使用 IMAP 服务器的邮件

列出服务器上的 MIME 消息 ID

ImapMessageInfo 提供 MIME MessageId 用于在不提取完整邮件的情况下识别邮件。以下代码片段展示了如何列出 MIME messageId。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
ImapClient client = new ImapClient();
client.setHost("domain.com");
client.setUsername("username");
client.setPassword("password");

try {
    ImapMessageInfoCollection messageInfoCol = client.listMessages("Inbox");
    for (ImapMessageInfo info : messageInfoCol) {
        // Display MIME Message ID
        System.out.println("Message Id = " + info.getMessageId());
    }
} catch (java.lang.RuntimeException ex) {
    System.out.println(ex.getMessage());
}

列出服务器上的邮件

Aspose.Email 提供了一个含 2 个成员的重载变体 listMessages() 根据查询检索指定数量的邮件。以下代码片段展示了如何列出邮件。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
// Create an imapclient with host, user and password
ImapClient client = new ImapClient("localhost", "user", "password");

// Select the inbox folder and Get the message info collection
ImapQueryBuilder builder = new ImapQueryBuilder();
MailQuery query = builder
        .or(builder.or(builder.or(builder.or(builder.getSubject().contains(" (1) "), builder.getSubject().contains(" (2) ")), builder.getSubject().contains(" (3) ")),
                builder.getSubject().contains(" (4) ")), builder.getSubject().contains(" (5) "));
ImapMessageInfoCollection messageInfoCol4 = client.listMessages(query, 4);
System.out.println((messageInfoCol4.size() == 4) ? "Success" : "Failure");

递归列出服务器上的邮件

IMAP 协议支持递归列出邮箱文件夹中的邮件。这也有助于列出文件夹的子文件夹中的邮件。以下代码片段展示了如何递归列出邮件。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
// Create an imapclient with host, user and password
ImapClient client = new ImapClient();
client.setHost("domain.com");
client.setUsername("username");
client.setPassword("password");
client.selectFolder("InBox");
ImapMessageInfoCollection msgsColl = client.listMessages(true);
System.out.println("Total Messages: " + msgsColl.size());

使用多连接列出消息

ImapClient 提供了一个 UseMultiConnection 属性可用于在繁重操作时创建多个连接。您也可以通过使用 ImapClient.ConnectionsQuantity。以下代码片段演示了使用多连接模式列出邮件，并将其性能与单连接模式进行比较。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
ImapClient imapClient = new ImapClient();
imapClient.setHost("<HOST>");
imapClient.setPort(993);
imapClient.setUsername("<USERNAME>");
imapClient.setPassword("<PASSWORD>");
imapClient.setSupportedEncryption(EncryptionProtocols.Tls);
imapClient.setSecurityOptions(SecurityOptions.SSLImplicit);

imapClient.selectFolder("Inbox");
imapClient.setConnectionsQuantity(5);
imapClient.setUseMultiConnection(MultiConnectionMode.Enable);
long multiConnectionModeStartTime = System.currentTimeMillis();
ImapMessageInfoCollection messageInfoCol1 = imapClient.listMessages(true);
long multiConnectionModeTimeSpan = System.currentTimeMillis() - multiConnectionModeStartTime;

imapClient.setUseMultiConnection(MultiConnectionMode.Disable);
long singleConnectionModeStartTime = System.currentTimeMillis();
ImapMessageInfoCollection messageInfoCol2 = imapClient.listMessages(true);
long singleConnectionModeTimeSpan = System.currentTimeMillis() - singleConnectionModeStartTime;

double performanceRelation = singleConnectionModeTimeSpan / multiConnectionModeTimeSpan;
System.out.println("Performance Relation: " + performanceRelation);

请注意，使用多连接模式并不保证性能提升。

按降序获取消息

Aspose.Email 提供 ImapClient.listMessagesByPage 方法，列出支持分页的消息。该方法的某些重载 ImapClient.listMessagesByPage 接受 PageSettings 作为参数。 PageSettings 提供一个 AscendingSorting 属性，将其设置为 false 时，返回按降序排列的电子邮件。

