polymorphism support POC

Author: aludwiko

samples/shopping-cart-quickstart/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>io.akka</groupId>
     <artifactId>akka-javasdk-parent</artifactId>
-    <version>3.0.2</version>
+    <version>3.0.2-5-898ec6f9-dev-SNAPSHOT</version>
   </parent>
 
   <groupId>com.example</groupId>

samples/shopping-cart-quickstart/src/main/java/shoppingcart/api/ShoppingCartEndpoint.java

@@ -27,7 +27,7 @@
 // For actual services meant for production this must be carefully considered, and often set more limited
 // tag::endpoint-component-interaction[]
 @Acl(allow = @Acl.Matcher(principal = Acl.Principal.INTERNET))
-@HttpEndpoint("/carts") // <1>
+@HttpEndpoint("/carts-old") // <1>
 public class ShoppingCartEndpoint {
 
   private final ComponentClient componentClient;

samples/shopping-cart-quickstart/src/main/java/shoppingcart/polymorphism/api/ShoppingCartEndpoint.java

@@ -0,0 +1,99 @@
+// tag::top[]
+package shoppingcart.polymorphism.api;
+
+import akka.http.javadsl.model.HttpResponse;
+import akka.javasdk.annotations.Acl;
+import akka.javasdk.annotations.http.Delete;
+import akka.javasdk.annotations.http.Get;
+import akka.javasdk.annotations.http.HttpEndpoint;
+import akka.javasdk.annotations.http.Post;
+import akka.javasdk.annotations.http.Put;
+import akka.javasdk.client.ComponentClient;
+import akka.javasdk.http.HttpResponses;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import shoppingcart.domain.ShoppingCart.LineItem;
+import shoppingcart.polymorphism.application.ShoppingCartEntity;
+import shoppingcart.polymorphism.domain.ShoppingCart;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.CheckedOutShoppingCartCommand.Cancel;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand.AddItem;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand.Checkout;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand.RemoveItem;
+
+import java.util.concurrent.CompletionStage;
+
+// end::top[]
+
+// tag::class[]
+
+// Opened up for access from the public internet to make the sample service easy to try out.
+// For actual services meant for production this must be carefully considered, and often set more limited
+// tag::endpoint-component-interaction[]
+@Acl(allow = @Acl.Matcher(principal = Acl.Principal.INTERNET))
+@HttpEndpoint("/carts") // <1>
+public class ShoppingCartEndpoint {
+
+  private final ComponentClient componentClient;
+
+  private static final Logger logger = LoggerFactory.getLogger(ShoppingCartEndpoint.class);
+
+  public ShoppingCartEndpoint(ComponentClient componentClient) { // <2>
+    this.componentClient = componentClient;
+  }
+
+  // end::class[]
+
+  // tag::get[]
+  @Get("/{cartId}") // <3>
+  public CompletionStage<ShoppingCart> get(String cartId) {
+    logger.info("Get cart id={}", cartId);
+    return componentClient.forEventSourcedEntity(cartId) // <4>
+        .method(ShoppingCartEntity::getCart)
+        .invokeAsync(); // <5>
+  }
+
+  // end::get[]
+
+  // tag::addItem[]
+  @Put("/{cartId}/item") // <6>
+  public CompletionStage<HttpResponse> addItem(String cartId, LineItem item) {
+    logger.info("Adding item to cart id={} item={}", cartId, item);
+    return componentClient.forEventSourcedEntity(cartId)
+      .method(ShoppingCartEntity::handleCommand)
+      .invokeAsync(new AddItem(item))
+      .thenApply(__ -> HttpResponses.ok()); // <7>
+  }
+  // end::endpoint-component-interaction[]
+
+  // end::addItem[]
+
+  @Delete("/{cartId}/item/{productId}")
+  public CompletionStage<HttpResponse> removeItem(String cartId, String productId) {
+    logger.info("Removing item from cart id={} item={}", cartId, productId);
+    return componentClient.forEventSourcedEntity(cartId)
+      .method(ShoppingCartEntity::handleCommand)
+      .invokeAsync(new RemoveItem(productId))
+      .thenApply(__ -> HttpResponses.ok());
+  }
+
+  @Post("/{cartId}/checkout")
+  public CompletionStage<HttpResponse> checkout(String cartId) {
+    logger.info("Checkout cart id={}", cartId);
+    return componentClient.forEventSourcedEntity(cartId)
+      .method(ShoppingCartEntity::handleCommand)
+      .invokeAsync(new Checkout())
+      .thenApply(__ -> HttpResponses.ok());
+  }
+
+  @Post("/{cartId}/cancel")
+  public CompletionStage<HttpResponse> cancel(String cartId) {
+    logger.info("Checkout cart id={}", cartId);
+    return componentClient.forEventSourcedEntity(cartId)
+      .method(ShoppingCartEntity::handleCommand)
+      .invokeAsync(new Cancel())
+      .thenApply(__ -> HttpResponses.ok());
+  }
+
+  // tag::class[]
+}
+// end::class[]

