library/src/main/java/com/bumptech/glide/load/data/HttpUrlFetcher.java

package com.bumptech.glide.load.data;

import android.text.TextUtils;

import com.bumptech.glide.Priority;
import com.bumptech.glide.load.model.GlideUrl;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URISyntaxException;
import java.net.URL;

/**
 * A DataFetcher that retrieves an {@link java.io.InputStream} for a Url.
 */
public class HttpUrlFetcher implements DataFetcher<InputStream> {
    private static final int MAXIMUM_REDIRECTS = 5;
    private static final HttpUrlConnectionFactory DEFAULT_CONNECTION_FACTORY = new DefaultHttpUrlConnectionFactory();

    private final GlideUrl glideUrl;
    private final HttpUrlConnectionFactory connectionFactory;

    private HttpURLConnection urlConnection;
    private InputStream stream;
    private volatile boolean isCancelled;

    public HttpUrlFetcher(GlideUrl glideUrl) {
        this(glideUrl, DEFAULT_CONNECTION_FACTORY);
    }

    // Visible for testing.
    HttpUrlFetcher(GlideUrl glideUrl, HttpUrlConnectionFactory connectionFactory) {
        this.glideUrl = glideUrl;
        this.connectionFactory = connectionFactory;
    }

    @Override
    public InputStream loadData(Priority priority) throws Exception {
        return loadDataWithRedirects(glideUrl.toURL(), 0 /*redirects*/, null /*lastUrl*/);
    }

    private InputStream loadDataWithRedirects(URL url, int redirects, URL lastUrl) throws IOException {
        if (redirects >= MAXIMUM_REDIRECTS) {
            throw new IOException("Too many (> " + MAXIMUM_REDIRECTS + ") redirects!");
        } else {
            // Comparing the URLs using .equals performs additional network I/O and is generally broken.
            // See http://michaelscharf.blogspot.com/2006/11/javaneturlequals-and-hashcode-make.html.
            try {
                if (lastUrl != null && url.toURI().equals(lastUrl.toURI())) {
                    throw new IOException("In re-direct loop");
                }
            } catch (URISyntaxException e) {
                // Do nothing, this is best effort.
            }
        }
        urlConnection = connectionFactory.build(url);
        urlConnection.setConnectTimeout(2500);
        urlConnection.setReadTimeout(2500);
        urlConnection.setUseCaches(false);
        urlConnection.setDoInput(true);

        // Connect explicitly to avoid errors in decoders if connection fails.
        urlConnection.connect();
        if (isCancelled) {
            return null;
        }
        final int statusCode = urlConnection.getResponseCode();
        if (statusCode / 100 == 2) {
            stream = urlConnection.getInputStream();
            return stream;
        } else if (statusCode / 100 == 3) {
            String redirectUrlString = urlConnection.getHeaderField("Location");
            if (TextUtils.isEmpty(redirectUrlString)) {
                throw new IOException("Received empty or null redirect url");
            }
            URL redirectUrl = new URL(url, redirectUrlString);
            return loadDataWithRedirects(redirectUrl, redirects + 1, url);
        } else {
            if (statusCode == -1) {
                throw new IOException("Unable to retrieve response code from HttpUrlConnection.");
            }
            throw new IOException("Request failed " + statusCode + ": " + urlConnection.getResponseMessage());
        }
    }

    @Override
    public void cleanup() {
        if (stream != null) {
            try {
                stream.close();
            } catch (IOException e) {
                // Ignore
            }
        }
        if (urlConnection != null) {
            urlConnection.disconnect();
        }
    }

    @Override
    public String getId() {
        return glideUrl.toString();
    }

    @Override
    public void cancel() {
        // TODO: we should consider disconnecting the url connection here, but we can't do so directly because cancel is
        // often called on the main thread.
        isCancelled = true;
    }

    interface HttpUrlConnectionFactory {
        HttpURLConnection build(URL url) throws IOException;
    }

    private static class DefaultHttpUrlConnectionFactory implements HttpUrlConnectionFactory {
        @Override
        public HttpURLConnection build(URL url) throws IOException {
            return (HttpURLConnection) url.openConnection();
        }
    }
}