Microservices are a software development style that has recently been developed to set up practices intended to increase the efficiency and speed of developing and managing software solutions so that they can be scaled easily. This set of practices is technology agnostic, which means that there is not one single programming language or technology to build microservices. In fact, you can build microservices with any programming language. It's more about applying a certain number of architectural patterns and principles to your program.

There are several different microservices design principles available. Different terms are likely to be used in different places. In this book, we will refer to the microservices design principles as follows:

• High cohesion among services: A microservice should have one single focus and the sole responsibility for that action. It should not change as a result of other related services. Services should be easily rewritable so that we can achieve scalability, reliability, and flexibility. It should handle a single business function and domain-specific functionality.
• Autonomous service: A service should independently handle its work without the help of any other services. It should not be tightly integrated with any other service; it should remain loosely coupled in nature. By autonomous, we mean that a microservice should not change because of the...

Let's start to think practically about microservice deployment. We are going to look at the latest container technologies and orchestrator tools that are dominating the microservice market. First, we will list the availability of tools and options and then we will look at an example to show you how things can be deployed in the microservice model.

Microservices can be deployed on the following platforms:

• Container platforms: These include technologies such as Docker, rkt, AWS ECS, and AWS EKS.
• Code as a function: We can deploy bare functions written in supported programming languages on AWS Lambda-like platforms. These platforms will run that configured code and store the result on an S3-like bucket or a supported database on a cloud vendor platform. Alternatively, the code might trigger a further configured action. It can be called through AWS...

In this section, we're going to look at some relevant examples using the latest technologies. This will give you an easy reference guide to consult when implementing your own deployment strategy.

In the following Kubernetes YAML configuration, we will define various Kubernetes keywords related to deployment. One important variable is container: image. Here, we are referring to an existing Docker container image that Kubernetes will use to create a container under pod deployment. This container image should already be customized to suit your requirements. The kubectl command will read this configuration...

The code bases of different companies often grow exponentially and increase in complexity. In a monolithic process, we have multiple independent development teams. These teams are not actually that independent at all; they simultaneously work on the same code bases and change the same sections of code. It is tough for new developers to contribute to the business, and the development process is slow. Because of this, we have seen a gradual shift toward microservices.

The following diagram shows the microservice container, the business logic image container, the data access layer container, and, in total, a working model of a microservice-based distributed model:

The Spring Framework is an enterprise Java framework that lets us write enterprise Java applications. Spring Boot is the way in which we can bootstrap, or quickly...

Jersey is an open source framework developed by Oracle. It is the official reference implementation of JAX-RS API, which is very similar to Apache CFX. On the server side, Jersey provides a servlet implementation that scans through the predefined classes we define to identified the restful resources. In the web.xml file, which is the deployment file for web applications, we can configure either the restful servlet or the jersey servlet.

Jersey provides the implementation of the client library, which is fully compliant with the JAX-RS API. It also provides several tools for security such as authorization or bean validation. Furthermore, it allows us to integrate testing for container deployments. The current version of Jersey is 2.27. You can learn more about Jersey by going to its official website at http://jersey.java.net.

For Spring integration...

This is used for the purpose of data communication across web APIs. The REST API works pretty much in the same way as a website: you make a call from the client to the server and get a HTTP response back. REST uses HTTP methods to interact with the client and the server. REST allows a variety of data formats such as JSON or XML. It is generally faster and uses less bandwidth. It is also easy to integrate with other applications.

Commonly used HTTP methods in REST APIs include the following:

• GET: This is used for retrieving a data through APIs. It is a read-only method. It is safe to use duplicate GET methods.
• PUT: This is used to change or update a data using APIs. It is a write method, and we can use duplicate PUT methods.
• POST: This is used to create or insert data. It is a write method.
• DELETE: This is used to remove a particular piece...