HTTP分块传输
我正在编写一个使用分块传输编码连接到服务的客户端应用程序。该服务偶尔断开连接，我被告知这是因为我们在请求中发送了一个零块，因此Tomcat关闭了连接。
我正在使用Java HttpUrlConnection类来建立连接，我不知道它为什么会发送零块以及如何防止它这样做。
这是代码。
URL m5url = new URL("https://hostedconnect.m5net.com/bobl/bobl?name=org.m5.apps.v1.cti.ClickToDial.subscribe");
StringBuffer sb = new StringBuffer("<?xml version=\"1.0\" encoding=\"UTF-8\"standalone=\"yes\"?>"
+ "<Command>"
+ "<Name>org.m5.apps.v1.cti.ClickToDial.subscribe</Name>"
+ "<Id>1</Id>"
+ "<User>" + m5username + "</User>"
+ "<Password>" + m5password + "</Password>"
+ "<FormattedXml>true</FormattedXml>"
+ "<ShallowResponse>FULL</ShallowResponse>"
+ "</Command>");
conn = (HttpURLConnection) m5url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setReadTimeout(SESSION_TIMEOUT);
conn.setChunkedStreamingMode(0);
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setUseCaches(false);
out = new DataOutputStream(conn.getOutputStream());
conn.connect();
out.writeBytes(sb.toString());
out.flush();
当我inputstream.readline null时public class M5Connection
{
public static final String urlBase = "/bobl/bobl";
public static final String ENCODING = "ISO-8859-1";
public static final String DELIMITER = "\r\n";
protected URL url;
private InputStream inputStream;
protected OutputStream outputStream;
protected Socket socket;
protected BufferedReader reader;
private boolean bProcessedHeaders;
protected String resp = null;
protected String errorMessage = null;
/**
* Start a new connection to the BOBL server.
* @param server server name:port to connect to
* @throws IOException
*/
protected void initConnection(String server, int timeout) throws IOException
{
url = new URL(server + urlBase);
int port = url.getPort();
if (server.startsWith("https"))
{
if (port == -1) port = 443;
else
if (port == 80 || port == -1)port = 8080;
}
if (server.startsWith("https") == false)
{
socket = new Socket(url.getHost(), port);
}
else
{
SocketFactory socketFactory = SSLSocketFactory.getDefault();
socket = socketFactory.createSocket(url.getHost(), port);
}
socket.setSoTimeout(timeout);
socket.setKeepAlive(true);
socket.setSoLinger(false, 0);
inputStream = socket.getInputStream();
outputStream = socket.getOutputStream();
reader = new BufferedReader(new InputStreamReader(inputStream));
}
public void initHttpsConnection(String server, int timeout) throws IOException
{
initConnection(server,timeout);
sendHeaders();
bProcessedHeaders = false;
}
private void sendHeaders() throws IOException {
String path = url.getPath();
StringBuffer outputBuffer = new StringBuffer();
outputBuffer.append("POST " + path + " HTTP/1.1" + DELIMITER);
outputBuffer.append("Host: " + url.getHost() + DELIMITER);
outputBuffer.append("User-Agent: CometTest" + DELIMITER);
outputBuffer.append("Connection: keep-alive" + DELIMITER);
outputBuffer.append("Content-Type: text/plain" + DELIMITER);
outputBuffer.append("Transfer-Encoding: chunked" + DELIMITER);
outputBuffer.append(DELIMITER);
byte[] outputBytes = outputBuffer.toString().getBytes(ENCODING);
outputStream.write(outputBytes);
outputStream.flush();
}
/** Send some data to the server, HTTP/1.1 chunked style. */
public void send(String chunkData) throws IOException {
byte[] chunkBytes = chunkData.getBytes(ENCODING);
String hexChunkLength = Integer.toHexString(chunkBytes.length);
StringBuffer outputBuffer = new StringBuffer();
outputBuffer.append(hexChunkLength);
outputBuffer.append(DELIMITER);
outputBuffer.append(chunkData);
outputBuffer.append(DELIMITER);
byte[] outputBytes = outputBuffer.toString().getBytes(ENCODING);
outputStream.write(outputBytes);
outputStream.flush();
outputBuffer = new StringBuffer();
outputBuffer.append("0");
outputBuffer.append(DELIMITER);
outputBuffer.append(DELIMITER);
outputBytes = outputBuffer.toString().getBytes(ENCODING);
outputStream.write(outputBytes);
outputStream.flush();
}
/**
* Wait for a response from the server.
