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《在jsp中用bean和servlet联合实现用户注册、登录》-JAVA中文站(www.j...

 Ethan的博客 2011-03-31

一、数据库设计
用MySQL Control Center打开MySQL数据库，新建数据库shopping，在其下新建表tbl_user，其中各字段设置如下：


二、编写连接数据库bean：DBConn.java


//DBConn.java

//include required classes
import java.sql.*;

//==========================================
//	Define Class DBConn
//==========================================
public class DBConn
{
	public String sql_driver = "org.gjt.mm.mysql.Driver";
	public String sql_url = "jdbc:mysql://localhost:3306";
	public String sql_DBName = "shopping";
	public String user = "sa";
	public String pwd = "";

	Connection conn = null;
	Statement stmt = null;
	ResultSet rs = null;

	public boolean setDriver(String drv)
	{
		this.sql_driver = drv;
		return true;
	}

	public String getDriver()
	{
		return this.sql_driver;
	}

	public boolean setUrl(String url)
	{
		this.sql_url = url;
		return true;
	}

	public boolean setDBName(String dbname)
	{
		this.sql_DBName = dbname;
		return true;
	}

	public String getDBName()
	{
		return this.sql_DBName;
	}

	public boolean setUser(String user)
	{
		this.user = user;
		return true;
	}

	public String getUser()
	{
		return this.user;
	}

	public boolean setPwd(String pwd)
	{
		this.pwd = pwd;
		return true;
	}

	public String getPwd()
	{
		return this.pwd;
	}

	public DBConn()
	{
		try{
			Class.forName(sql_driver);//加载数据库驱动程序
			this.conn = DriverManager.getConnection(sql_url + "/" + sql_DBName + "?user=" + user + "&password=" + pwd + "&useUnicode=true&characterEncoding=gb2312");
			this.stmt = this.conn.createStatement();
		}catch(Exception e){
			System.out.println(e.toString());
		}
	}

                //执行查询操作
	public ResultSet executeQuery(String strSql)
	{
		try{
			this.rs = stmt.executeQuery(strSql);
			return this.rs;
		}catch(SQLException e){
			System.out.println(e.toString());
			return null;
		}catch(NullPointerException e){
			System.out.println(e.toString());
			return null;
		}
	}

                //执行数据的插入、删除、修改操作
	public boolean execute(String strSql)
	{
		try{
			if(this.stmt.executeUpdate(strSql) == 0)
				return false;
			else
				return true;
		}catch(SQLException e){
			System.out.println(e.toString());
			return false;
		}catch(NullPointerException e){
			System.out.println(e.toString());
			return false;
		}
	}

                //结果集指针跳转到某一行
	public boolean rs_absolute(int row)
	{
		try{
			this.rs.absolute(row);
			return true;
		}catch(SQLException e){
			System.out.println(e.toString());
			return false;
		}
	}

	public void rs_afterLast()
	{
		try{
			this.rs.afterLast();
		}catch(SQLException e){
			System.out.println(e.toString());
		}
	}

	public void rs_beforeFirst()
	{
		try{
			this.rs.beforeFirst();
		}catch(SQLException e){
			System.out.print(e.toString());
		}
	}

	public void rs_close()
	{
		try{
			this.rs.close();
		}catch(SQLException e){
			System.out.print(e.toString());
		}
	}

	public void rs_deleteRow()
	{
		try{
			this.rs.deleteRow();
		}catch(SQLException e){
			System.out.print(e.toString());
		}
	}

	public boolean rs_first()
	{
		try{
			this.rs.first();
			return true;
		}catch(SQLException e){
			System.out.print(e.toString());
			return false;
		}
	}

	public String rs_getString(String column)
	{
		try{
			return this.rs.getString(column);
		}catch(SQLException e){
			System.out.println(e.toString());
			return null;
		}
	}

                //此方法用于获取大段文本，
                //将其中的回车换行替换为<br>
                //输出到html页面
	public String rs_getHtmlString(String column)
	{
		try{
			String str1 = this.rs.getString(column);
			String str2 = "\r\n";
			String str3 = "<br>";
			return this.replaceAll(str1,str2,str3);
		}catch(SQLException e){
			System.out.println(e.toString());
			return null;
		}
	}
	
