mirror of
https://github.com/tiennm99/java-design-patterns.git
synced 2026-05-14 10:58:42 +00:00
docs: collecting parameter docs + formatting
This commit is contained in:
Ilkka Seppälä
@@ -3,17 +3,16 @@ title: Async Method Invocation
|
||||
category: Concurrency
|
||||
language: en
|
||||
tag:
|
||||
- Asynchronous
|
||||
- Reactive
|
||||
- Scalability
|
||||
- Asynchronous
|
||||
- Reactive
|
||||
- Scalability
|
||||
---
|
||||
|
||||
## Intent
|
||||
|
||||
Asynchronous method invocation is a pattern where the calling thread
|
||||
is not blocked while waiting results of tasks. The pattern provides parallel
|
||||
processing of multiple independent tasks and retrieving the results via
|
||||
callbacks or waiting until everything is done.
|
||||
Asynchronous method invocation is a pattern where the calling thread is not blocked while waiting results of tasks. The
|
||||
pattern provides parallel processing of multiple independent tasks and retrieving the results via callbacks or waiting
|
||||
until everything is done.
|
||||
|
||||
## Also known as
|
||||
|
||||
@@ -23,54 +22,59 @@ callbacks or waiting until everything is done.
|
||||
|
||||
Real world example
|
||||
|
||||
> Launching space rockets is an exciting business. The mission command gives an order to launch and
|
||||
> Launching space rockets is an exciting business. The mission command gives an order to launch and
|
||||
> after some undetermined time, the rocket either launches successfully or fails miserably.
|
||||
|
||||
In plain words
|
||||
|
||||
> Asynchronous method invocation starts task processing and returns immediately before the task is
|
||||
> Asynchronous method invocation starts task processing and returns immediately before the task is
|
||||
> ready. The results of the task processing are returned to the caller later.
|
||||
|
||||
Wikipedia says
|
||||
|
||||
> In multithreaded computer programming, asynchronous method invocation (AMI), also known as
|
||||
> asynchronous method calls or the asynchronous pattern is a design pattern in which the call site
|
||||
> is not blocked while waiting for the called code to finish. Instead, the calling thread is
|
||||
> In multithreaded computer programming, asynchronous method invocation (AMI), also known as
|
||||
> asynchronous method calls or the asynchronous pattern is a design pattern in which the call site
|
||||
> is not blocked while waiting for the called code to finish. Instead, the calling thread is
|
||||
> notified when the reply arrives. Polling for a reply is an undesired option.
|
||||
|
||||
**Programmatic Example**
|
||||
|
||||
In this example, we are launching space rockets and deploying lunar rovers.
|
||||
|
||||
The application demonstrates the async method invocation pattern. The key parts of the pattern are
|
||||
`AsyncResult` which is an intermediate container for an asynchronously evaluated value,
|
||||
`AsyncCallback` which can be provided to be executed on task completion and `AsyncExecutor` that
|
||||
The application demonstrates the async method invocation pattern. The key parts of the pattern are
|
||||
`AsyncResult` which is an intermediate container for an asynchronously evaluated value,
|
||||
`AsyncCallback` which can be provided to be executed on task completion and `AsyncExecutor` that
|
||||
manages the execution of the async tasks.
|
||||
|
||||
```java
|
||||
public interface AsyncResult<T> {
|
||||
boolean isCompleted();
|
||||
|
||||
T getValue() throws ExecutionException;
|
||||
|
||||
void await() throws InterruptedException;
|
||||
}
|
||||
```
|
||||
|
||||
```java
|
||||
public interface AsyncCallback<T> {
|
||||
void onComplete(T value);
|
||||
void onError(Exception ex);
|
||||
void onComplete(T value);
|
||||
|
||||
void onError(Exception ex);
|
||||
}
|
||||
```
|
||||
|
||||
```java
|
||||
public interface AsyncExecutor {
|
||||
<T> AsyncResult<T> startProcess(Callable<T> task);
|
||||
|
||||
<T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback);
|
||||
|
||||
<T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException;
|
||||
}
|
||||
```
|
||||
|
||||
`ThreadAsyncExecutor` is an implementation of `AsyncExecutor`. Some of its key parts are highlighted
|
||||
`ThreadAsyncExecutor` is an implementation of `AsyncExecutor`. Some of its key parts are highlighted
|
||||
next.
|
||||
|
||||
```java
|
||||
@@ -85,14 +89,14 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
|
||||
public <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback) {
|
||||
var result = new CompletableResult<>(callback);
|
||||
new Thread(
|
||||
() -> {
|
||||
try {
|
||||
result.setValue(task.call());
|
||||
} catch (Exception ex) {
|
||||
result.setException(ex);
|
||||
}
|
||||
},
|
||||
"executor-" + idx.incrementAndGet())
|
||||
() -> {
|
||||
try {
|
||||
result.setValue(task.call());
|
||||
} catch (Exception ex) {
|
||||
result.setException(ex);
|
||||
}
|
||||
},
|
||||
"executor-" + idx.incrementAndGet())
|
||||
.start();
|
||||
return result;
|
||||
}
|
||||
@@ -111,50 +115,50 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
|
||||
Then we are ready to launch some rockets to see how everything works together.
