【Spring in action】SpringMVC的准备工作：Servlet实战

前言：

大概这篇文章应该应该已经没多少人能用到了。

一、本文用到的数据库连接：

先简单写一下Jdbc链接数据库（虽然现在这种方式应该是已经没人在用）

package com.jdbcdemo;import java.io.InputStream;import java.sql.Connection;import java.sql.Date;import java.sql.Driver;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Properties;import org.junit.Test;public class JdbcTest {//1.普通的jdbc@Testpublic void test() throws SQLException {Driver driver = new org.gjt.mm.mysql.Driver();String url = "jdbc:mysql://localhost:3306/samp_db";Properties info = new Properties();info.put("user", "root");info.put("password", "haibo1118");Connection connection =  driver.connect(url, info);System.out.println(connection);}//2.配置文件property的jdbc@Testpublic void testProperty() throws Exception{System.out.println(getConnection());}public Connection getConnection() throws Exception {// TODO Auto-generated method stubString driverClass;String url;String user;String password;InputStream in = getClass().getClassLoader().getResourceAsStream("jdbc.property");Properties properties = new Properties();properties.load(in);driverClass = properties.getProperty("driver");url = properties.getProperty("jdbcUrl");user = properties.getProperty("user");password = properties.getProperty("password");Driver driver = (Driver) Class.forName(driverClass).newInstance();Properties properties2 = new Properties();properties2.put("user", user);properties2.put("password", password);Connection connection =  driver.connect(url, properties2);return connection;}//3.通过DriverManager获得链接，比之前简化一部分@Testpublic void testDriverManager() throws Exception{System.out.println(getConnection2());}public Connection getConnection2() throws Exception{String driverClass;String url;String user;String password;InputStream in = getClass().getClassLoader().getResourceAsStream("jdbc.property");Properties properties = new Properties();properties.load(in);driverClass = properties.getProperty("driver");url = properties.getProperty("jdbcUrl");user = properties.getProperty("user");password = properties.getProperty("password");Class.forName(driverClass);Connection connection = DriverManager.getConnection(url, user, password);return connection;}//4、通过自己的工具类简化建立链接，释放链接，并对数据库执行插入操作@Testpublic void testStateMent(){Connection conn = null;Statement statement = null;String sql = "insert into customers (NAME,EMAIL,BIRTH) values('zhouhe','[e-mail]','1999-11-18');";//String sql = "update customers set name = 'tom' where id =2;";//String sql = "delete from customers where id=1;";try {conn = JdbcTools.getConnection();statement = conn.createStatement();statement.executeUpdate(sql);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {JdbcTools.release(conn, statement);}}//5、通过自己的工具类简化建立链接，释放链接，并对数据库执行查询操作，获得结果集@Testpublic void testResultSet(){Connection conn = null;Statement statement = null;ResultSet resultSet = null;String sql = "SELECT * FROM samp_db.customers;";try {conn = JdbcTools.getConnection();statement = conn.createStatement();resultSet = statement.executeQuery(sql);while(resultSet.next()){int id = resultSet.getInt(1);String name = resultSet.getString(2);String email = resultSet.getString(3);Date date = resultSet.getDate(4);System.out.println(" id:"+id+" name:"+name+" email:"+email+" date:"+date);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {JdbcTools.release(resultSet, conn, statement);}}}

一个自定义链接释放数据库链接的小工具：

package com.jdbcdemo;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Properties;public class JdbcTools {//释放public static void release(Connection connection,Statement statement){if (statement!=null) {try {statement.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if(connection!=null){try {connection.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}//释放public static void release(ResultSet resultSet,Connection connection,Statement statement){if(resultSet!=null){try {resultSet.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if (statement!=null) {try {statement.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if(connection!=null){try {connection.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}//获得链接public static Connection getConnection() throws Exception{String driverClass;String url;String user;String password;InputStream in = JdbcTools.class.getClassLoader().getResourceAsStream("jdbc.property");Properties properties = new Properties();properties.load(in);driverClass = properties.getProperty("driver");url = properties.getProperty("jdbcUrl");user = properties.getProperty("user");password = properties.getProperty("password");Class.forName(driverClass);Connection connection = DriverManager.getConnection(url, user, password);return connection;}}

配置文件jdbc.property：

driver=org.gjt.mm.mysql.DriverjdbcUrl=jdbc:mysql://localhost:3306/samp_dbuser=rootpassword=haibo1118

目录结构一览：

二、写一个登陆功能模块：

登陆也就是通过客户端提供用户名密码，去数据库查询是否有这一条数据，有则返回token。没有则做异常处理。

1、先写去数据库查询的代码：

package login;import model.UserInfo;public interface UserDao {public UserInfo login(String username,String password);}

实现UserDao接口：

package login;import java.sql.Connection;import org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.BeanHandler;import jdbc.JdbcTools;import model.UserInfo;public class UserDaoImpl implements UserDao {Connection conn;UserInfo obj;@Overridepublic UserInfo login(String username, String password) {// TODO Auto-generated method stubQueryRunner queryRunner = new QueryRunner();String sql ="select username,password from userTbl where username=? and password=?";Connection connection = null;try {connection = JdbcTools.getConnection();obj = (UserInfo) queryRunner.query(connection, sql, new BeanHandler(UserInfo.class),username,password);System.out.println(obj);} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}finally {JdbcTools.release(connection, null);}return obj;}}

