如何在java的fileinputstream中获取azure blob存储内容?

pbossiut  于 2021-07-08  发布在  Java
关注(0)|答案(1)|浏览(605)

我正在开发一个api(springboot)。其中我需要在get方法的响应体中返回fileinputstream。
预期-当前端调用get files api时,浏览器上应该打开一个文件下载提示。
问题-我们不能使用blob.downloadtofile方法,因为它将在本地计算机(或api所在的主机)上下载文件,并且我们需要一些可以在api调用时将文件直接发送到前端的东西。不过,还有另一个方法blob.download(),它返回的outputstream在api调用时无法返回。
那么,有没有什么方法可以将outputstream转换为fileinputstream,而不必保存到设备上的实际文件中呢。
示例代码-

public ByteArrayOutputStream downloadBlob() throws URISyntaxException, InvalidKeyException, StorageException, IOException {
        String storageConnectionString = "DefaultEndpointsProtocol=https;" + "AccountName=" + accountName + ";"
                + "AccountKey=" + accountKey;

        CloudStorageAccount storageAccount = CloudStorageAccount.parse(storageConnectionString);

        CloudBlobClient blobClient = storageAccount.createCloudBlobClient();

        final CloudBlobContainer container = blobClient.getContainerReference("container name");

        CloudBlockBlob blob = container.getBlockBlobReference("image.PNG");
        ByteArrayOutputStream outputStream =new ByteArrayOutputStream();
        blob.download(outputStream);
        System.out.println("file downloaded");

        return outputStream;
    }

注意-文件可以是任何类型。

kse8i1jr

kse8i1jr1#

下面是解决方案-在浏览器中点击api后,您的文件将在浏览器中下载-

package com.example.demo.controllers;

import com.azure.storage.blob.BlobClient;
import com.azure.storage.blob.BlobContainerClient;
import com.azure.storage.blob.BlobServiceClient;
import com.azure.storage.blob.BlobServiceClientBuilder;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

@RestController
public class FileDownload {
    @GetMapping(path="/download-file")
    public ResponseEntity<Resource> getFile(){
        String fileName = "Can not find symbol.docx";
        //azure credentials
        String connection_string = "Connection String of storage account on azure";

        BlobServiceClient blobServiceClient = new BlobServiceClientBuilder().connectionString(connection_string).buildClient();

        BlobContainerClient containerClient= blobServiceClient.getBlobContainerClient("Container name");
        System.out.println(containerClient.getBlobContainerName());

        BlobClient blob = containerClient.getBlobClient(fileName);

        //creating an object of output stream to recieve the file's content from azure blob.
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        blob.download(outputStream);

        //converting it to the inputStream to return
        final byte[] bytes = outputStream.toByteArray();
        ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes);
        ByteArrayResource resource = new ByteArrayResource(bytes);
        HttpHeaders headers = new HttpHeaders();
        headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + fileName + "\"");

        return ResponseEntity.ok().contentType(MediaType.APPLICATION_OCTET_STREAM)
                .headers(headers)
                .body(resource);
    }

}

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