com.android.repository.api

Interface Downloader

All Known Implementing Classes:

FakeDownloader, LocalFileAwareDownloader

public interface Downloader

Implementations provide a general mechanism for downloading files.

Method Summary

Modifier and Type	Method and Description
java.io.InputStream	downloadAndStream(java.net.URL url, ProgressIndicator indicator) Gets a stream associated with the content at the given URL.
void	downloadFully(java.net.URL url, java.io.File target, java.lang.String checksum, ProgressIndicator indicator) Downloads the content at the given URL to the given file.
java.nio.file.Path	downloadFully(java.net.URL url, ProgressIndicator indicator) Downloads the content at the given URL to a temporary file and returns a handle to that file.
default void	downloadFullyWithCaching(java.net.URL url, java.io.File target, java.lang.String checksum, ProgressIndicator indicator) Downloads the content at the given URL to the given file, using caching techniques if possible.
static java.lang.String	hash(java.io.InputStream in, long fileSize, ProgressIndicator progress) Hash the given input stream.

Method Detail

downloadAndStream

@Nullable
java.io.InputStream downloadAndStream(@NonNull
                                                java.net.URL url,
                                                @NonNull
                                                ProgressIndicator indicator)
                                         throws java.io.IOException

Gets a stream associated with the content at the given URL. This could be achieved by downloading the file completely, streaming it directly, or some combination.

Parameters:

url - The URL to fetch.

indicator - Facility for showing download progress and logging.

Returns:

An InputStream corresponding to the specified content, or null if the download is cancelled.

Throws:

java.io.IOException

downloadFully

@Nullable
java.nio.file.Path downloadFully(@NonNull
                                           java.net.URL url,
                                           @NonNull
                                           ProgressIndicator indicator)
                                    throws java.io.IOException

Downloads the content at the given URL to a temporary file and returns a handle to that file.

Parameters:

url - The URL to fetch.

indicator - Facility for showing download progress and logging.

Returns:

The temporary file, or null if the download is cancelled.

Throws:

java.io.IOException

downloadFully

void downloadFully(@NonNull
                   java.net.URL url,
                   @NonNull
                   java.io.File target,
                   @Nullable
                   java.lang.String checksum,
                   @NonNull
                   ProgressIndicator indicator)
            throws java.io.IOException

Downloads the content at the given URL to the given file. Calling this method instructs the downloader to fetch the content from the original server and bypass any caches.

For example, in case of HTTP connections, calling this method may be equivalent to adding "Cache-Control: no-cache" and "Pragma: no-cache" headers to the request, thus instructing the network facilities that no caching is expected to take place (e.g., on proxy servers).

Parameters:

url - The URL to fetch.

target - The location to download to.

checksum - If specified, first check target to see if the given checksum matches the existing file. If so, returns immediately.

indicator - Facility for showing download progress and logging.

Throws:

java.io.IOException

downloadFullyWithCaching

default void downloadFullyWithCaching(@NonNull
                                      java.net.URL url,
                                      @NonNull
                                      java.io.File target,
                                      @Nullable
                                      java.lang.String checksum,
                                      @NonNull
                                      ProgressIndicator indicator)
                               throws java.io.IOException

Downloads the content at the given URL to the given file, using caching techniques if possible. Which specific caching techniques to use is defined by the implementation. As far as the contract goes, calling this method instructs the downloader that the caller does not require the content to be fetched from the original server, and a previously cached copy may be re-used.

Note that calling this method does not guarantee caching or a better performance: it is an implementation detail how exactly this hint is used. For example, when checking for software updates availability, the caller will know that no caching must be used, so it should not call this method, and call downloadFully(java.net.URL, com.android.repository.api.ProgressIndicator) instead. On the other hand, for a large download which is not expected to change on the original server, the caller typically would not mind against intrinsic optimizations and caching, so in that case it should call this method.

Parameters:

url - The URL to fetch.

target - The location to download to.

checksum - If specified, first check target to see if the given checksum matches the existing file. If so, returns immediately.

indicator - Facility for showing download progress and logging.

Throws:

java.io.IOException

hash

@NonNull
static java.lang.String hash(@NonNull
                                      java.io.InputStream in,
                                      long fileSize,
                                      @NonNull
                                      ProgressIndicator progress)
                               throws java.io.IOException

Hash the given input stream.

Parameters:

in - The stream to hash. It will be fully consumed but not closed.

fileSize - The expected length of the stream, for progress display purposes.

progress - The indicator will be updated with the expected completion fraction.

Returns:

The sha1 hash of the input stream.

Throws:

java.io.IOException - IF there's a problem reading from the stream.