samples/shopping-cart-quickstart/src/main/java/shoppingcart/polymorphism/application/ShoppingCartEntity.java

@@ -0,0 +1,50 @@
+// tag::top[]
+package shoppingcart.polymorphism.application;
+
+import akka.Done;
+import akka.javasdk.annotations.ComponentId;
+import akka.javasdk.eventsourcedentity.EventSourcedEntity;
+import akka.javasdk.eventsourcedentity.EventSourcedEntityContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import shoppingcart.polymorphism.domain.OpenShoppingCart;
+import shoppingcart.polymorphism.domain.ShoppingCart;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent;
+
+import java.util.Collections;
+
+
+@ComponentId("shopping-cart-poly")
+public class ShoppingCartEntity extends EventSourcedEntity<ShoppingCart, ShoppingCartEvent> { // <1>
+
+  private final String entityId;
+
+  private static final Logger logger = LoggerFactory.getLogger(ShoppingCartEntity.class);
+
+  public ShoppingCartEntity(EventSourcedEntityContext context) {
+    this.entityId = context.entityId(); // <1>
+  }
+
+  @Override
+  public ShoppingCart emptyState() { // <2>
+    return new OpenShoppingCart(entityId, Collections.emptyList());
+  }
+
+  public Effect<Done> handleCommand(ShoppingCartCommand command) {
+    //todo some basic validation
+    var event = currentState().handleCommand(command);
+
+    return effects().persist(event).thenReply(__ -> Done.done());
+  }
+
+  public ReadOnlyEffect<ShoppingCart> getCart() {
+    return effects().reply(currentState()); // <3>
+  }
+
+
+  @Override
+  public ShoppingCart applyEvent(ShoppingCartEvent event) {
+    return currentState().applyEvent(event);
+  }
+}

samples/shopping-cart-quickstart/src/main/java/shoppingcart/polymorphism/domain/CheckedOutShoppingCart.java

@@ -0,0 +1,36 @@
+package shoppingcart.polymorphism.domain;
+
+import shoppingcart.domain.ShoppingCart.LineItem;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.CheckedOutShoppingCartCommand;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.CheckedOutShoppingCartCommand.Cancel;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.CheckedOutShoppingCartEvent;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.CheckedOutShoppingCartEvent.Cancelled;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.OpenShoppingCartEvent;
+
+import java.util.List;
+
+public record CheckedOutShoppingCart(String cartId, List<LineItem> items, Boolean cancelled) implements ShoppingCart {
+
+  @Override
+  public ShoppingCartEvent handleCommand(ShoppingCartCommand command) {
+    return switch (command) {
+      case OpenShoppingCartCommand __ -> throw new IllegalStateException("Cannot handle command on a checked out cart");
+      case CheckedOutShoppingCartCommand checkedOutCommand -> switch (checkedOutCommand) {
+        case Cancel cancel -> new Cancelled();
+      };
+    };
+  }
+
+  @Override
+  public ShoppingCart applyEvent(ShoppingCartEvent event) {
+    return switch (event) {
+      case OpenShoppingCartEvent __ -> {
+        throw new IllegalStateException("Cannot apply event on a checkout out cart");
+      }
+      case CheckedOutShoppingCartEvent checkedOutEvent -> switch (checkedOutEvent) {
+        case Cancelled cancelled -> new CheckedOutShoppingCart(cartId, items, true);
+      };
+    };
+  }
+}

samples/shopping-cart-quickstart/src/main/java/shoppingcart/polymorphism/domain/OpenShoppingCart.java