                //把str1字符串中的str2字符串替换为str3字符串
	private static String replaceAll(String str1,String str2,String str3)
	{
		StringBuffer strBuf = new StringBuffer(str1);
	    int index=0;
		while(str1.indexOf(str2,index)!=-1)
		{
			index=str1.indexOf(str2,index);
			strBuf.replace(str1.indexOf(str2,index),str1.indexOf(str2,index)+str2.length(),str3);
			index=index+str3.length();

			 str1=strBuf.toString();
		}
		return strBuf.toString();
	} 

	public int rs_getInt(String column)
	{
		try{
			return this.rs.getInt(column);
		}catch(SQLException e){
			System.out.println(e.toString());
			return -1;
		}
	}

	public int rs_getInt(int column)
	{
		try{
			return this.rs.getInt(column);
		}catch(SQLException e){
			System.out.println(e.toString());
			return -1;
		}
	}

	public boolean rs_next()
	{
		try{
			return this.rs.next();
		}catch(SQLException e){
			System.out.println(e.toString());
			return false;
		}
	}

                //判断结果集中是否有数据
	public boolean hasData()
	{
		try{
			boolean has_Data = this.rs.first();			
			this.rs.beforeFirst();
			return has_Data;
		}catch(SQLException e){
			System.out.println(e.toString());
			return false;
		}
	}

	public boolean rs_last()
	{
		try{
			return this.rs.last();
		}catch(SQLException e){
			System.out.println(e.toString());
			return false;
		}
	}

	public boolean rs_previous()
	{
		try{
			return this.rs.previous();
		}catch(Exception e){
			System.out.println(e.toString());
			return false;
		}
	}

                //main方法，调试用
	public static void main(String args[])
	{
		try{
			DBConn myconn = new DBConn();
			//myconn.setDBName("shopping");
			//myconn.DBConn();
			//myconn.execute("Insert Into tbl_test(id,name) values(´10´,´shandaer´)");
			//myconn.execute("Update tbl_test set name=´yyyyyyyyyyyy´ where id=10");
			//myconn.execute("Delete from tbl_test where id=1");
			ResultSet rs = myconn.executeQuery("select * from tbl_user order by id desc limit 1");
			//boolean hasData = myconn.hasData();
			//System.out.println("has data:" + hasData);
			//rs.first();
			while (myconn.rs.next())		
			{
				int id = myconn.rs_getInt("id") + 1;
				System.out.print(id);
				System.out.println(myconn.rs_getInt("id") + myconn.rs_getString("name"));
				
				//System.out.println(´\n´ + myconn.rs_getHtmlString("name"));
				//System.out.println(myconn.rs.getString("name") + myconn.rs_getInt(1));
			}
		}catch(Exception e){
			System.err.println(e.toString());
		}
	}
	
}



声明：因为使用的是MySQL数据库，所以需要MySQL数据库的驱动
下载后请将org包放至DBConn.java所在目录下
以确保该bean能正常运行


三、编写用户注册的bean：reg.java


//reg.java

//import required classes
import java.sql.*;

public class reg
{
	public int newID = 0;
	public boolean result = false;
	public boolean reg(String username,String password,String confirm,String email)
	{
		try{
			if(!this.checkUser(username))
				return false;
			if(!this.checkPwd(password))
				return false;
			if(!this.verifyPwd(password,confirm))
				return false;
			if(!this.checkEmail(email))
				return false;
			if(!this.userNotExit(username))
				return false;
			this.getNewID();		
			this.result = this.register(username,password,confirm,email);
			return this.result;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;
		}
	}//End boolean reg
	
	public boolean checkUser(String user)
	{
		try{			
			if(user.indexOf("´")!=-1)
			{
				System.out.println("姓名中含有非法字符！");
				return false;
			}else
				return true;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;
			}	
	}
	
	public boolean checkPwd(String pwd)
	{
		try{
			if(pwd.indexOf("´")!=-1)
			{
				System.out.println("密码中含有非法字符！");
				return false;
			}else
				return true;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;	
		}
	}
	
	public boolean verifyPwd(String pwd,String confirm)
	{
		try{
			if(!pwd.equals(confirm))
			{
				System.out.println("两次输入的密码不一致！");
				return false;
			}else
				return true;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;
		}
	}
	
