Java+jsp实现简单登录

        实现一个简单的登录界面，学习一下java的具体内容。

所要实现的效果：

        当我们点击添加按钮，将界面获取到的用户信息保存到数据库中，这是个简单的操作，咱们看下用java怎么实现！

实现步骤：

<span style="font-family:KaiTi_GB2312;font-size:18px;"><%@page import="com.bjpowernode.drp.sysmgr.UserManager"%>
<%@page import="com.bjpowernode.drp.domain.User"%>
<%@ page language="java" contentType="text/html; charset=GB18030"
    pageEncoding="GB18030"%>

    <%
	request.setCharacterEncoding("GB18030");
	String command = request.getParameter("command");
	//if (command != null && command.equals("add")) {
	if ("add".equals(command)) {	
		User user = new User();
		user.setUserId(request.getParameter("userId"));
		user.setUserName(request.getParameter("userName"));
		user.setPassword(request.getParameter("password"));
		user.setContactTel(request.getParameter("contactTel"));
		user.setEmail(request.getParameter("email"));
		
		UserManager.getInstance().addUser(user);
		out.println("添加用户成功！");
	}
%>    
	
</span>

         这里写了三个类，具体介绍了怎么连接数据库

       DbUtil：类似于.net的sqlhelper类的功能，控制连接数据库的操作（关闭或者打开数据库）

<span style="font-family:KaiTi_GB2312;font-size:18px;">package com.bjpowernode.drp.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
 * 封装连接数据库常用操作
 * @author Administrator
 *
 */
public class DbUtil {

	/**
	 * 取得Connection
	 * @return
	 */
	public static Connection getConnection() {
		Connection conn = null;
		try {
			JdbcConfig jdbcConfig = ConfigReader.getInstance().getJdbcConfig();
			Class.forName(jdbcConfig.getDriverName());
			conn = DriverManager.getConnection(jdbcConfig.getUrl(), jdbcConfig.getUsername(), jdbcConfig.getPassword());
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}
	
	public static void close(Connection conn) {
		if (conn != null) {
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
	
	public static void close(PreparedStatement pstmt) {
		if (pstmt != null) {
			try {
				pstmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
	
	public static void main(String[] args) {
		System.out.println(DbUtil.getConnection());
	}
}
</span>

         ConfigReader.java：解析配置文件类中的信息，读取配置文件中的信息

<span style="font-family:KaiTi_GB2312;font-size:18px;">package com.bjpowernode.drp.util;

import java.io.InputStream;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

/**
 * 采用单例模式解析sys-config.xml文件 
 * @author Administrator
 *
 */
public class ConfigReader {
	
	//懒汉式（延迟加载lazy）
	private static ConfigReader instance = null;
	
	//保存jdbc相关配置信息
	private JdbcConfig jdbcConfig = new JdbcConfig();
	
	private ConfigReader() {
		SAXReader reader = new SAXReader();
		InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream("sys-conf.xml");
		try {
			Document doc = reader.read(in);
			
			//取得jdbc相关配置信息
			Element driverNameElt = (Element)doc.selectObject("/config/db-info/driver-name");
			Element urlElt = (Element)doc.selectObject("/config/db-info/url");
			Element userNameElt = (Element)doc.selectObject("/config/db-info/username");
			Element passwordElt = (Element)doc.selectObject("/config/db-info/password");
			
			//设置jdbc相关的配置
			jdbcConfig.setDriverName(driverNameElt.getStringValue());
			
			System.out.println(driverNameElt.getStringValue());
			
			jdbcConfig.setUrl(urlElt.getStringValue());
			jdbcConfig.setUsername(userNameElt.getStringValue());
			jdbcConfig.setPassword(passwordElt.getStringValue());
		} catch (DocumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}			
	}
	
	public static synchronized ConfigReader getInstance() {
		if (instance == null) {
			instance = new ConfigReader();
		}
		return instance;
	}
	
	/**
	 * 返回jdbc相关配置
	 * @return
	 */
	public JdbcConfig getJdbcConfig() {
		return jdbcConfig;
	}
	
	public static void main(String[] args) {
		JdbcConfig jdbcConfig = ConfigReader.getInstance().getJdbcConfig();
//		System.out.println(jdbcConfig.getDriverName());
//		System.out.println(jdbcConfig.getUrl());
//		System.out.println(jdbcConfig.getUserName());
		System.out.println(jdbcConfig);
	}
}
</span>

           jdbcConfig：封装了一个类，这里面写了该获取配置文件中哪些具体信息

<span style="font-family:KaiTi_GB2312;font-size:18px;">package com.bjpowernode.drp.util;

/*
 * 加载数据库连接驱动
 */

public class JdbcConfig {
	private String driverName;
	public String getDriverName() {
		return driverName;
	}
	public void setDriverName(String driverName) {
		this.driverName = driverName;
	}
	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	private String url;
	private String username;
	private String password;
}
</span>

<span style="font-family:KaiTi_GB2312;font-size:18px;">package com.bjpowernode.drp.sysmgr;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.util.Date;
import com.bjpowernode.drp.domain.User;
import com.bjpowernode.drp.util.DbUtil;

/**
 * 采用单例管理用户
 * @author Administrator
 *
 */
public class UserManager {

	private static UserManager instance = new UserManager();
	
	private UserManager() {}
	
	public static UserManager getInstance() {
		return instance;
	}
	
	/**
	 * 添加用户
	 * @param user
	 */
	public void addUser(User user) {
		String sql = "insert into t_user (user_id, user_name, password, contact_tel, email, create_date) " +
				" values (?, ?, ?, ?, ?, ?)";
		Connection conn = null;
		PreparedStatement pstmt = null;
		try {
			conn = DbUtil.getConnection();
			pstmt = conn.prepareStatement(sql);
			pstmt.setString(1, user.getUserId());
			pstmt.setString(2, user.getUserName());
			pstmt.setString(3, user.getPassword());
			pstmt.setString(4, user.getContactTel());
			pstmt.setString(5, user.getEmail());
			//pstmt.setTimestamp(6, new Timestamp(System.currentTimeMillis()));
			pstmt.setTimestamp(6, new Timestamp(new Date().getTime()));
			pstmt.executeUpdate();
		}catch(SQLException e) {
			e.printStackTrace();
		}finally {
			DbUtil.close(pstmt);
			DbUtil.close(conn);
		}
	}
        /**
	 * 根据用户代码查询
	 * 
	 */
	public User findUserById(String userId){	
	  return null;
	}
}
</span>

          其实对比下之前所学习的.net语言实现的登录功能和现在所学习得java的登录功能，过程都是一样的，所以基础很重要！