@@ -0,0 +1,87 @@
+package shoppingcart.polymorphism.domain;
+
+import shoppingcart.domain.ShoppingCart.LineItem;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.CheckedOutShoppingCartCommand;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand.AddItem;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand.Checkout;
+import shoppingcart.polymorphism.domain.ShoppingCartCommand.OpenShoppingCartCommand.RemoveItem;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.CheckedOutShoppingCartEvent;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.OpenShoppingCartEvent;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.OpenShoppingCartEvent.CheckedOut;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.OpenShoppingCartEvent.ItemAdded;
+import shoppingcart.polymorphism.domain.ShoppingCartEvent.OpenShoppingCartEvent.ItemRemoved;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.Optional;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+
+public record OpenShoppingCart(String cartId, List<LineItem> items) implements ShoppingCart {
+
+  @Override
+  public ShoppingCartEvent handleCommand(ShoppingCartCommand command) {
+    return switch (command) {
+      case CheckedOutShoppingCartCommand __ -> throw new IllegalStateException("Cannot handle command on an open cart");
+      case OpenShoppingCartCommand openCommand -> switch (openCommand) {
+        case AddItem addItem -> new ItemAdded(addItem.item());
+        case RemoveItem removeItem -> new ItemRemoved(removeItem.productId());
+        case Checkout checkout -> new CheckedOut();
+      };
+    };
+  }
+
+  @Override
+  public ShoppingCart applyEvent(ShoppingCartEvent event) {
+    return switch (event) {
+      case CheckedOutShoppingCartEvent __ -> {
+        throw new IllegalStateException("Cannot apply event on an open cart");
+      }
+      case OpenShoppingCartEvent openEvent -> switch (openEvent) {
+        case CheckedOut checkedOut -> onCheckedOut();
+        case ItemAdded itemAdded -> onItemAdded(itemAdded);
+        case ItemRemoved itemRemoved -> onItemRemoved(itemRemoved);
+      };
+    };
+  }
+
+
+  public OpenShoppingCart onItemAdded(ItemAdded itemAdded) {
+    var item = itemAdded.item();
+    var lineItem = updateItem(item); // <1>
+    List<LineItem> lineItems = removeItemByProductId(item.productId()); // <2>
+    lineItems.add(lineItem); // <3>
+    lineItems.sort(Comparator.comparing(LineItem::productId));
+    return new OpenShoppingCart(cartId, lineItems); // <4>
+  }
+
+  private LineItem updateItem(LineItem item) {
+    return findItemByProductId(item.productId())
+      .map(li -> li.withQuantity(li.quantity() + item.quantity()))
+      .orElse(item);
+  }
+
+  private List<LineItem> removeItemByProductId(String productId) {
+    return items().stream()
+      .filter(lineItem -> !lineItem.productId().equals(productId))
+      .collect(Collectors.toList());
+  }
+
+  public Optional<LineItem> findItemByProductId(String productId) {
+    Predicate<LineItem> lineItemExists =
+      lineItem -> lineItem.productId().equals(productId);
+    return items.stream().filter(lineItemExists).findFirst();
+  }
+
+  public OpenShoppingCart onItemRemoved(ItemRemoved itemRemoved) {
+    List<LineItem> updatedItems =
+      removeItemByProductId(itemRemoved.productId());
+    updatedItems.sort(Comparator.comparing(LineItem::productId));
+    return new OpenShoppingCart(cartId, updatedItems);
+  }
+
+  public ShoppingCart onCheckedOut() {
+    return new CheckedOutShoppingCart(cartId, items, false);
+  }
+}

samples/shopping-cart-quickstart/src/main/java/shoppingcart/polymorphism/domain/ShoppingCart.java

