package ch03.section07;

import java.sql.*;

public class SQLTransaction {

  public Connection conn = null;
  public Statement stmt = null;
  ResultSet set = null;
  // 構造方法初始化數據庫連接，并將AutoCommit設定為False
  public SQLTransaction(Connection con) throws SQLException {
    this.conn = con;
    conn.setAutoCommit(false);
    this.stmt = con.createStatement();
  }

  public void executeUpdate(String sql) throws SQLException {
    //如果更新操作失敗，回滾到事務起點并拋出異常
    try {
      stmt.executeUpdate(sql);
    }
    catch (SQLException e) {
      rollbackTransaction();
      throw e;
    }
  }

  public ResultSet executeQuery(String sql) throws SQLException {
    // 獲得結果集。
    try {
      set = stmt.executeQuery(sql);
    }
    catch (SQLException e) {
      throw e;
    }
    finally {
      return set;
    }
  }

  public void commitTransaction() throws SQLException {
    // 事務結束，提交更新
    try {
      conn.commit();
      // 如果發生異常，回滾到事務起點
    }
    catch (Exception e) {
      rollbackTransaction();
      throw new SQLException("無法提交當前事務");
    }
  }

  public void rollbackTransaction() throws SQLException {
    // 回滾到事務起點
    try {
      conn.rollback();
      conn.setAutoCommit(true);
      // 如果在回滾過程中發生異常，忽略該異常
    }
    catch (SQLException e) {
      throw new SQLException(e.getMessage());
    }
  }

  public void close() throws SQLException {
    // 關閉連接
    try {
      if (set != null) {
        set.close();
      }
      if (stmt != null) {
        stmt.close();
      }
      if (conn != null) {
        conn.close();
      }
    }
    catch (SQLException e) {
      throw new SQLException(e.getMessage());
    }
  }

}