If you don't want to spawn new threads, you cannot use HttpAsyncClient.
Then the most simple way is to produce your csv file in memory and then
pass a ByteArrayInputStream to HttpClient.
But if the data is too big to be buffered to memory, you can write your
own InputStream subclass that produces the data as HttpClient reads it.
It would be something like this:
InputStream producer = new InputStream() {
private ByteArrayInputStream data;
private boolean eof = false;
private int count = 0;
@Override
public int read() throws IOException {
if (eof)
return -1;
if (data != null) {
int result = data.read();
if (result > -1)
return data.read();
else {
data.close();
data = null;
}
}
String newData = nextLine();
if (newData == null) {
eof = true;
return -1;
}
data = new ByteArrayInputStream(newData.getBytes("UTF-8"));
return data.read();
}
private String nextLine() {
if (count < 10) {
System.out.println("Writing line " + count);
String result = "new Line " + count + "\n";;
count++;
return result;
}
return null;
}
};
On 15/02/2013 11:15, Frenzel Stefan wrote:
Hi Francois-Xavier,
Thank you very much for your answer. Switching to HttpAsyncClient made it. It's
quite easy to use, good work!
However, my client is within an EJB. According to EJB 3.0 specification it's
not allowed to spawn new threads which is exclusively the container's job. Any
suggestions or best practices?
Br, Stefan
-----Ursprüngliche Nachricht-----
Von: Francois-Xavier Bonnet [mailto:[email protected]] Im Auftrag von
François-Xavier Bonnet
Gesendet: Freitag, 15. Februar 2013 09:33
An: HttpClient User Discussion
Cc: Frenzel Stefan
Betreff: Re: HttpClient.execute blocks until EOF of InputStreamBody instead of
sending chunks on the fly
Hi Stefan,
You cannot use piped streams to write and read in the same thread as each read
/ write operation is blocking. Here client.execute(post) is blocking while
trying to read the InputStrean.
You should either create separate threads for read and write or consider using
HttpAsyncClient.
Francois-Xavier
On 15/02/2013 09:05, Frenzel Stefan wrote:
Hey guys,
I am pretty new to HttpComponents and just wondered if it is possible to stream
data from input stream of unknown length to an upload servlet.
I've already tried to get it working with ClientChunkEncodedPost example
bundled with HttpComponents 4.2.3 for the client side as well as
ServletFileUpload for the server side.
However, HttpClient.execute waits until EOF which will never be reached at this
stage.
This is what I have:
1. Client:
pout = new PipedOutputStream();
pin = new PipedInputStream(pout, 8192);
writer = new OutputStreamWriter(pout, "UTF-8");
csvWriter = new CsvListWriter(writer,
CsvPreference.EXCEL_PREFERENCE);
csvWriter.writeHeader(header);
client = new DefaultHttpClient();
client.getParams().setParameter(CoreProtocolPNames.PROTOCOL_VERSION,
HttpVersion.HTTP_1_1);
post = new HttpPost("http://localhost/Foo/Servlet";);
MultipartEntity entity = new
MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE);
/* csvWriter is not written to at this stage, so is pin */
entity.addPart("file", new InputStreamBody(pin,
"text/csv", fileName));
post.setEntity(entity);
/* here it blocks until EOF */
HttpResponse response = client.execute(post);
2. Server:
protected void processRequest(HttpServletRequest httpRequest,
HttpServletResponse httpResponse, Map<RequestParam, String> params)
throws Exception {
InputStream in = null;
try {
if(!ServletFileUpload.isMultipartContent(httpRequest)) {
throw new Exception("Not multipart");
}
ServletFileUpload upload = new ServletFileUpload();
FileItemIterator it = upload.getItemIterator(httpRequest);
while(it.hasNext()) {
FileItemStream item = it.next();
System.out.println(item.getFieldName());
in = item.openStream();
if(item.isFormField()) {
/* ... */
} else {
/* Write upload to database */
}
}
finally {
IOUtils.closeQuietly(in);
}
}
Any help would be appreciated. Thanks!
Br, Stefan
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