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Code Issues Actions Releases 21 Activity

Implement stream reader for trips (#1)

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This commit is contained in:
Stefan Kalscheuer
2018-11-16 14:35:45 +01:00
parent e957553e80
commit 90b7c5cb35
5 changed files with 291 additions and 2 deletions
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73
src/main/java/de/stklcode/pubtrans/ura/UraClient.java
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@ -19,11 +19,14 @@ package de.stklcode.pubtrans.ura;
import com.fasterxml.jackson.databind.ObjectMapper;
import de.stklcode.pubtrans.ura.model.Stop;
import de.stklcode.pubtrans.ura.model.Trip;
import de.stklcode.pubtrans.ura.reader.AsyncUraTripReader;
import java.io.*;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.function.Consumer;
/**
* Client for URA based public transport API.
@ -237,6 +240,38 @@ public class UraClient implements Serializable {
return trips;
}
/**
* Get trips for given stopIDs and lineIDs using stream API and pass each result to given consumer.
*
* @param query The query.
* @param consumer Consumer(s) for single trips.
* @see #getTripsStream(Query, List)
* @since 1.2.0
*/
public AsyncUraTripReader getTripsStream(final Query query, final Consumer<Trip> consumer) throws IOException {
return getTripsStream(query, Collections.singletonList(consumer));
}
/**
* Get trips for given stopIDs and lineIDs using stream API and pass each result to given consumers.
*
* @param query The query.
* @param consumers Consumer(s) for single trips.
* @since 1.2.0
*/
public AsyncUraTripReader getTripsStream(final Query query, final List<Consumer<Trip>> consumers) throws IOException {
// Create the reader.
AsyncUraTripReader reader = new AsyncUraTripReader(
new URL(requestURL(baseURL + streamURL, REQUEST_TRIP, query)),
consumers
);
// Open the reader, i.e. start reading from API.
reader.open();
return reader;
}
/**
* Get list of stops without filters.
*
@ -280,7 +315,20 @@ public class UraClient implements Serializable {
* @throws IOException on errors
*/
private InputStream requestInstant(final String[] returnList, final Query query) throws IOException {
String urlStr = baseURL + instantURL + "?ReturnList=" + String.join(",", returnList);
return request(requestURL(baseURL + instantURL, returnList, query));
}
/**
* Build request URL from given parameters.
*
* @param endpointURL Endpoint URL.
* @param returnList Fields to fetch.
* @param query The query.
* @return The URL
* @since 1.2.0
*/
private String requestURL(final String endpointURL, final String[] returnList, final Query query) {
String urlStr = endpointURL + "?ReturnList=" + String.join(",", returnList);
if (query.stopIDs != null && query.stopIDs.length > 0) {
urlStr += "&" + PAR_STOP_ID + "=" + String.join(",", query.stopIDs);
@ -307,7 +355,7 @@ public class UraClient implements Serializable {
urlStr += "&" + PAR_CIRCLE + "=" + String.join(",", query.circle);
}
return request(urlStr);
return urlStr;
}
/**
@ -444,5 +492,26 @@ public class UraClient implements Serializable {
public List<Trip> getTrips() {
return UraClient.this.getTrips(this);
}
/**
* Get trips for set filters.
*
* @param consumer Consumer for single trips.
* @see #getTripsStream(List)
* @since 1.2.0
*/
public AsyncUraTripReader getTripsStream(Consumer<Trip> consumer) throws IOException {
return UraClient.this.getTripsStream(this, consumer);
}
/**
* Get trips for set filters.
*
* @param consumers Consumers for single trips.
* @since 1.2.0
*/
public AsyncUraTripReader getTripsStream(List<Consumer<Trip>> consumers) throws IOException {
return UraClient.this.getTripsStream(this, consumers);
}
}
}

127
src/main/java/de/stklcode/pubtrans/ura/reader/AsyncUraTripReader.java Normal file
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@ -0,0 +1,127 @@
/*
* Copyright 2016-2018 Stefan Kalscheuer
*
* 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
*
* http://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 de.stklcode.pubtrans.ura.reader;
import com.fasterxml.jackson.databind.ObjectMapper;
import de.stklcode.pubtrans.ura.model.Trip;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;
import java.util.function.Consumer;
/**
* Asynchronous stream reader foR URA stream API.
* <p>
* This reader provides a handler for asynchronous stream events.
*
* @author Stefan Kalscheuer
* @since 1.2.0
*/
public class AsyncUraTripReader implements AutoCloseable {
private static final Integer RES_TYPE_PREDICTION = 1;
private static final Integer RES_TYPE_URA_VERSION = 4;
private final List<Consumer<Trip>> consumers;
private final URL url;
private CompletableFuture<Void> future;
private boolean cancelled;
/**
* Initialize trip reader.
*
* @param url URL to read trips from.
* @param consumers Initial list of consumers.
*/
public AsyncUraTripReader(URL url, List<Consumer<Trip>> consumers) {
this.url = url;
this.consumers = new ArrayList<>(consumers);
}
public void open() {
// Throw exeption, if future is already present.
if (future != null) {
throw new IllegalStateException("Reader already opened");
}
this.future = CompletableFuture.runAsync(() -> {
ObjectMapper mapper = new ObjectMapper();
try (InputStream is = url.openStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is))) {
String version = null;
String line = br.readLine();
while (line != null && !this.cancelled) {
List l = mapper.readValue(line, List.class);
// Check if result exists and has correct response type.
if (l != null && !l.isEmpty()) {
if (l.get(0).equals(RES_TYPE_URA_VERSION)) {
version = l.get(1).toString();
} else if (l.get(0).equals(RES_TYPE_PREDICTION)) {
// Parse Trip and pass to each consumer.
Trip trip = new Trip(l, version);
this.consumers.forEach(c -> c.accept(trip));
}
}
line = br.readLine();
}
} catch (IOException e) {
throw new IllegalStateException("Failed to read from API", e);
}
});
}
/**
* Register an additional consumer.
*
* @param consumer New consumer.
*/
public void addConsumer(Consumer<Trip> consumer) {
consumers.add(consumer);
}
/**
* Close the reader.
* This is done by signaliung cancel to the asyncronous task. If the task is not completed
* within 1 second however it is cancelled hard.
*/
@Override
public void close() {
// Nothing to do if future is not yet started.
if (future == null) {
return;
}
// Signal cancelling to gracefully stop future.
cancelled = true;
try {
future.get(1, TimeUnit.SECONDS);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} catch (ExecutionException e) {
throw new IllegalStateException("Failed to read from API", e);
} catch (TimeoutException e) {
// Task failed to finish within 1 second.
future.cancel(true);
}
}
}