以下示例代码演示了 AscendingSorting 属性的 PageSettings 类用于更改电子邮件的顺序。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
ImapClient imapClient = new ImapClient();
imapClient.setHost("<HOST>");
imapClient.setPort(993);
imapClient.setUsername("<USERNAME>");
imapClient.setPassword("<PASSWORD>");
imapClient.setSupportedEncryption(EncryptionProtocols.Tls);
imapClient.setSecurityOptions(SecurityOptions.SSLImplicit);

PageSettings pageSettings = new PageSettings();
pageSettings.setAscendingSorting(false);
ImapPageInfo pageInfo = imapClient.listMessagesByPage(5, pageSettings);
ImapMessageInfoCollection messages = pageInfo.getItems();

for (ImapMessageInfo message : messages) {
    System.out.println(message.getSubject() + " -> " + message.getDate().toString());
}

从服务器获取消息并保存到磁盘

该 ImapClient 类可以从 IMAP 服务器获取消息，并将消息以 EML 格式保存到本地磁盘。以下步骤用于将消息保存到磁盘：

创建该类的实例 ImapClient 类。
在 ImapClient 中指定主机名、端口、用户名和密码构造函数.
使用以下方式选择文件夹 selectFolder() 方法。
调用 listMessages 方法以获取 ImapMessageInfoCollection 对象。
遍历 ImapMessageInfoCollection 集合，调用 saveMessage() 方法，并提供输出路径和文件名。

以下代码片段展示了如何从服务器获取电子邮件并保存。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
// Select the inbox folder and Get the message info collection
client.selectFolder(ImapFolderInfo.IN_BOX);
ImapMessageInfoCollection list = client.listMessages();

// Download each message
for (int i = 0; i < list.size(); i++) {
    // Save the EML file locally
    client.saveMessage(list.get_Item(i).getUniqueId(), dataDir + list.get_Item(i).getUniqueId() + ".eml");
}

以 MSG 格式保存消息

在上述示例中，邮件保存为 EML 格式。要将邮件保存为 MSG 格式，请使用 ImapClient.fetchMessage() 需要调用该方法。它返回一个实例化的 MailMessage 类。该 MailMessage.save() 随后可以调用该方法将消息保存为 MSG。以下代码片段展示了如何将消息保存为 MSG 格式。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
// The path to the file directory.
String dataDir = "data/";

// Create an imapclient with host, user and password
ImapClient client = new ImapClient("localhost", "user", "password");

// Select the inbox folder and Get the message info collection
client.selectFolder(ImapFolderInfo.IN_BOX);
ImapMessageInfoCollection list = client.listMessages();

// Download each message
for (int i = 0; i < list.size(); i++) {
    // Save the message in MSG format
    MailMessage message = client.fetchMessage(list.get_Item(i).getUniqueId());
    message.save(dataDir + list.get_Item(i).getUniqueId() + "_out.msg", SaveOptions.getDefaultMsgUnicode());
}

批量获取邮件

ImapClient 提供了一个 fetchMessages 接受序列号或唯一标识的可迭代对象并返回列表的方法 MailMessage。下面的代码片段演示了 fetchMessages 根据序列号和唯一标识获取邮件的方法。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
ImapClient imapClient = new ImapClient();
imapClient.setHost("<HOST>");
imapClient.setPort(993);
imapClient.setUsername("<USERNAME>");
imapClient.setPassword("<PASSWORD>");
imapClient.setSupportedEncryption(EncryptionProtocols.Tls);
imapClient.setSecurityOptions(SecurityOptions.SSLImplicit);

ImapMessageInfoCollection messageInfoCol = imapClient.listMessages();
System.out.println("ListMessages Count: " + messageInfoCol.size());

List<Integer> sequenceNumberAr = new ArrayList<Integer>();
List<String> uniqueIdAr = new ArrayList<String>();
for (ImapMessageInfo mi : messageInfoCol) {
    sequenceNumberAr.add(mi.getSequenceNumber());
    uniqueIdAr.add(mi.getUniqueId());
}

for (MailMessage m : imapClient.fetchMessagesBySequences(sequenceNumberAr)) {
    System.out.println("FetchMessages-sequenceNumberAr : " + m.getSubject());
}

for (MailMessage m : imapClient.fetchMessagesByUids(uniqueIdAr)) {
    System.out.println("FetchMessages-uniqueIdAr : " + m.getSubject());
}

