docs: add Oracle connector tut for lb4

docs/site/tutorials/connectors/Mongodb-tutorial.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-title: 'MongoDB connector tutorial'
+title: 'MongoDB Connector Tutorial'
 keywords:
   LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI, Connector, MongoDB,
   Tutorial

docs/site/tutorials/connectors/Mysql-tutorial.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-title: 'MySQL connector tutorial'
+title: 'MySQL Connector Tutorial'
 keywords:
   LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI, Connector, MySQL,
   Tutorial
@@ -260,7 +260,7 @@ details:
 export class User extends Entity {
   @property({
     type: 'number',
-    required: true,
+    required: true, // set this to false if the value is auto-generated by the db
     precision: 10,
     scale: 0,
     id: 1,

docs/site/tutorials/connectors/Oracle-tutorial.md

@@ -0,0 +1,319 @@
+---
+lang: en
+title: 'Oracle Connector Tutorial'
+keywords:
+  LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI, Connector, Oracle,
+  Tutorial
+sidebar: lb4_sidebar
+permalink: /doc/en/lb4/Connecting-to-Oracle.html
+---
+
+# Connecting to Oracle
+
+The following tutorial introduces how to set up Oracle as the data source of
+LoopBack 4 applications with
+[LoopBack Oracle connector](https://github.com/strongloop/loopback-connector-oracle).
+
+## Prerequisites
+
+Before starting this tutorial, make sure you have the following installed:
+
+- Node.js version 10 or higher
+- LoopBack 4 CLI; see
+  [Getting Started with LoopBack 4](../../Getting-started.md)
+
+## Tutorial - Oracle
+
+### 1. Create a new LoopBack 4 app
+
+Let's use the [LB4 CLI](../../Command-line-interface.md) `lb4 app` to create a
+LoopBack 4 application called `MyApp`:
+
+```bash
+$ lb4 app
+? Project name: my-app
+? Project description: Oracle connector tutorial
+? Project root directory: my-app
+? Application class name: MyAppApplication
+? Select features to enable in the project (Press <space> to select, <a> to togg
+le all, <i> to invert selection)
+❯◉ Enable eslint: add a linter with pre-configured lint rules
+ ◉ Enable prettier: install prettier to format code conforming to rules
+ ◉ Enable mocha: install mocha to run tests
+ ◉ Enable loopbackBuild: use @loopback/build helpers (e.g. lb-eslint)
+ ◉ Enable vscode: add VSCode config files
+ ◉ Enable docker: include Dockerfile and .dockerignore
+ ◉ Enable repositories: include repository imports and RepositoryMixin
+(Move up and down to reveal more choices)
+```
+
+### 2. Create models
+
+Let's create a simple model `User`. To keep the tutorial short, the prompts of
+`lb4 model` are skipped:
+
+{% include code-caption.html content="user.model.ts" %}
+
+```ts
+// imports
+@model()
+export class User extends Entity {
+  @property({
+    type: 'number',
+    id: true,
+    generated: true,
+  })
+  id: number;
+
+  @property({
+    type: 'string',
+  })
+  name?: string;
+
+  @property({
+    type: 'boolean',
+  })
+  hasAccount: boolean;
+
+  constructor(data?: Partial<User>) {
+    super(data);
+  }
+}
+```
+
+### 3. Create a data source
+
+LoopBack allows you to connect to your Oracle database via different methods:
+[Easy connect with host/port/database, TNS, and LDAP](https://loopback.io/doc/en/lb4/Oracle-connector.html#connector-properties).
+Let's create a DataSource `db` using the Oracle connector with Easy connect
+method by the prompts below:
+
+```bash
+$ lb4 datasource
+? Datasource name: db
+? Select the connector for db:
+  ...
+  PostgreSQL (supported by StrongLoop)
+❯ Oracle (supported by StrongLoop)
+  Microsoft SQL (supported by StrongLoop)
+  ...
+? Connection String tns (eg: DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=MY_HOST)(P
+ORT=MY_PORT))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=MY_DB))):
+? host: localhost
+? port: 1521
+? user: loopback
+? password: [hidden] // example password: pa55w0rd
+? database: xe
+
+Datasource Db was created in src/datasources/
+```
+
+Under `src/datasources/db.datasource.ts`, we can find the `DbDataSource` class
+and the config we just set:
+
+```ts
+const config = {
+  name: 'db',
+  connector: 'oracle',
+  tns: '',
+  host: 'localhost',
+  port: 1521,
+  user: 'loopback',
+  password: 'pa55w0rd',
+  database: 'xe',
+};
+```
+
+The DataSource would then connect to your back-end service(Oracle) with the
+config when the app starts.
+
+### 4. Create repositories
+
+A [Repository](../../Repository.md) is an artifact that ties the model and the
+datasource. We will need to create the repository for the `User` class to access
+the database. The steps of creating `UserRepository` by running `lb4 repository`
+are skipped here:
+
+{% include code-caption.html content="user.repository.ts" %}
+
+```ts
+// imports
+export class UserRepository extends DefaultCrudRepository<
+  User,
+  typeof User.prototype.id,
+  UserRelations
+> {
+  constructor(@inject('datasources.db') dataSource: DbDataSource) {
+    super(User, dataSource);
+  }
+}
+```
+
+### 5. Database migration
+
+LoopBack provides a convenient way to create schemas/tables for our models if we
+don't have corresponding schemas defined in the relational database. Once we
+created the above artifacts, run the following commands:
+
+**1.** Build the project:
+
+```bash
