StorageSample.java Source code

Introduction

Here is the source code for StorageSample.java

Source

/*
 * Copyright (c) 2014 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License 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.
 */

import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.GenericUrl;
import com.google.api.client.http.HttpRequest;
import com.google.api.client.http.HttpRequestFactory;
import com.google.api.client.http.HttpResponse;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.util.Preconditions;

import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.net.URLEncoder;
import java.security.GeneralSecurityException;
import java.util.Collections;

import javax.xml.transform.OutputKeys;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

/**
 * Sample code used in the Cloud Storage Java documentation.
 * https://cloud.google.com/storage/docs/xml-api-java-samples
 */
public final class StorageSample {

    /** This class is never instantiated. */
    private StorageSample() {
    }

    /** Global configuration of Google Cloud Storage OAuth 2.0 scope. */
    private static final String STORAGE_SCOPE = "https://www.googleapis.com/auth/devstorage.read_write";

    /**
     * Fetches the listing of the given bucket.
     *
     * @param bucketName the name of the bucket to list.
     *
     * @return the raw XML containing the listing of the bucket.
     * @throws IOException if there's an error communicating with Cloud Storage.
     * @throws GeneralSecurityException for errors creating https connection.
     */
    public static String listBucket(final String bucketName) throws IOException, GeneralSecurityException {
        //[START snippet]
        // Build an account credential.
        GoogleCredential credential = GoogleCredential.getApplicationDefault()
                .createScoped(Collections.singleton(STORAGE_SCOPE));

        // Set up and execute a Google Cloud Storage request.
        String uri = "https://storage.googleapis.com/" + URLEncoder.encode(bucketName, "UTF-8");

        HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
        HttpRequestFactory requestFactory = httpTransport.createRequestFactory(credential);
        GenericUrl url = new GenericUrl(uri);

        HttpRequest request = requestFactory.buildGetRequest(url);
        HttpResponse response = request.execute();
        String content = response.parseAsString();
        //[END snippet]

        return content;
    }

    /**
     * Prints out the contents of the given xml, in a more readable form.
     *
     * @param bucketName the name of the bucket you're listing.
     * @param content the raw XML string.
     */
    private static void prettyPrintXml(final String bucketName, final String content) {
        // Instantiate transformer input.
        Source xmlInput = new StreamSource(new StringReader(content));
        StreamResult xmlOutput = new StreamResult(new StringWriter());

        // Configure transformer.
        try {
            Transformer transformer = TransformerFactory.newInstance().newTransformer(); // An identity transformer
            transformer.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, "testing.dtd");
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
            transformer.transform(xmlInput, xmlOutput);

            // Pretty print the output XML.
            System.out.println("\nBucket listing for " + bucketName + ":\n");
            System.out.println(xmlOutput.getWriter().toString());
        } catch (TransformerException e) {
            e.printStackTrace();
        }
    }

    /**
     * A command-line handler to display the bucket passed in as an argument.
     *
     * @param args the array of command-line arguments.
     */
    public static void main(final String[] args) {
        try {
            // Check for valid setup.
            Preconditions.checkArgument(args.length == 1,
                    "Please pass in the Google Cloud Storage bucket name to display");
            String bucketName = args[0];

            String content = listBucket(bucketName);

            prettyPrintXml(bucketName, content);
            System.exit(0);

        } catch (IOException e) {
            System.err.println(e.getMessage());
        } catch (Throwable t) {
            t.printStackTrace();
        }
        System.exit(1);
    }
}