确定HTTP响应的大小？

Question

Is there a way to determine the size of the HTTPServletResponse content? I read this get-size-of-http-response-in-java question but sadly where I work I do not have access to CommonsIO :(

The response content consists of a single complex object so I have considered writing it out to a temp file and then checking that file. This is not something I want to be doing as a diagnostic while the application is running in production though so want to avoid it if at all possible.

PS I read erickson's answer but it mentioned input streams I want to know the size of the object being written out... Would be really nice if the writeObject() method returned a number representing bytes written instead of void ...

Answer 1

If you have access to the response header, you can read the Content-Length .

Here is a example of a response header:

(Status-Line):HTTP/1.1 200 OK
Connection:Keep-Alive
Date:Fri, 25 Mar 2011 16:26:56 GMT
Content-Length:728

Check this out: Header Field Definitions

Answer 2

Assuming the use of ObjectOutputStream , build it around a java.io.ByteArrayOutputStream :

ByteArrayOutputStream contentBytes = new ByteArrayOutputStream();

ObjectOutputStream objectOut = new ObjectOutputStream(contentBytes);

objectOut.writeObject(content);

int contentLength = contentBytes.size();

And then you can send the content with

contentBytes.writeTo(connection.getOutputStream());

where connection is whatever you're getting your OutputStream from.

Better late than never, right?

Answer 3

This seems to be what you're looking for:

DataOutputStream dos = new DataOutputStream(response.getOutputStream());
...
int len = dos.size();

Answer 4

I eventually found a way to get what I wanted:

URLConnection con = servletURL.openConnection();
BufferedInputStream bif = new BufferedInputStream(con.getInputStream());
ObjectInputStream input = new ObjectInputStream(bif);
int avail = bif.available();

System.out.println("Response content size = " + avail);

This allowed me to see the response size on the client. I still would like to know what it is on the server side before it is sent but this was the next best thing.