	public boolean checkEmail(String email)
	{
		try{
			if(email.indexOf("´")!=-1)
			{
				System.out.println("E-mail中含有非法字符！");
				return false;
			}else
				return true;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;	
		}
	}
	
	public boolean userNotExit(String user)
	{
		try{
			DBConn userDBConn = new DBConn();
			userDBConn.executeQuery("select * from tbl_user where name=´" + user + "´");
			if(userDBConn.rs_next())
			{
				System.out.println("用户名已存在，请选择其它的用户名！");
				return false;
			}else
				return true;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;
			}	
	}
	
	public int getNewID()
	{
		try{
			DBConn newIDDBConn = new DBConn();
			newIDDBConn.executeQuery("select * from tbl_user order by id desc limit 1");
			if(newIDDBConn.rs_next())
			{
				this.newID = newIDDBConn.rs_getInt("id") + 1;
				System.out.println(this.newID);
			}else{
				this.newID = 1;
			}
			return this.newID;
		}catch(Exception e){
			System.out.println(e.toString());
			return -1;
			}				
	}
	
	public int getID()
	{
		return this.newID;
	}
	
	public boolean register(String username,String password,String confirm,String email)
	{
		try{
			DBConn regDBConn = new DBConn();
			String strSQL = "insert into tbl_user(id,name,pwd,email) values(´" + this.newID +"´,´" + username + "´,´" + password + "´,´" + email + "´)";
			regDBConn.execute(strSQL);
			return true;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;
			}	
	}

	public static void main(String args[])
	{
		try{
			
			reg newreg = new reg();			
			
			System.out.println(newreg.reg("sssssssss","ssssss","ssssss","imagebear@163.com"));
			
			DBConn myconn = new DBConn();
			myconn.executeQuery("select * from tbl_user");
			while(myconn.rs_next())
			{
				System.out.println(myconn.rs_getInt("id") + "    " + myconn.rs_getString("name") + "    " + myconn.rs_getString("pwd") + "    " + myconn.rs_getString("email"));
			}
			System.out.println(newreg.getID());
		}catch(Exception e){
			System.err.println(e.toString());
		}
	}
};



说明：
1、该bean文件应和上文所述DBConn.class文件放于同一目录下
2、本例主要研究注册的过程，其中的Email检测等方法并不完善，若要应用请自行设计方法


 


四、编写用户登陆的Servlet：login.java


//login.java

//import required classes
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

//class login
public class login extends HttpServlet
{
	public void doGet(HttpServletRequest req,HttpServletResponse res)
	throws IOException,ServletException
	{
		String username = req.getParameter("username");
		String password = req.getParameter("password");
		if(this.checklogin(username,password))
		{
			Cookie mylogin = new Cookie("username",username);
			mylogin.setVersion(1);
			mylogin.setPath("/");
			mylogin.setComment("Your login username");
			res.addCookie(mylogin);	
		}
		//Cookie[] myCookies = req.getCookies();
		//String nameValue = this.getCookieValue(myCookies,"username","not found");
		//PrintWriter out = res.getWriter();
		//out.println("username" + ":" + nameValue);
		//out.println("Test Cookie Success!");
		res.sendRedirect("/index.jsp");
	}
	
	public void doPost(HttpServletRequest req,HttpServletResponse res)
	throws IOException,ServletException
	{
		doGet(req,res);
	}
	
	public static String getCookieValue(Cookie[] cookies,String cookieName,String defaultValue)
	{
		for(int i=0;i<cookies.length;i++) {
		Cookie cookie = cookies[i];
		if (cookieName.equals(cookie.getName()))
		return(cookie.getValue());
	}
		return(defaultValue);
	} 


		
	public boolean checklogin(String username,String password)
	{
		try{
			DBConn loginConn = new DBConn();
			loginConn.executeQuery("select * from tbl_user where name=´" + username + "´");
			if(loginConn.rs_next())
			{
				System.out.println("Connection created!");
				if(loginConn.rs_getString("pwd").trim().equals(password))
				{
					System.out.println(loginConn.rs_getString("name"));
					return true;
				}
				else
				{
					return false;
				}
			}
			System.out.println("Test Login Success!");
			return false;
		}catch(Exception e){
			System.out.println(e.toString());
			return false;
			}	
	}
	
	public static void main(String args[])
	{
		login mylogin = new login();
		System.out.println(mylogin.checklogin("shandong","shandong"));
	}
	
