如何使用 java 中的 Oauth 圖形服務客戶端 api 檢索 Office 365 郵件文件（如圖像、文本文件等）附件？

Question

這是我如何獲取附加到消息的附件對象列表：

IAttachmentCollectionRequest attachmentsPage = graphClient
    .users(emailServer.getEmailAddress())
    .mailFolders("Inbox")
    .messages(mail.id)
    .attachments()
    .buildRequest();

List<Attachment> attachmentsData = attachmentsPage.get().getCurrentPage();
List<AttachmentData> attachmentDataToStore = new java.util.ArrayList<AttachmentData>();

for(Attachment attachment : attachmentsData)
{
    attachmentData.setInputStream(
        new ByteArrayInputStream(
            attachment.getRawObject()
                .get("contentBytes")
                .getAsString()
                .getBytes()));
}

現在，我相信內容字節到輸入 stream 的轉換沒有正確發生，最終 data(image.png) 被損壞。 有什么建議么？

Answer 1

使用FileAttachment類為您處理所有這些。 不幸的是，SDK 並沒有以最“干凈”的方式處理這個問題——您必須再次請求附件。

public static void saveAttachments(String accessToken) {
    ensureGraphClient(accessToken);

    final String mailId = "message-id";

    // Get the list of attachments
    List<Attachment> attachments = graphClient
        .me()
        .messages(mailId)
        .attachments()
        .buildRequest()
        // Use select here to avoid getting the content in this first request
        .select("id,contentType,size")
        .get()
        .getCurrentPage();

    for(Attachment attachment : attachments) {
        // Attachment is a base type - need to re-get the attachment as a fileattachment
        if (attachment.oDataType.equals("#microsoft.graph.fileAttachment")) {

            // Use the client to generate the request URL
            String requestUrl = graphClient
                .me()
                .messages(mailId)
                .attachments(attachment.id)
                .buildRequest()
                .getRequestUrl()
                .toString();

            // Build a new file attachment request
            FileAttachmentRequestBuilder requestBuilder =
                new FileAttachmentRequestBuilder(requestUrl, graphClient, null);

            FileAttachment fileAttachment = requestBuilder.buildRequest().get();

            // Get the content directly from the FileAttachment
            byte[] content = fileAttachment.contentBytes;

            try (FileOutputStream stream = new FileOutputStream("C:\\Source\\test.png")) {
                stream.write(content);
            } catch (IOException exception) {
                // Handle it
            }
        }
    }
}

Answer 2

您從 rawObject JSON 讀取 contentBytes 的方法將起作用。 您只需要使用 Base64 解碼器而不是String.getBytes()因為 contentBytes 是 base64 編碼的。 這在我的網絡上比使用 FileAttachmentRequestBuilder 再次請求附件要快一些。

IAttachmentCollectionRequest attachmentsPage = graphClient
    .users(emailServer.getEmailAddress())
    .mailFolders("Inbox")
    .messages(mail.id)
    .attachments()
    .buildRequest();

List<Attachment> attachmentsData = attachmentsPage.get().getCurrentPage();
List<AttachmentData> attachmentDataToStore = new java.util.ArrayList<AttachmentData>();

for(Attachment attachment : attachmentsData)
{
    attachmentData.setInputStream(
        new ByteArrayInputStream(
                Base64.getDecoder().decode(attachment.getRawObject()
                    .get("contentBytes")
                    .getAsString());
}

Answer 3

從 microsoft-graph 版本 5.34.0 開始，不再需要一些東西，例如解碼，您將能夠簡單地轉換您的 object。

獲取 File/ItemAttachments 的復雜方式：

List<Attachment> attachments = new ArrayList<>();

        try {
            AttachmentCollectionPage mgAttachmentList =
                    graphClient.users(emailAddress)
                            .messages(mail.id)
                            .attachments()
                            .buildRequest()
                            .get();

            do {
                attachments.addAll(mgAttachmentList.getCurrentPage());

                // Check for next page
                if (mgAttachmentList.getNextPage() != null) {
                    mgAttachmentList = mgAttachmentList.getNextPage().buildRequest().get();
                } else {
                    mgAttachmentList = null;
                }
            } while (mgAttachmentList != null);

            attachments.stream()
                    .filter(Objects::nonNull)
                    .forEach(attachment -> {
                        try {
                            // attachment equals a FileAttachment
                            if ("#microsoft.graph.fileAttachment".equalsIgnoreCase(attachment.oDataType)) {
                                byte[] attachmentContentBytes = ((FileAttachment) attachment).contentBytes;
                                if (attachmentContentBytes != null) {
                                    // your own logic here
                                }
                            } else if ("#microsoft.graph.itemAttachment".equalsIgnoreCase(attachment.oDataType)) {
                                /*
                                 *  We need to convert each Attachment.
                                 *  If it's an ItemAttachment, we need to do another call to retrieve the item-object.
                                 *
                                 *  The standard call with expand option gives us an Attachment (again)
                                 */
                                if (StringUtils.isNotBlank(attachment.contentType)) {
                                    Attachment attachment = graphClient.users(emailAddress)
                                            .messages(mail.id)
                                            .attachments(attachment.id)
                                            .buildRequest()
                                            .expand("microsoft.graph.itemattachment/item")
                                            .get();
                                    if (attachment != null) {
                                        // cast the object to whatever you need, in this example I retrieve the webLink
                                        String linkToMessage = ((Message) ((ItemAttachment) attachment).item).webLink;
                                        // your own logic here
                                    }
                                } else {
                                    log.info("Unknown attachment contentType for an ItemAttachment - Could not read attachment.");
                                }
                            } else {
                                log.error("Unable to read an attachment for mail.");
                            }
                        } catch (Exception e) {
                            log.error("Could not read attachment: '" + attachment.name + "' for message: '" + message.subject + ". " + e.getMessage(), e);
                        }
                    });
        } catch (Exception e) {
            log.error("Something went wrong while receiving attachments for message: '" + message.subject + "'. " + e.getMessage(), e);
        }