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package org.jooby;
import static java.util.Objects.requireNonNull;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.ForkJoinPool;
/**
* async request processing
*
* A Deferred result, useful for async request processing.
*
*
* Application can produces a result from a different thread. Once result is ready, a call to
* {@link #resolve(Object)} is required. Please note, a call to {@link #reject(Throwable)} is
* required in case of errors.
*
*
* usage
*
*
* {
* get("/async", deferred(() {@literal ->} {
* return "Success";
* }));
* }
*
*
* From MVC route:
*
* {@code
*
* public class Controller {
* @GET
* @Path("/async")
* public Deferred async() {
* return Deferred.deferred(() -> "Success");
* }
* }
* }
*
* If you add the {@link AsyncMapper} then your controller method can return a {@link Callable}.
*
* Previous example runs in the default executor, which always run deferred results in the
* same/caller thread.
*
* To effectively run a deferred result in new/different thread you need to provide an
* {@link Executor}:
*
* {@code
* {
* executor(new ForkJoinPool());
* }
* }
*
* This line override the default executor with a {@link ForkJoinPool}. You can add two or more
* named executor:
*
* {@code
* {
* executor(new ForkJoinPool());
*
* executor("cached", Executors.newCachedExecutor());
*
* get("/async", deferred("cached", () -> "Success"));
* }
* }
*
* A {@link Deferred} object works as a promise too, given you {@link #resolve(Object)} and
* {@link #reject(Throwable)} methods. Examples:
*
* As promise using the default executor (execute promise in same/caller thread):
*
* {
* get("/async", promise(deferred {@literal ->} {
* try {
* deferred.resolve(...); // success value
* } catch (Throwable ex) {
* deferred.reject(ex); // error value
* }
* }));
* }
*
*
* As promise using a custom executor:
*
* {
* executor(new ForkJoinPool());
*
* get("/async", promise(deferred {@literal ->} {
* try {
* deferred.resolve(...); // success value
* } catch (Throwable ex) {
* deferred.reject(ex); // error value
* }
* }));
* }
*
*
* As promise using an alternative executor:
*
*
* {
* executor(new ForkJoinPool());
*
* executor("cached", Executors.newCachedExecutor());
*
* get("/async", promise("cached", deferred {@literal ->} {
* try {
* deferred.resolve(...); // success value
* } catch (Throwable ex) {
* deferred.reject(ex); // error value
* }
* }));
* }
*
*
* @author edgar
* @since 0.10.0
*/
public class Deferred extends Result {
/**
* Deferred initializer, useful to provide a more functional API.
*
* @author edgar
* @since 0.10.0
*/
public interface Initializer0 {
/**
* Run the initializer block.
*
* @param deferred Deferred object.
* @throws Exception If something goes wrong.
*/
void run(Deferred deferred) throws Exception;
}
/**
* Deferred initializer with {@link Request} access, useful to provide a more functional API.
*
* @author edgar
* @since 0.10.0
*/
public interface Initializer {
/**
* Run the initializer block.
*
* @param req Current request.
* @param deferred Deferred object.
* @throws Exception If something goes wrong.
*/
void run(Request req, Deferred deferred) throws Exception;
}
/**
* A deferred handler. Application code should never use this class. INTERNAL USE ONLY.
*
* @author edgar
* @since 0.10.0
*/
public interface Handler {
void handle(@Nullable Result result, Throwable exception);
}
/** Deferred initializer. Optional. */
private Initializer initializer;
/** Deferred handler. Internal. */
private Handler handler;
private String executor;
private String callerThread;
/**
* Creates a new {@link Deferred} with an initializer.
*
* @param executor Executor to use.
* @param initializer An initializer.
*/
public Deferred(final String executor, final Initializer0 initializer) {
this(executor, (req, deferred) -> initializer.run(deferred));
}
/**
* Creates a new {@link Deferred} with an initializer.
*
* @param initializer An initializer.
*/
public Deferred(final Initializer0 initializer) {
this(null, initializer);
}
/**
* Creates a new {@link Deferred} with an initializer.
*
* @param initializer An initializer.
*/
public Deferred(final Initializer initializer) {
this(null, initializer);
}
/**
* Creates a new {@link Deferred} with an initializer.
*
* @param executor Executor to use.
* @param initializer An initializer.
*/
public Deferred(@Nullable final String executor, final Initializer initializer) {
this.executor = executor;
this.initializer = requireNonNull(initializer, "Initializer is required.");
this.callerThread = Thread.currentThread().getName();
}
/**
* Creates a new {@link Deferred}.
*/
public Deferred() {
}
/**
* {@link #resolve(Object)} or {@link #reject(Throwable)} the given value.
*
* @param value Resolved value.
