Table of Contents

Building Microservices with Spring Boot

Book: Hands on Microservices with Spring Boot and Spring Cloud

Configuring Application

Config Files

• For each MS
  • build.gradle or pom.xml for dependencies
  • application.properties or application.yml to configure server, DB, and deployment (host/port + docker profile)
  • Dockerfile to find what JAR to package into Docker image
• For landscape
  • settings.gradle to import individual dependency files and build all MSes
  • docker-compose.yml to list all MSes and deployment settings

Databases

• If you want your project to use a database, don’t install it locally.
• Instead, configure the project to use a Docker image for the database.

Error Handling

• Add this to config file to have Spring Boot include error details on failed HTTP responses
  • server.error.include-message=always

Building a v1.0 Backend

• Separate API/backend into layers:
  • Objects: POJOs
  • Controller / Protocol Layer: API-level code, endpoints/URIs.
  • Service / Service Layer: Business logic before accessing database
  • Repository / Persistence Layer: Code used to access/modify the database for transactions.
  • Integration Layer: Only for composite microservice. Used to link to the service layer of core/internal microservices, so that it can call them to complete requests.
• Each microservice is its own complete app. It has its own separate:
  • Config files
  • Database
  • Backend (all the components above)

Objects

• Entity objects mapped to the database.
  • Use @Entity and @Table to map to DB
  • @GeneratedValue, GenerationType = Identity to autogenerate unique table IDs on insertion
• API objects (optional) if you want to add extra service-specific fields to Entity objects.
• Add a field to track the version of each DB Entity
  • @Version, int
  • Keeps track of version of each entity in table. When a entity is updated, the version number is incremented.
  • If you try to save an object with an outdated version, the request will fail.
    • repository.save(updatedObj), but updatedObj.version < version of entity in DB.