我有这个代码从s3存储桶下载文件到lambda服务器的tmp空间。
String url = "https://slack-automation.s3.amazonaws.com/slack.xlsx";
URL link = new URL(url);
/* //AmazonS3 s3Client = new AmazonS3Client(new ProfileCredentialsProvider());
AmazonS3 s3Client = AmazonS3ClientBuilder.standard().build() ;
S3Object object = s3Client.getObject(new GetObjectRequest(bucketName, key));
InputStream objectData = object.getObjectContent();
// Process the objectData stream.
objectData.close();
*/
// Code to download
InputStream in = new BufferedInputStream(link.openStream());
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int n = 0;
while (-1 != (n = in.read(buf))) {
out.write(buf, 0, n);
}
out.close();
in.close();
byte[] response = out.toByteArray();
FileOutputStream fos = new FileOutputStream("/tmp/" + fileName);
fos.write(response);
fos.close();
file = new File("/tmp/" + fileName);
//file = new File(filePath);
inputStream = new FileInputStream(file);
workBook = new XSSFWorkbook(inputStream);
workBookSheet = workBook.getSheet(workBook.getSheetName(0));
rowCount = workBookSheet.getPhysicalNumberOfRows();
formatter = new DataFormatter();
但问题是要访问此文件，必须提供公共权限。
如何通过获取此处提供的临时凭证将此文件下载到lambda服务器tmp空间：https://docs.aws.amazon.com/AmazonS3/latest/dev/AuthUsingTempSessionTokenJava.html
我无法实现，有人可以帮助我使用临时凭证下载文件的代码，而不像上面提到的方法那样传递我的accesskey和secretkey吗？
感谢Akshay Sing，我不知道如何用代码发表评论，我在你的回答后尝试的代码就在这里
public void setupWorkbook（String filePath）抛出IOException {
String clientRegion = "eu-central-1";
String roleARN = "myAwsArnRoleOverHere";
String roleSessionName = "slackautomation";
String bucketName = "slack-automation";
String key = "slack.xlsx";
String fileName = "slack.xlsx";
try {
AWSSecurityTokenService stsClient = AWSSecurityTokenServiceClientBuilder.standard()
.withCredentials(new ProfileCredentialsProvider())
.withRegion(clientRegion)
.build();
AssumeRoleRequest roleRequest = new AssumeRoleRequest()
.withRoleArn(roleARN)
.withRoleSessionName(roleSessionName);
stsClient.assumeRole(roleRequest);
// Start a session.
GetSessionTokenRequest getSessionTokenRequest = new GetSessionTokenRequest();
// The duration can be set to more than 3600 seconds only if temporary
// credentials are requested by an IAM user rather than an account owner.
getSessionTokenRequest.setDurationSeconds(900);
GetSessionTokenResult sessionTokenResult = stsClient.getSessionToken(getSessionTokenRequest);
Credentials sessionCredentials = sessionTokenResult.getCredentials();
// Package the temporary security credentials as a BasicSessionCredentials object
// for an Amazon S3 client object to use.
BasicSessionCredentials basicSessionCredentials = new BasicSessionCredentials(
sessionCredentials.getAccessKeyId(), sessionCredentials.getSecretAccessKey(),
sessionCredentials.getSessionToken());
// Provide temporary security credentials so that the Amazon S3 client
// can send authenticated requests to Amazon S3. You create the client
// using the basicSessionCredentials object.
AmazonS3 s3Client = AmazonS3ClientBuilder.standard()
.withCredentials(new AWSStaticCredentialsProvider(basicSessionCredentials))
.withRegion(clientRegion)
.build();
// Verify that assuming the role worked and the permissions are set correctly
// by getting a set of object keys from the bucket.
ObjectListing objects = s3Client.listObjects(bucketName);
System.out.println("No. of Objects: " + objects.getObjectSummaries().size());
S3Object fileObject = s3Client.getObject(new GetObjectRequest(bucketName, key));
InputStream in = new BufferedInputStream(fileObject.getObjectContent());
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int n = 0;
while (-1 != (n = in.read(buf))) {
out.write(buf, 0, n);
}
out.close();
in.close();
byte[] response = out.toByteArray();
FileOutputStream fos = new FileOutputStream("/tmp/" + fileName);
fos.write(response);
fos.close();
file = new File("/tmp/" + fileName);
//file = new File(filePath);
inputStream = new FileInputStream(file);
workBook = new XSSFWorkbook(inputStream);
workBookSheet = workBook.getSheet(workBook.getSheetName(0));
rowCount = workBookSheet.getPhysicalNumberOfRows();
formatter = new DataFormatter();
}
catch(AmazonServiceException e) {
// The call was transmitted successfully, but Amazon S3 couldn't process
// it, so it returned an error response.
