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JavaV2: Check if bucket exists example that provides replacement for V1's doesBucketExistV2 (#7057)
* Create code example for Java V1's AmazonS3Client#doesBucketExistV2()
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‎.doc_gen/metadata/s3_metadata.yaml‎

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@@ -3524,3 +3524,20 @@ s3_Scenario_DownloadS3Directory:
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- s3.tm.java2.download-s3-directories.main
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services:
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s3: {}
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s3_Scenario_DoesBucketExist:
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title: Check if a bucket exists
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title_abbrev: Check if a bucket exists
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synopsis: check if a bucket exists.
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category: Scenarios
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languages:
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Java:
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versions:
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- sdk_version: 2
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github: javav2/example_code/s3
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sdkguide:
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excerpts:
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- description: You can use the following <code>doesBucketExists</code> method as a replacement for the the &Java; V1 <ulink url="https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/s3/AmazonS3Client.html#doesBucketExistV2-java.lang.String-">AmazonS3Client#doesBucketExistV2(String)</ulink> method.
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snippet_tags:
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- s3.java2.does-bucket-exist-main
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services:
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s3: {GetBucketAcl}

‎javav2/example_code/s3/README.md‎

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@@ -79,6 +79,7 @@ Code excerpts that show you how to call individual service functions.
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Code examples that show you how to accomplish a specific task by calling multiple
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functions within the same service.
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- [Check if a bucket exists](src/main/java/com/example/s3/DoesBucketExist.java)
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- [Delete incomplete multipart uploads](src/main/java/com/example/s3/AbortMultipartUploadExamples.java)
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- [Download S3 'directories'](src/main/java/com/example/s3/transfermanager/S3DirectoriesDownloader.java)
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- [Download objects to a local directory](src/main/java/com/example/s3/transfermanager/DownloadToDirectory.java)
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<!--custom.basics.s3_Scenario_GettingStarted.end-->
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#### Check if a bucket exists
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This example shows you how to check if a bucket exists.
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<!--custom.scenario_prereqs.s3_Scenario_DoesBucketExist.start-->
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<!--custom.scenario_prereqs.s3_Scenario_DoesBucketExist.end-->
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<!--custom.scenarios.s3_Scenario_DoesBucketExist.start-->
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<!--custom.scenarios.s3_Scenario_DoesBucketExist.end-->
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#### Delete incomplete multipart uploads
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This example shows you how to how to delete or stop incomplete Amazon S3 multipart uploads.

‎javav2/example_code/s3/src/main/java/com/example/s3/DoesBucketExist.java‎

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// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
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// SPDX-License-Identifier: Apache-2.0
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package com.example.s3;
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// snippet-start:[s3.java2.does-bucket-exist-main]
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import software.amazon.awssdk.awscore.exception.AwsServiceException;
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import software.amazon.awssdk.http.HttpStatusCode;
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import software.amazon.awssdk.services.s3.S3Client;
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import software.amazon.awssdk.utils.Validate;
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public class DoesBucketExist {
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private static final Logger logger = LoggerFactory.getLogger(DoesBucketExist.class);
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public static void main(String[] args) {
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DoesBucketExist doesBucketExist = new DoesBucketExist();
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final S3Client s3SyncClient = S3Client.builder().build();
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final String bucketName = "amzn-s3-demo-bucket"; // Change to the bucket name that you want to check.
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boolean exists = doesBucketExist.doesBucketExist(bucketName, s3SyncClient);
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logger.info("Bucket exists: {}", exists);
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}
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/**
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* Checks if the specified bucket exists. Amazon S3 buckets are named in a global namespace; use this method to
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* determine if a specified bucket name already exists, and therefore can't be used to create a new bucket.
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* <p>
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* Internally this method uses the <a
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* href="https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/s3/S3Client.html#getBucketAcl(java.util.function.Consumer)">S3Client.getBucketAcl(String)</a>
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* operation to determine whether the bucket exists.
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* <p>
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* This method is equivalent to the AWS SDK for Java V1's <a
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* href="https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/s3/AmazonS3Client.html#doesBucketExistV2-java.lang.String-">AmazonS3Client#doesBucketExistV2(String)</a>.
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*
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* @param bucketName The name of the bucket to check.
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* @param s3SyncClient An <code>S3Client</code> instance. The method checks for the bucket in the AWS Region
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* configured on the instance.
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* @return The value true if the specified bucket exists in Amazon S3; the value false if there is no bucket in
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* Amazon S3 with that name.
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*/
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public boolean doesBucketExist(String bucketName, S3Client s3SyncClient) {
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try {
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Validate.notEmpty(bucketName, "The bucket name must not be null or an empty string.", "");
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s3SyncClient.getBucketAcl(r -> r.bucket(bucketName));
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return true;
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} catch (AwsServiceException ase) {
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// A redirect error or an AccessDenied exception means the bucket exists but it's not in this region
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// or we don't have permissions to it.
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if ((ase.statusCode() == HttpStatusCode.MOVED_PERMANENTLY) || "AccessDenied".equals(ase.awsErrorDetails().errorCode())) {
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return true;
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}
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if (ase.statusCode() == HttpStatusCode.NOT_FOUND) {
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return false;
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}
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throw ase;
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}
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}
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}
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// snippet-end:[s3.java2.does-bucket-exist-main]

