从“BlobDownloadHeaders.getContentLength()”的 Blob 存储下载文件时出错

Question

@Override
    public byte[] getBlobAsByteArray(String customerId, String docTypeId, String fileName, boolean isUser) {
        String blobName = formBlobName(customerId, docTypeId, fileName);
        BlobClient blobClient = configureBlobClient(blobName, isUser, false);
        try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
            blobClient.downloadStream(outputStream);
            return outputStream.toByteArray();
        } catch (Exception e) {
            throw new MSSNotFoundException("Failed to download blob for docTypeId: "+docTypeId, e.getMessage());
        }
    } 

错误：

java.lang.Long.longValue()" because the return value of "com.azure.storage.blob.models.BlobDownloadHeaders.getContentLength()" is null
java.lang.NullPointerException: Cannot invoke "java.lang.Long.longValue()" because the return value of "com.azure.storage.blob.models.BlobDownloadHeaders.getContentLength()" is null
    at com.azure.storage.blob.implementation.util.ModelHelper.getBlobLength(ModelHelper.java:467)
    at com.azure.storage.blob.specialized.BlobAsyncClientBase.lambda$downloadStreamWithResponse$18(BlobAsyncClientBase.java:1289)
    at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:106)
    at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79)
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:158)
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:158)
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129)
    at reactor.core.publisher.FluxHide$SuppressFuseableSubscriber.onNext(FluxHide.java:137)
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129)
    at reactor.core.publisher.FluxHide$SuppressFuseableSubscriber.onNext(FluxHide.java:137)
    at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79)
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:158)
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129)
    at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:158)
    at reactor.core.publisher.SerializedSubscriber.onNext(SerializedSubscriber.java:99)
    at reactor.core.publisher.FluxRetryWhen$RetryWhenMainSubscriber.onNext(FluxRetryWhen.java:178)
    at reactor.core.publisher.FluxOnErrorResume$ResumeSubscriber.onNext(FluxOnErrorResume.java:79)
    at reactor.core.publisher.Operators$MonoInnerProducerBase.complete(Operators.java:2864)
    at reactor.core.publisher.MonoSingle$SingleSubscriber.onComplete(MonoSingle.java:180)
    at reactor.core.publisher.MonoFlatMapMany$FlatMapManyInner.onComplete(MonoFlatMapMany.java:261)
    at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onComplete(FluxContextWrite.java:126)
    at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2573)
    at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.request(FluxContextWrite.java:136)
    at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onSubscribeInner(MonoFlatMapMany.java:150)
    at reactor.core.publisher.MonoFlatMapMany$FlatMapManyInner.onSubscribe(MonoFlatMapMany.java:246)
    at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onSubscribe(FluxContextWrite.java:101)
    at reactor.core.publisher.FluxJust.subscribe(FluxJust.java:68)
    at reactor.core.publisher.Flux.subscribe(Flux.java:8891)
    at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onNext(MonoFlatMapMany.java:196)
    at reactor.core.publisher.SerializedSubscriber.onNext(SerializedSubscriber.java:99)
    at reactor.core.publisher.FluxRetryWhen$RetryWhenMainSubscriber.onNext(FluxRetryWhen.java:178)
    at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:176)
    at reactor.netty.http.client.HttpClientConnect$HttpIOHandlerObserver.onStateChange(HttpClientConnect.java:435)
    at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNe

Answer 1

从“BlobDownloadHeaders.getContentLength()”的 Blob 存储下载文件时出错

由于

getContentLength()

方法返回null而发生错误。此方法用于获取正在从 blob 存储下载的内容的长度。

您可以使用以下代码检查 blob 大小，并使用 Azure Java SDK 将内容下载为字节数组。

代码：

public static void main(String[] args) {
        try {
            String customerId = "customer123";
            String docTypeId = "doc456";
            String fileName = "example.txt";

            byte[] blobData = getBlobAsByteArray(customerId, docTypeId, fileName);
            System.out.println("Blob downloaded successfully, size: " + blobData.length + " bytes");
        } catch (Exception e) {
            System.err.println("Error downloading blob: " + e.getMessage());
            e.printStackTrace();
        }
    }

    public static byte[] getBlobAsByteArray(String customerId, String docTypeId, String fileName) {
        String blobName = formBlobName(customerId, docTypeId, fileName);
        System.out.println(blobName);
        BlobClient blobClient = configureBlobClient(blobName);

        try {
            // Check if blob exists
            if (!blobClient.exists()) {
                throw new RuntimeException("Blob does not exist: " + blobName);
            }

            // Fetch blob properties and log metadata
            BlobProperties properties = blobClient.getProperties();
            System.out.println("Blob Size: " + properties.getBlobSize() + " bytes");

            // Download blob content
            try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
                blobClient.downloadStream(outputStream);
                return outputStream.toByteArray();
            }

        } catch (BlobStorageException e) {
            throw new RuntimeException("BlobStorageException occurred: " + e.getErrorCode(), e);
        } catch (IOException e) {
            throw new RuntimeException("IOException occurred while downloading blob: " + blobName, e);
        }
    }

    private static String formBlobName(String customerId, String docTypeId, String fileName) {
        return customerId + "/" + docTypeId + "/" + fileName;
    }

    private static BlobClient configureBlobClient(String blobName) {
        return new BlobClientBuilder()
                .connectionString(CONNECTION_STRING)
                .containerName(CONTAINER_NAME)
                .blobName(blobName)
                .buildClient();
    }

上面的代码将检查 blob 是否存在，获取其属性，并将其内容下载为字节数组。最后，它记录下载的 blob 的大小。

输出：

customer123/doc456/example.txt
Blob Size: 1739 bytes
Blob downloaded successfully, size: 1739 bytes

参考：

使用 Java 下载 blob - Azure 存储 |微软学习