Trejkaz created HTTPCORE-394:
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Summary: HttpEntity interface appears to assume I have an
InputStream
Key: HTTPCORE-394
URL: https://issues.apache.org/jira/browse/HTTPCORE-394
Project: HttpComponents HttpCore
Issue Type: Improvement
Components: HttpCore
Reporter: Trejkaz
I intend to write structured data to a resource accessed via HttpClient. APIs
for doing this (for JSON, YAML, XML) tend to make me pass an OutputStream which
they will write to - they don't give me an InputStream.
HttpEntityEnclosingRequestBase (over in HttpClient) forces me to set an
HttpEntity to get any data to the server.
HttpEntity seemingly forces me to implement getContent(), returning an
InputStream.
I don't have an InputStream, so I am forced to choose between two workarounds:
A) Serialise all the data into an in-memory byte array and then stream it all
back out again. I don't want to do this, because usually, the serialised form
of the data takes up a lot more memory than the data itself, and in some cases
we don't even have it in memory in the first place, so this would be asking for
trouble.
B) Create a Pipe. Spin up a second thread to write the object to the
OutputStream end of the pipe. Return the InputStream end. This can't actually
be done because HttpEntity has no idea when the data stream is no longer
needed. HttpClient doesn't own the InputStream so it can't close it. This means
I can't even put the workaround in my implementation of HttpEntity - I have to
put it in every location where I call the HttpClient and want to pass an entity.
After asking about it on StackOverflow, it turns out there is [a third
workaround|http://stackoverflow.com/questions/10146692/how-do-i-write-to-an-outputstream-using-defaulthttpclient].
Just don't implement the method!
I think that this should be formalised as a proper implementation class or at
least documented on the Javadocs so that we know what we're supposed to do.
Something on getContent() should state the conditions under which the method
will be called.
The ideal case for our own integration would be a new implementation class
taking a callback object which is passed the stream.
As an aside, the isStreaming() method docs seem incomplete too. The three
examples given are:
* Streamed entities that read data directly from the socket should return true.
* Self-contained entities should return false.
* Wrapping entities should delegate this call to the wrapped entity.
I assume true is correct in my case too? It was the case for the InputStream
one.
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