e.printStackTrace();
}
catch(SdkClientException e) {
// Amazon S3 couldn't be contacted for a response, or the client
// couldn't parse the response from Amazon S3.
e.printStackTrace();
}
但它没有工作，它在“stsClient.assumeRole（roleRequest）;”
上抛出错误错误，只是行号没有多少线索。
答案 0 :(得分：1)
上述问题的解决方案，我在这里写完整个代码
public void setupWorkbook(String filePath) throws IOException {
// String bucketName = "slack-automation";
String key = "slack.xlsx";
String fileName = "slack.xlsx";
String bucketName = System.getenv("bucket_name");
try {
AmazonS3 s3Client = new AmazonS3Client();
ObjectListing objects = s3Client.listObjects(bucketName);
System.out.println("No. of Objects: " + objects.getObjectSummaries().size());
S3Object fileObject = s3Client.getObject(new GetObjectRequest(bucketName, key));
InputStream in = new BufferedInputStream(fileObject.getObjectContent());
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int n = 0;
while (-1 != (n = in.read(buf))) {
out.write(buf, 0, n);
}
out.close();
in.close();
byte[] response = out.toByteArray();
FileOutputStream fos = new FileOutputStream("/tmp/" + fileName);
fos.write(response);
fos.close();
file = new File("/tmp/" + fileName);
//file = new File(filePath);
inputStream = new FileInputStream(file);
workBook = new XSSFWorkbook(inputStream);
workBookSheet = workBook.getSheet(workBook.getSheetName(0));
rowCount = workBookSheet.getPhysicalNumberOfRows();
formatter = new DataFormatter();
}
catch(AmazonServiceException e) {
// The call was transmitted successfully, but Amazon S3 couldn't process
// it, so it returned an error response.
e.printStackTrace();
System.out.println("FIRST EXCEPTION"+e.getMessage());
}
catch(SdkClientException e) {
// Amazon S3 couldn't be contacted for a response, or the client
// couldn't parse the response from Amazon S3.
e.printStackTrace();
System.out.println("SECOND EXCEPTION"+e.getMessage());
}
只是这部分代码需要添加
AmazonS3 s3Client = new AmazonS3Client();
ObjectListing objects = s3Client.listObjects(bucketName);
System.out.println("No. of Objects: " + objects.getObjectSummaries().size());
S3Object fileObject = s3Client.getObject(new GetObjectRequest(bucketName, key));
InputStream in = new BufferedInputStream(fileObject.getObjectContent());
“AmazonS3 s3Client = new AmazonS3Client（）”这一行将采用IAM角色，并且在不传递我的accesskey和secretkey的情况下将获取临时凭证，因为代码是从AWS Lambda运行的。就是这样，谢谢大家的帮助
答案 1 :(得分：0)
我目前正在使用以下程序从我的S3存储桶下载图像并存储它们以向用户返回图像的zip。我将为您排除zip创建代码：
要将文件下载到临时服务器，您必须首先获得所需S3Object的访问权限。在您的情况下，slack.xlsx存储在slack-automation桶中。
您提到要使用IAM角色提供给您的临时凭证。明智的做法是不在代码中披露凭据，同时确保提供给服务的凭据将自动刷新。您需要初始化s3Client
像这样：
AmazonS3Client s3Client = new AmazonS3Client(new InstanceProfileCredentialsProvider());
InstanceProfileCredentialsProvider从Amazon EC2实例元数据服务加载凭据（基于您的IAM角色）。
注意：确保正在使用的IAM角色实际上具有对存储桶的读访问权。
要获取S3Object，请使用：
S3Object fileObject = s3Client.getObject(new GetObjectRequest(bucketName, key));
在您的情况下，bucketName将是松弛自动化，密钥将是S3存储桶上的文件的名称（此处为slack.xlsx）。
然后，要将文件存储在您的服务器上，请使用copyInputStreamToFile
org.apache.commons.io.FileUtils功能
FileUtils.copyInputStreamToFile(s3Object.getObjectContent(), new File(fileName));