问题描述
在Azure Blob的官方示例中，都是对文件进行上传到Blob操作，没有实现对已创建的Blob进行追加的操作。如果想要实现对一个文件的多次追加操作，每一次写入的时候，只传入新的内容？
问题解答
Azure Storage Blob 有三种类型： Block Blob, Append Blob 和 Page Blob。其中，只有Append Blob类型支持追加(Append)操作。并且Blob类型在创建时就已经确定，无法后期修改。
在查看Java Storage SDK后，发现可以使用AppendBlobClient来实现。
/** * Creates a new {@link AppendBlobClient} associated with this blob. * * @return A {@link AppendBlobClient} associated with this blob. */ public AppendBlobClient getAppendBlobClient() { return new SpecializedBlobClientBuilder() .blobClient(this) .buildAppendBlobClient(); }
在 AppendBlobClient 类，有 appendBlock 和 appendBlockWithResponse 等多种方法来实现追加。方法定义源码如下：
View Code
代码实现
第一步: 在Java项目 pom.xml 中引入Azure Storage Blob依赖
<dependency> <groupId>com.azure</groupId> <artifactId>azure-storage-blob</artifactId> <version>12.13.0</version> </dependency>
第二步: 引入必要的 Storage 类
import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.net.URISyntaxException; import java.nio.charset.StandardCharsets; import java.security.InvalidKeyException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.time.LocalTime; import com.azure.core.http.rest.Response; import com.azure.storage.blob.BlobContainerClient; import com.azure.storage.blob.BlobServiceClient; import com.azure.storage.blob.BlobServiceClientBuilder; import com.azure.storage.blob.models.AppendBlobItem; import com.azure.storage.blob.models.AppendBlobRequestConditions; import com.azure.storage.blob.specialized.AppendBlobClient;
第三步：创建 AppendBlobClient 对象，使用 BlobServiceClient 及连接字符串(Connection String)
String storageConnectionString = "DefaultEndpointsProtocol=https;AccountName=*****;AccountKey=*******;EndpointSuffix=core.chinacloudapi.cn"; String containerName = "appendblob"; String fileName = "test.txt"; // Create a BlobServiceClient object which will be used to create a container System.out.println("\nCreate a BlobServiceClient Object to Connect Storage Account"); BlobServiceClient blobServiceClient = new BlobServiceClientBuilder() .connectionString(storageConnectionString) .buildClient(); BlobContainerClient containerClient = blobServiceClient.getBlobContainerClient(containerName); if (!containerClient.exists()) containerClient.create(); // Get a reference to a blob AppendBlobClient appendBlobClient = containerClient.getBlobClient(fileName).getAppendBlobClient();
第四步：调用 appendBlockWithResponse 方法追加内容，并根据返回状态码判断是否追加成功
boolean overwrite = true; // Default value if (!appendBlobClient.exists()) System.out.printf("Created AppendBlob at %s%n", appendBlobClient.create(overwrite).getLastModified()); String data = "Test to append new content into exists blob! by blogs lu bian liang zhan deng @" + LocalTime.now().toString() + "\n"; InputStream inputStream = new ByteArrayInputStream(data.getBytes(StandardCharsets.UTF_8)); byte[] md5 = MessageDigest.getInstance("MD5").digest(data.getBytes(StandardCharsets.UTF_8)); AppendBlobRequestConditions requestConditions = new AppendBlobRequestConditions(); // Context context = new Context("key", "value"); long length = data.getBytes().length; Response<AppendBlobItem> rsp = appendBlobClient.appendBlockWithResponse(inputStream, length, md5, requestConditions, null, null); if (rsp.getStatusCode() == 201) { System.out.println("append content successful........"); }
运行结果展示
但如果操作的Blob类型不是Append Blob，就会遇见错误 Status code 409 ---- The blob type is invalid for this operation 错误
Exception in thread "main" com.azure.storage.blob.models.BlobStorageException: Status code 409, " <?xml version="1.0" encoding="utf-8"?><Error>><Code>InvalidBlobType</Code> <Message>The blob type is invalid for this operation. RequestId:501ee0b9-301e-0003-4f7b-829ca6000000 Time:2023-05-09T13:37:17.7509942Z</Message></Error>" at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:67) at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500) at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:484) at com.azure.core.http.rest.RestProxy.instantiateUnexpectedException(RestProxy.java:343) at com.azure.core.http.rest.RestProxy.lambda$ensureExpectedStatus$5(RestProxy.java:382) at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:125) at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1815) at reactor.core.publisher.MonoCacheTime$CoordinatorSubscriber.signalCached(MonoCacheTime.java:337) at reactor.core.publisher.MonoCacheTime$CoordinatorSubscriber.onNext(MonoCacheTime.java:354) at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2397) at reactor.core.publisher.MonoCacheTime$CoordinatorSubscriber.onSubscribe(MonoCacheTime.java:293) at reactor.core.publisher.FluxFlatMap.trySubscribeScalarMap(FluxFlatMap.java:192) at reactor.core.publisher.MonoFlatMap.subscribeOrReturn(MonoFlatMap.java:53) at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:57) at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) at reactor.core.publisher.MonoCacheTime.subscribeOrReturn(MonoCacheTime.java:143) at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:57) at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) at reactor.core.publisher.FluxDoFinally$DoFinallySubscriber.onNext(FluxDoFinally.java:130) at reactor.core.publisher.FluxHandle$HandleSubscriber.onNext(FluxHandle.java:118) at reactor.core.publisher.FluxMap$MapConditionalSubscriber.onNext(FluxMap.java:220) at reactor.core.publisher.FluxDoFinally$DoFinallySubscriber.onNext(FluxDoFinally.java:130) at reactor.core.publisher.FluxHandleFuseable$HandleFuseableSubscriber.onNext(FluxHandleFuseable.java:184) at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onNext(FluxContextWrite.java:107) at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1815) at reactor.core.publisher.MonoCollectList$MonoCollectListSubscriber.onComplete(MonoCollectList.java:128) at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:259) at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:142) at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:401) at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:416) at reactor.netty.channel.ChannelOperations.terminate(ChannelOperations.java:470) at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:685) at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:94) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655) at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581) at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493) at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) at java.base/java.lang.Thread.run(Thread.java:1589) Suppressed: java.lang.Exception: #block terminated with an error at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:99) at reactor.core.publisher.Mono.block(Mono.java:1703) at com.azure.storage.common.implementation.StorageImplUtils.blockWithOptionalTimeout(StorageImplUtils.java:128) at com.azure.storage.blob.specialized.AppendBlobClient.appendBlockWithResponse(AppendBlobClient.java:259) at test.App.AppendBlobContent(App.java:68) at test.App.main(App.java:31)
参考资料
Blob（对象）存储简介 : https://docs.azure.cn/zh-cn/storage/blobs/storage-blobs-introduction
