todos-mysql

Todo(s) MySQL

Howdy and welcome...data, data and more data, the world is full of data. Inevitably you'll need to implement Microservices to connect with Databases. This repository contains a sample implemented in Kotlin using Spring Boot and Spring Data libraries.

Primary dependencies

• Spring Boot Starter Web (Embedded Tomcat)
• Spring Boot Actuators (actuator endpoints)
• Spring Data JPA (easy database access)
• Spring Data Rest (generated Rest API for data model)
• Flyway (Database schema migration)

Kotlin

Spring 5 added support for a 3rd language in the Framework. Developers can now implement Microservices in Java, Groovy and Kotlin. Kotlin is slowly starting to show up in development communities given most like the simplified syntax.

Kotlin is a statically typed open source language originated by JetBrains and now officially supported by Spring. This sample leverages Kotlin to do what Java can do but with less code.

Flyway - Database Migrations

This sample uses Flyway to handle database schema versioning. Using Flyway from Spring Boot starts with declaring a dependency on org.flywaydb:flyway-core in pom.xml. Spring Boot handles Auto-Configuration of Flyway on start-up when org.flyway:flyway-core is on the classpath.

Todo(s) MySQL uses a default Spring Boot/Flyway setup and overrides spring.flyway.locations for different profiles. The default profile application.yml sets the location for H2 schema while the cloud profile sets the schema location for MySQL as MySQL for PCF is assumed to be used with this sample.

> tree ./src/main/resources
|____application-cloud.yml
|____application.yml
|____db
| |____migration
| | |____h2
| | | |____V1.0.0__create_todos_table.sql
| | |____mysql
| | | |____V1.0.0__create_todos_table.sql

If for some reason you need to disable schema migration just override spring.flyway.enabled=false, by default Spring Boot will run Flyway.migrate() on startup which will run new migrations.

Todo(s) Data JPA

One of the most underrated features of Spring is the Spring Data family. Connecting Microservices to databases and stores is one of the cornerstones of the framework. Giving developers a similar framework components to access data in a low touch manner.

Our model is the Todo and since we're using Flyway we're controlling the schema creation through migrations in src/main/resources/db/migrations. We could allow JPA to create the schema but we're choosing not too as most enterprise shops favor this level of separation. This finer grained control comes with more responsibility on the developer. We need to ensure our Object matches the schema, so as a safe guard we enable spring.jpa.hibernate.ddl-auto=validate which will halt-and-catch-fire should those two be outta wack.

Todo(s) Data Rest API

Todo(s) MySQL sample uses spring-boot-starter-data-rest to blanked our data model in a REST API, one that supports paging and sorting (whoop-whoop).

Spring Data Rest will use the Repository and Entity to generate a HAL based api. Since this sample has a @RestController wired to the root / context down we'll need to provide another basePath for the generated Spring Data Rest API. We do that by slipping the basePath under the existing Spring Boot Actuator /actuator/* path.

Spring Data Rest API endpoint

# application.yml
spring:
  data:
    rest:
      base-path: '/actuator/data' # spring-data-rest generated API here

Relevant Spring Data objects

@Entity
@Table(name="todos")
class Todo {
    @Id
    var id: String? = null
    var title: String? = null
    var complete: Boolean = false
    fun complete() {
        this.complete = true
    }
    fun incomplete() {
        this.complete = false
    }
}
@Repository("todosRepo")
interface TodosRepo : PagingAndSortingRepository<Todo, String>

Build

git clone https://github.com/Pivotal-Field-Engineering/todos-apps.git
cd todos-apps
# to build only the todos-mysql module
./mvnw -pl todos-mysql clean package

Run on PCF

Configure your manifest.yml to meet your needs, it's simple enough to create a MySQL Service Instance and bind to it on push like so...

Create the on-demand MySQL Service Instance.

cf create-service p.mysql db-small todos-database

Configure your manifest.yml, declaring a binding to the MySQL Service Instance.

---
applications:
- name: todos-mysql
  memory: 1G
  path: target/todos-mysql-1.0.0.SNAP.jar
  services:
  - todos-database
  env:
    TODOS_API_LIMIT: 1024

cd todos-apps/todos-mysql
cf push -f manifest.yml # aweeee yeah

Verify

http todos-mysql.apps.retro.io/
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
X-Vcap-Request-Id: 638993f6-e2d9-40ec-5ab3-286d0ff36d4a

[]

Check Actuator Info

http todos-mysql.apps.retro.io/actuator/info
HTTP/1.1 200 OK
Content-Type: application/vnd.spring-boot.actuator.v2+json;charset=UTF-8
X-Vcap-Request-Id: 200207f3-96ea-4d81-5b1c-938b6b56483b
{
    "build": {
        "artifact": "todos-mysql",
        "group": "io.todos",
        "name": "todos-mysql",
        "time": "2019-07-01T17:59:43.781Z",
        "version": "1.0.0.SNAP"
    }
}

Check Spring Data Rest API

http todos-mysql.apps.retro.io/actuator/data/todos/
HTTP/1.1 200 OK
Content-Length: 399
Content-Type: application/hal+json;charset=UTF-8
X-Vcap-Request-Id: abe90cc3-b5e6-4efc-47b6-2eeb08cc98ee
{
    "_embedded": {
        "todos": []
    },
    "_links": {
        "profile": {
            "href": "http://todos-mysql.apps.retro.io/actuator/data/profile/todos"
        },
        "self": {
            "href": "http://todos-mysql.apps.retro.io/actuator/data/todos{?page,size,sort}",
            "templated": true
        }
    },
    "page": {
        "number": 0,
        "size": 20,
        "totalElements": 0,
        "totalPages": 0
    }
}

Next Steps

• Configure as a backend for the todos-webui
• Load data into MySQL via the Spring Data API and Application API
• Fetch data from MySQL via the Spring Data API and Application API
• Switch to cloud branch, build and push as part of a Spring Cloud deployment