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DefaultWotThingModelFetcher.java
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DefaultWotThingModelFetcher.java
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/*
* Copyright (c) 2022 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0
*
* SPDX-License-Identifier: EPL-2.0
*/
package org.eclipse.ditto.wot.integration.provider;
import java.net.MalformedURLException;
import java.net.URL;
import java.text.MessageFormat;
import java.util.List;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.Executor;
import javax.annotation.Nullable;
import org.eclipse.ditto.base.model.exceptions.DittoRuntimeException;
import org.eclipse.ditto.base.model.headers.DittoHeaders;
import org.eclipse.ditto.internal.utils.akka.logging.DittoLoggerFactory;
import org.eclipse.ditto.internal.utils.akka.logging.ThreadSafeDittoLogger;
import org.eclipse.ditto.internal.utils.cache.Cache;
import org.eclipse.ditto.internal.utils.cache.CacheFactory;
import org.eclipse.ditto.internal.utils.http.DefaultHttpClientFacade;
import org.eclipse.ditto.internal.utils.http.HttpClientFacade;
import org.eclipse.ditto.json.JsonFactory;
import org.eclipse.ditto.json.JsonObject;
import org.eclipse.ditto.json.JsonValue;
import org.eclipse.ditto.wot.integration.config.WotConfig;
import org.eclipse.ditto.wot.model.IRI;
import org.eclipse.ditto.wot.model.ThingDefinitionInvalidException;
import org.eclipse.ditto.wot.model.ThingModel;
import org.eclipse.ditto.wot.model.WotThingModelInvalidException;
import org.eclipse.ditto.wot.model.WotThingModelNotAccessibleException;
import com.github.benmanes.caffeine.cache.AsyncCacheLoader;
import akka.actor.ActorSystem;
import akka.http.javadsl.model.HttpHeader;
import akka.http.javadsl.model.HttpRequest;
import akka.http.javadsl.model.HttpResponse;
import akka.http.javadsl.model.MediaRanges;
import akka.http.javadsl.model.MediaTypes;
import akka.http.javadsl.model.headers.Accept;
import akka.http.javadsl.model.headers.Location;
import akka.stream.Materializer;
import akka.stream.SystemMaterializer;
import akka.stream.javadsl.Sink;
import akka.util.ByteString;
/**
* Default implementation of {@link WotThingModelFetcher} which should be not Ditto specific.
*/
final class DefaultWotThingModelFetcher implements WotThingModelFetcher {
private static final ThreadSafeDittoLogger LOGGER =
DittoLoggerFactory.getThreadSafeLogger(DefaultWotThingModelFetcher.class);
private static final HttpHeader ACCEPT_HEADER = Accept.create(
MediaRanges.create(MediaTypes.applicationWithOpenCharset("tm+json")),
MediaRanges.create(MediaTypes.APPLICATION_JSON)
);
private final HttpClientFacade httpClient;
private final Materializer materializer;
private final Cache<URL, ThingModel> thingModelCache;
DefaultWotThingModelFetcher(final ActorSystem actorSystem, final WotConfig wotConfig) {
this.httpClient = DefaultHttpClientFacade.getInstance(actorSystem, wotConfig.getHttpProxyConfig());
materializer = SystemMaterializer.get(actorSystem).materializer();
final AsyncCacheLoader<URL, ThingModel> loader = this::loadThingModelViaHttp;
thingModelCache = CacheFactory.createCache(loader,
wotConfig.getCacheConfig(),
"ditto_wot_thing_model_cache",
actorSystem.dispatchers().lookup("wot-dispatcher-cache-loader"));
}
@Override
public CompletableFuture<ThingModel> fetchThingModel(final IRI iri, final DittoHeaders dittoHeaders) {
try {
return fetchThingModel(new URL(iri.toString()), dittoHeaders);
} catch (final MalformedURLException e) {
throw ThingDefinitionInvalidException.newBuilder(iri)
.dittoHeaders(dittoHeaders)
.build();
}
}
@Override
public CompletableFuture<ThingModel> fetchThingModel(final URL url, final DittoHeaders dittoHeaders) {
LOGGER.withCorrelationId(dittoHeaders)
.debug("Fetching ThingModel (from cache or downloading as fallback) from URL: <{}>", url);
