When we design an api for our software components, then a couple of confusing terms are just at the front of us. Let's first cope with the conceptual confusion about the terms in this question. What is an API ? API is the acronym for the Application Programming Interface. It is a group of methods  that is exported by a provider software components/modules  and is supplied to its consumer software components/modules and the messages(XML, JSON, etc.) of these method calls are transported accross the client and server sides. Web API In the context of web, an API is refered as a group of methods that is the web protocol HTTP is used for the communication  by transferring the messages,  generally of the form; XML or JSON format. Okay then, if a consumer is using an API; then it is communicating via a service provider with dependency to a contract defined by the API over some communication protocols such as HTTP and exchanging the messages in a structured forma

In this tutorial, we will examine the usage of the in-memory database h2 in a Spring Boot application. H2 is an in-memory database, we can use it for simple case-studies and quick show cases. Maven Dependencies This can be easily generated with Spring Starter. The dependency for Spring Data and JPA: <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> The dependency for H2: <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <scope>runtime</scope> </dependency> H2 Configuration Now, we can configure the database settings in application.properties file: spring.datasource.url=jdbc:h2:mem:testdb spring.datasource.driverClassName=org.h2.Driver spring.jpa.database-platform=org.hibernate.dialect.H2Dialect spring.datasource.username=sa spring.datasource.password=password spring.h2.console.enabled