Flutter插件ecleus4dart的使用方法详解

一个灵活的数据库版本管理包概念

例如，参见./example/ecleus4dart_example.dart。

实际应用示例，参见PgEcleus4Dart。

完整示例Demo

以下是一个完整的示例代码，演示了如何使用ecleus4dart插件来管理数据库版本。该示例模拟了一个简单的数据库操作，并展示了如何逐步更新数据库版本。

import 'package:ecleus4dart/ecleus4dart.dart';

// 模拟数据库连接。DBMS类型对Ecleus无关紧要
class DummyDatabase implements EcleusDatabaseInterface {
  [@override](/user/override)
  void execute(String command) {
    print('Executing command $command');
  }

  [@override](/user/override)
  void insertVersionInfo(int version, int release) {
    print('>>> Insert version info');
    print('Insert into ecleus.control values ($version, $release);');
  }

  [@override](/user/override)
  EcleusVersionInfo? getDatabaseVersion() => null;
}

// 模拟在没有控制结构的环境中执行Ecleus的情况：一个“原始”数据库
class DummyControlDatabaseWithoutControlStructure extends EcleusVersionControl {
  DummyControlDatabaseWithoutControlStructure(EcleusDatabaseInterface database) : super(database);

  [@override](/user/override)
  void buildVersionStructure() {
    print('>>> Creating control structure');
    print('create schema ecleus;');
    print('create table ecleus.control (version int not null, release int not null, primary key(version, info));');
  }

  [@override](/user/override)
  EcleusVersionInfo? getDatabaseVersion() => database.getDatabaseVersion();

  [@override](/user/override)
  void lockDatabase() {
    print('** start transaction **');
    try {
      print('>>> Locking database');
      throw 'No structure found';
      print('lock table ecleus.control in access exclusive mode;');
    } catch (e) {
      print('$e');
    }
  }

  [@override](/user/override)
  void unlockDatabase() {
    print('>>> Unlocking database');
    print('** commiting transaction or rollbacking **');
  }
}

// 模拟一个已经处于版本0.0的数据库环境
class DummyControlV0R0 extends EcleusVersionControl {
  DummyControlV0R0(EcleusDatabaseInterface database) : super(database);

  [@override](/user/override)
  void buildVersionStructure() {
    print('>>> Creating control structure');
    print('create schema ecleus;');
    print('create table ecleus.control (version int not null, release int not null, primary key(version, info));');
  }

  [@override](/user/override)
  EcleusVersionInfo? getDatabaseVersion() => EcleusVersionInfo(0, 0);

  [@override](/user/override)
  void lockDatabase() {
    print('** start transaction **');
    try {
      print('>>> Locking database');
      print('lock table ecleus.control in access exclusive mode;');
    } catch (e) {
      print('$e');
    }
  }

  [@override](/user/override)
  void unlockDatabase() {
    print('>>> Unlocking database');
    print('** commiting transaction or rollbacking **');
  }
}

// 第一次数据库部署：v0.0
class DummyUpdaterV0R0 extends EcleusUpdater {
  final _version = EcleusVersionInfo(0, 0);

  DummyUpdaterV0R0(EcleusDatabaseInterface database) : super(database);

  [@override](/user/override)
  EcleusUpdater? getPriorUpdater() => null;

  [@override](/user/override)
  EcleusVersionInfo getVersionInfo() => _version;

  [@override](/user/override)
  void updateDatabase() {
    database.execute(
      'create table user ('
        'email varchar(20) not null primary key, '
        'password char(32) not null, '
        'creation_timestamp timestamp not null default current_timestamp'
      ');'
    );

    database.execute(
      'insert into user (email, password) values ("administrator@ecleus.com.br", "123456");'
    );
  }
}

// 第二次数据库部署：v0.1
class DummyUpdaterV0R1 extends EcleusUpdater {
  final _version = EcleusVersionInfo(0, 1);

  DummyUpdaterV0R1(EcleusDatabaseInterface database) : super(database);

  [@override](/user/override)
  EcleusUpdater? getPriorUpdater() => DummyUpdaterV0R0(database);

  [@override](/user/override)
  EcleusVersionInfo getVersionInfo() => _version;

  [@override](/user/override)
  void updateDatabase() {
    database.execute('alter table user add column active bool not null default true;');
  }
}

// 第三次数据库部署：v0.2
class DummyUpdaterV0R2 extends EcleusUpdater {
  final _version = EcleusVersionInfo(0, 2);

  DummyUpdaterV0R2(EcleusDatabaseInterface database) : super(database);

  [@override](/user/override)
  EcleusUpdater? getPriorUpdater() => DummyUpdaterV0R1(database);

  [@override](/user/override)
  EcleusVersionInfo getVersionInfo() => _version;

  [@override](/user/override)
  void updateDatabase() {
    database.execute('create table log(msg varchar(128) not null, timestamp timestamp not null default current_time;');
  }
}

// 在这种情况下，数据库控制结构需要创建。这模拟了一个场景
// 其中数据库没有任何表/模式，需要从头开始创建。
//
// 这将运行DummyUpdaterV0R0到DummyUpdaterV0R2
void runVirginEnvironment() {
  var database = DummyDatabase();
  var ecleus = Ecleus(DummyControlDatabaseWithoutControlStructure(database), DummyUpdaterV0R2(database));
  ecleus.run();
}

// 在这种情况下，数据库控制结构已经存在并且位于V0.0。因此，Ecleus
// 将识别当前数据库版本（0.0）并仅应用DummyUpdaterV0R1和DummyUpdateV0R2
void runAlreadyDeployedV0R0() {
  var database = DummyDatabase();
  var ecleus = Ecleus(DummyControlV0R0(database), DummyUpdaterV0R2(database));
  ecleus.run();
}

void main() {
  runVirginEnvironment();
  runAlreadyDeployedV0R0();
}