邮件线程/将邮件组织为对话

Aspose.Email 可以将与同一对话相关的所有转发、回复和全部回复邮件以层次结构方式分组。基本上，IMAP 协议可能支持 RFC-5256 中定义的 THREAD 功能。此外，Gmail 还提供了另一种 IMAP 扩展，称为 X-GM-EXT-1。

以下邮件线程功能可供使用：

getMessageThreads 方法 - 通过以下方式接收邮件线程 ImapClient.
boolean getGmExt1Supported - 获取是否支持 Gmail X-GM-EXT-1 扩展的信息。
boolean getThreadSupported - 获取是否支持 THREAD 扩展的信息。
String[] getThreadAlgorithms - 获取支持的 THREAD 算法。

以下代码示例展示了如何使用这些功能从 Gmail 获取邮件线程：

  ImapClient client = new ImapClient("imap.gmail.com", 993, "username", "password", SecurityOptions.SSLImplicit);

try {

    client.selectFolder(ImapFolderInfo.IN_BOX);

   // get a list of messages that we'll group by conversation

   ImapMessageInfoCollection messages = client.listMessages();

   // make sure the IMAP server supports X-GM-EXT-1 extension

   if (client.getGmExt1Supported()) {

       // gets unique conversationId for our example

       Set<String> conversationIds = new HashSet<String>();

       for (ImapMessageInfo messageInfo : messages) {

           if (messageInfo.getConversationId() != null)

                conversationIds.add(messageInfo.getConversationId());

       }

       for (String conversationId : conversationIds) {

           // create the necessary search conditions for a thread

           XGMThreadSearchConditions conditions = new XGMThreadSearchConditions();

            conditions.setConversationId(conversationId);

            conditions.setUseUId(true);

           // get results

           List<MessageThreadResult> conversation = client.getMessageThreads(conditions);

           // print the email conversation in hierarchically manner

           printConversaton("", conversation, messages);

            System.out.println("--------------------");

       }

   }

} finally {

    client.dispose();

}

/**

 * <p>

 * Prints the email conversation in hierarchically manner

 * </p>

 */

public static void printConversaton(String indent, Iterable<MessageThreadResult> conversation,

    Iterable<ImapMessageInfo> messages) {

   for (MessageThreadResult thread : conversation) {

       for (ImapMessageInfo messageInfo : messages) {

           if (thread.getUniqueId().equals(messageInfo.getUniqueId())) {

                System.out.println(indent + " (" + thread.getUniqueId() + ") " + messageInfo.getSubject());

               break;

           }

       }

       if (thread.getChildMessages().size() != 0) {

            printConversaton(indent += "-", thread.getChildMessages(), messages);

       }

   }

}

如果 IMAP 服务器支持 THREAD 功能，代码会略有变化：

检查 IMAP 服务器是否支持 THREAD 扩展：

 if (client.getThreadSupported())

为邮件线程创建合适的搜索条件：

 ThreadSearchConditions conditions = new ThreadSearchConditions();

conditions.setAlgorithm(client.getThreadAlgorithms()[0]);

conditions.setUseUId(true);

分页列出消息

在邮箱中包含大量消息的电子邮件服务器场景下，通常希望使用分页支持列出或检索消息。Aspose.Email API ImapClient 让您能够使用分页支持从服务器检索消息。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
// This example shows the paging support of ImapClient for listing messages from the server
// Available in Aspose.Email for Java and onwards
final ImapClient client = new ImapClient("host.domain.com", 993, "username", "password");
try {
    try {
        int messagesNum = 12;
        int itemsPerPage = 5;
        MailMessage message = null;
        // Create some test messages and append these to server's inbox
        for (int i = 0; i < messagesNum; i++) {
            message = new MailMessage("from@domain.com", "to@domain.com", "EMAILNET-35157 - " + UUID.randomUUID(),
                    "EMAILNET-35157 Move paging parameters to separate class");
            client.appendMessage(ImapFolderInfo.IN_BOX, message);
        }

        // List messages from inbox
        client.selectFolder(ImapFolderInfo.IN_BOX);
        ImapMessageInfoCollection totalMessageInfoCol = client.listMessages();
        // Verify the number of messages added
        System.out.println(totalMessageInfoCol.size());

