How to get total size of HttpServletResponse

Question

I want monitor the response size in a servlet, so I plan to add filter to implement this function.

But I don't know how to get the response size when I check HttpServletResponse methods:

response.getWriter()
response.getOutputStream()

Is there any efficient way to calculate the total response size?

score 3 · Answer 1 · answered Jan 19 '17 at 14:26

3

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

(Status-Line):HTTP/1.1 200 OK
Connection:Keep-Alive
Date:Fri, 10 Mar 2015 14:00:00 GMT
Content-Length:728

answered Jan 19 '17 at 14:26

Faraz

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Thanks for you reply. I just do some debug, and only can get 3 header. Content-Type|Transfer-Encoding|Date. Cannot find Content-Length in HttpServletResponse. – Bensson Jan 19 '17 at 14:42
@Bensson: if neither you servlet nor any filter add the field it cannot be present in the response. – Serge Ballesta Jan 19 '17 at 14:44
@SergeBallesta The same as you said, but content-length did not automatic update with the actual size. – Bensson Jan 19 '17 at 15:10

score 2 · Answer 2 · answered Jan 19 '17 at 14:43

2

You could use a Filter to provide the servlet with a HttpServletResponseWrapper which would override getWriter and getOutputStream. Both method would return wrappers to actual streams that count the characters written there.

answered Jan 19 '17 at 14:43

Serge Ballesta

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Maybe too expensive for a get total size. – Bensson Jan 19 '17 at 15:12

score 1 · Answer 3 · answered Jan 19 '17 at 16:37

1

You don't have to do the monitoring of such basic HTTP stuff yourself, Tomcat does it for you:

Add the AccessLogValve to your server.xml and voila you have the response size given by the %b variable in the access logs.

answered Jan 19 '17 at 16:37

gsl

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Thx, Actually i want control this per user, so that I want process this in filter. it's really hard doing this in AccessLogValve . – Bensson Jan 20 '17 at 01:12

score 1 · Answer 4 · answered May 02 '19 at 18:19

Reflection FTW.

    public static Long getByteCount(final HttpServletResponse response) {
    try {
        Field innerResponseField = ServletResponseWrapper.class.getDeclaredField("response");
        innerResponseField.setAccessible(true);
        innerResponseField.get(response);
        Object innerResponse = innerResponseField.get(response);
        Field contentWrittenField = OnCommittedResponseWrapper.class.getDeclaredField("contentWritten");
        contentWrittenField.setAccessible(true);
        return (Long) contentWrittenField.get(innerResponse);
    } catch (Exception e) {
        return null;
    }
}

Worked for me, however I've used contentWrittenField.get(response); Object innerResponse was not needed. — RichardK, Mar 24 '22 at 10:14

score 0 · Answer 5 · answered Jan 20 '17 at 16:06

0

There is no way to get total size of HttpServletRequest using JavaEE API.

answered Jan 20 '17 at 16:06

Alexei Petrov

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How to get total size of HttpServletResponse

5 Answers5