@@ -0,0 +1,15 @@
+package shoppingcart.polymorphism.domain;
+
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "@type")
+@JsonSubTypes({
+  @JsonSubTypes.Type(value = OpenShoppingCart.class, name = "open"),
+  @JsonSubTypes.Type(value = CheckedOutShoppingCart.class, name = "checked-out")})
+public sealed interface ShoppingCart permits OpenShoppingCart, CheckedOutShoppingCart {
+
+  ShoppingCartEvent handleCommand(ShoppingCartCommand command);
+
+  ShoppingCart applyEvent(ShoppingCartEvent event);
+}

samples/shopping-cart-quickstart/src/main/java/shoppingcart/polymorphism/domain/ShoppingCartCommand.java

@@ -0,0 +1,37 @@
+package shoppingcart.polymorphism.domain;
+
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import shoppingcart.domain.ShoppingCart;
+
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "@type")
+@JsonSubTypes({
+  @JsonSubTypes.Type(value = ShoppingCartCommand.OpenShoppingCartCommand.class, name = "open"),
+  @JsonSubTypes.Type(value = ShoppingCartCommand.CheckedOutShoppingCartCommand.class, name = "checked-out")})
+public sealed interface ShoppingCartCommand {
+
+  @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "@type")
+  @JsonSubTypes({
+    @JsonSubTypes.Type(value = OpenShoppingCartCommand.AddItem.class, name = "a"),
+    @JsonSubTypes.Type(value = OpenShoppingCartCommand.RemoveItem.class, name = "r"),
+    @JsonSubTypes.Type(value = OpenShoppingCartCommand.Checkout.class, name = "c")})
+  sealed interface OpenShoppingCartCommand extends ShoppingCartCommand {
+    record AddItem(ShoppingCart.LineItem item) implements OpenShoppingCartCommand {
+    }
+
+    record RemoveItem(String productId) implements OpenShoppingCartCommand {
+    }
+
+    record Checkout() implements OpenShoppingCartCommand {
+    }
+  }
+
+  @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "@type")
+  @JsonSubTypes({
+    @JsonSubTypes.Type(value = CheckedOutShoppingCartCommand.Cancel.class, name = "cc")})
+  sealed interface CheckedOutShoppingCartCommand extends ShoppingCartCommand {
+
+    record Cancel() implements CheckedOutShoppingCartCommand {
+    }
+  }
+}

samples/shopping-cart-quickstart/src/main/java/shoppingcart/polymorphism/domain/ShoppingCartEvent.java

@@ -0,0 +1,33 @@
+package shoppingcart.polymorphism.domain;
+
+import akka.javasdk.annotations.TypeName;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import shoppingcart.domain.ShoppingCart;
+
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "@type")
+@JsonSubTypes({
+  @JsonSubTypes.Type(value = ShoppingCartEvent.OpenShoppingCartEvent.class, name = "open"),
+  @JsonSubTypes.Type(value = ShoppingCartEvent.CheckedOutShoppingCartEvent.class, name = "checked-out")})
+public sealed interface ShoppingCartEvent {
+
+  sealed interface OpenShoppingCartEvent extends ShoppingCartEvent {
+    @TypeName("item-added") // <2>
+    record ItemAdded(ShoppingCart.LineItem item) implements OpenShoppingCartEvent {
+    }
+
+    @TypeName("item-removed")
+    record ItemRemoved(String productId) implements OpenShoppingCartEvent {
+    }
+
+    @TypeName("checked-out")
+    record CheckedOut() implements OpenShoppingCartEvent {
+    }
+  }
+
+  sealed interface CheckedOutShoppingCartEvent extends ShoppingCartEvent {
+    @TypeName("cancelled")
+    record Cancelled() implements CheckedOutShoppingCartEvent {
+    }
+  }
+}