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herbs2knex

herbs2knex creates repositories to retrieve and store Entities using Knex.

Installing

   npm install @herbsjs/herbs2knex

Using

connection.js - Knex initialization:

const knex = require('knex')
const config = require('./config')
module.exports = knex(config)

itemRepository.js:

const { Repository } = require('@herbsjs/herbs2knex')
const connection = require('connection')
const { Item } = require('../domain/entities/item')

class ItemRepository extends Repository {
constructor() {
super({
entity: Item,
table: 'aTable',
ids: ['id'],
knex: connection
})
}

excludedItemFromLastWeek() {
...
}
}

someUsecase.js:

const repo = new ItemRepository()
const ret = await repo.findByID(1)

What is a Repository?

A repository, by definition, is part of the layer to retrieve and store entities abstracting the underlying implementation. By using repositories, details of these implementation such as relational database, document-oriented databases, etc., should not leak to the domain code. In other words, no raw SQL queries on your use case or entity files.

Herbs2knex Repository

In order to boost productivity, Herbs2knex provides ways to dynamically generate, on the fly (no code generation), a repository class based on your Entities and other metadata.

These metadata are necessary to close the gap between OOP concepts and paradigms and those of relational databases. For example, it is necessary to specify primary keys and foreign keys as these information do not exist in the description of your domain.

Following Herbs architecture principals, it is not the intention of this lib to create yet another ORM or query builder but to create a bridge between your domain and an existing one (Knex).

Why Knex?

Herbs2knex is just one of many bridges possible between Herbs and other packages.

The advantage of using Knex is that is a simple and flexible SQL query builder. It also supports Postgres, MSSQL, MySQL, MariaDB, SQLite3, Oracle and Amazon Redshift. Therefore, you can build your system using these databases out of the box.

Repository setup

const { Repository } = require('@herbsjs/herbs2knex')
const connection = require('connection') // Knex initialize instance
const { ProductItem } = require('../domain/entities/productItem')

class YourRepository extends Repository {
constructor() {
super({
entity: ProductItem,
schema: 'main',
table: 'product_items',
ids: ['id'],
foreignKeys: [{ customerId: String }],
knex: connection
})
}
}
  • entity - The Entity to be used as reference

    entity: ProductItem
  • schema - The schema to be used

    schema: 'production'
  • table - The name of the table in database

    table: 'product_items'
  • ids - Primary keys

    Format: ['fieldName', 'fieldName', ...]

    There must be corresponding fields in the entity.

    ids: ['id']  // productItem.id

    or for composite primary key:

    ids: [`customerId`, `productId`]  // productItem.customerId , productItem.productId
  • foreignKeys (optional) - Foreign keys for the database table

    Usually, there is no corresponding fields declared in the entity for foreign keys. That is the reason it is necessary to inform the name and the type of the fields.

    Format: [{ fieldName: Type }, { fieldName: Type }, ...]

    foreignKeys: [{ customerId: String }]

    The field names will te converted to a database names using conventions. Ex: customer_id

  • knex - Knex initialize instance

    Check Knex documentation

Retrieving and Persisting Data

findByID

Find entities by IDs

Format: .findByID(id) where id is a value or an array.

Return: Entity array

const repo = new ItemRepository(injection)
const ret = await repo.findByID(10)

findBy

Find entities by any Entity field.

Format: .findBy(where) where where is a object containing {fieldName1: value1, fieldName2: value2, ...}

Return: Entity array

const repo = new ItemRepository(injection)
const ret = await repo.findBy({ name: ["Anne"] })

insert

Insert an Entity into a table.

Format: .insert(entity) where entity is a Entity instance with values to be persisted.

Return: The inserted entity with the values from database.

const repo = new ItemRepository(injection)
const ret = await repo.insert(aNewEntity)

update

Update an Entity.

Format: .update(entity) where entity is an Entity instance with values to be persisted.

Return: The updated entity with the values from database.

const repo = new ItemRepository(injection)
const ret = await repo.update(aModifiedEntity)

delete

Delete an Entity.

Format: .delete(entity) where entity is an Entity instance to be deleted.

Return: true for success or false for error

const repo = new ItemRepository(injection)
const ret = await repo.delete(entity)

Conventions - Defaul implementation

Fields

Code: Camel Case - ex: productName

Database: Snake Case - ex: product_name

Object-Oriented versus Relational models - Relationships

An entity can define a reference for others entities but will not (and should not) define a foreign key. For instance:

+------------------+         +------------------+         +------------------+
| Orders | | OrderItems | | Products |
+------------------+ +------------------+ +------------------+
| id: int |----\ | id: int | --| id: int |
| customer_id: int | ----| order_id: int | ----/ | name: string |
+------------------+ | product_id: int |-/ +------------------+
+------------------+
const Product = entity('Product', {
id: field(Number),
name: field(String),
...
})

const OrderItem = entity('Order Items', {
id: field(Number),
product: field(Product), // optional
...
})

const Order = entity('Order', {
id: field(Number),
item: field([OrderItem]), // optional
...
})

More about: https://en.wikipedia.org/wiki/Object%E2%80%93relational_impedance_mismatch

TODO

  • Allow only scalar types for queries (don't allow entity / object types)
  • Allow to ommit schema's name

Features:

  • Be able to change the conventions (injection)
  • Exclude / ignore fields on a sql statement
  • Awareness of created/updated at/by fields
  • Plug-and-play knex
  • Easy access knex structure

Retrieving and Persist:

  • insert
    • batchs
  • update
    • batchs
  • delete
  • persist (upsert)
  • find (ID)
    • deal with entities / tables with multiples IDs
  • find by (any field)
    • deal with entities / tables with multiples IDs
    • order by
  • find All
    • order by
  • find with pages
  • first
  • last

Tests:

  • Pure JS
  • Postgress
  • Sql Server