        ////////////////// RETREIVE THE MESSAGES USING PAGING SUPPORT////////////////////////////////////

        List<ImapPageInfo> pages = new ArrayList<ImapPageInfo>();
        PageSettings pageSettings = new PageSettings();
        ImapPageInfo pageInfo = client.listMessagesByPage(itemsPerPage, 0, pageSettings);
        System.out.println(pageInfo.getTotalCount());
        pages.add(pageInfo);
        while (!pageInfo.getLastPage()) {
            pageInfo = client.listMessagesByPage(itemsPerPage, pageInfo.getNextPage().getPageOffset(), pageSettings);
            pages.add(pageInfo);
        }
        int retrievedItems = 0;

        // foreach to while statements conversion
        for (ImapPageInfo folderCol : pages) {
            retrievedItems += folderCol.getItems().size();
        }
        System.out.println(retrievedItems);
    } finally {
    }
} finally {
    if (client != null)
        client.dispose();
}

递归获取文件夹并读取消息

在本文中，大多数 ImapClient 这些功能用于创建一个应用程序，递归列出来自 IMAP 服务器的所有文件夹及子文件夹。它还将每个文件夹和子文件夹中的消息以 MSG 格式保存到本地磁盘。磁盘上的文件夹和消息以与 IMAP 服务器相同的层次结构创建和保存。以下代码片段展示了如何递归获取消息和子文件夹信息。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
public static void run() throws Exception {
    // Create an instance of the ImapClient class
    ImapClient client = new ImapClient();

    // Specify host, username, password, Port and SecurityOptions for your client
    client.setHost("imap.gmail.com");
    client.setUsername("your.username@gmail.com");
    client.setPassword("your.password");
    client.setPort(993);
    client.setSecurityOptions(SecurityOptions.Auto);
    try {
        // The root folder (which will be created on disk) consists of host and username
        String rootFolder = client.getHost() + "-" + client.getUsername();

        // Create the root folder and List all the folders from IMAP server
        new File(rootFolder).mkdirs();
        ImapFolderInfoCollection folderInfoCollection = client.listFolders();
        for (ImapFolderInfo folderInfo : folderInfoCollection) {
            // Call the recursive method to read messages and get sub-folders
            listMessagesInFolder(folderInfo, rootFolder, client);
        }
        // Disconnect to the remote IMAP server
        client.dispose();
    } catch (java.lang.RuntimeException ex) {
        System.out.println(ex);
    }

    System.out.println("Downloaded messages recursively from IMAP server.");
}

/// Recursive method to get messages from folders and sub-folders
private static void listMessagesInFolder(ImapFolderInfo folderInfo, String rootFolder, ImapClient client) {
    // Create the folder in disk (same name as on IMAP server)
    String currentFolder = "data/";
    new File(currentFolder).mkdirs();

    // Read the messages from the current folder, if it is selectable
    if (folderInfo.getSelectable()) {
        // Send status command to get folder info
        ImapFolderInfo folderInfoStatus = client.getFolderInfo(folderInfo.getName());
        System.out.println(folderInfoStatus.getName() + " folder selected. New messages: " + folderInfoStatus.getNewMessageCount() + ", Total messages: "
                + folderInfoStatus.getTotalMessageCount());

        // Select the current folder and List messages
        client.selectFolder(folderInfo.getName());
        ImapMessageInfoCollection msgInfoColl = client.listMessages();
        System.out.println("Listing messages....");
        for (ImapMessageInfo msgInfo : msgInfoColl) {
            // Get subject and other properties of the message
            System.out.println("Subject: " + msgInfo.getSubject());
            System.out.println("Read: " + msgInfo.isRead() + ", Recent: " + msgInfo.getRecent() + ", Answered: " + msgInfo.getAnswered());

            // Get rid of characters like ? and :, which should not be included in a file name and Save the message in MSG format
            String fileName = msgInfo.getSubject().replace(":", " ").replace("?", " ");
            MailMessage msg = client.fetchMessage(msgInfo.getSequenceNumber());
            msg.save(currentFolder + "\\" + fileName + "-" + msgInfo.getSequenceNumber() + ".msg", SaveOptions.getDefaultMsgUnicode());
        }
        System.out.println("============================\n");
    } else {
        System.out.println(folderInfo.getName() + " is not selectable.");
    }

    try {
        // If this folder has sub-folders, call this method recursively to get messages
        ImapFolderInfoCollection folderInfoCollection = client.listFolders(folderInfo.getName());
        for (ImapFolderInfo subfolderInfo : folderInfoCollection) {
            listMessagesInFolder(subfolderInfo, rootFolder, client);
        }
    } catch (java.lang.RuntimeException e) {
    }
}