‎javav2/example_code/s3/src/main/java/com/example/s3/transfermanager/S3DirectoriesDownloader.java‎

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public class S3DirectoriesDownloader {
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private static final Logger logger = LoggerFactory.getLogger(S3DirectoriesDownloader.class);
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public final String bucketName = "amzn-s3-demo-bucket" + UUID.randomUUID(); // Change bucket name.
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public final String bucketName = "junk-s3-demo-bucket" + UUID.randomUUID(); // Change bucket name.
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public URI destinationPathURI;
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private final Set<String> downloadedFileNameSet = new HashSet<>();
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private final String destinationDirName = "downloadDirectory";

‎javav2/example_code/s3/src/main/resources/xml_testing.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<AccessControlPolicy xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
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<AccessControlList>
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<Grant>
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<Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="CanonicalUser">
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<DisplayName>owner</DisplayName>
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<ID>dad784318ac45facc6a8c74b9b44f18afd317c85fa8776eeb2b000c8942bc8d9</ID>
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</Grantee>
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<Permission>FULL_CONTROL</Permission>
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</Grant>
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<Grant>
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<Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Group">
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<DisplayName>my-grantee</DisplayName>
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<URI>http://acs.amazonaws.com/groups/global/AuthenticatedUsers</URI>
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</Grantee>
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<Permission>READ_ACP</Permission>
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</Grant>
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</AccessControlList>
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<Owner>
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<ID>dad784318ac45facc6a8c74b9b44f18afd317c85fa8776eeb2b000c8942bc8d9</ID>
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</Owner>
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</AccessControlPolicy>

