一 .Amazon S3介绍

Amazon Simple Storage Service (Amazon S3) 是一种对象存储，它具有简单的 Web 服务接口，可用于在 Web 上的任何位置存储和检索任意数量的数据。它能够提供 99.999999999% 的持久性，并且可以在全球大规模传递数万亿对象。

客户使用 S3 作为云原生应用程序的主要存储；作为分析的批量存储库或“数据湖”；作为备份和恢复以及灾难恢复的目标；并将其与无服务器计算配合使用。

使用 Amazon 的云数据迁移选项，客户可以轻松地将大量数据移入或移出 Amazon S3。数据在存储到 S3 中之后，会自动采用成本更低、存储期限更长的云存储类 (如 S3 Standard – Infrequent Access 和 Amazon Glacier) 进行存档。

二.Java S3 Example
准备工作：
1.导入依赖包
    <dependency>
        <groupId>com.amazonaws</groupId>
        <artifactId>aws-java-sdk</artifactId>
        <version>1.9.2</version>
    </dependency>
2.在s3服务中创建用户，获取用户的Access key和Secret Access Key，使用这个作为凭证连接s3
3.在s3服务中配置AWSConnector和AmazonS3FullAccess的连接权限。可以通过这个配置，在访问的时候进行authenticate验证。
s3 api简单操作：
1.创建凭证
    AWSCredentials credentials = new BasicAWSCredentials(“YourAccessKeyID”, “YourSecretAccessKey”);
2.创建S3 Client
    AmazonS3 s3client = new AmazonS3Client(credentials);
3.创建Bucket
    String bucketName = “javatutorial-net-example-bucket”;
    s3client.createBucket(bucketName);
4.获取s3 Bucket的list
    for (Bucket bucket : s3client.listBuckets()) {
        System.out.println(” – ” + bucket.getName());
    }
5.在s3 Bucket中创建文件
    public static void createFolder(String bucketName, String folderName, AmazonS3 client) {
        // create meta-data for your folder and set content-length to 0
        ObjectMetadata metadata = new ObjectMetadata();
        metadata.setContentLength(0);
        // create empty content
        InputStream emptyContent = new ByteArrayInputStream(new byte[0]);
        // create a PutObjectRequest passing the folder name suffixed by /
        PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName,
                    folderName + SUFFIX, emptyContent, metadata);
        // send request to S3 to create folder
        client.putObject(putObjectRequest);
    }
6.上传文件
    String fileName = folderName + SUFFIX + “testvideo.mp4”;
    s3client.putObject(new PutObjectRequest(bucketName, fileName,
            new File(“C:\Users\user\Desktop\testvideo.mp4”)));
7.删除Bucket
    s3client.deleteBucket(bucketName);
8.删除文件
    s3client.deleteObject(bucketName, fileName);
    
完整实例
    import java.io.ByteArrayInputStream;
    import java.io.File;
    import java.io.InputStream;
    import java.util.List;
    import com.amazonaws.auth.AWSCredentials;
    import com.amazonaws.auth.BasicAWSCredentials;
    import com.amazonaws.services.s3.AmazonS3;
    import com.amazonaws.services.s3.AmazonS3Client;
    import com.amazonaws.services.s3.model.Bucket;
    import com.amazonaws.services.s3.model.CannedAccessControlList;
    import com.amazonaws.services.s3.model.ObjectMetadata;
    import com.amazonaws.services.s3.model.PutObjectRequest;
    import com.amazonaws.services.s3.model.S3ObjectSummary;
    public class AmazonS3Example {
        
        private static final String SUFFIX = “/”;
        
        public static void main(String[] args) {
            // credentials object identifying user for authentication
            // user must have AWSConnector and AmazonS3FullAccess for
            // this example to work
            AWSCredentials credentials = new BasicAWSCredentials(
                    “YourAccessKeyID”,
                    “YourSecretAccessKey”);
            
            // create a client connection based on credentials
            AmazonS3 s3client = new AmazonS3Client(credentials);
            
            // create bucket – name must be unique for all S3 users
            String bucketName = “javatutorial-net-example-bucket”;
            s3client.createBucket(bucketName);
            
            // list buckets
            for (Bucket bucket : s3client.listBuckets()) {
                System.out.println(” – ” + bucket.getName());
            }
            
            // create folder into bucket
            String folderName = “testfolder”;
            createFolder(bucketName, folderName, s3client);
            
            // upload file to folder and set it to public
            String fileName = folderName + SUFFIX + “testvideo.mp4”;
            s3client.putObject(new PutObjectRequest(bucketName, fileName,
                    new File(“C:\Users\user\Desktop\testvideo.mp4”))
                    .withCannedAcl(CannedAccessControlList.PublicRead));
            
            deleteFolder(bucketName, folderName, s3client);
            
            // deletes bucket
            s3client.deleteBucket(bucketName);
        }
        
        public static void createFolder(String bucketName, String folderName, AmazonS3 client) {
            // create meta-data for your folder and set content-length to 0
            ObjectMetadata metadata = new ObjectMetadata();
            metadata.setContentLength(0);
            // create empty content
            InputStream emptyContent = new ByteArrayInputStream(new byte[0]);
            // create a PutObjectRequest passing the folder name suffixed by /
            PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName,
                    folderName + SUFFIX, emptyContent, metadata);
            // send request to S3 to create folder
            client.putObject(putObjectRequest);
        }
        /**
         * This method first deletes all the files in given folder and than the
         * folder itself
         */
        public static void deleteFolder(String bucketName, String folderName, AmazonS3 client) {
            List fileList =
                    client.listObjects(bucketName, folderName).getObjectSummaries();
            for (S3ObjectSummary file : fileList) {
                client.deleteObject(bucketName, file.getKey());
            }
            client.deleteObject(bucketName, folderName);
        }
    }

参考：

https://javatutorial.net/java-s3-example

https://aws.amazon.com/cn/s3/getting-started/

python版的s3 api：

http://boto3.readthedocs.io/en/latest/guide/quickstart.html