、Book中bean类

package example.bean.book; public class Book { // 编号 private int id; // 图书名称 private String name; // 价格 private double price; // 数量 private int bookCount; // 作者 private String author; 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 double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public int getBookCount() { return bookCount; } public void setBookCount(int bookCount) { this.bookCount = bookCount; } public String getAuthor() { return author; } public void setAuthor(String author) { this.author = author; } }

3、Servlet类

1)、FindServlet.java

package example.servlet.book; import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; import java.util.ArrayList; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import example.bean.book.Book; /** * Servlet implementation class FindServlet */ public class FindServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse * response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { // 加载数据库驱动，注册到驱动管理器 Class.forName("com.mysql.jdbc.Driver"); // 数据库连接字符串 String url = "jdbc:mysql://localhost:3306/db_book?useUnicode=true&characterEncoding=utf-8"; // 数据库用户名 String username = "root"; // 数据库密码 String password = ""; // 创建Connection连接 Connection conn = DriverManager.getConnection(url, username, password); // 添加图书信息的SQL语句 String sql = "select * from tb_books"; // 获取Statement Statement statement = conn.createStatement(); ResultSet resultSet = statement.executeQuery(sql); List<Book> list = new ArrayList<Book>(); while (resultSet.next()) { Book book = new Book(); book.setId(resultSet.getInt("id")); book.setName(resultSet.getString("name")); book.setPrice(resultSet.getDouble("price")); book.setBookCount(resultSet.getInt("bookCount")); book.setAuthor(resultSet.getString("author")); list.add(book); } request.setAttribute("list", list); resultSet.close(); statement.close(); conn.close(); } catch (Exception e) { e.printStackTrace(); } request.getRequestDispatcher("book_list.jsp") .forward(request, response); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }

2)、UpdateServlet.java类

package example.servlet.book; import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class UpdateServlet */ public class UpdateServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse * response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int id = Integer.valueOf(request.getParameter("id")); int bookCount = Integer.valueOf(request.getParameter("bookCount")); try { // 加载数据库驱动，注册到驱动管理器 Class.forName("com.mysql.jdbc.Driver"); // 数据库连接字符串 String url = "jdbc:mysql://localhost:3306/db_book"; // 数据库用户名 String username = "root"; // 数据库密码 String password = ""; // 创建Connection连接 Connection conn = DriverManager.getConnection(url, username, password); // 更新SQL语句 String sql = "update tb_books set bookcount=? where id=?"; // 获取PreparedStatement PreparedStatement ps = conn.prepareStatement(sql); // 对SQL语句中的第一个参数赋值 ps.setInt(1, bookCount); // 对SQL语句中的第二个参数赋值 ps.setInt(2, id); // 执行更新操作 ps.executeUpdate(); // 关闭PreparedStatement ps.close(); // 关闭Connection conn.close(); } catch (Exception e) { e.printStackTrace(); } // 重定向到FindServlet response.sendRedirect("FindServlet"); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }

3）、DeleteServlet类

package example.servlet.book; import java.io.IOException; import java.sql.Connection; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import example.dao.book.BookJdbcDao; import example.dao.book.ConnectionFactory; /** * Servlet implementation class DeleteServlet */ public class DeleteServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse * response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int id = Integer.valueOf(request.getParameter("id")); try { // // 加载数据库驱动，注册到驱动管理器 // Class.forName("com.mysql.jdbc.Driver"); // // 数据库连接字符串 // String url = "jdbc:mysql://localhost:3306/db_book"; // // 数据库用户名 // String username = "root"; // // 数据库密码 // String password = ""; // // 创建Connection连接 // Connection conn = DriverManager.getConnection(url, username, // password); // // 删除图书信息的SQL语句 // String sql = "delete from tb_books where id=?"; // // 获取PreparedStatement // PreparedStatement ps = conn.prepareStatement(sql); // // 对SQL语句中的第一个占位符赋值 // ps.setInt(1, id); // // 执行更新操作 // ps.executeUpdate(); // // 关闭PreparedStatement // ps.close(); // // 关闭Connection // conn.close(); BookJdbcDao bookDao=new BookJdbcDao(); Connection conn=ConnectionFactory.getInstance().getConnection(); bookDao.delete(conn,id); } catch (Exception e) { e.printStackTrace(); } // 重定向到FindServlet response.sendRedirect("FindServlet"); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }

4、servlet访问url映射配置：

由于客户端是通过URL地址访问web服务器中的资源，所以Servlet程序若想被外界访问，必须把servlet程序映射到一个URL地址上，这个工作在web.xml文件中使用<servlet>元素和<servlet-mapping>元素完成，<servlet>元素用于注册Servlet，它包含有两个主要的子元素：<servlet-name>和<servlet-class>，分别用于设置Servlet的注册名称和Servlet的完整类名。

一个<servlet-mapping>元素用于映射一个已注册的Servlet的一个对外访问路径，它包含有两个子元素：<servlet-name>和<url-pattern>，分别用于指定Servlet的注册名称和Servlet的对外访问路径.另外：同一个Servlet可以被映射到多个URL上，即多个<servlet-mapping>元素的<servlet-name>子元素的设置值可以是同一个Servlet的注册名.

eg:上例中的web.xml

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://.mysql.jdbc.Driver"; private String url = "jdbc:mysql://localhost:3306/db_book?useUnicode=true&characterEncoding=utf-8"; private String userName = "root"; private String password = ""; private static ConnectionFactory connectionFactory=null; private ConnectionFactory() { try { Class.forName(driverClassName); } catch (ClassNotFoundException e) { e.printStackTrace(); } } public Connection getConnection() throws SQLException { return DriverManager.getConnection(url, userName, password); } public static ConnectionFactory getInstance() { if (null==connectionFactory) { connectionFactory=new ConnectionFactory(); } return connectionFactory; } }

2）、BookJdbcDao.java数据库操作封装类

package example.dao.book; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import example.bean.book.Book; public class BookJdbcDao { private PreparedStatement ptmt = null; private ResultSet rs = null; public BookJdbcDao() { } public void findAll(Connection conn) throws SQLException { //to do } public void delete(Connection conn, int id) throws SQLException { String sql = "delete from tb_books where id=?"; try{ ptmt = conn.prepareStatement(sql); // 对SQL语句中的第一个占位符赋值 ptmt.setInt(1, id); // 执行更新操作 ptmt.executeUpdate(); }finally{ if (null!=ptmt) { ptmt.close(); } if (null!=conn) { conn.close(); } } } public void update(Connection conn, int id ,int bookcount) throws SQLException { //to do } }

源代码下载链接

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