Prerequisite

Java 17 or later
Maven 3.6 or later
Docker 20.10.14 or higher (to run locally)

Introduction

If you have gone through the Explore Kalix Virtaully journey, you are all set to :

• Run locally in prod-like environment
  
• Deploy and run on Kalix Platform on Cloud Provider of your choice

However, if you would like to better understand the Kalix Developer Experience and how to build applications on Kalix, here is more details on the same-use.

Kalix Trial - eCommerce - Java

Designing Kalix Services

Use case

eCommerce use case is a simple shopping cart example consisting of product stock and shopping cart. Product stock models stock (simple quantity) of products that are being sold and Shopping Cart models list of products customer intends to buy.
In this exercise focus is on implementing Product Stock functionalities

Product Stock

Data model:

• quantity

Note: Product stock data model does not hold the productId because the HTTP/REST API is designed around productId itself. Operations:

• CREATE/READ/UPDATE/DELETE product stock

Kalix components

Kalix components serve to abstract functionalities.
In this particular use case, we will utilize a Kalix component known as Entity.

Entity:

• component for modeling of data and data business logic operations
• removes complexities around data:
  • caching
  • concurrency
  • distributed locking
• simplifies data modeling, business logic implementation with out-of-the box scalability, resilience Kalix provides other components that are not used in this use case and more details can be found in Kalix documentation:
  
  

Design Product Stock Kalix service

Product Stock Service

• implements Product Stock functionalities
• Kalix component used: Entity

ProductStock Entity

• models one product stock instance and business logic operations over that one instance

Data model

• quantity

API

• HTTP/RES
• Endpoints:

  • Create POST /product-stock/{productId}/create

    Request (JSON):

    • quantity (int)

    Response (String): "OK"

  • Read GET /product-stock/{productId}/get Request (JSON): No body

    Response (JSON):

    • quantity (int)

  • Update PUT /product-stock/{productId}/update

    Request (JSON):

    • quantity (int)

    Response (String): "OK"

  • Delete DELETE /product-stock/{productId}/delete

    Request (JSON): No body

    Response (String): "OK"

Kickstart Kalix development project

Kalix Maven ArchType

Kalix Maven ArchType generates a new Maven development project from Kalix template

Create shopping cart Maven project from Kalix template

Execute in command line:

mvn archetype:generate \
  -DarchetypeGroupId=io.kalix \
  -DarchetypeArtifactId=kalix-spring-boot-archetype \
  -DarchetypeVersion=1.3.7

Use this setup:

Define value for property 'groupId': com.example
Define value for property 'artifactId': kalix-trial-shoppingcart
Define value for property 'version' 1.0-SNAPSHOT: :
Define value for property 'package' com.example: : com.example.shoppingcart

Maven ArchType generates Maven project:

• pom.xml with all pre-configured Maven plugins and dependencies required development, testing and packaging of Kalix service code
• Main, Java Class for bootstrapping Kalix service
• resources directory with minimal required configuration
• it directory with integration test example

Define data structure

Create ProductStock Java record in com.example.shoppingcart package.
Add helper methods for creating empty product stock structure and to validate if isEmpty.

public record ProductStock(Integer quantity){
    public static ProductStock empty(){
        return new ProductStock(null);
    }
    @JsonIgnore
    public boolean isEmpty(){
        return quantity == null;
    }
}

Define API - Product Stock Entity API

1. Create ProductStockEntity Java class in com.example.shoppingcart package that extends kalix.javasdk.valueentity.ValueEntity with inner type ProductStock type
2. Add productId class parameter
3. Add constructor for Kalix to inject ValueEntityContext from which entityId is used set productId
4. Annotate ProductStockEntity class with spring web bind annotation @RequestMapping and configure path with productId as in-path parameter
5. Annotate class with @Id("productId") to configure parameter productId as the entity key
6. Annotate class with @TypeId("product-stock") to assign reference name to the entity
7. Override emptyState method and return empty ProductStock value

@Id("productId")
@TypeId("product-stock")
@RequestMapping("/product-stock/{productId}")
public class ProductStockEntity extends ValueEntity<ProductStock>{
    private final String productId;
    public ProductStockEntity(ValueEntityContext context) {
            this.productId = context.entityId();
    }
    @Override
    public ProductStock emptyState() {
       return ProductStock.empty();
    }
}

8. Annotate ProductStockEntity class with spring web bind annotation @RequestMapping and configure path with productId as in-path parameter
9. For each endpoints:
   • To ProductStockEntity class add method per endpoint (create, get, update, delete)
   • Each method:
     • input: HTTP request data structure (using spring web annotations)
     • return: ValueEntity.Effect with HTTP response data structure as an inner type
     • using spring web annotation mappings for REST method and path mapping (@PostMapping,...)

