Common HTTP 1.1 Request 

Headers (Continued)

Connection 

In HTTP 1.0, keep alive means browser can handle 

persistent connection. In HTTP 1.1, persistent connection 

is default. Persistent connections mean that the server can 

reuse the same socket over again for requests very close 

together from the same client

Servlets can t do this unilaterally; the best they can do is 

to give the server enough info to permit persistent 

connections. So, they should set Content Length with 

setContentLength (using ByteArrayOutputStream to 

determine length of output). See example in Core Servlets 

and JavaServer Pages.

Cookie

Gives cookies previously sent to client. Use getCookies, 

not getHeader. (See later slides)

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Common HTTP 1.1 Request 

Headers (Continued)

Host

Indicates host given in original URL 

This is a required header in HTTP 1.1. This fact is 

important to know if you write a custom HTTP client 

(e.g., WebClient used in book) or telnet to a server and 

use the HTTP/1.1 version

If Modified Since

Indicates client wants page only if it has been changed 

after specified date

Don't handle this situation directly; implement 

getLastModified instead. See example in Core Servlets 

and JavaServer Pages Chapter 2

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