}



说明：
1、默认的jdk1.4中并没有servlet包，请至sun公司网页下载servlet.jar，放至jdk目录下的jre\lib\目录下，并在JCreator中设置jdk处添加servlet.jar包，如图所示：
按此在新窗口浏览图片
2、本Servlet用于检验用户名和密码，若正确则将用户名写入Cookie，完成后将当前页重定向到index.jsp页


 


五、编写检测用户是否已经登陆的bean：checkLogin.java


//checkLogin.java

//import required classes
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

//class checkLogin
public class checkLogin
{
	public String username = "";
	
	public boolean check(HttpServletRequest req,HttpServletResponse res)
	throws IOException,ServletException
	{
		String cookieName = "username";
		Cookie[] myCookies = req.getCookies();
		this.username = this.getCookieValue(myCookies,cookieName,"not found");
		PrintWriter out = res.getWriter();
		if(this.username != null)
		{			
			//out.println("早上好，" + this.username + "！");
			return true;
		}else{
			out.println("登陆失败！");
			return false;
			}
			
	}
	
	public String getUserName()
	{
		return this.username;
	}
	
	public static String getCookieValue(Cookie[] cookies,String cookieName,String defaultValue)
	{
		for(int i=0;i<cookies.length;i++) {
		Cookie cookie = cookies[i];
		if (cookieName.equals(cookie.getName()))
		return(cookie.getValue());
	}
		return(defaultValue);
	}
}



说明：此bean检测cookie中的username，若不为空则说明已登录，反之说明没有登录。方法不够完善，您可以自行扩充。


 


六、在JRun中建立shopping服务器
打开JRun Administrator，新建shopping服务器，这里端口为8101。
将上文所述所有编译后的class文件连同org包拷至JRun的shopping服务器所在目录中的classes文件夹下，路径为：


C:\JRun4\servers\shopping\default-ear\default-war\WEB-INF\classes\



七、建立jsp文件
应用DW，在C:\JRun4\servers\shopping\default-ear\default-war\目录下新建如下的jsp文件：
index.jsp：


<%@ page contentType="text/html;charset=gb2312" pageEncoding="gb2312" %>
<html>
<head>
<title>Shopping123</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<link href="styles/shoppingstyle.css" rel="stylesheet" type="text/css">
</head>
<body bgcolor="#FFFFFF" leftmargin="0" topmargin="0">
<jsp:useBean id="checklogin" class="checkLogin" scope="page"/>
<%
	boolean login = checklogin.check(request,response);
%>
<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
  <tr bgcolor="#990000"> 
    <td height="80" colspan="5"><table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
        <tr>
          <td width="120"> </td>
          <td class="caption">Shopping123</td>
          <td width="200"> </td>
        </tr>
      </table></td>
  </tr>
  <tr> 
    <td width="200" align="center" valign="top"><table width="100%" height="20" border="0" cellpadding="0" cellspacing="0">
        <tr>
          <td> </td>
        </tr>
      </table>
	  <%
	  	if(!login){
	  %>
      <table width="90%" border="0" align="center" cellpadding="0" cellspacing="1" bgcolor="#CCCCCC">
	  <form name="form1" method="post" action="/servlet/login">
        <tr align="center" bgcolor="#CCCCCC"> 
          <td height="30" colspan="2" class="deepred">卖场入口</td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">会员</td>
          <td align="center" bgcolor="#FFFFFF"><input name="username" type="text" id="username" size="10"></td>
        </tr>
        <tr> 
          <td height="24" align="center" bgcolor="#FFFFFF">密码</td>
          <td align="center" bgcolor="#FFFFFF"><input name="password" type="text" id="password" size="10"></td>
        </tr>
        <tr> 
          <td height="24" align="center" bgcolor="#FFFFFF"><a href="reg.jsp" target="_blank" class="red">注册</a></td>
          <td align="center" bgcolor="#FFFFFF"><input type="submit" name="Submit" value="进入"></td>
        </tr>
		</form>
      </table>
	  <%
	  	}	
		else
		{
			out.println("您好，" + checklogin.getUserName() + "!");
		}
	  %>
	  </td>
	<td width="1" valign="top" bgcolor="#CCCCCC"></td>
    <td width="400"> </td>
	<td width="1" valign="top" bgcolor="#CCCCCC"></td>
    <td width="200"> </td>
  </tr>
  <tr align="center" bgcolor="#990000"> 
    <td height="60" colspan="5" class="white">copyright&copy; 2003 Shopping123</td>
  </tr>
</table>
</body>
</html>
 