|
||||
|
||||
```java
|
||||
public static void main(String[] args) throws Exception {
|
||||
// construct a new executor that will run async tasks
|
||||
var executor = new ThreadAsyncExecutor();
|
||||
public static void main(String[]args)throws Exception{
|
||||
// construct a new executor that will run async tasks
|
||||
var executor=new ThreadAsyncExecutor();
|
||||
|
||||
// start few async tasks with varying processing times, two last with callback handlers
|
||||
final var asyncResult1 = executor.startProcess(lazyval(10, 500));
|
||||
final var asyncResult2 = executor.startProcess(lazyval("test", 300));
|
||||
final var asyncResult3 = executor.startProcess(lazyval(50L, 700));
|
||||
final var asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Deploying lunar rover"));
|
||||
final var asyncResult5 =
|
||||
executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
|
||||
// start few async tasks with varying processing times, two last with callback handlers
|
||||
final var asyncResult1=executor.startProcess(lazyval(10,500));
|
||||
final var asyncResult2=executor.startProcess(lazyval("test",300));
|
||||
final var asyncResult3=executor.startProcess(lazyval(50L,700));
|
||||
final var asyncResult4=executor.startProcess(lazyval(20,400),callback("Deploying lunar rover"));
|
||||
final var asyncResult5=
|
||||
executor.startProcess(lazyval("callback",600),callback("Deploying lunar rover"));
|
||||
|
||||
// emulate processing in the current thread while async tasks are running in their own threads
|
||||
Thread.sleep(350); // Oh boy, we are working hard here
|
||||
log("Mission command is sipping coffee");
|
||||
// emulate processing in the current thread while async tasks are running in their own threads
|
||||
Thread.sleep(350); // Oh boy, we are working hard here
|
||||
log("Mission command is sipping coffee");
|
||||
|
||||
// wait for completion of the tasks
|
||||
final var result1 = executor.endProcess(asyncResult1);
|
||||
final var result2 = executor.endProcess(asyncResult2);
|
||||
final var result3 = executor.endProcess(asyncResult3);
|
||||
asyncResult4.await();
|
||||
asyncResult5.await();
|
||||
// wait for completion of the tasks
|
||||
final var result1=executor.endProcess(asyncResult1);
|
||||
final var result2=executor.endProcess(asyncResult2);
|
||||
final var result3=executor.endProcess(asyncResult3);
|
||||
asyncResult4.await();
|
||||
asyncResult5.await();
|
||||
|
||||
// log the results of the tasks, callbacks log immediately when complete
|
||||
log("Space rocket <" + result1 + "> launch complete");
|
||||
log("Space rocket <" + result2 + "> launch complete");
|
||||
log("Space rocket <" + result3 + "> launch complete");
|
||||
}
|
||||
// log the results of the tasks, callbacks log immediately when complete
|
||||
log("Space rocket <"+result1+"> launch complete");
|
||||
log("Space rocket <"+result2+"> launch complete");
|
||||
log("Space rocket <"+result3+"> launch complete");
|
||||
}
|
||||
```
|
||||
|
||||
Here's the program console output.
|
||||
|
||||
```java
|
||||
21:47:08.227 [executor-2] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launched successfully
|
||||
21:47:08.269 [main] INFO com.iluwatar.async.method.invocation.App - Mission command is sipping coffee
|
||||
21:47:08.318 [executor-4] INFO com.iluwatar.async.method.invocation.App - Space rocket <20> launched successfully
|
||||
21:47:08.335 [executor-4] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <20>
|
||||
21:47:08.414 [executor-1] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launched successfully
|
||||
21:47:08.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Space rocket <callback> launched successfully
|
||||
21:47:08.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <callback>
|
||||
21:47:08.616 [executor-3] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launched successfully
|
||||
21:47:08.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launch complete
|
||||
21:47:08.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launch complete
|
||||
21:47:08.618 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launch complete
|
||||
21:47:08.227[executor-2]INFO com.iluwatar.async.method.invocation.App-Space rocket<test> launched successfully
|
||||
21:47:08.269[main]INFO com.iluwatar.async.method.invocation.App-Mission command is sipping coffee
|
||||
21:47:08.318[executor-4]INFO com.iluwatar.async.method.invocation.App-Space rocket<20>launched successfully
|
||||
21:47:08.335[executor-4]INFO com.iluwatar.async.method.invocation.App-Deploying lunar rover<20>
|
||||
21:47:08.414[executor-1]INFO com.iluwatar.async.method.invocation.App-Space rocket<10>launched successfully
|
||||
21:47:08.519[executor-5]INFO com.iluwatar.async.method.invocation.App-Space rocket<callback> launched successfully
|
||||
21:47:08.519[executor-5]INFO com.iluwatar.async.method.invocation.App-Deploying lunar rover<callback>
|
||||
21:47:08.616[executor-3]INFO com.iluwatar.async.method.invocation.App-Space rocket<50>launched successfully
|
||||
21:47:08.617[main]INFO com.iluwatar.async.method.invocation.App-Space rocket<10>launch complete
|
||||
21:47:08.617[main]INFO com.iluwatar.async.method.invocation.App-Space rocket<test> launch complete
|
||||
21:47:08.618[main]INFO com.iluwatar.async.method.invocation.App-Space rocket<50>launch complete
|
||||
```
|
||||
|
||||
# Class diagram
|
||||
@@ -166,14 +170,16 @@ Here's the program console output.