*/
@Override
@Nonnull
public Result set(final Object value) {
if (value instanceof Throwable) {
reject((Throwable) value);
} else {
resolve(value);
}
return this;
}
/**
* Get an executor to run this deferred result. If the executor is present, then it will be use it
* to execute the deferred object. Otherwise it will use the global/application executor.
*
* @return Executor to use or fallback to global/application executor.
*/
@Nonnull
public Optional executor() {
return Optional.ofNullable(executor);
}
/**
* Name of the caller thread (thread that creates this deferred object).
*
* @return Name of the caller thread (thread that creates this deferred object).
*/
@Nonnull
public String callerThread() {
return callerThread;
}
/**
* Resolve the deferred value and handle it. This method will send the response to a client and
* cleanup and close all the resources.
*
* @param value A value for this deferred.
*/
public void resolve(@Nullable final Object value) {
if (value == null) {
handler.handle(null, null);
} else {
Result result;
if (value instanceof Result) {
super.set(value);
result = (Result) value;
} else {
super.set(value);
result = clone();
}
handler.handle(result, null);
}
}
/**
* Resolve the deferred with an error and handle it. This method will handle the given exception,
* send the response to a client and cleanup and close all the resources.
*
* @param cause A value for this deferred.
*/
public void reject(final Throwable cause) {
super.set(cause);
handler.handle(null, cause);
}
/**
* Setup a handler for this deferred. Application code should never call this method: INTERNAL USE
* ONLY.
*
* @param req Current request.
* @param handler A response handler.
* @throws Exception If initializer fails to start.
*/
public void handler(final Request req, final Handler handler) throws Exception {
this.handler = requireNonNull(handler, "Handler is required.");
if (initializer != null) {
initializer.run(req, this);
}
}
/**
* Functional version of {@link Deferred#Deferred(Initializer)}.
*
* Using the default executor (current thread):
*
* {@code
* {
* get("/fork", deferred(req -> {
* return req.param("value").value();
* }));
* }
* }
*
* Using a custom executor:
*
* {@code
* {
* executor(new ForkJoinPool());
*
* get("/fork", deferred(req -> {
* return req.param("value").value();
* }));
* }
* }
*
* This handler automatically {@link Deferred#resolve(Object)} or
* {@link Deferred#reject(Throwable)} a route handler response.
*
* @param handler Application block.
* @return A new deferred handler.
*/
@Nonnull
public static Deferred deferred(final Route.OneArgHandler handler) {
return deferred(null, handler);
}
/**
* Functional version of {@link Deferred#Deferred(Initializer)}.
*
* Using the default executor (current thread):
*
* {@code
* {
* get("/fork", deferred(() -> {
* return req.param("value").value();
* }));
* }
* }
*
* Using a custom executor:
*
* {@code
* {
* executor(new ForkJoinPool());
*
* get("/fork", deferred(() -> {
* return req.param("value").value();
* }));
* }
* }
*
* This handler automatically {@link Deferred#resolve(Object)} or
* {@link Deferred#reject(Throwable)} a route handler response.
*
* @param handler Application block.
* @return A new deferred.
*/
@Nonnull
public static Deferred deferred(final Route.ZeroArgHandler handler) {
return deferred(null, handler);
}
/**
* Functional version of {@link Deferred#Deferred(Initializer)}. To use ideally with one
* or more {@link Executor}:
*
* {@code
* {
* executor("cached", Executors.newCachedExecutor());
*
* get("/fork", deferred("cached", () -> {
* return "OK";
* }));
* }
* }
*
* This handler automatically {@link Deferred#resolve(Object)} or
* {@link Deferred#reject(Throwable)} a route handler response.
*
* @param executor Executor to run the deferred.
* @param handler Application block.
* @return A new deferred handler.
*/
@Nonnull
public static Deferred deferred(final String executor, final Route.ZeroArgHandler handler) {
return deferred(executor, req -> handler.handle());
}
/**
* Functional version of {@link Deferred#Deferred(Initializer)}. To use ideally with one
* or more {@link Executor}:
*
* {@code
* {
* executor("cached", Executors.newCachedExecutor());
*
* get("/fork", deferred("cached", req -> {
* return req.param("value").value();
* }));
* }
* }
*
* This handler automatically {@link Deferred#resolve(Object)} or
* {@link Deferred#reject(Throwable)} a route handler response.
*
* @param executor Executor to run the deferred.
* @param handler Application block.
* @return A new deferred handler.
*/
@Nonnull
public static Deferred deferred(final String executor, final Route.OneArgHandler handler) {
return new Deferred(executor, (req, deferred) -> {
try {
deferred.resolve(handler.handle(req));
} catch (Throwable x) {
deferred.reject(x);
}
});
}
}