loginchecker.java

这是一个网上卖衣服的网站项目

/***************************
 *用户登录时验证其合法性
 *
 *该类实例由静态厂类函数提供,该对象只能实例化一次
 *
 *在多线程的代码中使用该类的实例，必须把调用方法修饰为synchronized
 ******************************/

package mylib;

public class LoginChecker {
	
	private LoginChecker() {
	}
	
	public static LoginChecker getInstance() {
		return lc;
	}
	
	synchronized public void check(String userName,String password) {
		
		this.userName = userName;
		this.password = password;
		
		try {
			ConnectionDB cdb = new ConnectionDB();
			String sqlstr = "SELECT UserName FROM tb_Customer where UserName = \'"+
							userName+"\' and Password = \'"+password+"\'";
			java.sql.ResultSet rs = cdb.executeQuery(sqlstr);
			if(rs.next()) {
				System.out.println("通过验证!");
			}
			else {
				System.out.println("用户名或密码错误!");
			}
			cdb.close();              
		}
		catch(Exception ex) {
			System.out.println("***LoginChecker.check(){}中异常***");
			System.out.println("*********************************");
			ex.printStackTrace();
			System.out.println("*********************************");
		}
	}
	
	private String userName = null;
	private String password = null;
	
	private static LoginChecker lc = new LoginChecker();
	
	
	/*********************************
	 *用于测试的main()
	 *********************************/
	 public static void main(String[] args) {
	 	String userName = "kan";
	 	String password = "123456";
	 	LoginChecker lc = LoginChecker.getInstance();
	 	lc.check(userName,password);
	 }
	 
}