com.exasol.projectkeeper.stream.AsyncStreamReader Maven / Gradle / Ivy

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Project keeper is a tool that verifies and fixes project setups.

There is a newer version: 4.4.0

package com.exasol.projectkeeper.stream;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.Thread.UncaughtExceptionHandler;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.Executor;
import java.util.function.Consumer;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.exasol.errorreporting.ExaError;

/**
 * This class starts a new {@link Thread} that reads from an {@link InputStream} and forwards the input line by line to
 * a given {@link Consumer}.
 */
public class AsyncStreamReader {
    private static final Logger LOGGER = Logger.getLogger(AsyncStreamReader.class.getName());

    private Executor executor;

    /**
     * Creates a new {@link AsyncStreamReader} that starts a new thread for reading the stream.
     */
    public AsyncStreamReader() {
        this(createThreadExecutor());
    }

    AsyncStreamReader(Executor executor) {
        this.executor = executor;
    }

    private static Executor createThreadExecutor() {
        return runnable -> {
            Thread thread = new Thread(runnable);
            thread.setUncaughtExceptionHandler(new LoggingExceptionHandler());
            thread.start();
        };
    }

    /**
     * Start a new {@link Thread} that reads from the given {@link InputStream} and forwards the input to a
     * {@link CollectingConsumer}.
     * 
     * @param stream the input stream to read
     * @return a {@link CollectingConsumer} that collects the data from the input stream
     */
    public CollectingConsumer startCollectingConsumer(InputStream stream) {
        CollectingConsumer consumer = new CollectingConsumer();
        executor.execute(() -> readStream(stream, consumer));
        return consumer;
    }

    private void readStream(InputStream stream, StreamConsumer consumer) {
        try (final BufferedReader reader = new BufferedReader(new InputStreamReader(stream, StandardCharsets.UTF_8))) {
            String line = null;
            while ((line = reader.readLine()) != null) {
                consumer.accept(line);
            }
            consumer.readFinished();
        } catch (IOException exception) {
            consumer.readFailed(exception);
            LOGGER.log(Level.WARNING,
                    ExaError.messageBuilder("E-PK-CORE-98").message("Failed to read input stream").toString(),
                    exception);
        }
    }

    private static class LoggingExceptionHandler implements UncaughtExceptionHandler {
        @Override
        public void uncaughtException(Thread thread, Throwable throwable) {
            LOGGER.log(Level.SEVERE, ExaError.messageBuilder("E-PK-CORE-97").message("Failed to read input stream")
                    .ticketMitigation().toString(), throwable);
        }
    }
}