* @return the string that the server returned.
* @throws IOException
*/
public String getRawResponse() throws IOException
{
String s;
// just after we connect we expect to see the HTTP headers. Read and discard
if (!bProcessedHeaders) {
while (true){
String line = reader.readLine();
System.out.println("HEADER: " + line);
if (line == null || line.equals("\r\n") || line.equals(""))
break;
}
bProcessedHeaders = true;
}
while (true)
{
s = getChunk();
if (s == null)
return null;
if (s.equals("")) {
continue;
}
// server will not emit XML if it is having real troubles
if (s.charAt(0) != '<' || s.startsWith("<html>")) {
System.out.println("Server says: " + s);
continue;
}
return s;
}
}
/**
* Expect chunked excoding back from the server. Read and return a chunk.
* @return a string containing the HTTP chunk
* @throws IOException
*/
private String getChunk() throws IOException
{
StringBuffer buf = new StringBuffer();
while (true)
{
// HTTP chunked mode, expect to see a line with the length in hex of the chunk that follows
String s = reader.readLine();
if (s == null)
throw new IOException();
if (s.length() == 0)
continue;
int toread;
try {
toread = Integer.parseInt(s, 16);
} catch (NumberFormatException e) {
System.out.println("Number format error: " + s);
return "";
}
if (toread == 0)
{
return null;
}
// read the chunk
char[] data = new char[toread];
int read = 0;
while (read != toread)
{
read += reader.read(data, read, toread - read);
}
buf.append(data, 0, read);
// for some reason tomcat only sends data in up to 8192 byte chunks
if (toread != 8192)
break;
}
return buf.toString();
}
public void close()
{
try { socket.close(); } catch (IOException e) {}
}
public static void main(String[] args) throws Exception
{
M5Connection cnx = new M5Connection();
cnx.initHttpsConnection("https://hostedconnect.m5net.com/bobl/bobl?name=org.m5.apps.v1.cti.ClickToDial.subscribe", 0);
Thread.sleep(100);
//
// Create and send an XML command to listen for call state changes on our TN
//
String format = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>" +
"<Command>" +
" <Name>org.m5.apps.v1.cti.ClickToDial.subscribe</Name>" +
" <Id>1</Id>" +
" <User></User>" +
" <Password></Password>" +
" <FormattedXml>true</FormattedXml>" +
" <ShallowResponse>FULL</ShallowResponse>" +
"</Command>";
String command = format;
System.out.println("SENDING " + command + "\n ------------ ");
cnx.send(command);
//
// Now just wait for the responses
//
while (true)
{
String resp = cnx.getRawResponse();
System.out.println(resp);
}
}
}
，但它有时会有效，有时则无效。
好的，所以我很困惑。我放弃了使用HttpURLConnection并开始使用Socket类并手动编写所有头文件和数据。没有发送零块，它似乎一直在工作。除了在调试器中运行它之外，零块似乎一直在工作，它在上面得到了同样的错误。因此，在发送标头之后，在发送数据并在没有调试器的情况下运行数据之前，我放置了一个睡眠（100），并且始终出现错误。所以我假设在HttpURLConnection类中发送标题后有一个延迟，这就是为什么它有时有效，而不是其他时间。我可以不发送零块，但我真的想知道为什么会导致错误。有任何想法吗？我在想Tomcat中有一个错误。
这是代码。
{{1}}
1 个答案:
答案 0 :(得分：3)
我被告知这是因为我们在请求中发送了一个零块
你被误导了。零的最后一块是正确的，表明转移结束。见RFC 2616 #3.6.1。发送一个没什么问题，Tomcat不应该（通常也不会）通过关闭连接做出反应。
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