我目前拥有功能齐全的电子邮件通知系统。这一切都正常，但已注意到其中一个内嵌图像，通过休息服务附加到电子邮件，正在被请求三次。
一旦调用transport.send，似乎就会发生这种情况。我假设当javamail发送电子邮件时，它会调用引用的所有内联图像并生成base64图像并将其放入外发电子邮件中。
我的问题是...... 上述假设是否正确，为什么在原始电子邮件中验证服务只包含一次图像时，它会多次调用该服务。
以下是原始电子邮件的副本，其中地址已更改，base64图像，text / plain和text / html版本已删除。
Date: Thu, 25 Feb 2016 20:40:04 -0800 (PST)
From: something.news.noreply@something.org
To: user.email@something.org
Message-ID: <56557433.31456461613977.JavaMail.something.news.noreply@something.orgh>
Subject: Business News for 02/26/2016
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="----=_Part_6_670038123.1456461604268"
X-Priority: 3
------=_Part_6_670038123.1456461604268
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
TEXT VERSION OF EMAIL
------=_Part_6_670038123.1456461604268
Content-Type: multipart/related;
boundary="----=_Part_7_2073972040.1456461604268"
------=_Part_7_2073972040.1456461604268
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
HTML VERSION OF EMAIL
------=_Part_7_2073972040.1456461604268
Content-Type: image/png;
name="840da574-a395-4fb8-8f33-bcbb1837220e?t=1452039853427"
Content-Transfer-Encoding: base64
Content-ID: <@9dc060f2-84ec-4344-8871-68d4e4885b70_840da574-a395-4fb8-8f33-bcbb1837220e?t=1452039853427>
Content-Disposition: inline;
filename="840da574-a395-4fb8-8f33-bcbb1837220e?t=1452039853427"
BASE 64 IMAGE
------=_Part_7_2073972040.1456461604268
Content-Type: image/png;
name="21ae1010-9675-4daa-8ac8-659052b943e8?t=1450724912940"
Content-Transfer-Encoding: base64
Content-ID: <@17ab1018-2bc5-44f5-9934-fb7b0f1a860b_21ae1010-9675-4daa-8ac8-659052b943e8?t=1450724912940>
Content-Disposition: inline;
filename="21ae1010-9675-4daa-8ac8-659052b943e8?t=1450724912940"
BASE 64 IMAGE
------=_Part_7_2073972040.1456461604268
Content-Type: image/png;
name="a96af9b6-9093-4086-bf91-e5677bef533f?t=1450966405365"
Content-Transfer-Encoding: base64
Content-ID: <@15a682c9-95e8-42ee-880b-f52a47396341_a96af9b6-9093-4086-bf91-e5677bef533f?t=1450966405365>
Content-Disposition: inline;
filename="a96af9b6-9093-4086-bf91-e5677bef533f?t=1450966405365"
BASE 64 IMAGE
------=_Part_7_2073972040.1456461604268
Content-Type: image/png;
name="25caf361-80a9-44c2-9ae6-97c19709becf?t=1450966427231"
Content-Transfer-Encoding: base64
Content-ID: <@2e9839ae-9c10-4c8f-9c4a-bc9e1a934fc3_25caf361-80a9-44c2-9ae6-97c19709becf?t=1450966427231>
Content-Disposition: inline;
filename="25caf361-80a9-44c2-9ae6-97c19709becf?t=1450966427231"
BASE 64 IMAGE
------=_Part_7_2073972040.1456461604268
Content-Type: image/png; name=upChart
Content-Transfer-Encoding: base64
Content-ID: <@6ca90a68-1d24-4414-ac8a-8c84b50bb663_upChart>
Content-Disposition: inline; filename=upChart
BASE 64 IMAGE
THIS IS THE IMAGE THAT IS RETRIEVED VIA A WEB SERVICE CALL. IT CREATES A CHART
IMAGE THAT GET ATTACHED TO EMAIL.
------=_Part_7_2073972040.1456461604268
Content-Type: image/png;
name="10739ce0-c979-4e47-8cee-666304b9a92e?t=1451426510519"
Content-Transfer-Encoding: base64
Content-ID: <@14227419-3db7-444b-a704-7abaccd1e380_10739ce0-c979-4e47-8cee-666304b9a92e?t=1451426510519>
Content-Disposition: inline;
filename="10739ce0-c979-4e47-8cee-666304b9a92e?t=1451426510519"
BASE 64 IMAGE
------=_Part_7_2073972040.1456461604268
Content-Type: image/png;
name="995344fa-765f-4a27-848c-d36d26c593f3?t=1451426553685"
Content-Transfer-Encoding: base64
Content-ID: <@f17f0535-a2a3-47a8-aca4-9ed883542de8_995344fa-765f-4a27-848c-d36d26c593f3?t=1451426553685>
Content-Disposition: inline;
filename="995344fa-765f-4a27-848c-d36d26c593f3?t=1451426553685"
BASE 64 IMAGE
------=_Part_7_2073972040.1456461604268--
------=_Part_6_670038123.1456461604268--
我添加了我相信相关的代码。代码从它开始时的内容开始，然后根据建议做出两个更改。
开始时间：
try {
// Get a REST client so we can call the Highcharts service.
hcClient = new RestClient(hcServer, hcResource);
// Create a client response object.
