GraphQL backend service with Kotlin and Spring Boot

In this blog I will show how to create a very basic GraphQL backend service using Kotlin, Spring and the graphql-kotlin library.

This example is based on the following documentation: https://expediagroup.github.io/graphql-kotlin/docs/spring-server/spring-overview

Mutual SSL authentication

In deze blog laat ik zien wat de stappen zijn om certificaten te maken voor server en client applicaties.

Voor testen kun je de key- en trust stores maken zonder CA. Op productie zal er altijd een CA tussen zitten. Beide manieren worden hieronder besproken.

Een demo project met een server en client die ssl gebruiken (ook als authenticatie) is hier te vinden:

https://github.com/robbertvdzon/clientcertificateexample

Going springless: no more magic!

Working with Spring Boot (but also working with JEE/Jakarta EE) can be a joyful experience. Within minutes you can create a  new RESTfull webservice  to which you can quickly and easily add circuit breakers, distributed tracing, security, database access, accessing other microservices, fallbacks, retries, service discovery, configuration management, many other things and of course you can use the great Spring DI framework.

Spring tips (1)

[Index of Spring blogs]

This blog contains a set of small Spring tips.

List of Spring Boot Starter Dependencies

[Index of Spring blogs]

Core:

• Dev Tools
  feat: Reload application on class changes, debug and upload code to remote applications
  see: https://www.baeldung.com/spring-boot-devtools
  
• Security
  https://spring.io/guides/gs/securing-web/
  https://spring.io/guides/tutorials/spring-boot-oauth2/
  https://spring.io/guides/gs/authenticating-ldap/
  https://docs.spring.io/spring-boot/docs/2.1.0.RELEASE/reference/htmlsingle/#boot-features-security
  
• Lombok
• Configuration processor
  Using @ConfigurationProperties
  see: https://www.baeldung.com/configuration-properties-in-spring-boot
  
• Session
  managing user sessions
  see: https://www.baeldung.com/spring-session
• Cache
  Using @Cacheable
  see: https://www.baeldung.com/spring-cache-tutorial
• Validation
  see: https://spring.io/guides/gs/validating-form-input/
• Retry
  Using @Retryable
  see: https://www.baeldung.com/spring-retry
• Aspects
  Create your own aspects using Spring AOP and AspectJ

Index of Spring blogs

Spring tips (1)

List of Spring Boot Starter Dependencies

Testing the Spring MVC layer

Spring WebFlux samples and links

Spring WebMVC samples and links

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Other links:

List of all spring properties:
https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html

Testing the Spring MVC layer

[Index of Spring blogs]

Use “spring-boot-starter-test” to add all dependencies:

    org.springframework.boot
    spring-boot-starter-test
    test

You can annotate the test class with :

• (nothing)
• @SpringBootTest(webEnvironment = MOCK / RANDOM_PORT / DEFINED_PORT)
• @AutoConfigureMockMvc
• @WebMvcTest

To make rest call’s to the controllers, you can use one of the following:

• RestTemplate
• TestRestTemplate
• RestAssuredMockMvc
• MockMvc
• WebTestClient (only when using webflux)

@SpringBootTest will load your complete Spring application, but without the Servlet container when specifying (webEnvironment = MOCK).
When using webEnvironment = RANDOM_PORT, a random port is used (which you can find in the test using @LocalServerPort).
It is also possible to autowire a TestRestTemplate, RestAssuredMockMvc or MockMvc which you can use to test the application using relative url’s.

@MockBean can be used to mock any bean in the application environment.

To test the serialization and deserialization of a JSON object, you can use @JsonTest

To test a web client, you can use @RestClientTest

Examples of using the different annotations and rest clients can be found below:

Spring WebFlux samples and links

[Index of Spring blogs]

Samples:
https://github.com/robbertvdzon/springfluxsamples/blob/master/src/main/java/com/example/springwebflux/SpringwebfluxApplication.java

Spring5 documentation about webFlux:
https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html#webflux

Spring Boot documentation about webFlux:
https://docs.spring.io/spring-boot/docs/2.1.0.RELEASE/reference/htmlsingle/#boot-features-webflux

Spring testing documentation about Spring Web Reactive:
https://docs.spring.io/spring/docs/current/spring-framework-reference/testing.html#mock-objects-web-reactive

 

Spring WebMVC samples and links

[Index of Spring blogs]

Samples:
https://github.com/robbertvdzon/spring-web-mvc-samples/blob/master/src/main/java/com/example/demo/DemoApplication.java

Spring5 documentation about webMVC:
https://docs.spring.io/spring/docs/current/spring-framework-reference/web.html

Spring Boot documentation about webMVC:
https://docs.spring.io/spring-boot/docs/2.1.0.RELEASE/reference/htmlsingle/#boot-features-developing-web-applications

Spring testing documentation about MVC Test Framework:
https://docs.spring.io/spring/docs/current/spring-framework-reference/testing.html#spring-mvc-test-framework

 

Java REST services, search for smallest footprint

For my private projects I have rented a virtual Linux server in the cloud.
Since this server has a limited amount of memory I would like my microservices to be as small as possible.
Most of my microservers expose a REST API, so I decided to test some different implementations to implement a REST service.