获取消息 UID 或序列号

Aspose.Email 公共 API 提供以下功能，以获取消息标识信息（如 UID 或序列号），这些信息在处理从服务器接收的消息时可能需要：

MailboxInfo 类 - 表示邮箱中邮件的标识信息。

getSequenceNumber() 方法 - 获取消息的序列号。
getUniqueId() 方法 - 获取消息的唯一 ID。

MailMessage 类 - 表示电子邮件消息，并允许访问消息属性，例如主题、正文、发件人和收件人地址等。

getItemId 方法 - 表示邮箱中消息的标识信息。

以下代码示例演示了如何使用该类从 IMAP 服务器的 "INBOX" 文件夹获取并显示消息详情 ImapClient 类：

try (ImapClient client = new ImapClient(imapHost, port, emailAddress, password, securityOption)) {
    ImapMessageInfoCollection msgs = client.listMessages("INBOX");
    List<Integer> seqIds = new ArrayList<>();
    for (ImapMessageInfo msg : msgs) {
        seqIds.add(msg.getSequenceNumber());
    }
    Iterable<MailMessage> msgsViaFetch = client.fetchMessagesBySequences(seqIds);
    for (MailMessage thisMsg : msgsViaFetch) {
        System.out.println("Message ID: " + thisMsg.getItemId().getUniqueId()
                + " SequenceNumber: " + thisMsg.getItemId().getSequenceNumber()
                + " Subject: " + thisMsg.getSubject());
    }
}

检索额外参数作为摘要信息

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
final ImapClient client = new ImapClient("host.domain.com", "username", "password");
try {
    MailMessage message = new MailMessage("from@domain.com", "to@doman.com", "EMAILNET-38466 - " + UUID.randomUUID().toString(),
            "EMAILNET-38466 Add extra parameters for UID FETCH command");

    // append the message to the server
    String uid = client.appendMessage(message);

    // wait for the message to be appended
    Thread.sleep(5000);

    // Define properties to be fetched from server along with the message
    List<String> messageExtraFields = Arrays.asList("X-GM-MSGID", "X-GM-THRID");

    // retreive the message summary information using it's UID
    ImapMessageInfo messageInfoUID = client.listMessage(uid, messageExtraFields);

    // retreive the message summary information using it's sequence number
    ImapMessageInfo messageInfoSeqNum = client.listMessage(1, messageExtraFields);

    // List messages in general from the server based on the defined properties
    ImapMessageInfoCollection messageInfoCol = client.listMessages(messageExtraFields);

    ImapMessageInfo messageInfoFromList = messageInfoCol.get_Item(0);

    // verify that the parameters are fetched in the summary information
    for (String paramName : messageExtraFields) {
        System.out.println(messageInfoFromList.getExtraParameters().containsKey(paramName));
        System.out.println(messageInfoUID.getExtraParameters().containsKey(paramName));
        System.out.println(messageInfoSeqNum.getExtraParameters().containsKey(paramName));
    }
} finally {
    if (client != null)
        client.dispose();
}

获取 List-Unsubscribe 标头信息

List-Unsubscribe 标头包含用于取消订阅电子邮件列表（例如广告、新闻稿等）的 URL。要获取 List-Unsubscribe 标头，请使用 listUnsubscribe 属性的 ImapMessageInfo 类。以下示例展示了该类的使用 listUnsubscribe 获取 List-Unsubscribe 标头的属性。

// For complete examples and data files, please go to https://github.com/aspose-email/Aspose.Email-for-Java
ImapClient imapClient = new ImapClient();
imapClient.setHost("<HOST>");
imapClient.setPort(993);
imapClient.setUsername("<USERNAME>");
imapClient.setPassword("<PASSWORD>");
imapClient.setSupportedEncryption(EncryptionProtocols.Tls);
imapClient.setSecurityOptions(SecurityOptions.SSLImplicit);

ImapMessageInfoCollection messageInfoCol = imapClient.listMessages();
for (ImapMessageInfo imapMessageInfo : messageInfoCol) {
    System.out.println("ListUnsubscribe Header: " + imapMessageInfo.getListUnsubscribe());
}

连接到 IMAP 服务器使用 IMAP 处理邮件附件