|
||||
Use the async method invocation pattern when
|
||||
|
||||
* When operations do not need to complete before proceeding with the next steps in a program.
|
||||
* For tasks that are resource-intensive or time-consuming, such as IO operations, network requests, or complex computations, where making the operation synchronous would significantly impact performance or user experience.
|
||||
* For tasks that are resource-intensive or time-consuming, such as IO operations, network requests, or complex
|
||||
computations, where making the operation synchronous would significantly impact performance or user experience.
|
||||
* In GUI applications to prevent freezing or unresponsiveness during long-running tasks.
|
||||
* In web applications for non-blocking IO operations.
|
||||
|
||||
## Known Uses
|
||||
|
||||
* Web servers handling HTTP requests asynchronously to improve throughput and reduce latency.
|
||||
* Desktop and mobile applications using background threads to perform time-consuming operations without blocking the user interface.
|
||||
* Desktop and mobile applications using background threads to perform time-consuming operations without blocking the
|
||||
user interface.
|
||||
* Microservices architectures where services perform asynchronous communications via messaging queues or event streams.
|
||||
* [FutureTask](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/FutureTask.html)
|
||||
* [CompletableFuture](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html)
|
||||
@@ -184,21 +190,29 @@ Use the async method invocation pattern when
|
||||
|
||||
Benefits:
|
||||
|
||||
* Improved Responsiveness: The main thread or application flow remains unblocked, improving the user experience in GUI applications and overall responsiveness.
|
||||
* Better Resource Utilization: By enabling parallel execution, system resources (like CPU and IO) are utilized more efficiently, potentially improving the application's throughput.
|
||||
* Improved Responsiveness: The main thread or application flow remains unblocked, improving the user experience in GUI
|
||||
applications and overall responsiveness.
|
||||
* Better Resource Utilization: By enabling parallel execution, system resources (like CPU and IO) are utilized more
|
||||
efficiently, potentially improving the application's throughput.
|
||||
* Scalability: Easier to scale applications, as tasks can be distributed across available resources more effectively.
|
||||
|
||||
Trade-offs:
|
||||
|
||||
* Complexity: Introducing asynchronous operations can complicate the codebase, making it more challenging to understand, debug, and maintain.
|
||||
* Resource Management: Requires careful management of threads or execution contexts, which can introduce overhead and potential resource exhaustion issues.
|
||||
* Error Handling: Asynchronous operations can make error handling more complex, as exceptions may occur in different threads or at different times.
|
||||
* Complexity: Introducing asynchronous operations can complicate the codebase, making it more challenging to understand,
|
||||
debug, and maintain.
|
||||
* Resource Management: Requires careful management of threads or execution contexts, which can introduce overhead and
|
||||
potential resource exhaustion issues.
|
||||
* Error Handling: Asynchronous operations can make error handling more complex, as exceptions may occur in different
|
||||
threads or at different times.
|
||||
|
||||
Related Patterns:
|
||||
|
||||
* [Command](https://java-design-patterns.com/patterns/command/): Asynchronous method invocation can be used to implement the Command pattern, where commands are executed asynchronously.
|
||||
* [Observer](https://java-design-patterns.com/patterns/observer/): Asynchronous method invocation can be used to notify observers asynchronously when a subject's state changes.
|
||||
* [Promise](https://java-design-patterns.com/patterns/promise/): The AsyncResult interface can be considered a form of Promise, representing a value that may not be available yet.
|
||||
* [Command](https://java-design-patterns.com/patterns/command/): Asynchronous method invocation can be used to implement
|
||||
the Command pattern, where commands are executed asynchronously.
|
||||
* [Observer](https://java-design-patterns.com/patterns/observer/): Asynchronous method invocation can be used to notify
|
||||
observers asynchronously when a subject's state changes.
|
||||
* [Promise](https://java-design-patterns.com/patterns/promise/): The AsyncResult interface can be considered a form of
|
||||
Promise, representing a value that may not be available yet.
|
||||
|
||||
## Credits
|
||||
|
||||
|
||||
Reference in New Issue
Block a user