使用Java代码实现MySQ通过表添加tenant_id列来标识不同租户

实现MySQL多租户数据隔离的另一种常见方法是通过在表中添加一个`tenant_id`列来标识不同的租户。下面是使用Java代码实现该方法的步骤：

1. 创建一个Java类来管理数据库连接和操作。这个类应该包含以下方法：

public class DatabaseManager {
 
  private static final String DATABASE_HOST = "localhost";
  private static final String DATABASE_USERNAME = "root";
  private static final String DATABASE_PASSWORD = "password";
  private static final String DATABASE_NAME = "my_database";
  private static final String DATABASE_DRIVER = "com.mysql.jdbc.Driver";
 
  private Connection connection;
 
  public DatabaseManager() throws SQLException, ClassNotFoundException {
    Class.forName(DATABASE_DRIVER);
    this.connection = DriverManager.getConnection("jdbc:mysql://" + DATABASE_HOST + "/" + DATABASE_NAME, DATABASE_USERNAME, DATABASE_PASSWORD);
  }
 
  public void executeQuery(String query) throws SQLException {
    Statement statement = connection.createStatement();
    statement.executeQuery(query);
    statement.close();
  }
 
  public void executeUpdate(String query) throws SQLException {
    Statement statement = connection.createStatement();
    statement.executeUpdate(query);
    statement.close();
  }
 
  public void closeConnection() throws SQLException {
    this.connection.close();
  }
 
}

2. 创建一个Java类来管理租户列表。这个类应该包含以下方法：

public class TenantManager {
 
  private Map<String, DatabaseManager> tenantDatabaseManagerMap = new HashMap<>();
 
  public void addTenant(String tenantId) throws SQLException, ClassNotFoundException {
    if (!tenantDatabaseManagerMap.containsKey(tenantId)) {
      DatabaseManager databaseManager = new DatabaseManager();
      databaseManager.executeUpdate("CREATE TABLE IF NOT EXISTS table_name (id INT PRIMARY KEY, column1 VARCHAR(255), column2 VARCHAR(255), tenant_id VARCHAR(36))");
      tenantDatabaseManagerMap.put(tenantId, databaseManager);
    }
  }
 
  public DatabaseManager getDatabaseManager(String tenantId) {
    return tenantDatabaseManagerMap.get(tenantId);
  }
 
  public void closeAllConnections() throws SQLException {
    for (DatabaseManager databaseManager : tenantDatabaseManagerMap.values()) {
      databaseManager.closeConnection();
    }
    tenantDatabaseManagerMap.clear();
  }
 
}

3. 在每次请求到达时，从请求中获取租户ID，并使用TenantManager获取对应的DatabaseManager对象。然后使用该对象执行数据库操作。例如：

public class RequestHandler {
 
  private static final String TENANT_HEADER = "Tenant-Id";
 
  private TenantManager tenantManager;
 
  public RequestHandler() {
    tenantManager = new TenantManager();
  }
 
  public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException, SQLException, ClassNotFoundException {
    String tenantId = request.getHeader(TENANT_HEADER);
    if (tenantId == null) {
      response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
      response.getWriter().println("Tenant Id is required.");
      return;
    }
 
    DatabaseManager databaseManager = tenantManager.getDatabaseManager(tenantId);
    if (databaseManager == null) {
      tenantManager.addTenant(tenantId);
      databaseManager = tenantManager.getDatabaseManager(tenantId);
    }
 
    String insertQuery = "INSERT INTO table_name (id, column1, column2, tenant_id) VALUES (1, 'value1', 'value2', '" + tenantId + "')";
    databaseManager.executeUpdate(insertQuery);
 
    String selectQuery = "SELECT * FROM table_name WHERE tenant_id = '" + tenantId + "'";
    ResultSet resultSet = databaseManager.executeQuery(selectQuery);
    while (resultSet.next()) {
      int id = resultSet.getInt("id");
      String column1 = resultSet.getString("column1");
      String column2 = resultSet.getString("column2");
      // process results
    }
    resultSet.close();
  }
 
  public void destroy() throws SQLException {
    tenantManager.closeAllConnections();
  }
 
}

以上就是使用Java代码实现MySQL通过表添加`tenant_id`列来标识不同租户的方法。