Java, Spring Boot, Microservices, Cloud and DevOps Tutorials
I have been working with Spring and SpringBoot for many years and I needed to create lot of Spring(Boot) applications for various reasons like blog posts, sample apps, book sample code and for my personal learning as well. So, I needed some tool/mechanism to quickly create Spring(Boot) application with most commonly used configuration.
Postman is the most popular tool for testing REST APIs. I guess most of the developers are familiar with how to use Postman to send various types (GET, POST, PUT, DELETE, etc) of HTTP requests with various types of payloads (form data, JSON etc).
SpringBoot is the most popular tech stack for building Java based REST APIs. In this tutorial we will learn how to write tests for SpringBoot applications.
In the previous post Kafka Tutorial - Java Producer and Consumer we have learned how to implement a Producer and Consumer for a Kafka topic using plain Java Client API.
In this post we are going to look at how to use Spring for Kafka which provides high level abstraction over Kafka Java Client API to make it easier to work with Kafka.
Kafka, depending on how you use it, can be seen as a Message Broker, Event Store or a Streaming Platform etc. Kafka became a preferred technology for many of the modern applications because of various reasons like:
I have been working with SpringBoot for many years and over the time I worked with many SpringBoot based codebases. There are few common mistakes that I observe in the projects that use SpringBoot. So, I thought of writing down few good practices that can be followed while using SpringBoot.
One of the challenges in microservices architecture is the ability to debug issues. A simple user action might trigger a chain of downstream microservice calls. It would be tedious to trace the logs related to a particular user action across microservices. In addition to that, we might want to track down why a certain microservice call is taking so much time. We can use Spring Cloud Sleuth to handle these kinds of issues.
In microservices architecture, there could be a number of API services and few UI components that are talking to APIs. As of now, many microservices based application still use monolithic front-ends where the entire UI is built as a single module. You may choose to go with micro-frontends where the UI is also decomposed into multiple microservice talking to APIs to get the relevant data. Instead of letting UI know about all our microservices details we can provide a unified proxy interface that will delegate the calls to various microservices based on URL pattern. In this post, we will learn how to create API Gateway using Spring Cloud Zuul Proxy.
In the microservices world, to fulfill a client request one microservice may need to talk to other microservices. We should minimize this kind of direct dependencies on other microservices but in some cases it is unavoidable. If a microservice is down or not functioning properly then the issue may cascade up to the upstream services. Netflix created Hystrix library implementing Circuit Breaker pattern to address these kinds of issues.
In the microservices world, Service Registry and Discovery plays an important role because we most likely run multiple instances of services and we need a mechanism to call other services without hardcoding their hostnames or port numbers. In addition to that, in Cloud environments service instances may come up and go down anytime. So we need some automatic service registration and discovery mechanism. Spring Cloud provides Service Registry and Discovery features, as usual, with multiple options. We can use Netflix Eureka or Consul for Service Registry and Discovery.