org.springframework.core.ReactiveAdapterRegistry Maven / Gradle / Ivy
/*
* Copyright 2002-2022 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.core;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.Flow;
import java.util.function.Function;
import kotlinx.coroutines.CompletableDeferredKt;
import kotlinx.coroutines.Deferred;
import org.reactivestreams.Publisher;
import reactor.adapter.JdkFlowAdapter;
import reactor.blockhound.BlockHound;
import reactor.blockhound.integration.BlockHoundIntegration;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;
import org.springframework.util.ConcurrentReferenceHashMap;
/**
* A registry of adapters to adapt Reactive Streams {@link Publisher} to/from
* various async/reactive types such as {@code CompletableFuture}, RxJava
* {@code Flowable}, and others.
*
* By default, depending on classpath availability, adapters are registered
* for Reactor, RxJava 3, {@link CompletableFuture}, {@code Flow.Publisher},
* and Kotlin Coroutines' {@code Deferred} and {@code Flow}.
*
* @author Rossen Stoyanchev
* @author Sebastien Deleuze
* @author Juergen Hoeller
* @since 5.0
*/
public class ReactiveAdapterRegistry {
@Nullable
private static volatile ReactiveAdapterRegistry sharedInstance;
private static final boolean reactorPresent;
private static final boolean rxjava3Present;
private static final boolean kotlinCoroutinesPresent;
private static final boolean mutinyPresent;
static {
ClassLoader classLoader = ReactiveAdapterRegistry.class.getClassLoader();
reactorPresent = ClassUtils.isPresent("reactor.core.publisher.Flux", classLoader);
rxjava3Present = ClassUtils.isPresent("io.reactivex.rxjava3.core.Flowable", classLoader);
kotlinCoroutinesPresent = ClassUtils.isPresent("kotlinx.coroutines.reactor.MonoKt", classLoader);
mutinyPresent = ClassUtils.isPresent("io.smallrye.mutiny.Multi", classLoader);
}
private final List adapters = new ArrayList<>();
/**
* Create a registry and auto-register default adapters.
* @see #getSharedInstance()
*/
public ReactiveAdapterRegistry() {
// Reactor
if (reactorPresent) {
new ReactorRegistrar().registerAdapters(this);
}
// RxJava
if (rxjava3Present) {
new RxJava3Registrar().registerAdapters(this);
}
// Kotlin Coroutines
if (reactorPresent && kotlinCoroutinesPresent) {
new CoroutinesRegistrar().registerAdapters(this);
}
// SmallRye Mutiny
if (mutinyPresent) {
new MutinyRegistrar().registerAdapters(this);
}
}
/**
* Whether the registry has any adapters.
*/
public boolean hasAdapters() {
return !this.adapters.isEmpty();
}
/**
* Register a reactive type along with functions to adapt to and from a
* Reactive Streams {@link Publisher}. The function arguments assume that
* their input is neither {@code null} nor {@link Optional}.
*/
public void registerReactiveType(ReactiveTypeDescriptor descriptor,
Function> toAdapter, Function, Object> fromAdapter) {
if (reactorPresent) {
this.adapters.add(new ReactorAdapter(descriptor, toAdapter, fromAdapter));
}
else {
this.adapters.add(new ReactiveAdapter(descriptor, toAdapter, fromAdapter));
}
}
/**
* Get the adapter for the given reactive type.
* @return the corresponding adapter, or {@code null} if none available
*/
@Nullable
public ReactiveAdapter getAdapter(Class reactiveType) {
return getAdapter(reactiveType, null);
}
/**
* Get the adapter for the given reactive type. Or if a "source" object is
* provided, its actual type is used instead.
