usermgr.java

精通java核心技术》随书源代码

// ==================== Program Discription ==========================
// 程序名称：示例13-3: UserMgr.java
// 程序目的：利用JDBC对数据库进行增删查改操作
// ==============================================================
import java.sql.*;
import test.DBConnection;

public class UserMgr 
{
    // 向数据库中添加用户信息
    public boolean addUser(User user) 
    {
        // 构造SQL语句
        String sql = "insert into tbl_user (vcUsername, vcPassword,dtRegDate) values('" +
                     user.getUsername() + "','" + user.getPassword() +"',getDate())";
        Statement stmt;
        Connection conn;
        try {
            // 获取数据库连接
            conn = DBConnection.getConnection();

            // 创建Statement对象
            stmt = conn.createStatement();

            // 执行SQL语句
            stmt.executeUpdate(sql);
            stmt.close();
            conn.close();

            return true;
        } 
        catch (SQLException e) {
            System.out.println(e.getMessage());
        }

        return false;
    }

    // 删除数据库中某个用户的信息
    public boolean deleteUser(User user)
    {
        String sql="delete from tbl_user where vcUsername="+"'"+user.getUsername()+"'";
        Connection conn;
        Statement stmt;

        try {
            conn=DBConnection.getConnection();
            stmt=conn.createStatement();
            stmt.executeUpdate(sql);
            stmt.close();
            conn.close();

            return true;
        }
        catch (SQLException e)
        {
            System.out.println(e.getMessage());
        }

        return false;
    }

    // 根据用户名查询数据库获取一个用户对象
    public User getUser( String username )
    {
        User user;
        String sql="select * from tbl_user where vcUsername='"+username+"'";
        Statement stmt;
        Connection conn;

        try {
            conn= DBConnection.getConnection();
            stmt=conn.createStatement();

            // 执行SQL语句并将查询结果放入结果集中
            ResultSet rs=stmt.executeQuery(sql);

            // 将结果集中的数据取出放入User类的对象中
            if (rs.next())
            {
                user=new User();
                user.setUsername(rs.getString("vcUsername"));
                user.setPassword(rs.getString("vcPassword"));
                user.setRegDate(rs.getDate("dtRegDate").toString());
                stmt.close();
                conn.close();
                return user;
            }
        }
        catch (SQLException e)
        {
            System.out.println(e.getMessage());
        }

        return null;
    }

    // 通过验证密码鉴定用户的身份
    public int checkUser(User user)
    {
        User dbUser= getUser(user.getUsername());
        if (dbUser==null)
           return 0;
        else if (dbUser.getPassword().equals(user.getPassword()) )
           return 1;
        else return -1;
    }

    // 修改数据库中某个用户的信息
    public boolean modifyUser(User user)
    {
        Connection conn;
        Statement stmt;
        String sql="update tbl_user set vcPassword='"+user.getPassword()+"' where vcUsername='"+user.getUsername()+"'";

        try {
            conn=DBConnection.getConnection();
            stmt=conn.createStatement();
            stmt.executeUpdate(sql);
            stmt.close();
            conn.close();

            return true;
        }
        catch (SQLException e)
        {
            System.out.println(e.getMessage());
        }

        return false;
    }
}