从 Gmail 下载邮件附件，获取 Exchange[MailMessage: null]答案

【问题标题】：Download mail attachments from Gmail, getting Exchange[MailMessage: null]从 Gmail 下载邮件附件，获取 Exchange[MailMessage: null]
【发布时间】：2014-11-01 12:55:31
【问题描述】：

我需要使用 java 程序从 Gmail 帐户下载附件。使用Apache Camel。

在跑步时，我得到了，

Exchange[MailMessage: null]，因此 attachments.size() 为 0

我也发布了我的测试代码

@Test
public void configureExcange() throws Exception {

    try {
        CamelContext context = new DefaultCamelContext();

        Endpoint endpoint =
                context.getEndpoint("imaps://imap.gmail.com?username=" + mailId + "&password=" + password
                        + "&delete=false&unseen=true&consumer.delay=60000");

        // PollingConsumer consumer = endpoint.createPollingConsumer();
        Exchange exchange = endpoint.createExchange();

        process(exchange);

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

public void process(Exchange exchange) throws Exception {
    // the API is a bit clunky so we need to loop
    Map<String, DataHandler> attachments = exchange.getIn().getAttachments();
    if (attachments.size() > 0) {
        for (String name : attachments.keySet()) {
            DataHandler dh = attachments.get(name);
            // get the file name
            String filename = dh.getName();

            // get the content and convert it to byte[]
            byte[] data = exchange.getContext().getTypeConverter().convertTo(byte[].class, dh.getInputStream());

            // write the data to a file
            FileOutputStream out = new FileOutputStream(filename);
            out.write(data);
            out.flush();
            out.close();
        }
    }
}

如何获取附件？

【问题讨论】：

标签： java email apache-camel email-attachments

【解决方案1】：

Endpoint.createExchange() 只是创建要使用的交换，它不会从邮件服务器中提取消息。您需要使用 ConsumerTemplate 从 gmail 服务器中提取消息。

【讨论】：

【解决方案2】：

更新功能，展示如何轮询邮件账户。

@Test
public void configureExcange() throws Exception {

    PollingConsumer pollingConsumer = null;
    try {
        CamelContext context = new DefaultCamelContext();
        Endpoint endpoint =
                context.getEndpoint("imaps://imap.gmail.com?username="
                + mailId + "&password=" + password
                + "&delete=false&peek=false&unseen=true&consumer.delay=60000&closeFolder=false&disconnect=false");
            // options unseen=true, will only poll unread mails

            //Polling an END point
            pollingConsumer = endpoint.createPollingConsumer();
            pollingConsumer.start();
            pollingConsumer.getEndpoint().createExchange();

            Exchange exchange = pollingConsumer.receive(60000);

            while (exchange != null) {
                process(exchange);
                //each time "pollingConsumer" will poll 1 mail at a time
                exchange = pollingConsumer.receive(60000);
            }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

【讨论】：