* @param reactiveType the reactive type
* (may be {@code null} if a concrete source object is given)
* @param source an instance of the reactive type
* (i.e. to adapt from; may be {@code null} if the reactive type is specified)
* @return the corresponding adapter, or {@code null} if none available
*/
@Nullable
public ReactiveAdapter getAdapter(@Nullable Class reactiveType, @Nullable Object source) {
if (this.adapters.isEmpty()) {
return null;
}
Object sourceToUse = (source instanceof Optional ? ((Optional) source).orElse(null) : source);
Class clazz = (sourceToUse != null ? sourceToUse.getClass() : reactiveType);
if (clazz == null) {
return null;
}
for (ReactiveAdapter adapter : this.adapters) {
if (adapter.getReactiveType() == clazz) {
return adapter;
}
}
for (ReactiveAdapter adapter : this.adapters) {
if (adapter.getReactiveType().isAssignableFrom(clazz)) {
return adapter;
}
}
return null;
}
/**
* Return a shared default {@code ReactiveAdapterRegistry} instance,
* lazily building it once needed.
* NOTE: We highly recommend passing a long-lived, pre-configured
* {@code ReactiveAdapterRegistry} instance for customization purposes.
* This accessor is only meant as a fallback for code paths that want to
* fall back on a default instance if one isn't provided.
* @return the shared {@code ReactiveAdapterRegistry} instance
* @since 5.0.2
*/
public static ReactiveAdapterRegistry getSharedInstance() {
ReactiveAdapterRegistry registry = sharedInstance;
if (registry == null) {
synchronized (ReactiveAdapterRegistry.class) {
registry = sharedInstance;
if (registry == null) {
registry = new ReactiveAdapterRegistry();
sharedInstance = registry;
}
}
}
return registry;
}
/**
* ReactiveAdapter variant that wraps adapted Publishers as {@link Flux} or
* {@link Mono} depending on {@link ReactiveTypeDescriptor#isMultiValue()}.
* This is important in places where only the stream and stream element type
* information is available like encoders and decoders.
*/
private static class ReactorAdapter extends ReactiveAdapter {
ReactorAdapter(ReactiveTypeDescriptor descriptor,
Function> toPublisherFunction,
Function, Object> fromPublisherFunction) {
super(descriptor, toPublisherFunction, fromPublisherFunction);
}
@Override
public Publisher toPublisher(@Nullable Object source) {
Publisher publisher = super.toPublisher(source);
return (isMultiValue() ? Flux.from(publisher) : Mono.from(publisher));
}
}
private static class ReactorRegistrar {
private static final Flow.Publisher EMPTY_FLOW = JdkFlowAdapter.publisherToFlowPublisher(Flux.empty());
void registerAdapters(ReactiveAdapterRegistry registry) {
// Register Flux and Mono before Publisher...
registry.registerReactiveType(
ReactiveTypeDescriptor.singleOptionalValue(Mono.class, Mono::empty),
source -> (Mono) source,
Mono::from);
registry.registerReactiveType(
ReactiveTypeDescriptor.multiValue(Flux.class, Flux::empty),
source -> (Flux) source,
Flux::from);
registry.registerReactiveType(
ReactiveTypeDescriptor.multiValue(Publisher.class, Flux::empty),
source -> (Publisher) source,
source -> source);
registry.registerReactiveType(
ReactiveTypeDescriptor.nonDeferredAsyncValue(CompletionStage.class, EmptyCompletableFuture::new),
source -> Mono.fromCompletionStage((CompletionStage) source),
source -> Mono.from(source).toFuture());
registry.registerReactiveType(
ReactiveTypeDescriptor.multiValue(Flow.Publisher.class, () -> EMPTY_FLOW),
source -> JdkFlowAdapter.flowPublisherToFlux((Flow.Publisher) source),
JdkFlowAdapter::publisherToFlowPublisher);
}
}
private static class EmptyCompletableFuture extends CompletableFuture {
