在Java控制台模拟dos命令下操作MySQL

Posted 2020-08-17

一、导入mysql的驱动：“com.mysql.jdbc.Driver”, 必须将mysql的驱动 包（jar文件）导入到本工程中。

Class.forName("com.mysql.jdbc.Driver");

 

二、由DriverManager驱动的管理类对象去获得Connection，在此之前需要先导入mysql的驱动包（或者驱动类）。

Connection conn = DriverManager.getConnection(url, userName, userPassword);

 

三、由Connection对象，获得执行增删改的sql语句的状态对象Statement

Statement stmt = conn.createStatement();

 

四、执行增删改查。

 

主要代码：

1、获得连接对象

/**
	 * 
	 * @return：返回获得的连接对象
	 * @throws SQLException
	 * @throws ClassNotFoundException
	 */
	public static Connection getConn(String database, String user,
			String password) throws ClassNotFoundException
	{
		Class.forName("com.mysql.jdbc.Driver");
		Connection conn = null;
		try
		{
			conn = DriverManager.getConnection(url + database, user, password);
			System.out.println("Database changed");
		} catch (SQLException e)
		{
			System.out.println(e.getMessage());
		}
		return conn;
	}

2、执行查询语句返回查询结果

	public static ArrayList<String[]> queryDB(String sql)
			throws ClassNotFoundException
	{
		ArrayList<String[]> list = null;
		try
		{
			list = new ArrayList<String[]>();
			ResultSet result = statement.executeQuery(sql);
			ResultSetMetaData rsd = result.getMetaData();
			num = rsd.getColumnCount();
			String[] columnName = new String[num];
			for (int i = 1; i <= num; i++)
			{
				columnName[i - 1] = rsd.getColumnName(i);
				queryLen[i - 1] = Math.max(queryLen[i - 1],
						columnName[i - 1].length());
			}
			list.add(columnName);
			while (result.next())
			{
				int index = 0;
				String[] string = new String[num];
				for (int i = 1; i <= num; i++)
				{
					string[i - 1] = String.valueOf(result.getObject(i));
					queryLen[index] = Math.max(queryLen[index],
							string[i - 1].length());
					index++;
				}
				list.add(string);
			}
		} catch (SQLException e)
		{
			 System.out.println(e.getMessage());
		}
		return list;
	}

3、格式化输出

public static void main(String[] args) throws SQLException,
			ClassNotFoundException, IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		Connection conn = null;
		while (true)
		{
			System.out.print(">");
			String command = br.readLine();
			if (command.equals("mysql -u root -p"))
			{
				System.out.print("Enter password:");
				String password = br.readLine();
				System.out.print("mysql>");
				String database = br.readLine();
				if (database.split(" ")[0].equals("use"))
				{
					conn = getConn(database.split(" ")[1], "root", password);
					if (conn == null)
						continue;
				}
				break;
			}
		}
		statement = conn.createStatement();
		while (true)
		{
			System.out.print("\\nmysql>");
			String sql = br.readLine();
			sql = sql.replace(";", "");
			if (sql.trim().equals("quit"))
			{
				break;
			} else if (sql.trim().startsWith("select"))
			{
				ArrayList<String[]> list = queryDB(sql);
				for (int i = 0; i < list.size(); i++)
				{
					if (0 == i || 1 == i)
					{
						System.out.print("|");
						for (int j = 0; j < list.get(i).length; j++)
						{
							for (int a = 0; a < queryLen[j]; a++)
							{
								System.out.print("-");
							}
							System.out.print("|");
						}
						System.out.println();
					}
					for (int j = 0; j < list.get(i).length; j++)
					{
						System.out.print("|" + list.get(i)[j]);
						for (int k = list.get(i)[j].length(); k < queryLen[j]; k++)
						{
							System.out.print(" ");
						}
					}
					System.out.println("|");
					if (i == list.size() - 1)
					{
						System.out.print("|");
						for (int j = 0; j < list.get(i).length; j++)
						{
							for (int a = 0; a < queryLen[j]; a++)
							{
								System.out.print("-");
							}
							System.out.print("|");
						}
						System.out.println();
					}
				}
			} else
			{
				updateDB(sql);
			}
		}
	}

运行测试：