com.amazonaws.services.s3.iterable.S3Versions Maven / Gradle / Ivy
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/*
* Copyright 2012-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
package com.amazonaws.services.s3.iterable;
import java.util.Iterator;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.model.ListVersionsRequest;
import com.amazonaws.services.s3.model.S3VersionSummary;
import com.amazonaws.services.s3.model.VersionListing;
/**
* Provides an easy way to iterate Amazon S3 object versions in a "foreach"
* statement. For example:
*
*
* for ( S3VersionSummary summary : S3Versions.forPrefix(s3, "my-bucket", "photos/") ) {
* System.out.printf("Version '%s' of key '%s'\n", summary.getVersionId(), summary.getKey());
* }
*
*
* The list of {@link S3VersionSummary}s will be fetched lazily, a page at a
* time, as they are needed. The size of the page can be controlled with the
* {@link S3Versions#withBatchSize(int)} method.
*/
public class S3Versions implements Iterable {
private AmazonS3 s3;
private String bucketName;
private String prefix;
private String key;
private Integer batchSize;
private S3Versions(AmazonS3 s3, String bucketName) {
this.s3 = s3;
this.bucketName = bucketName;
}
/**
* Constructs an iterable that covers all the object versions in an Amazon
* S3 bucket.
*
* @param s3
* The Amazon S3 client.
* @param bucketName
* The bucket name.
* @return An iterator for object version summaries.
*/
public static S3Versions inBucket(AmazonS3 s3, String bucketName) {
return new S3Versions(s3, bucketName);
}
/**
* Constructs an iterable that covers the versions in an Amazon S3 bucket
* where the object key begins with the given prefix.
*
* @param s3
* The Amazon S3 client.
* @param bucketName
* The bucket name.
* @param prefix
* The prefix.
* @return An iterator for object version summaries.
*/
public static S3Versions withPrefix(AmazonS3 s3, String bucketName,
String prefix) {
S3Versions versions = new S3Versions(s3, bucketName);
versions.prefix = prefix;
return versions;
}
/**
* Constructs an iterable that covers the versions of a single Amazon S3
* object.
*
* @param s3
* The Amazon S3 client.
* @param bucketName
* The bucket name.
* @param key
* The key.
* @return An iterator for object version summaries.
*/
public static S3Versions forKey(AmazonS3 s3, String bucketName, String key) {
S3Versions versions = new S3Versions(s3, bucketName);
versions.key = key;
return versions;
}
/**
* Sets the batch size, i.e., how many {@link S3VersionSummary}s will be fetched at
* once.
*
* @param batchSize
* How many object summaries to fetch at once.
*/
public S3Versions withBatchSize(int batchSize) {
this.batchSize = batchSize;
return this;
}
public Integer getBatchSize() {
return batchSize;
}
public String getPrefix() {
return prefix;
}
public String getKey() {
return key;
}
public AmazonS3 getS3() {
return s3;
}
public String getBucketName() {
return bucketName;
}
private class VersionIterator implements Iterator {
private VersionListing currentListing = null;
private Iterator currentIterator = null;
private S3VersionSummary nextSummary = null;
@Override
public boolean hasNext() {
prepareCurrentListing();
return nextMatchingSummary() != null;
}
@Override
public S3VersionSummary next() {
prepareCurrentListing();
S3VersionSummary returnValue = nextMatchingSummary();
nextSummary = null;
return returnValue;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
private S3VersionSummary nextMatchingSummary() {
if (getKey() == null
|| (nextSummary != null && nextSummary.getKey().equals(
getKey()))) {
return nextSummary;
} else {
return null;
}
}
private void prepareCurrentListing() {
while (currentListing == null
|| (!currentIterator.hasNext() && currentListing
.isTruncated())) {
if (currentListing == null) {
ListVersionsRequest req = new ListVersionsRequest();
req.setBucketName(getBucketName());
if (getKey() != null) {
req.setPrefix(getKey());
} else {
req.setPrefix(getPrefix());
}
req.setMaxResults(getBatchSize());
currentListing = getS3().listVersions(req);
} else {
currentListing = getS3().listNextBatchOfVersions(
currentListing);
}
currentIterator = currentListing.getVersionSummaries()
.iterator();
}
if (nextSummary == null && currentIterator.hasNext()) {
nextSummary = currentIterator.next();
}
}
}
@Override
public Iterator iterator() {
return new VersionIterator();
}
}