protected void implGet()

in maven-resolver-transport-jdk-parent/maven-resolver-transport-jdk-11/src/main/java/org/eclipse/aether/transport/jdk/JdkTransporter.java [268:374]
101 lines of code
22 McCabe index (conditional complexity)

    protected void implGet(GetTask task) throws Exception {
        boolean resume = task.getResumeOffset() > 0L && task.getDataPath() != null;
        HttpResponse<InputStream> response = null;

        try {
            while (true) {
                HttpRequest.Builder request =
                        HttpRequest.newBuilder().uri(resolve(task)).method("GET", HttpRequest.BodyPublishers.noBody());
                headers.forEach(request::setHeader);

                if (resume) {
                    long resumeOffset = task.getResumeOffset();
                    long lastModified = pathProcessor.lastModified(task.getDataPath(), 0L);
                    request.header(RANGE, "bytes=" + resumeOffset + '-');
                    request.header(
                            IF_UNMODIFIED_SINCE,
                            RFC7231.format(Instant.ofEpochMilli(lastModified - MODIFICATION_THRESHOLD)));
                    request.header(ACCEPT_ENCODING, "identity");
                }

                try {
                    response = send(request.build(), HttpResponse.BodyHandlers.ofInputStream());
                    if (response.statusCode() >= MULTIPLE_CHOICES) {
                        if (resume && response.statusCode() == PRECONDITION_FAILED) {
                            closeBody(response);
                            resume = false;
                            continue;
                        }
                        try {
                            JdkRFC9457Reporter.INSTANCE.generateException(response, (statusCode, reasonPhrase) -> {
                                throw new HttpTransporterException(statusCode);
                            });
                        } finally {
                            closeBody(response);
                        }
                    }
                } catch (ConnectException e) {
                    closeBody(response);
                    throw enhance(e);
                }
                break;
            }

            long offset = 0L,
                    length = response.headers().firstValueAsLong(CONTENT_LENGTH).orElse(-1L);
            if (resume) {
                String range = response.headers().firstValue(CONTENT_RANGE).orElse(null);
                if (range != null) {
                    Matcher m = CONTENT_RANGE_PATTERN.matcher(range);
                    if (!m.matches()) {
                        throw new IOException("Invalid Content-Range header for partial download: " + range);
                    }
                    offset = Long.parseLong(m.group(1));
                    length = Long.parseLong(m.group(2)) + 1L;
                    if (offset < 0L || offset >= length || (offset > 0L && offset != task.getResumeOffset())) {
                        throw new IOException("Invalid Content-Range header for partial download from offset "
                                + task.getResumeOffset() + ": " + range);
                    }
                }
            }

            final boolean downloadResumed = offset > 0L;
            final Path dataFile = task.getDataPath();
            if (dataFile == null) {
                try (InputStream is = response.body()) {
                    utilGet(task, is, true, length, downloadResumed);
                }
            } else {
                try (FileUtils.CollocatedTempFile tempFile = FileUtils.newTempFile(dataFile)) {
                    task.setDataPath(tempFile.getPath(), downloadResumed);
                    if (downloadResumed && Files.isRegularFile(dataFile)) {
                        try (InputStream inputStream = new BufferedInputStream(Files.newInputStream(dataFile))) {
                            Files.copy(inputStream, tempFile.getPath(), StandardCopyOption.REPLACE_EXISTING);
                        }
                    }
                    try (InputStream is = response.body()) {
                        utilGet(task, is, true, length, downloadResumed);
                    }
                    tempFile.move();
                } finally {
                    task.setDataPath(dataFile);
                }
            }
            if (task.getDataPath() != null) {
                String lastModifiedHeader = response.headers()
                        .firstValue(LAST_MODIFIED)
                        .orElse(null); // note: Wagon also does first not last
                if (lastModifiedHeader != null) {
                    try {
                        pathProcessor.setLastModified(
                                task.getDataPath(),
                                ZonedDateTime.parse(lastModifiedHeader, RFC7231)
                                        .toInstant()
                                        .toEpochMilli());
                    } catch (DateTimeParseException e) {
                        // fall through
                    }
                }
            }
            Map<String, String> checksums = checksumExtractor.extractChecksums(headerGetter(response));
            if (checksums != null && !checksums.isEmpty()) {
                checksums.forEach(task::setChecksum);
            }
        } finally {
            closeBody(response);
        }
    }