@Id("productId")
@TypeId("product-stock")
@RequestMapping("/product-stock/{productId}")
public class ProductStockEntity extends ValueEntity<ProductStock>{
   private final String productId;
   public ProductStockEntity(ValueEntityContext context) {
   		this.productId = context.entityId();
   }
   @Override
   public ProductStock emptyState() {
     return ProductStock.empty();
   }
   @PostMapping("/create")
   public Effect<String> create(@RequestBody ProductStock productStock){}
   @GetMapping("/get")
   public Effect<ProductStock> get(){}
   @PutMapping("/update")
   public Effect<String> update(@RequestBody ProductStock productStock){}
   @DeleteMapping("/delete")
   public Effect<String> delete(){}
}

Implementing business logic

Helper methods from ValueEntity class:

• currentState() facilitates access to current value of the data for that product stock instance (e.g. productId: 111)
• effects() facilitates actions that Kalix needs to perform
• updateState() - to persist data
• thenReply() - to send response after persistence is successful
• error() - to send error response back
• Kalix ensures that each method (create, get, update, delete) is executed in sequence for one product stock instance (e.g. productId: 111) ensuring consistency and resolving concurrent access.

create endpoint

Business logic for create is to persist product stock data if not yet exists. In other cases returns an ERROR.

@PostMapping("/create")
public Effect<String> create(@RequestBody ProductStock productStock){
   if(currentState().isEmpty())
       return effects().updateState(productStock).thenReply("OK");
   else
       return effects().error("Already created");
}

get endpoint

Business logic for get is to product stock data if exists and if not return not found error.

@GetMapping("/get")
public Effect<ProductStock> get(){
   if(currentState().isEmpty())
       return effects().error("Not found", Status.Code.NOT_FOUND);
   else
       return effects().reply(currentState());
}

update endpoint

Business logic for update is to update product stock data if product was already created. If product is not found, return NOT FOUND error.

@PutMapping("/update")
public Effect<String> update(@RequestBody ProductStock productStock){
   if(currentState().isEmpty())
       return effects().error("Not found", Status.Code.NOT_FOUND);
   else
       return effects().updateState(productStock).thenReply("OK");
}

delete endpoint

Business logic for delete is delete data if product stock exists and return NOT FOUND error if not. Here the soft delete is done by emptying the Product Stock.

@DeleteMapping("/delete")
public Effect<String> delete(){
   if(currentState().isEmpty())
       return effects().error("Not found", Status.Code.NOT_FOUND);
   else
       return effects().updateState(ProductStock.empty()).thenReply("OK");
}

Test

Kalix comes with very rich test kit for unit and integration testing of Kalix code

Test kit provides help (custom assertions, mocks,...) with:

• unit testing of individual Kalix components (e.g Entity) in isolation

• integration testing in Kalix Platform simulated environment in isolation

• Allows easy test automation with very high test coverage

Unit test

1. Create a new test/java directories in src directory
2. Create com.example.shoppingcart package in test/java
3. Create ProductStockEntityTest class created package
4. Create testCreate method with JUnit Jupiter Test annotation
5. ValueEntityTestKit class is used for unit testing Value Entity component. Inner types are ProductStock and ProductStockEntity. It is for unit testing one product instance so productId needs to be provided
6. Testkit call method is used for triggering each entity endpoint and result is ValueEntityResult with inner type as a HTTP result
7. result can be used for test assertion
   • isError - assert error
   • getReply - assert reply
   • getUpdatedState - assert persistent data

public class ProductStockEntityTest {
   @Test
   public void testCreate()throws Exception{
       var productId = UUID.randomUUID().toString();
       ProductStock productStock = new ProductStock(10);

       ValueEntityTestKit<ProductStock, ProductStockEntity> testKit = ValueEntityTestKit.of(productId, ProductStockEntity::new);

       ValueEntityResult<String> res = testKit.call(entity -> entity.create(productStock));
       assertFalse(res.isError());
       assertEquals("OK",res.getReply());
       ProductStock persistedProductStock = (ProductStock)res.getUpdatedState();
       assertEquals(productStock.quantity(),persistedProductStock.quantity());
   }
}

