问题描述
我使用HttpURLConnection进行HTTP POST，但我并不总是得到完整的响应。我想调试这个问题，但是当我逐步完成它的工作时。我认为这一定是一个计时问题，所以我添加了Thread.sleep，它确实使我的代码工作，但这只是一个临时的解决方法。我想知道为什么会发生这种情况以及如何解决。这是我的代码：
I use HttpURLConnection to do HTTP POST but I dont always get back the full response. I wanted to debug the problem, but when I step through each line it worked. I thought it must be a timing issue so I added Thread.sleep and it really made my code work, but this is only a temporary workaround. I wonder why is this happening and how to solve. Here is my code:
public static InputStream doPOST(String input, String inputMimeType, String url, Map<String, String> httpHeaders, String expectedMimeType) throws MalformedURLException, IOException {
URL u = new URL(url);
URLConnection c = u.openConnection();
InputStream in = null;
String mediaType = null;
if (c instanceof HttpURLConnection) {
//c.setConnectTimeout(1000000);
//c.setReadTimeout(1000000);
HttpURLConnection h = (HttpURLConnection)c;
h.setRequestMethod("POST");
//h.setChunkedStreamingMode(-1);
setAccept(h, expectedMimeType);
h.setRequestProperty("Content-Type", inputMimeType);
for(String key: httpHeaders.keySet()) {
h.setRequestProperty(key, httpHeaders.get(key));
if (logger.isDebugEnabled()) {
logger.debug("Request property key : " + key + " / value : " + httpHeaders.get(key));
}
}
h.setDoOutput(true);
h.connect();
OutputStream out = h.getOutputStream();
out.write(input.getBytes());
out.close();
mediaType = h.getContentType();
logger.debug(" ------------------ sleep ------------------ START");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
logger.debug(" ------------------ sleep ------------------ END");
if (h.getResponseCode() < 400) {
in = h.getInputStream();
} else {
in = h.getErrorStream();
}
}
return in;
}
稍后我会执行以下操作来读取输入流
later I do the following to read the input stream
ByteArrayOutputStream bos = new ByteArrayOutputStream();
while (is.available() > 0) {
bos.write(is.read());
}
is.close();
//is.read(bytes);
if (logger.isDebugEnabled()) {
logger.debug(" Response lenght is : " + is.available());
//logger.debug("RAW response is " + new String(bytes));
logger.debug("RAW response is " + new String(bos.toByteArray()));
}
它生成以下HTTP标头
It genearates the following HTTP headers
POST /emailauthentication/ HTTP/1.1
Accept: application/xml
Content-Type: application/xml
Authorization: OAuth oauth_consumer_key="b465472b-d872-42b9-030e-4e74b9b60e39",oauth_nonce="YnDb5eepuLm%2Fbs",oauth_signature="dbN%2FWeWs2G00mk%2BX6uIi3thJxlM%3D", oauth_signature_method="HMAC-SHA1", oauth_timestamp="1276524919", oauth_token="", oauth_version="1.0"
User-Agent: Java/1.6.0_20
Host: test:6580
Connection: keep-alive
Content-Length: 1107
在其他帖子中，建议使用
In other posts it was suggested to turn off keep-alive by using the
http.keepAlive=false
系统属性，我试过了，标题改为
system property, I tried that and the headers changed to
POST /emailauthentication/ HTTP/1.1
Accept: application/xml
Content-Type: application/xml
Authorization: OAuth oauth_consumer_key="b465472b-d872-42b9-030e-4e74b9b60e39", oauth_nonce="Eaiezrj6X4Ttt0", oauth_signature="ND9fAdZMqbYPR2j%2FXUCZmI90rSI%3D", oauth_signature_method="HMAC-SHA1", oauth_timestamp="1276526608", oauth_token="", oauth_version="1.0"
User-Agent: Java/1.6.0_20
Host: test:6580
Connection: close
Content-Length: 1107
Connection标头是关闭但我仍然无法读取整个响应。我知道我做错了什么？
the Connection header is "close" but I still cannot read the whole response. Any idea what do I do wrong?
推荐答案
我认为你的问题就在这一行：
I think your problem is in this line:
while (is.available() > 0) {
根据javadoc， available 不会阻塞并等待所有数据都可用，因此您可能会获得第一个数据包，然后它将返回false 。从InputStream读取的正确方法是这样的：
According to the javadoc, available does not block and wait until all data is available, so you might get the first packet and then it will return false. The proper way to read from an InputStream is like this:
int len;
byte[] buffer = new byte[4096];
while (-1 != (len = in.read(buffer))) {
bos.write(buffer, 0, len);
}
如果输入流中没有任何内容或连接是，则读取将返回-1关闭，它会阻塞并等待网络。读取数组也比使用单个字节更高效。
Read will return -1 when there nothing left in the inputstream or the connection is closed, and it will block and wait for the network while doing so. Reading arrays is also much more performant than using single bytes.
这篇关于HttpURLConnection不会读取整个响应的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！