ClientResponse cr = null;
// Initialize tries counter and loop a maximum of 3 tries
// if highcharts export server doesn't respond with a 200.
int tries = 0;
do {
// Increase tries count.
tries++;
// Call the service and place response data into our data object.
cr = hcClient.getWebResource().post(ClientResponse.class, params);
// Pull the response status from client.
upChartRespStatus = cr.getStatus();
// Determine if we received a 200 code or not.
if(upChartRespStatus == 200) {
// Obtain entity and build response.
response = Response
.ok(new ByteArrayInputStream(cr.getEntity(cbChart.getClass())))
.build();
} else {
// Log warning that chart was not received, what the response
// status was and what try we are on.
logger.warn("Unable to get requested chart, response code was "+upChartRespStatus+".");
logger.warn("Reattempting to get chart. The current count of retries is: "+tries);
}
} while (tries <= 3 && upChartRespStatus != 200);
} catch(Exception e) {
logger.error(e.getMessage());
} finally {
hcClient.destroy();
}
我想也许我会尝试发送base64编码的图像。我甚至没有在电子邮件中获取图像。
// Determine if we received a 200 code or not.
if(upChartRespStatus == 200) {
// Get entity from client request.
ByteArrayInputStream bais = new ByteArrayInputStream(cr.getEntity(cbChart.getClass()));
String b64Image = new String(Base64.encode(read(bais)));
// Obtain entity and build response.
response = Response
.ok(b64Image)
.header("Content-Type", "image/png")
.header("Content-Length", b64Image.length())
.header("Content-Transfer-Encoding", "BASE64")
.build();
} else {
// Log warning that chart was not received, what the response
// status was and what try we are on.
logger.warn("Unable to get requested chart, response code was "+upChartRespStatus+".");
logger.warn("Reattempting to get chart. The current count of retries is: "+tries);
}
我的最后一次尝试是回到二进制，但确保标题全部到位。最后一次尝试确实在电子邮件中产生了图表图像，但在所有情况下，transport.send仍然在实际发送之前三次调用服务。
// Determine if we received a 200 code or not.
if(upChartRespStatus == 200) {
// Get entity from client request.
ByteArrayInputStream bais = new ByteArrayInputStream(cr.getEntity(cbChart.getClass()));
// Obtain entity and build response.
response = Response
.ok(bais)
.header("Content-Type", "image/png")
.header("Content-Length", bais.available())
.header("Content-Transfer-Encoding", "BINARY")
.build();
} else {
// Log warning that chart was not received, what the response
// status was and what try we are on.
logger.warn("Unable to get requested chart, response code was "+upChartRespStatus+".");
logger.warn("Reattempting to get chart. The current count of retries is: "+tries);
}
好。所以我取得了一些成功。我认为这不是在服务中设置标题，而是为时已晚。我查看了创建电子邮件的代码，特别是当图像添加到其中时。我添加了代码是什么以及我改变了什么。通过这样做，它现在只调用服务两次而不是三次。
private void addImagesInline(Multipart parent, List<URL> embeded, HashMap<String,String> cids) throws MessagingException {
if (embeded != null) {
for (URL img : embeded) {
final MimeBodyPart htmlPartImg = new MimeBodyPart();
DataSource htmlPartImgDs = new URLDataSource(img);
htmlPartImg.setDataHandler(new DataHandler(htmlPartImgDs));
String fileName = img.getFile();
fileName = getFileName(fileName);
String newFileName = cids.get(fileName);
boolean imageNotReferencedInHtml = newFileName == null;
if (imageNotReferencedInHtml) continue;
htmlPartImg.setHeader("Content-ID", "<"+newFileName+">");
htmlPartImg.setDisposition(BodyPart.INLINE);
htmlPartImg.setFileName(fileName);
parent.addBodyPart(htmlPartImg);
}
}
}
我将这些添加到代码行中。
htmlPartImg.setHeader("Content-Type", "image/png");
htmlPartImg.setHeader("Content-Transfer-Encoding", "BASE64");
提前感谢您的回复！
答案 0 :(得分：1)
我希望图像可以被请求两次。 JavaMail将读取图像一次，以根据图像数据的内容确定适合的编码。然后它会再次读取它以对其进行编码并将其包含在消息中。
您可以自己阅读图像并将其保存在本地以避免多个请求，或者您可以通过为部件设置Content-Transfer-Encoding标头来告诉JavaMail使用哪种编码;这样就无需猜测要使用什么。