Run the unit test:

mvn test

Integration test

Kalix test kit for integration testing runs code using test containers to simulate Kalix Platform runtime environment. Integration test uses spring reactive WebClient to interact with running code. IntegrationTest class is created during development project kick start and is pre-configured with WebClient Each endpoint is tested from the client perspective

public class IntegrationTest extends KalixIntegrationTestKitSupport {
 @Autowired
 private WebClient webClient;
 private Duration timeout = Duration.of(5, ChronoUnit.SECONDS);
 @Test
 public void test() throws Exception {
   var productId = UUID.randomUUID().toString();
   ProductStock productStock = new ProductStock(10);
   var res = webClient.post()
               .uri("/product-stock/%s/create".formatted(productId))
               .bodyValue(productStock)
               .retrieve()
               .toEntity(String.class)
               .block(timeout);
   var getProductStock = webClient.get()
           .uri("/product-stock/%s/get".formatted(productId))
           .retrieve()
           .toEntity(ProductStock.class)
           .block(timeout)
           .getBody();
   assertEquals(productStock.quantity(),getProductStock.quantity());
 }
}

Run the integration test:

mvn -Pit verify

Run locally in prod-like environment

Run Kalix service locally:

mvn kalix:runAll

This command runs the Kalix service locally and exposes it on localhost:9000.

Test

Testing using CURL:

1. Create product:

curl -XPOST -d '{ 
  "quantity": 10
}' http://localhost:9000/product-stock/apple/create -H "Content-Type: application/json"

Result:

"OK"

2. Get product:

curl -XGET http://localhost:9000/product-stock/apple/get

Result:

{"quantity":10}

3. Update product:

curl -XPUT -d '{
"quantity": 20
}' http://localhost:9000/product-stock/apple/update -H "Content-Type: application/json"

Result:

"OK"

4. Delete product:

curl -XDELETE http://localhost:9000/product-stock/apple/delete

Result:

"OK"

Deploy and run on Kalix Platform on Cloud Provider of your choice

1. Install Kalix CLI https://docs.kalix.io/kalix/install-kalix.html

2. Kalix CLI

   1. Register (FREE)

   kalix auth signup
   

   Note: The above command will open a browser where registration information can be filled in
   2. Login

   kalix auth login
   

   Note: The above command will open a browser where authentication approval needs to be provided
   

   3. Check your organization name

   kalix organization list
   

   Execute the above command to view a list of organizations associated with your account. Find your organization name, likely the same as your username.

   4. Create a project

   kalix projects new kalix-trial-java-ecommerce --region=gcp-us-east1 --organization=your-organization-name
   

   For trial projects, provide gcp-us-east1 as the region. Replace your-organization-name with your actual organization name obtained from the previous step.
   

   5. Authenticate local docker for pushing docker image to Kalix Container Registry (KCR)

   kalix auth container-registry configure
   

   Note: The command will output Kalix Container Registry (KCR) path that will be used to configure dockerImage in pom.xml
   

   6. Extract Kalix user username

   kalix auth current-login
   

   Note: The command will output Kalix user details and column USERNAME will be used to configure dockerImage in pom.xml
   

3. Configure dockerImage path in pom.xml Replace my-docker-repo in dockerImage in pom.xml with:
   Kalix Container Registry (KCR) path + / + USERNAME + /kalix-trial-java-ecommerce
   Example where Kalix Container Registry (KCR) path is kcr.us-east-1.kalix.io and USERNAME is myuser:
   

<dockerImage>kcr.us-east-1.kalix.io/myuser/kalix-trial-java-ecommerce/${project.artifactId}</dockerImage>

4. Deploy service in Kalix project:

mvn deploy kalix:deploy

This command will:

• compile the code
• execute tests
• package into a docker image
• push the docker image to Kalix docker registry
• trigger service deployment by invoking Kalix CLI

5. Check deployment:

kalix service list

Result:

kalix service list                                                                         
NAME                                         AGE    REPLICAS   STATUS        IMAGE TAG                     
kalix-trial-shoppingcart                     50s    0          Ready         1.0-SNAPSHOT                  

Note: When deploying service for the first time it can take up to 1 minute for internal provisioning

Proxy connection to Kalix service via Kalix CLI

1. Proxy connection to Kalix service via Kalix CLI

kalix service proxy kalix-trial-shoppingcart

Proxy Kalix CLI command will expose service proxy connection on localhost:8080.

Test

Testing using CURL:

1. Create product:

curl -XPOST -d '{ 
  "quantity": 10
}' http://localhost:8080/product-stock/apple/create -H "Content-Type: application/json"

Result:

"OK"

2. Get product:

curl -XGET http://localhost:8080/product-stock/apple/get

Result:

{"quantity":10}

3. Update product:

curl -XPUT -d '{
"quantity": 20
}' http://localhost:8080/product-stock/apple/update -H "Content-Type: application/json"

Result:

"OK"

4. Delete product:

curl -XDELETE http://localhost:8080/product-stock/apple/delete

Result:

"OK"