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https://github.com/kpavlov/await4j
Simplify asynchronous programming in Java with Project Loom virtual threads and a familiar async/await style API
https://github.com/kpavlov/await4j
async-await java project-loom virtual-threads-java-21
Last synced: 7 days ago
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Simplify asynchronous programming in Java with Project Loom virtual threads and a familiar async/await style API
- Host: GitHub
- URL: https://github.com/kpavlov/await4j
- Owner: kpavlov
- License: mit
- Created: 2024-07-14T07:03:06.000Z (6 months ago)
- Default Branch: main
- Last Pushed: 2024-12-18T08:52:33.000Z (9 days ago)
- Last Synced: 2024-12-19T02:37:52.122Z (8 days ago)
- Topics: async-await, java, project-loom, virtual-threads-java-21
- Language: Java
- Homepage:
- Size: 440 KB
- Stars: 1
- Watchers: 0
- Forks: 0
- Open Issues: 4
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Await4J
[](https://repo1.maven.org/maven2/me/kpavlov/await4j/await4j/)
[](https://github.com/kpavlov/await4j/actions/workflows/maven.yml)
[](https://github.com/kpavlov/await4j/actions/workflows/github-code-scanning/codeql)
_Simplify Java async programming with virtual threads using an async/await style API._
## TL;DR: Features
The `Async` class provides utility methods for executing code asynchronously on virtual threads. It simplifies handling of asynchronous operations and exceptions and provides familiar API.
- **`await(() -> {/* blocking code */})`**:
Executes a code block on a virtual thread. Handles checked exceptions and wraps them into `RuntimeException`. `RuntimeException` and `Error`are thrown as it is. If any other unexpected `Throwable` occurs, it throws an `IllegalStateException`.
- **`await(Callable block)`**:
Executes a `Callable` block on a virtual thread and returns the result. Handles `InterruptedException`, `ExecutionException`, and other general exceptions by wrapping them in a `RuntimeException`.
- **`await(Future future)`**:
Waits for the `Future` to complete and returns its result. Internally calls `await(Callable block)`.
- **`await(CompletableFuture completableFuture)`**:
Waits for the `CompletableFuture` to complete and returns its result. Internally calls `await(Callable block)`.
See [Sample.java](src/test/java/me/kpavlov/await4j/Sample.java).
## Background
Project Loom has introduced Virtual Threads, but the API requires some boilerplate code to use it effectively in real-life projects:
To run blocking code in a Virtual Thread, it should be wrapped in:
```java
Thread.ofVirtual().start(() -> {
// run some blocking code here
}).join()
```
When you need to get the execution result back, a common approach is to run it in an executor:
```java
int returnFromVirtualThread() {
try (final var executor = Executors.newVirtualThreadPerTaskExecutor()) {
final var task = executor.submit(() -> {
// Do some expensive calculation here
return 42; // Return result
});
return task.get(); // Get result from task
} catch (ExecutionException e) {
throw new RuntimeException(e);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new RuntimeException(e);
}
}
```
## The Better Async API
What if it were possible to use syntax similar to Javascript's `async/await` style?
This library introduces helpful utilities to simplify calls in Virtual Threads:
For example, to call a lambda function, even throwing exceptions, use:
```java
import me.kpavlov.await4j.Async.await;
...
final var completed = new AtomicBoolean();
final var slowCalculation = () -> {
// Do something slow in a virtual thread
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
// Set flag to "true" to indicate, that the task is completed
completed.set(true);
};
await(slowCalculation);
// Verify that calculation has been completed
System.out.println("Completed: " + completed.get()); // "Completed: true"
```
To call a lambda that returns a value (Callable), use:
```java
import me.kpavlov.await4j.Async.await;
...
final var result = await(() -> {
// Do some expensive calculation here
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
// Return the result
return 42;
});
System.out.println("Result: " + result); // "Result: 42"
```
Lambdas may throw exceptions, unlike the `java.lang.Runnable` interface. All non-runtime exceptions are wrapped in `java.lang.RuntimeException`, and `java.lang.Error` will be re-thrown.
## Wrapping `CompletableFuture` and `Future`
Using `java.util.concurrent.CompletableFuture` and `java.util.concurrentFuture` from the Java API is also simplified:
```java
final CompletableFuture completableFuture = CompletableFuture.supplyAsync(() -> {
// Do some expensive calculation here
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
// Return the result
return 42;
});
final var completableFutureResult = await(completableFuture);
System.out.println("CompletableFuture result: " + completableFutureResult); // "Result: 42"
final var futureResult = await((Future) completableFuture);
System.out.println("Future Result: " + futureResult); // "Result: 42"
```
See full list of requirements [here](REQUIREMENTS.md).
## Useful Utility Classes
- [Result<T>](src/main/java/me/kpavlov/utils/Result.java) - A discriminated union that encapsulates a successful outcome with a value of type T or a failure with an arbitrary Throwable exception. Similar to [Result](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-result/) in Kotlin.
- [ThrowingRunnable](src/main/java/me/kpavlov/utils/ThrowingRunnable.java) - Runnable, which can throw Exception
## Final Notes
**If you want to write better code on JVM, use [Kotlin Coroutines](https://kotlinlang.org/docs/coroutines-overview.html).** This library remains a simpler choice for Java projects where adopting or migrating to [Kotlin](https://kotlinlang.org) is not feasible.
The library focuses on running blocking code on Virtual Threads without providing additional parallelism optimizations. If your IO operations are slow, they will not run faster. If a lambda takes one second to run, `await(...)` will also take approximately one second, but on a virtual thread.
## How to Get Started
1. Add project dependency. Latest version can be found on [maven central repository](https://mvnrepository.com/artifact/me.kpavlov.await4j/await4j):
Maven:
```xml
me.kpavlov.await4j
await4j
[LATEST]
```
Gradle:
```kotlin
// https://mvnrepository.com/artifact/me.kpavlov.await4j/await4j
implementation("me.kpavlov.await4j:await4j:${await4jVersion}")
```
2. Import methods from [Async](src/main/java/me/kpavlov/await4j/Async.java)
```java
import me.kpavlov.await4j.Async.await;
```
## Links
- [JEP 444: Virtual Threads](https://openjdk.org/jeps/444) -- Virtual threads are lightweight threads that dramatically reduce the effort of writing, maintaining, and observing high-throughput concurrent applications.
- [JEP 480: Structured Concurrency](https://openjdk.org/jeps/480) -- Simplify concurrent programming by introducing an API for structured concurrency. Structured concurrency treats groups of related tasks running in different threads as a single unit of work, thereby streamlining error handling and cancellation, improving reliability, and enhancing observability. This is a preview API.
- [JEP 429: ScopedValues](https://openjdk.org/jeps/429) -- Scoped values enables sharing of immutable data within and across threads. They are preferred to thread-local variables, especially when using large numbers of virtual threads. This is an incubating API.
- [Java Async-Await](https://github.com/AugustNagro/java-async-await) -- Async-Await support for Java CompletionStage.