Heute ein Tutorial für alle Java Liebhaber da draußen. An dieser Stelle erfährst du, wie du den S3-kompatiblen Object Storage von Tech4Hosting mittels Java ansprichst. Das von uns bereitgestellte Code-Sample bildet die Grundfunktionalitäten Upload, Download, Namensanpassung und Zugriffsrechteverwaltung ab.

Tech4Hosting S3 Object Storage ist komplett Amazon S3 kompatibel, dementsprechend greifen wir im Code auf die AWS SDK Libraries für Java zurück. Unser Beispielprogramm und seine Abhängigkeiten werden von dem Build-Management Tool Apache Maven mit einer pom.xml verwaltet.

Sample einrichten:

1. Clone unser BitBucket Repository unter folgendem Link:
https://bitbucket.org/Tech4Hosting/java-s3example/
2.. Erstelle ein neues Maven Projekt.
3. Setze alle benötigten Umgebungsvariablen (Bucket Name, Key Name, Tech4HostingS3 Access Key, Tech4HostingS3 Secret) in deiner Umgebung.

Sample ausführen:

Nachdem du den Code ausgeführt hast, wirst du im Dialog dazu aufgefordert die Pre-Signed URL zu klicken. Durch klicken der URL wird deine Datei final in deinen Object Storage übertragen. Am Ende des Beispiels wirst du weiterhin gefragt, ob die soeben übertragenen Dateien wieder gelöscht werden sollen.

Code:

package io.Tech4Hosting.s3example;


import com.amazonaws.ClientConfiguration;
import com.amazonaws.HttpMethod;
import com.amazonaws.SdkClientException;
import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3ClientBuilder;
import com.amazonaws.services.s3.model.*;

import javax.swing.*;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;


public class Main {

    public static void main(String[] args) throws IOException {

        for (int j = 0; j < 2; j++) {

            // file to upload
            String filePath = "example/logo.png";

            // bucket target - needs to exist!
            String bucketName = "karl";

            // object key
            String keyName = "s3test_" + j;

            // S3 Endpoint for Tech4Hosting
            String endpoint = "https://gos3.io";

            // these values come from the object storage settings in the Tech4Hosting panel
            String accessKey = System.getenv("GRIDSCALE_S3_ACCESS_KEY");
            String secret = System.getenv("GRIDSCALE_S3_SECRET");

            if (accessKey == null || secret == null) {
                System.out.println("Please define GRIDSCALE_S3_ACCESS_KEY and GRIDSCALE_S3_SECRET in your environment.");
                System.exit(-1);
            }

            BasicAWSCredentials awsCredentials = new BasicAWSCredentials(accessKey, secret);

            ClientConfiguration clientConfiguration = new ClientConfiguration();
            clientConfiguration.setSignerOverride("S3SignerType");
            
            // Connection Object
            AmazonS3 objectStorageClient = AmazonS3ClientBuilder.standard()
                    .withCredentials(new AWSStaticCredentialsProvider(awsCredentials))
                    .withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration(endpoint,
                            Regions.DEFAULT_REGION.getName()))
                    .withClientConfiguration(clientConfiguration)
                    .build();


            File file = new File(filePath);
            long contentLength = file.length();
            long partSize = 5 * 1024 * 1024; // Set part size to 5 MB.

            // Create a list of ETag objects. You retrieve ETags for each object part uploaded,
            // then, after each individual part has been uploaded, pass the list of ETags to
            // the request to complete the upload.
            List partETags = new ArrayList();

            // Initiate the multipart upload.
            InitiateMultipartUploadRequest initRequest = new InitiateMultipartUploadRequest(bucketName, keyName);
            InitiateMultipartUploadResult initResponse = objectStorageClient.initiateMultipartUpload(initRequest);

            // Upload the file parts.
            long filePosition = 0;
            for (int i = 1; filePosition < contentLength; i++) {
                // Because the last part could be less than 5 MB, adjust the part size as needed.
                partSize = Math.min(partSize, (contentLength - filePosition));

                // Create the request to upload a part.
                UploadPartRequest uploadRequest = new UploadPartRequest()
                        .withBucketName(bucketName)
                        .withKey(keyName)
                        .withUploadId(initResponse.getUploadId())
                        .withPartNumber(i)
                        .withFileOffset(filePosition)
                        .withFile(file)
                        .withPartSize(partSize);

                // Upload the part and add the response's ETag to our list.
                UploadPartResult uploadResult = objectStorageClient.uploadPart(uploadRequest);
                partETags.add(uploadResult.getPartETag());

                filePosition += partSize;
            }

            // Set the presigned URL to expire after one hour.
            java.util.Date expiration = new java.util.Date();
            long expTimeMillis = expiration.getTime();
            expTimeMillis += 1000 * 60 * 60;
            expiration.setTime(expTimeMillis);

            // Complete the multipart upload.
            CompleteMultipartUploadRequest compRequest = new CompleteMultipartUploadRequest(bucketName, keyName,
                    initResponse.getUploadId(), partETags);
            objectStorageClient.completeMultipartUpload(compRequest);

            GeneratePresignedUrlRequest generatePresignedUrlRequest =
                    new GeneratePresignedUrlRequest(bucketName, keyName)
                            .withMethod(HttpMethod.POST) // Change this to 'GET' if you want to Download
                            .withExpiration(expiration);
            URL url = objectStorageClient.generatePresignedUrl(generatePresignedUrlRequest);

            System.out.println("Please click on the link in the next 12 seconds" + "n" + "Pre-Signed URL: " + url.toString());

            try {
                TimeUnit.SECONDS.sleep(12);

                // Set ACLs to file
                AccessControlList acl = objectStorageClient.getObjectAcl(bucketName, keyName);

                acl.getGrantsAsList().clear();

                // change '.Read' to whatever Property you want to set the acl to
                acl.grantPermission(new CanonicalGrantee(acl.getOwner().getId()), Permission.Read);

                // set ACLs to file
                objectStorageClient.setObjectAcl(bucketName, keyName, acl);

                // Delete
                if (JOptionPane.showInputDialog(null, "Do you want to delete this example now?" +
                        " y/n?").toLowerCase().equals("y")) {
                    objectStorageClient.deleteObject(new DeleteObjectRequest(bucketName, keyName));
                    System.out.println("File " + keyName + "got removed from Bucket " + bucketName);
                } else {
                    System.out.println("File successfully created in " + bucketName);
                }
            
            } catch (InterruptedException e) {
                e.printStackTrace();

            } catch (SdkClientException e) {
                e.printStackTrace();

            }

        }
    }
}

Hoffentlich konnten wir dir mit unserem Beispielcode bei der Nutzung des S3 kompatiblen Object Storage von Tech4Hosting mittels Java weiterhelfen. Mehr Informationen zur allgemeinen Verwaltung des Object Storages erhältst du in Tech4Hosting Kurzanleitung: S3-kompatiabler Object Storage.

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