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Servlet 数据库访问
Servlet 数据库访问本教程假定您已经了解了 JDBC 应用程序的工作方式。在您开始学习 Servlet 数据库访问之前，请访问 Java MySQL 连接 来设置相关驱动及配置。注意：你可以下载本站提供的 jar 包：mysql-connector-java-5.1.39-bin.jar在 java 项目中，只需要在 Eclipse 中引入 mysql-connector-java-5.1.39-bin.jar 就可以运行java项目。但是在 Eclipse web 项目中，当执行 Class.forName("com.mysql.jdbc.Driver");时 不会去查找驱动的。所以本实例中我们需要把 mysql-connector-java-5.1.39-bin.jar 拷贝到 tomcat 下 lib 目录。从基本概念下手，让我们来创建一个简单的表，并在表中创建几条记录。创建测试数据接下来我们在 MySQL 中创建 RUNOOB 数据库，并创建 websites 数据表，表结构如下：CREATE TABLE `websites` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` char(20) NOT NULL DEFAULT '' COMMENT '站点名称', `url` varchar(255) NOT NULL DEFAULT '', `alexa` int(11) NOT NULL DEFAULT '0' COMMENT 'Alexa 排名', `country` char(10) NOT NULL DEFAULT '' COMMENT '国家', PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;插入一些数据：INSERT INTO `websites` VALUES ('1', 'Google', 'https:
//www.google.cm/', '1', 'USA'), ('2', '淘宝', 'https:
//www.taobao.com/', '13', 'CN'), ('3', 'k88.net', 'http:
//www.k88.net', '5892', ''), ('4', '微博', 'http:
//weibo.com/', '20', 'CN'), ('5', 'Facebook', 'https:
//www.facebook.com/', '3', 'USA');数据表显示如下：访问数据库下面的实例演示了如何使用 Servlet 访问 RUNOOB 数据库。package com.k88.test;import java.io.IOException;import java.io.PrintWriter;import java.sql.*;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class DatabaseAccess */@WebServlet("/DatabaseAccess")public class DatabaseAccess extends HttpServlet { private static final long serialVersionUID = 1L; // JDBC 驱动名及数据库 URL static final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; static final String DB_URL = "jdbc:
mysql:
//localhost:
3306/RUNOOB"; // 数据库的用户名与密码，需要根据自己的设置 static final String USER = "root"; static final String PASS = "123456"; /** * @see HttpServlet
#HttpServlet() */ public DatabaseAccess() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet
#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Connection conn = null; Statement stmt = null; // 设置响应内容类型 response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String title = "Servlet Mysql 测试 - k88.net"; String docType = "<!DOCTYPE html>\n"; out.println(docType + "<html>\n" + "<head><title>" + title + "</title></head>\n" + "<body bgcolor=\"
#f0f0f0\">\n" + "<h1 align=\"center\">" + title + "</h1>\n"); try{ // 注册 JDBC 驱动器 Class.forName("com.mysql.jdbc.Driver"); // 打开一个连接 conn = DriverManager.getConnection(DB_URL,USER,PASS); // 执行 SQL 查询 stmt = conn.createStatement(); String sql; sql = "SELECT id, name, url FROM websites"; ResultSet rs = stmt.executeQuery(sql); // 展开结果集数据库 while(rs.next()){ // 通过字段检索 int id = rs.getInt("id"); String name = rs.getString("name"); String url = rs.getString("url"); // 输出数据 out.println("ID:
" + id); out.println(", 站点名称:
" + name); out.println(", 站点 URL:
" + url); out.println("<br />"); } out.println("</body></html>"); // 完成后关闭 rs.close(); stmt.close(); conn.close(); } catch(SQLException se) { // 处理 JDBC 错误 se.printStackTrace(); } catch(Exception e) { // 处理 Class.forName 错误 e.printStackTrace(); }finally{ // 最后是用于关闭资源的块 try{ if(stmt!=null) stmt.close(); }catch(SQLException se2){ } try{ if(conn!=null) conn.close(); }catch(SQLException se){ se.printStackTrace(); } } } /** * @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); }}现在让我们来编译上面的 Servlet，并在 web.xml 文件中创建以下条目：.... <servlet> <servlet-name>DatabaseAccess</servlet-name> <servlet-class>com.k88.test.DatabaseAccess</servlet-class> </servlet> <servlet-mapping> <servlet-name>DatabaseAccess</servlet-name> <url-pattern>/TomcatTest/DatabaseAccess</url-pattern> </servlet-mapping>....现在调用这个 Servlet，输入链接：http:
//localhost:
8080/TomcatTest/DatabaseAccess，将显示以下响应结果：
//www.google.cm/', '1', 'USA'), ('2', '淘宝', 'https:
//www.taobao.com/', '13', 'CN'), ('3', 'k88.net', 'http:
//www.k88.net', '5892', ''), ('4', '微博', 'http:
//weibo.com/', '20', 'CN'), ('5', 'Facebook', 'https:
//www.facebook.com/', '3', 'USA');数据表显示如下：访问数据库下面的实例演示了如何使用 Servlet 访问 RUNOOB 数据库。package com.k88.test;import java.io.IOException;import java.io.PrintWriter;import java.sql.*;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class DatabaseAccess */@WebServlet("/DatabaseAccess")public class DatabaseAccess extends HttpServlet { private static final long serialVersionUID = 1L; // JDBC 驱动名及数据库 URL static final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; static final String DB_URL = "jdbc:
mysql:
//localhost:
3306/RUNOOB"; // 数据库的用户名与密码，需要根据自己的设置 static final String USER = "root"; static final String PASS = "123456"; /** * @see HttpServlet
#HttpServlet() */ public DatabaseAccess() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet
#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Connection conn = null; Statement stmt = null; // 设置响应内容类型 response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String title = "Servlet Mysql 测试 - k88.net"; String docType = "<!DOCTYPE html>\n"; out.println(docType + "<html>\n" + "<head><title>" + title + "</title></head>\n" + "<body bgcolor=\"
#f0f0f0\">\n" + "<h1 align=\"center\">" + title + "</h1>\n"); try{ // 注册 JDBC 驱动器 Class.forName("com.mysql.jdbc.Driver"); // 打开一个连接 conn = DriverManager.getConnection(DB_URL,USER,PASS); // 执行 SQL 查询 stmt = conn.createStatement(); String sql; sql = "SELECT id, name, url FROM websites"; ResultSet rs = stmt.executeQuery(sql); // 展开结果集数据库 while(rs.next()){ // 通过字段检索 int id = rs.getInt("id"); String name = rs.getString("name"); String url = rs.getString("url"); // 输出数据 out.println("ID:
" + id); out.println(", 站点名称:
" + name); out.println(", 站点 URL:
" + url); out.println("<br />"); } out.println("</body></html>"); // 完成后关闭 rs.close(); stmt.close(); conn.close(); } catch(SQLException se) { // 处理 JDBC 错误 se.printStackTrace(); } catch(Exception e) { // 处理 Class.forName 错误 e.printStackTrace(); }finally{ // 最后是用于关闭资源的块 try{ if(stmt!=null) stmt.close(); }catch(SQLException se2){ } try{ if(conn!=null) conn.close(); }catch(SQLException se){ se.printStackTrace(); } } } /** * @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); }}现在让我们来编译上面的 Servlet，并在 web.xml 文件中创建以下条目：.... <servlet> <servlet-name>DatabaseAccess</servlet-name> <servlet-class>com.k88.test.DatabaseAccess</servlet-class> </servlet> <servlet-mapping> <servlet-name>DatabaseAccess</servlet-name> <url-pattern>/TomcatTest/DatabaseAccess</url-pattern> </servlet-mapping>....现在调用这个 Servlet，输入链接：http:
//localhost:
8080/TomcatTest/DatabaseAccess，将显示以下响应结果：
Servlet 数据库访问