‎javav2/example_code/s3/src/test/java/com/example/s3/DoesBucketExistTest.java‎

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// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
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// SPDX-License-Identifier: Apache-2.0
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package com.example.s3;
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//
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import org.junit.jupiter.api.Tag;
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import org.junit.jupiter.api.Test;
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import software.amazon.awssdk.policybuilder.iam.IamConditionKey;
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import software.amazon.awssdk.policybuilder.iam.IamConditionOperator;
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import software.amazon.awssdk.policybuilder.iam.IamEffect;
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import software.amazon.awssdk.policybuilder.iam.IamPolicy;
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import software.amazon.awssdk.policybuilder.iam.IamPrincipalType;
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import software.amazon.awssdk.regions.Region;
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import software.amazon.awssdk.services.iam.IamClient;
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import software.amazon.awssdk.services.iam.model.PutRolePolicyResponse;
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import software.amazon.awssdk.services.s3.S3Client;
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import software.amazon.awssdk.services.sts.StsClient;
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import software.amazon.awssdk.services.sts.auth.StsAssumeRoleCredentialsProvider;
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import java.util.List;
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import java.util.UUID;
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import static org.junit.jupiter.api.Assertions.assertFalse;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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class DoesBucketExistTest {
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private static final String ROLE_NAME = "minimal-s3-perms-role";
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private static final String POLICY_NAME = "minimum-s3-ability-policy";
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private static final IamClient iamClient = IamClient.builder().build();
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@Test
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@Tag("IntegrationTest")
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void doesBucketExist_exists_but_not_in_client_region_should_return_true() {
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S3Client usWestS3Client = S3Client.builder().region(Region.US_WEST_2).build();
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final String bucketName = "my-us-west2-bucket-" + UUID.randomUUID();
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createBucket(usWestS3Client, bucketName);
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DoesBucketExist doesBucketExist = new DoesBucketExist();
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S3Client euCentralS3Client = S3Client.builder().region(Region.EU_CENTRAL_1).build();
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boolean exists = doesBucketExist.doesBucketExist(bucketName, euCentralS3Client);
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assertTrue(exists);
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deleteBucket(usWestS3Client, bucketName);
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}
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@Test
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@Tag("IntegrationTest")
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void doesBucketExist_does_not_exist_should_return_false() {
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DoesBucketExist doesBucketExist = new DoesBucketExist();
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final String bucketName = "xx-xx-xxxx-xxxx" + UUID.randomUUID();
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boolean exists = doesBucketExist.doesBucketExist(bucketName, S3Client.create());
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assertFalse(exists);
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}
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@Test
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@Tag("IntegrationTest")
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void doesBucketExist_returns_true_when_bucket_exists_but_caller_does_not_have_permission() {
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StsClient stsClient = StsClient.create();
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createAssumableRole(stsClient);
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S3Client s3Client = S3Client.create();
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final String bucketName = "my-bucket-" + UUID.randomUUID();
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createBucket(s3Client, bucketName);
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try {
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String roleArn = iamClient.getRole(b -> b.roleName(ROLE_NAME)).role().arn();
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S3Client s3ClientWithoutPermission = S3Client.builder()
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.credentialsProvider(StsAssumeRoleCredentialsProvider.builder()
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.stsClient(stsClient)
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.refreshRequest(arr -> arr
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.roleArn(roleArn)
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.roleSessionName("test-session"))
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.build())
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.build();
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DoesBucketExist doesBucketExist = new DoesBucketExist();
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boolean existsButNoAccess = doesBucketExist.doesBucketExist(bucketName, s3ClientWithoutPermission);
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assertTrue(existsButNoAccess);
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boolean exists = doesBucketExist.doesBucketExist("non-existent-bucket" + UUID.randomUUID(), s3ClientWithoutPermission);
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assertFalse(exists);
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} finally {
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deleteBucket(s3Client, bucketName);
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deleteRole();
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}
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}
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private static void createBucket(S3Client s3Client, String bucketName) {
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s3Client.createBucket(b -> b.bucket(bucketName));
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s3Client.waiter().waitUntilBucketExists(b -> b.bucket(bucketName));
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}
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private static void deleteBucket(S3Client s3Client, String bucketName) {
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s3Client.deleteBucket(b -> b.bucket(bucketName));
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s3Client.waiter().waitUntilBucketNotExists(b -> b.bucket(bucketName));
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}
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private static void createAssumableRole(StsClient stsClient) {
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final String accountID = stsClient.getCallerIdentity().account();
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IamPolicy trustIamPolicyForAnyoneInSameAccount = IamPolicy.builder()
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.addStatement(statement -> statement
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.effect(IamEffect.ALLOW)
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.addPrincipal(principal -> principal
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.type(IamPrincipalType.AWS)
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.id("arn:aws:iam::" + accountID + ":root")
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)
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.addAction("sts:AssumeRole")
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.addConditions(IamConditionOperator.STRING_EQUALS,
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IamConditionKey.create("aws:PrincipalType"),
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List.of("User", "AssumedRole")
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).addConditions(IamConditionOperator.STRING_LIKE,
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"aws:userId",
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List.of("AIDAX*", "AROA*:*", "AIDA*:*"))
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)
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.build();
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iamClient.createRole(crb -> crb
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.roleName(ROLE_NAME)
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.assumeRolePolicyDocument(trustIamPolicyForAnyoneInSameAccount.toJson())
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);
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IamPolicy getBucketLocationOnlyPolicy = IamPolicy.builder()
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.addStatement(statement -> statement
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.effect(IamEffect.ALLOW)
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.addAction("s3:GetBucketLocation")
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.addResource("arn:aws:s3:::*")
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)
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.build();
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iamClient.putRolePolicy(prprb -> prprb
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.roleName(ROLE_NAME)
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.policyName(POLICY_NAME)
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.policyDocument(getBucketLocationOnlyPolicy.toJson()));
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// Add a delay for the role to propagate.
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try {
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Thread.sleep(8000);
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} catch (InterruptedException e) {
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throw new RuntimeException(e);
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}
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}
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private static void deleteRole(){
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iamClient.deleteRolePolicy(drbrb -> drbrb
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.roleName(ROLE_NAME)
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.policyName(POLICY_NAME));
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iamClient.deleteRole(drb -> drb
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.roleName(ROLE_NAME)
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);
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}
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}
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