reg.jsp



<%@ page contentType="text/html;charset=gb2312" pageEncoding="gb2312" %>
<html>
<head>
<title>Shopping123</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<link href="styles/shoppingstyle.css" rel="stylesheet" type="text/css">
</head>
<body bgcolor="#FFFFFF" leftmargin="0" topmargin="0">
<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
  <tr bgcolor="#990000"> 
    <td height="80" colspan="5"><table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
        <tr> 
          <td width="120"> </td>
          <td class="caption">Shopping123</td>
          <td width="200"> </td>
        </tr>
      </table></td>
  </tr>
  <tr> 
    <td width="100" align="center" valign="top"> </td>
    <td width="1" valign="top"></td>
    <td width="400" align="center" valign="top"><table width="100%" height="20" border="0" cellpadding="0" cellspacing="0">
        <tr>
          <td> </td>
        </tr>
      </table>
      <table width="100%" border="0" cellpadding="0" cellspacing="1" bgcolor="#CCCCCC">
	  <form action="regpost.jsp" method="post" name="form1">
        <tr align="center"> 
          <td height="30" colspan="2" bgcolor="#CCCCCC" class="deepred">会员注册</td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">会员</td>
          <td align="center" bgcolor="#FFFFFF"><input name="username" type="text" id="username" size="16"></td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">密码</td>
          <td align="center" bgcolor="#FFFFFF"><input name="password" type="password" id="password" size="16"></td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">验证密码</td>
          <td align="center" bgcolor="#FFFFFF"><input name="confirm" type="password" id="confirm" size="16"></td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">E-mail</td>
          <td align="center" bgcolor="#FFFFFF"><input name="email" type="text" id="email" size="16"></td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF"><input type="submit" name="Submit" value="重写"></td>
          <td align="center" bgcolor="#FFFFFF"><input type="submit" name="Submit2" value="注册"></td>
        </tr>
		</form>
      </table></td>
    <td width="1" valign="top"></td>
    <td width="100"> </td>
  </tr>
  <tr align="center" bgcolor="#990000"> 
    <td height="60" colspan="5" class="white">copyright&copy; 2003 Shopping123</td>
  </tr>
</table>
</body>
</html>


 


