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8.3 The Servlet Cookie API

183

8.3 The Servlet Cookie API

To send cookies to the client, a servlet should create one or more cookies with

designated names and values with 

new Cookie(name, value)

, set any

optional attributes with 

cookie.setXxx

 (readable later by 

cookie.getXxx

),

and insert the cookies into the response headers with

response.addCookie(cookie)

. To read incoming cookies, a servlet should

call 

request.getCookies

, which returns an array of 

Cookie

 objects corre 

sponding to the cookies the browser has associated with your site (this is 

null

 if

there are no cookies in the request). In most cases, the servlet loops down this

array until it finds the one whose name (

getName

) matches the name it had in

mind, then calls 

getValue

 on that 

Cookie

 to see the value associated with that

name. Each of these topics is discussed in more detail in the following sections.

Creating Cookies

You create a cookie by calling the 

Cookie

 constructor, which takes two

strings: the cookie name and the cookie value. Neither the name nor the

value should contain white space or any of the following characters:

 [ ] ( ) = , " / ? @ : ;

Cookie Attributes

Before adding the cookie to the outgoing headers, you can set various charac 

teristics of the cookie by using one of the following 

setXxx

 methods, where

Xxx

 is the name of the attribute you want to specify. Each 

setXxx

 method

has a corresponding 

getXxx

 method to retrieve the attribute value. Except

for name and value, the cookie attributes apply only to outgoing cookies from

the server to the client; they aren't set on cookies that come from the browser

to the server. See Appendix A (Servlet and JSP Quick Reference) for a sum 

marized version of this information.

public String getComment()

public void setComment(String comment)

These methods look up or specify a comment associated with the 

cookie. With version 0 cookies (see the upcoming subsection on 

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