API First tutorial

This project contains an example of how to generate the API interfaces from an OpenApi specification using the spring generator.

API First with Spring boot:

1. How Virtualan works?

Virtualan would be built with spring boot framework that would convert API service as Virtualized service in matter of adding couple of annotations. Simply as Virtualized service which currently supports spring-boot based Rest service(API) with Spring-RestController or CXF-Jaxrs as Virtualized service with @VirtualService and @ApiVirtual annotations.

Add the "virtualan-plugin" dependency

• Add "virtualan-plugin" dependency in the  pom.xml  
	<dependency>
		<groupId>io.virtualan</groupId>
		<artifactId>virtualan-plugin</artifactId>
		<version>${virtualan.version}</version>
	</dependency>

Add @VirtualService and @ApiVirtual annotations

• @VirtualService - Annotation should be added in the class level
• @ApiVirtual - Annotation should be added in the method level that the API would you like to Virtualize.

Service Data base setup (Optional)

• Add the entries in the **application.properties** of the database to be used to store the test data (Example: hsql with in memory DB).
	virtualan.datasource.driver-class-name=<org.hsqldb.jdbcDriver>
	virtualan.datasource.jdbc-url=<jdbc:hsqldb:mem:dataSource>
	virtualan.datasource.username=<sa>
	virtualan.datasource.password=<>

2. Api First

The API first (or design first) approach focuses on the API’s design before starting to write the code. The resulting code will be the output of our design, which means that the first thing we need to do is to write the API specification (OpenApi). That is, we will design how our API will look like and how it should work before starting to write any line of the code.

Open API generator

Generate the open api spring boot rest application using the following plugin for the Open API contract

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>5.0.0</version>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/spec/openapi-spec.yml</inputSpec>
                <generatorName>spring</generatorName>
                <apiPackage>${project-base-package}</apiPackage>
                <modelPackage>${project-base-package}.model</modelPackage>
                <invokerPackage>${project-base-package}.swagger</invokerPackage>
                <skipValidateSpec>false</skipValidateSpec>
                <strictSpec>true</strictSpec>
                <ignoreFileOverride>${project.basedir}/.openapi-generator-ignore</ignoreFileOverride>
                <generateApiDocumentation>false</generateApiDocumentation>
                <generateModelDocumentation>true</generateModelDocumentation>
                <configOptions>
                    <configPackage>${project-base-package}.swagger</configPackage>
                </configOptions>
            </configuration>
        </execution>
    </executions>
</plugin>

Add Depandency to virtualize

Add the following depandency for service virtulization

<!-- START Virtual Service API support -->
<dependency>
    <groupId>io.virtualan</groupId>
    <artifactId>virtualan-plugin</artifactId>
    <version>2.2.1</version>
</dependency>

<!-- HyperSQL DB -->
<dependency>
    <groupId>org.hsqldb</groupId>
    <artifactId>hsqldb</artifactId>
    <version>2.5.0</version>
</dependency>
<!-- END Virtual Service API support -->

Virtualize Generated API

Add <virtualService>true</virtualService> under configOptions and this will generate code and create service virtulization or Mocking

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>5.0.0</version>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/spec/openapi-spec.yml</inputSpec>
                <generatorName>spring</generatorName>
                <apiPackage>${project-base-package}</apiPackage>
                <modelPackage>${project-base-package}.model</modelPackage>
                <invokerPackage>${project-base-package}.swagger</invokerPackage>
                <skipValidateSpec>false</skipValidateSpec>
                <strictSpec>true</strictSpec>
                <importMappings>Problem=org.zalando.problem.Problem</importMappings>
                <ignoreFileOverride>${project.basedir}/.openapi-generator-ignore</ignoreFileOverride>
                <generateApiDocumentation>false</generateApiDocumentation>
                <generateModelDocumentation>true</generateModelDocumentation>
                <configOptions>
                    <configPackage>${project-base-package}.swagger</configPackage>
                    <!-----START: FOLLOWING TAG converts and generate OPEN API AS MOCK SERVICE  --->
                    <virtualService>true</virtualService>
                    <!-----END  --->
                </configOptions>
            </configuration>
        </execution>
    </executions>
</plugin>

How it could be useful

In the Agile world, We need to develop (Micro)services & Test the services in parallel. How can tester or development team can develop or test parallel to all the APIs before the real Microservices would be developed? Here Virtualized service comes into the picture.

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