GoogleCredentialクラスを使ったGCSの認証

GoogleCredential.java

private final HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
private final JsonFactory jsonFactory = new JacksonFactory();

private hoge() throws IOException, GeneralSecurityException
{
    GoogleCredential credentials = new GoogleCredential.Builder().setTransport(httpTransport) // (1)
                        .setJsonFactory(jsonFactory)
                        .setServiceAccountId(<サービスアカウント メールアドレス>)
                        .setServiceAccountScopes( // (2)
                                ImmutableList.of(
                                        StorageScopes.DEVSTORAGE_READ_ONLY
                                        BigqueryScopes.BIGQUERY
                                )
                        )
                        .setServiceAccountPrivateKeyFromP12File(new File(<P12秘密鍵のフルパス>))
                        .build();

    Storage client = new Storage.Builder(httpTransport, jsonFactory, credentials)
                    .setApplicationName(<アプリケーション名>) // (3)
                    .build();
    return client;
}