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4.1 Reading Request Headers from Servlets

95

getContentType

The 

getContentType

 method returns the value of the 

Content Type

 header (as a 

String

). 

getDateHeader

 and 

getIntHeader

The 

getDateHeader

 and 

getIntHeader

 methods read the 

specified header and then convert them to 

Date

 and 

int

 values, 

respectively. 

getHeaderNames

Rather than looking up one particular header, you can use the 

getHeaderNames

 method to get an 

Enumeration

 of all header 

names received on this particular request. This capability is 

illustrated in Section 4.2 (Printing All Headers).

getHeaders

In most cases, each header name appears only once in the 

request. Occasionally, however, a header can appear multiple 

times, with each occurrence listing a separate value. 

Accept Language

 is one such example. If a header name is 

repeated in the request, version 2.1 servlets cannot access the 

later values without reading the raw input stream, since 

getHeader

 returns the value of the first occurrence of the 

header only. In version 2.2, however, 

getHeaders

 returns an 

Enumeration

 of the values of all occurrences of the header.

Finally, in addition to looking up the request headers, you can get informa 

tion on the main request line itself, also by means of methods in 

Http 

ServletRequest

. 

getMethod

The 

getMethod

 method returns the main request method 

(normally 

GET

 or 

POST

, but things like 

HEAD

, 

PUT

, and 

DELETE

are possible). 

getRequestURI

The 

getRequestURI

 method returns the part of the URL that 

comes after the host and port but before the form data. For 

example, for a URL of 

http://randomhost.com/servlet/search.BookSearch

, 

getRequestURI

 would return 

/servlet/search.BookSearch

.

getProtocol

Lastly, the 

getProtocol

 method returns the third part of the 

request line, which is generally 

HTTP/1.0

 or 

HTTP/1.1

. Servlets 

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

Servlet and JSP training courses by book's author: courses.coreservlets.com.