regpost.jsp：注册表单提交页面



<%@ page contentType="text/html;charset=gb2312" pageEncoding="gb2312" %>
<%@ page import="reg"%>
<html>
<head>
<title>Shopping123</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<link href="styles/shoppingstyle.css" rel="stylesheet" type="text/css">
</head>
<body bgcolor="#FFFFFF" leftmargin="0" topmargin="0">
<%
	String username = new String(request.getParameter("username").getBytes("ISO8859_1")).trim();
	String password = new String(request.getParameter("password").getBytes("ISO8859_1")).trim();
	String confirm = new String(request.getParameter("confirm").getBytes("ISO8859_1")).trim();
	String email = new String(request.getParameter("email").getBytes("ISO8859_1")).trim();
%>
<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
  <tr bgcolor="#990000"> 
    <td height="80" colspan="5"><table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
        <tr> 
          <td width="120"> </td>
          <td class="caption">Shopping123</td>
          <td width="200"> </td>
        </tr>
      </table></td>
  </tr>
  <tr> 
    <td width="100" align="center" valign="top"> </td>
    <td width="1" valign="top"></td>
    <td width="400" align="center" valign="top">
<table width="100%" height="20" border="0" cellpadding="0" cellspacing="0">
        <tr>
          <td> </td>
        </tr>
      </table>
<jsp:useBean id="regID" class="reg" scope="session"/>
<%
	if(regID.reg(username,password,confirm,email))
	{
		out.print("ok");
		String newID = regID.getID() + "";	
%>
      <table width="100%" border="0" cellpadding="0" cellspacing="1" bgcolor="#CCCCCC">
        <tr align="center"> 
          <td height="30" colspan="2" bgcolor="#CCCCCC" class="deepred">恭喜您，注册成功！</td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">编号</td>
          <td align="center" bgcolor="#FFFFFF"><%=newID%></td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">会员</td>
          <td align="center" bgcolor="#FFFFFF"><%=username%></td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">密码</td>
          <td align="center" bgcolor="#FFFFFF"><%=password%></td>
        </tr>
        <tr> 
          <td width="50%" height="24" align="center" bgcolor="#FFFFFF">E-mail</td>
          <td align="center" bgcolor="#FFFFFF"><%=email%></td>
        </tr>
      </table>
<%
		out.print("<br>");
		out.print("<a href=javascript :window.close()>关闭</a>");
	}else{
		out.print("注册失败！<br>");
		out.print("该用户名已有人使用，请使用另外的用户名！");
		out.print("<a href=javascript :history.go(-1)>返回</a>");
	}	
%>
	  </td>
    <td width="1" valign="top"></td>
    <td width="100"> </td>
  </tr>
  <tr align="center" bgcolor="#990000"> 
    <td height="60" colspan="5" class="white">copyright&copy; 2003 Shopping123</td>
  </tr>
</table>
</body>
</html>


 


1. 在第一个类中不应加入字符串操作的方法，如replaceAll、rs_getHtmlString等
跟数据库无关的对字符串操作属“工具方法”，应加入到“工具类”中

2.
public String sql_driver = "org.gjt.mm.mysql.Driver";
public String sql_url = "jdbc:mysql://localhost:3306";
public String sql_DBName = "shopping";
public String user = "sa";
public String pwd = "";
这些变量既然是不可改变的，就应设为不可改变的私有静态变量，而不是public

3. 既然是正式教程，上面这些变量就不应该写死在类里面，要用properties文件保存，如下：

使用properties文件可以在更改服务器地址后不重新编译
类的情况下继续使用

在bean所在目录里用纯文本建立 db.properties 文件，内容如下：
sql_driver=org.gjt.mm.mysql.Driver
sql_url=jdbc:mysql://localhost:3306
sql_DBName=shopping
user=sa
pwd=





if(sql_driver == "" || sql_url == "")
{
	Properties prop	= new Properties();

	//连接db.properties文件
	try
	{
		InputStream is	= getClass().getResourceAsStream("db.properties");
		prop.load(is);
		if(is!=null)
			is.close();
	}
	catch(IOException e)
	{
		System.out.println(" The file ´db.properties´ can´t open ");
		return false;
	}

	读取各项参数
	this.sql_driver		= prop.getProperty("sql_driver");
	this.sql_url		= prop.getProperty("sql_url");
	this.sql_DBName		= prop.getProperty("sql_DBName");
	this.user		= prop.getProperty("user");
	this.pwd		= prop.getProperty("pwd");
}



在顶部再引入：
import java.util.*;
import java.io.*;

4. 为了避免单引号引发的异常而禁止用户输入单引号是不可取的，应在将变量写入sql语句的时候把该变量的值里面的所有单引号替换成一对一对的单引号

5. 
String username = new String(request.getParameter("username").getBytes("ISO8859_1")).trim();
String password = new String(request.getParameter("password").getBytes("ISO8859_1")).trim();
String confirm = new String(request.getParameter("confirm").getBytes("ISO8859_1")).trim();
String email = new String(request.getParameter("email").getBytes("ISO8859_1")).trim();
转换中文没有做成方法，不可取，要尽可能地重用

6. 凡用户输入的字符串都必须在显示的时候替换某些HTML“关键字”（先这么叫着），
如尖括号、&、双引号、空格

7. 用户注册后不应把密码显示出来，而应该按密码位数显示星号

8. 注册失败后应显示详尽的错误信息，把所有的错误都显示出来（这其中应有一公共的错误页面）

9. JSP页面应整个被一个try包起来，出错就转错误页面，以防未知错误使页面显示500

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