本文通过一个第三方工具dbutils简化查询操作：org.apache.commons.dbutils.QueryRunner;本例子，如果查到用户名密码结果则返回一个对象，如果没找到则返回空对象。

此处为注释分割线---------可忽略此部分（下文）----------

PS1：此处提供一个较为完整的Jdbctools工具类：（包含事务，虽然本例并没有用到，可忽略）

package jdbc;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Properties;public class JdbcTools {public static void beginTx(Connection conn){try {conn.setAutoCommit(false);} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public static void commitTx(Connection conn){try {conn.commit();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public static void rollback(Connection connection){try {connection.rollback();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public static void setTransactionLevel(Connection conn){try {conn.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}public static void update(String sql){Connection connection = null;Statement statement = null;try {connection = getConnection();statement = connection.createStatement();statement.execute(sql);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {release(connection, statement);}}public static void release(Connection connection,Statement statement){if (statement!=null) {try {statement.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if(connection!=null){try {connection.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}public static void release(ResultSet resultSet,Connection connection,Statement statement){if(resultSet!=null){try {resultSet.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if (statement!=null) {try {statement.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if(connection!=null){try {connection.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}public static Connection getConnection() throws Exception{String driverClass;String url;String user;String password;InputStream in = JdbcTools.class.getClassLoader().getResourceAsStream("jdbc.property");Properties properties = new Properties();properties.load(in);driverClass = properties.getProperty("driver");url = properties.getProperty("jdbcUrl");user = properties.getProperty("user");password = properties.getProperty("password");Class.forName(driverClass);Connection connection = DriverManager.getConnection(url, user, password);return connection;}public static void update(String sql,Object ...args){Connection connection = null;PreparedStatement preparedStatement = null;try {connection = getConnection();preparedStatement = connection.prepareStatement(sql);for(int i = 0 ;i<args.length;i++){preparedStatement.setObject(i+1, args[i]);}preparedStatement.executeUpdate();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {release(connection, preparedStatement);}}}

PS2:建议在使用jdbc时先写一个测试用例试试是否成功连接数据库：

package jdbc;import java.sql.Connection;import org.junit.Test;public class TestJdbc {Connection conn;@Testpublic void test() {try {conn = JdbcTools.getConnection();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}System.out.println(conn);}}

执行结果如下：则成功。

com.mysql.jdbc.JDBC4Connection@3cd1f1c8

此处为注释分割线---------可忽略此部分（上文）----------

2、写访问服务端代码：

package login;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import model.UserInfo;/** * Servlet implementation class MyLoginServlet * @WebServlet("/MyLoginServlet") */public class MyLoginServlet extends HttpServlet {private static final long serialVersionUID = 1L;           /**     * @see HttpServlet#HttpServlet()     */    public MyLoginServlet() {        super();        // TODO Auto-generated constructor stub    }/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubString username = request.getParameter("username");String password = request.getParameter("password");UserDao userDao = new UserDaoImpl();UserInfo u = userDao.login(username, password);PrintWriter out = response.getWriter();if (u!=null) {HttpSession session = request.getSession();session.setAttribute("userSession", u);request.getRequestDispatcher("welcome.jsp").forward(request, response);}else{out.print("username or password is incorrect!");}}/** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}

当前代码配置一下web.xml其实就可以直接执行了:

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns="http://xmlns.jcp.org/xml/ns/javaee"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"version="3.1"><display-name>LoginServlet</display-name><welcome-file-list><welcome-file>index.html</welcome-file><welcome-file>index.htm</welcome-file><welcome-file>index.jsp</welcome-file><welcome-file>default.html</welcome-file><welcome-file>default.htm</welcome-file><welcome-file>default.jsp</welcome-file></welcome-file-list><servlet><servlet-name>MyLoginServlet</servlet-name><servlet-class>login.MyLoginServlet</servlet-class></servlet><servlet-mapping><servlet-name>MyLoginServlet</servlet-name><url-pattern>/MyLoginServlet</url-pattern></servlet-mapping></web-app>

执行执行地址如下：http://localhost:8080/LoginServlet/MyLoginServlet

浏览器将根据我们的代码显示：username or password is incorrect!因为我们未传入用户名密码。

3、写一个login.html网页提交用户名，密码：

<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body><h1>hello servlet</h1><form action="MyLoginServlet" method="post">Username:<input type="text" name="username">Password:<input type="text" name="password"><input type="submit" value="login"></form></body></html>

由于我们查询成功

if (u!=null) {

HttpSession session =request.getSession();

session.setAttribute("userSession",u);

request.getRequestDispatcher("welcome.jsp").forward(request,response);

}else{

out.print("username or password is incorrect!");

}

会执行跳转welcome.jsp。

4、那么就写一个成功后的欢迎页面welcome.jsp吧。

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body>Welcome,${userSession.username}</body></html>

测试一下：http://localhost:8080/LoginServlet/login.html

输入正确的用户名，密码，页面显示：Welcome,xionghaibo。

大功告成！下一步SpringMVC实现一遍。