EmptyCompletableFuture() {
complete(null);
}
}
private static class RxJava3Registrar {
void registerAdapters(ReactiveAdapterRegistry registry) {
registry.registerReactiveType(
ReactiveTypeDescriptor.multiValue(
io.reactivex.rxjava3.core.Flowable.class,
io.reactivex.rxjava3.core.Flowable::empty),
source -> (io.reactivex.rxjava3.core.Flowable) source,
io.reactivex.rxjava3.core.Flowable::fromPublisher);
registry.registerReactiveType(
ReactiveTypeDescriptor.multiValue(
io.reactivex.rxjava3.core.Observable.class,
io.reactivex.rxjava3.core.Observable::empty),
source -> ((io.reactivex.rxjava3.core.Observable) source).toFlowable(
io.reactivex.rxjava3.core.BackpressureStrategy.BUFFER),
io.reactivex.rxjava3.core.Observable::fromPublisher);
registry.registerReactiveType(
ReactiveTypeDescriptor.singleRequiredValue(io.reactivex.rxjava3.core.Single.class),
source -> ((io.reactivex.rxjava3.core.Single) source).toFlowable(),
io.reactivex.rxjava3.core.Single::fromPublisher);
registry.registerReactiveType(
ReactiveTypeDescriptor.singleOptionalValue(
io.reactivex.rxjava3.core.Maybe.class,
io.reactivex.rxjava3.core.Maybe::empty),
source -> ((io.reactivex.rxjava3.core.Maybe) source).toFlowable(),
io.reactivex.rxjava3.core.Maybe::fromPublisher);
registry.registerReactiveType(
ReactiveTypeDescriptor.noValue(
io.reactivex.rxjava3.core.Completable.class,
io.reactivex.rxjava3.core.Completable::complete),
source -> ((io.reactivex.rxjava3.core.Completable) source).toFlowable(),
io.reactivex.rxjava3.core.Completable::fromPublisher);
}
}
private static class CoroutinesRegistrar {
@SuppressWarnings("KotlinInternalInJava")
void registerAdapters(ReactiveAdapterRegistry registry) {
registry.registerReactiveType(
ReactiveTypeDescriptor.singleOptionalValue(Deferred.class,
() -> CompletableDeferredKt.CompletableDeferred(null)),
source -> CoroutinesUtils.deferredToMono((Deferred) source),
source -> CoroutinesUtils.monoToDeferred(Mono.from(source)));
registry.registerReactiveType(
ReactiveTypeDescriptor.multiValue(kotlinx.coroutines.flow.Flow.class, kotlinx.coroutines.flow.FlowKt::emptyFlow),
source -> kotlinx.coroutines.reactor.ReactorFlowKt.asFlux((kotlinx.coroutines.flow.Flow) source),
kotlinx.coroutines.reactive.ReactiveFlowKt::asFlow);
}
}
private static class MutinyRegistrar {
void registerAdapters(ReactiveAdapterRegistry registry) {
registry.registerReactiveType(
ReactiveTypeDescriptor.singleOptionalValue(
io.smallrye.mutiny.Uni.class,
() -> io.smallrye.mutiny.Uni.createFrom().nothing()),
uni -> ((io.smallrye.mutiny.Uni) uni).convert().toPublisher(),
publisher -> io.smallrye.mutiny.Uni.createFrom().publisher(publisher));
registry.registerReactiveType(
ReactiveTypeDescriptor.multiValue(
io.smallrye.mutiny.Multi.class,
() -> io.smallrye.mutiny.Multi.createFrom().empty()),
multi -> (io.smallrye.mutiny.Multi) multi,
publisher -> io.smallrye.mutiny.Multi.createFrom().publisher(publisher));
}
}
/**
* {@code BlockHoundIntegration} for spring-core classes.
* Explicitly allows locking within {@link ConcurrentReferenceHashMap}.
* @since 5.2.4
*/
public static class SpringCoreBlockHoundIntegration implements BlockHoundIntegration {
@Override
public void applyTo(BlockHound.Builder builder) {
// Avoid hard references potentially anywhere in spring-core (no need for structural dependency)
String className = "org.springframework.util.ConcurrentReferenceHashMap$Segment";
builder.allowBlockingCallsInside(className, "doTask");
builder.allowBlockingCallsInside(className, "clear");
builder.allowBlockingCallsInside(className, "restructure");
}
}
}