pip_services4_persistence

Description:

pip services4 persistence

Persistence components for Dart #
This module is a part of the Pip.Services polyglot microservices toolkit. It contains generic interfaces for data access components as well as abstract implementations for in-memory and file persistence.
The persistence components come in two kinds. The first kind is a basic persistence that can work with any object types and provides only minimal set of operations.
The second kind is so called "identifieable" persistence with works with "identifable" data objects, i.e. objects that have unique ID field. The identifiable persistence provides a full set or CRUD operations that covers most common cases.
The module contains the following packages:

Read - generic data reading interfaces.
Write - generic data writing interfaces.
Persistence - in-memory and file persistence components, as well as JSON persister class.

Quick links:


Memory persistence


API Reference


Change Log


Get Help


Contribute


Warning! For the library to work correctly, the stored type must have a default costructor without parameters, as well as methods for converting from/to JSON.


Use #
Add this to your package's pubspec.yaml file:
dependencies:
pip_services4_persistence: version
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Now you can install package from the command line:
pub get
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For example, you need to implement persistence for a data object defined as following.
import 'package:pip_services4_data/src/data/IIdentifiable.dart';

class MyObject implements IIdentifiable<String> {
@override
String? id;
String key;
String value;

Dummy({String? id, String key, String value})
: id = id,
key = key,
content = content;

void fromJson(Map<String, dynamic> json) {
id = json['id'];
key = json['key'];
content = json['content'];
}
}

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Our persistence component shall implement the following interface with a basic set of CRUD operations.
abstract class IMyPersistence {
void getPageByFilter(IContext? context, FilterParams filter, PagingParams paging);

getOneById(IContext? context, String id);

getOneByKey(IContext? context, String key;

create(IContext? context, MyObject item);

update(IContext? context, MyObject item);

deleteById(IContext? context, String id);
}
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To implement in-memory persistence component you shall inherit IdentifiableMemoryPersistence.
Most CRUD operations will come from the base class. You only need to override getPageByFilter method with a custom filter function.
And implement a getOneByKey custom persistence method that doesn't exist in the base class.
import 'package:pip_services4_persistence/src/persistence/IdentifiableMemoryPersistence.dart';
import 'package:pip_services4_data/src/query/FilterParams.dart';
import 'package:pip_services4_data/src/query/PagingParams.dart';

class MyMemoryPersistence extends IdentifiableMemoryPersistence {
MyMemoryPersistence(): super() {}

composeFilter(FilterParams filter) {
filter = filter != null ? filter : FilterParams();

String id = filter.getAsNullableString("id");
String tempIds = filter.getAsNullableString("ids");
List<String> ids = tempIds != null ? tempIds.split(",") : null;
String key = filter.getAsNullableString("key");

return (item) {
if (id != null && item.id != id)
return false;
if (ids != null && ids.indexOf(item.id) < 0)
return false;
if (key != null && item.key != key)
return false;
return true;
};
}

Future<DataPage<MyData>> getPageByFilter(IContext? context, FilterParams filter, PagingParams paging){
return super.getPageByFilterEx(context, composeFilter(filter), paging, null);
}

Future<String> getOneByKey(IContext? context, String key) {

final item =
this._items.firstWhere((item) =>
item.name == item.key == key,
orElse: () {
return null;
});

if (item != null) {
this._logger.trace(context, "Found object by key=%s", key);
} else {
this._logger.trace(context, "Cannot find by key=%s", key);
}
}
}
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It is easy to create file persistence by adding a persister object to the implemented in-memory persistence component.
import 'package:pip_services4_data/src/query/ConfigParams.dart';
import 'package:pip_services4_persistence/src/persistence/JsonFilePersister.dart';


class MyFilePersistence extends MyMemoryPersistence {
JsonFilePersister<MyObject> _persister;

MyFilePersistence([String path]):super(){
this._persister = new JsonFilePersister<MyObject>(path);
this._loader = this._persister;
this._saver = this._persister;
}

configure(ConfigParams config) {
super.configure(config);
this._persister.configure(config);
}
}
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Develop #
For development you shall install the following prerequisites:

Dart SDK 3
Visual Studio Code or another IDE of your choice
Docker

Install dependencies:
pub get
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Run automated tests:
pub run test
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Generate API documentation:
./docgen.ps1
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Before committing changes run dockerized build and test as:
./build.ps1
./test.ps1
./clear.ps1
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Contacts #
The Dart version of Pip.Services is created and maintained by:

Sergey Seroukhov
Levichev Dmitry

The documentation is written by:

Levichev Dmitry