+$ npm run build
+```
+
+**2.** Migrate database schemas (alter existing tables):
+
+```bash
+$ npm run migrate
+```
+
+This would generate the corresponding Oracle table `USER` using the metadata
+from `User` model via auto-migrate if it does not exist. See
+[Database Migration](#database-migration) section below for information.
+
+If you check the database, you should able to see the table `USER`.
+
+```
+SQL> SELECT column_name,data_type,data_length FROM all_tab_columns
+     WHERE table_name='USER' AND owner='LOOPBACK';
+
+COLUMN_NAME    DATA_TYPE    DATA_LENGTH
+-----------------------------------------
+ID              NUMBER         22
+NAME           VARCHAR2       1024
+HASACCOUNT       CHAR          1
+```
+
+### 6. Create endpoints and view data using API Explorer
+
+Once we built a [controller](../../Controllers.md) with `lb4 controller` to
+handle requests:
+
+```bash
+$ lb4 controller
+? Controller class name: user
+Controller User will be created in src/controllers/user.controller.ts
+
+? What kind of controller would you like to generate? REST Controller with CRUD
+functions
+? What is the name of the model to use with this CRUD repository? User
+? What is the name of your CRUD repository? UserRepository
+? What is the name of ID property? id
+? What is the type of your ID? number
+? Is the id omitted when creating a new instance? Yes
+? What is the base HTTP path name of the CRUD operations? /users
+```
+
+Notice that the id is omitted in the request here because it is autogenerated.
+
+From the project root, start the app:
+
+```bash
+$ npm start
+```
+
+We can verify what we just created with API Explorer
+[http://localhost:3000/explorer/](http://localhost:3000/explorer/).
+
+## Database Migration
+
+As we showed in the previous steps,
+[Database migration](../../Database-migrations.md) helps you create relational
+database schemas based on definitions of your models. Here are some tips:
+
+- if you make further changes to models, make sure to run `npm run build` before
+  running the migrate script again
+- `npm run migrate` alters existing tables for you. If you'd like to drop any
+  existing schemas, you can do `npm run migrate -- --rebuild`. But notice that
+  all the data will be lost.
+
+Please check [Database migration](../../Database-migrations.md) for details.
+
+Besides the basic model metadata, you can also specify part of the database
+schema definition via the property definition, which would be mapped to the
+database. See
+[Data Mapping Properties](https://loopback.io/doc/en/lb4/MySQL-connector.html#data-mapping-properties).
+
+## Model Discovery
+
+While database migration allows you to migrate models to the DB, LoopBack also
+provides a command [`lb4 discover`](../../Discovering-models.md) to generate
+models based on schemas from the database. For example, we can try to discover
+the `USER` table we created previously:
+
+```bash
+$ npm run build
+$ lb4 discover
+? Select the connector to discover  db
+? Select the models which to discover  User
+? Select a convention to convert db column names(EXAMPLE_COLUMN) to model proper
+ty names: Camel case (exampleColumn) (Recommended)
+? Overwrite src/models/user.model.ts? overwrite
+    force src/models/user.model.ts
+   update src/models/index.ts
+
+Models User was created in src/models/
+```
+
+As we can see, the newly generated `User` model would contain database specific
+details:
+
+```ts
+// imports
+@model({
+  settings: {idInjection: false, oracle: {schema: 'LOOPBACK', table: 'USER'}},
+})
+export class User extends Entity {
+  @property({
+    type: 'number',
+    required: true, // set this to false if the value is auto-generated by the db
+    length: 22,
+    id: 1,
+    oracle: {
+      columnName: 'ID',
+      dataType: 'NUMBER',
+      dataLength: 22,
+      dataPrecision: null,
+      dataScale: null,
+      nullable: 'N',
+    },
+  })
+  id: number;
+
+  @property({
+    type: 'string',
+    required: true,
+    length: 1024,
+    oracle: {
+      columnName: 'NAME',
+      dataType: 'VARCHAR2',
+      dataLength: 1024,
+      dataPrecision: null,
+      dataScale: null,
+      nullable: 'N',
+    },
+  })
+  name: string;
+
+  @property({
+    type: 'boolean',
+    required: true,
+    length: 1,
+    oracle: {
+      columnName: 'HASACCOUNT',
+      dataType: 'CHAR',
+      dataLength: 1,
+      dataPrecision: null,
+      dataScale: null,
+      nullable: 'N',
+    },
+  })
+  hasaccount: boolean;
+  // ...
+}
+```
+
+The field `oracle.<property>` maps to the database definition of a table/column.
+This allows you to customize the table/column names and also specify some
+database related settings. See
+[Data Mapping Properties](https://loopback.io/doc/en/lb4/Model.html#data-mapping-properties).

docs/site/tutorials/connectors/Postgresql-tutorial.md

@@ -1,6 +1,6 @@
 ---
 lang: en
-title: 'PostgreSQL connector tutorial'
+title: 'PostgreSQL Connector Tutorial'
 keywords:
   LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI, Connector, PostgreSQL,
   Tutorial
@@ -259,7 +259,7 @@ details:
 export class User extends Entity {
   @property({
     type: 'number',
-    required: true,
+    required: true, // set this to false if the value is auto-generated by the db
     scale: 0,
     id: 1,
     postgresql: {