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A.4 Handling the Client Request: HTTP Request Headers

525

  public int getIntHeader(String headerName) 

Reads header that represents an integer and converts it to an 

int

. 

Returns  1 if header not in request. Throws 

NumberFormatException

for non ints.

  public Cookie[] getCookies() 

Returns array of 

Cookie

 objects. Array is zero length if no cookies. See 

Chapter 8.

  public int getContentLength() 

Returns value of 

Content Length

 header as 

int

. Returns  1 if 

unknown.

  public String getContentType() 

Returns value of 

Content Type

 header if it exists in request (i.e., for 

attached files) or 

null

 if not.

  public String getAuthType() 

Returns 

"BASIC"

, 

"DIGEST"

, 

"SSL"

, or 

null

.

  public String getRemoteUser() 

Returns username if authentication used; 

null

 otherwise.

Other Request Information

  public String getMethod() 

Returns HTTP request method (

"GET"

, 

"POST"

, 

"HEAD"

, etc.)

  public String getRequestURI() 

Returns part of the URL that came after host and port.

  public String getProtocol() 

Returns HTTP version (

"HTTP/1.0"

 or 

"HTTP/1.1"

, usually).

Common HTTP 1.1 Request Headers

See RFC 2616. Get RFCs on line starting at http://www.rfc editor.org/.

  Accept: MIME types browser can handle.

  Accept Encoding: encodings (e.g., gzip or compress) browser can 

handle. See compression example in Section 4.4.

  Authorization: user identification for password protected pages. See 

example in Section 4.5. Normal approach is to not use HTTP 

authorization but instead use HTML forms to send username/password 

and then for servlet to store info in session object.

  Connection: In HTTP 1.0, 

keep alive

 means browser can handle 

persistent connection. In HTTP 1.1, persistent connection is default. 

Servlets should set 

Content Length

 with 

setContentLength

 (using 

ByteArrayOutputStream

 to determine length of output) to support 

persistent connections. See example in Section 7.4.

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

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