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Some Java vs C# differences explained

Project Structure

Domain Objects

Maybe just me, but I've always found the deeply nested folders in java code annoying, we generally don't do so much of that in C#, but larger projects head in that direction.

Java

quarkus-cafe-barista

/src/main/java/com/redhat/quarkus/cafe/barista/domain/Barista.java

C#

quarkus.cafe.barista

/Domain/Barista.cs

Services

KafkaService.java vs BaristaKafkaService.cs - I only deviated here because it's a pain when you're debugging multiple microservices and they use the same class name; it leads to unnecessary confusion.

Java

quarkus-cafe-barista

/src/main/java/com/redhat/quarkus/cafe/barista/infrastructure/KafkaService.java

C#

quarkus.cafe.barista

/Domain/Service/BaristaKafkaService.cs

References

Java

I guess this depends on your Java environment (Maven, Gradle, or something else), but your external packages and internal references are in these pom.xml files.

quarkus-cafe-barista/pom.xml

C#

In C#, these go into the .csproj file in the root of each project like:

dotnet.cafe.barista/dotnet.cafe.barista.csproj

If you're using an IDE, you pretty much never edit these by hand.

Serialization

Java

For Quarkus, we use the @RegisterForReflection annotation to tell the SAXParser how to serialize to JSON as per: https://quarkus.io/guides/writing-native-applications-tips#alternative-with-registerforreflection

@RegisterForReflection
public class LineItem {
    public Item item;
    public String name;   
    ...

C#

In C#, we're using the relatively new System.Text.Json serializer/deserializer, which requires get/set for properties and behaves slightly differently from the Newtonsoft.Json library everyone used to use. Docs: https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-how-to

public class LineItem
{
    public Item item { get; set; }
    public String name { get; set; }
    ...

This makes the marshalling code really easy, and we do it throughout like:

    OrderInEvent orderIn = JsonSerializer.Deserialize<OrderInEvent>(message);

Lambda Expressions

Glad you guys finally got these in Java 8, because we've been doing this in C# since 3.0 in 2007

Java

kitchen.make(orderIn).thenApply(o -> {

C#

_kitchen.make(orderIn).ContinueWith(async kitchenOutput => {

Async

Each of these functions takes in an OrderInEvent, and returns a list of events wrapped in asynchronous code.

Note that CompletableFuture and Task are very similar, but a good writeup of the differences (if you want to go down the rabbit hole) is available here: https://softwareengineering.stackexchange.com/questions/393264/is-the-c-async-task-construct-equivalent-to-javas-executor-future

Java

public CompletableFuture<Collection<Event>> make(final OrderInEvent orderInEvent) {

C#

public async Task<List<Event>> make(OrderInEvent orderInEvent)