return thingModelCache.get(url)
.thenApply(optTm -> resolveThingModel(optTm.orElse(null), url, dittoHeaders));
}
private ThingModel resolveThingModel(@Nullable final ThingModel thingModel,
final URL tmUrl,
final DittoHeaders dittoHeaders) {
if (null != thingModel) {
LOGGER.withCorrelationId(dittoHeaders).debug("Resolved ThingModel: <{}>", thingModel);
return thingModel;
} else {
throw WotThingModelNotAccessibleException.newBuilder(tmUrl)
.dittoHeaders(dittoHeaders)
.build();
}
}
/* this method is used to asynchronously load the ThingModel into the cache */
private CompletableFuture<ThingModel> loadThingModelViaHttp(final URL url, final Executor executor) {
LOGGER.debug("Loading ThingModel from URL <{}>.", url);
final CompletionStage<HttpResponse> responseFuture = getThingModelFromUrl(url);
final CompletionStage<ThingModel> thingModelFuture = responseFuture.thenCompose(
response -> mapResponseToThingModel(response, url));
return thingModelFuture.toCompletableFuture();
}
private CompletionStage<HttpResponse> getThingModelFromUrl(final URL url) {
return httpClient.createSingleHttpRequest(HttpRequest.GET(url.toString()).withHeaders(List.of(ACCEPT_HEADER)))
.thenCompose(response -> {
if (response.status().isRedirection()) {
return response.getHeader(Location.class)
.map(location -> {
try {
LOGGER.debug("Following redirect to location: <{}>", location);
return new URL(location.getUri().toString());
} catch (final MalformedURLException e) {
throw DittoRuntimeException.asDittoRuntimeException(e,
cause -> handleUnexpectedException(cause, url));
}
})
.map(this::getThingModelFromUrl) // recurse following the redirect
.orElseGet(() -> CompletableFuture.completedFuture(response));
} else {
return CompletableFuture.completedFuture(response);
}
})
.thenApply(response -> {
if (!response.status().isSuccess() || response.status().isRedirection()) {
handleNonSuccessResponse(response, url);
}
return response;
})
.exceptionally(e -> {
throw DittoRuntimeException.asDittoRuntimeException(e,
cause -> handleUnexpectedException(cause, url));
});
}
private CompletableFuture<ThingModel> mapResponseToThingModel(final HttpResponse response, final URL url) {
final CompletableFuture<JsonObject> bodyFuture = mapResponseToJsonObject(response)
.toCompletableFuture();
return bodyFuture
.thenApply(ThingModel::fromJson)
.exceptionally(t -> {
LOGGER.warn("Failed to extract ThingModel from response <{}> because of <{}: {}>", response,
t.getClass().getSimpleName(), t.getMessage());
throw WotThingModelInvalidException.newBuilder(url)
.cause(t)
.build();
});
}
private CompletionStage<JsonObject> mapResponseToJsonObject(final HttpResponse response) {
return response.entity().getDataBytes().fold(ByteString.emptyByteString(), ByteString::concat)
.map(ByteString::utf8String)
.map(JsonFactory::readFrom)
.map(JsonValue::asObject)
.runWith(Sink.head(), materializer);
}
private void handleNonSuccessResponse(final HttpResponse response, final URL url) {
final String msg = MessageFormat.format(
"Got non success response from ThingModel endpoint with status code: <{0}>", response.status());
getBodyAsString(response)
.thenAccept(stringBody -> LOGGER.info("{} and body: <{}>.", msg, stringBody));
throw WotThingModelNotAccessibleException.newBuilder(url)
.build();
}
private CompletionStage<String> getBodyAsString(final HttpResponse response) {
return response.entity().getDataBytes().fold(ByteString.emptyByteString(), ByteString::concat)
.map(ByteString::utf8String)
.runWith(Sink.head(), materializer);
}
private static DittoRuntimeException handleUnexpectedException(final Throwable e, final URL url) {
final String msg = MessageFormat.format("Got Exception from ThingModel endpoint <{0}>.", url);
LOGGER.warn(msg, e);
throw WotThingModelNotAccessibleException.newBuilder(url)
.cause(e)
.build();
}
}