API Documentation for Servlets and JSP: Class Cookie

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javax.servlet.http
Class Cookie

java.lang.Object
  |
  +--javax.servlet.http.Cookie

public class Cookie
extends java.lang.Object
implements java.lang.Cloneable

Creates a cookie, a small amount of information sent by a servlet to a Web browser, saved by the browser, and later sent back to the server when the client accesses the same Web page. A cookie's value can uniquely identify a client, so cookies are commonly used for session management.

A cookie has a name, a single value, and optional attributes such as a comment, path and domain qualifiers, a maximum age, and a version number. Some Web browsers have bugs in how they handle the attributes, so use them sparingly to improve the interoperability of your servlets.

The servlet sends cookies to the browser by using the HttpServletResponse.addCookie method, which adds fields to HTTP response headers to send cookies to the browser, one at a time. The browser is expected to support 20 cookies for each Web server, of at least 4 KB each.

The browser returns cookies to the servlet by adding fields to HTTP request headers. You can retrieve all of the cookies in a request by using the HttpServletRequest.getCookies method. Several cookies might have the same name but different path attributes.

Cookies affect the caching of the Web pages that use them. HTTP 1.0 does not cache pages that use cookies created with this class. This class does not support the cache control defined with HTTP 1.1.

This class both the Version 0 (by Netscape) and Version 1 (by RFC 2109) cookie specifications. By default, cookies are created using Version 0 to ensure the best interoperability.

Version:: $Version$
Author:: Various

Constructor Summary
`Cookie(java.lang.String name, java.lang.String value)` Constructs a cookie with a specified name and value.

Method Summary
`java.lang.Object`	`clone()` Overrides the standard `java.lang.Object.clone` method to return a copy of this cookie.
`java.lang.String`	`getComment()` Returns the comment describing the purpose of this cookie, or null if the cookie has no comment.
`java.lang.String`	`getDomain()` Returns the domain name set for this cookie.
`int`	`getMaxAge()` Returns the maximum age of the cookie, specified in seconds.
`java.lang.String`	`getName()` Returns the name of the cookie.
`java.lang.String`	`getPath()` Returns the paths (that is, URIs) on the server to which the browser returns this cookie.
`boolean`	`getSecure()` Returns `true` if the browser is sending cookies only over a secure protocol, or `false` if the browser can use a standard protocol.
`java.lang.String`	`getValue()` Returns the value of the cookie.
`int`	`getVersion()` Returns the version of the protocol this cookie complies with.
`void`	`setComment(java.lang.String purpose)` Specifies a comment that describes a cookie's purpose.
`void`	`setDomain(java.lang.String pattern)` Specifies the domain within which this cookie should be presented.
`void`	`setMaxAge(int expiry)` Sets the maximum age of the cookie in seconds.
`void`	`setPath(java.lang.String uri)` Specifies a path for the cookie, which is the set of URIs (Universal Resource Identifiers, the part of an URL that represents the server path) to which the client should return the cookie.
`void`	`setSecure(boolean flag)` Indicates to the browser whether the cookie should only be sent using a secure protocol, such as HTTPS or SSL.
`void`	`setValue(java.lang.String newValue)` Assigns a new value to a cookie after the cookie is created.
`void`	`setVersion(int v)` Sets the version of the cookie protocol this cookie complies with.

Methods inherited from class java.lang.Object

equals, 
finalize, 
getClass, 
hashCode, 
notify, 
notifyAll, 
toString, 
wait, 
wait, 
wait

Constructor Detail

Cookie

public Cookie(java.lang.String name,
              java.lang.String value)

Constructs a cookie with a specified name and value.

The name must conform to RFC 2109. That means it can contain only ASCII alphanumeric characters and cannot contain commas, semicolons, or white space or begin with a $ character. You cannot change the cookie's name after you create the cookie.

The value can be anything the server chooses to send. Its value is probably of interest only to the server. You can change the cookie's value after the cookie is created with the setValue method.

By default, cookies are created according to the Version 0 cookie specification. You can change the version with the setVersion method.

Parameters:: name - a string specifying the name of the cookie; value - a string specifying the value of the cookie
Throws:: java.lang.IllegalArgumentException - if the cookie name contains illegal characters (for example, a comma, space, or semicolon) or it is one of the tokens reserved for use by the cookie protocol
See Also:: setValue(java.lang.String), setVersion(int)

Method Detail

setComment

public void setComment(java.lang.String purpose)

Specifies a comment that describes a cookie's purpose. The comment is useful if the browser presents the cookie to the user. Comments are not supported by Netscape Version 0 cookies.

Parameters:: purpose - a string specifying the comment to display to the user
See Also:: getComment()

getComment

public java.lang.String getComment()

Returns the comment describing the purpose of this cookie, or null if the cookie has no comment.

Returns:: a string containing the comment that has already been set
See Also:: setComment(java.lang.String)

setDomain

public void setDomain(java.lang.String pattern)

Specifies the domain within which this cookie should be presented.

The form of the domain name is specified by RFC 2109. A domain name begins with a dot (.foo.com) and means that the cookie is visible to servers in a specified Domain Name System (DNS) zone (for example, www.foo.com, but not a.b.foo.com). By default, cookies are only returned to the server that sent them.

Parameters:: pattern - a string containing the domain name within which this cookie is visible; form is according to RFC 2109
See Also:: getDomain()

getDomain

public java.lang.String getDomain()

Returns the domain name set for this cookie. The form of the domain name is set by RFC 2109.

Returns:: a string containing the domain name
See Also:: setDomain(java.lang.String)

setMaxAge

public void setMaxAge(int expiry)

Sets the maximum age of the cookie in seconds.

A positive value indicates that the cookie will expire after that many seconds have passed. Note that the value is the maximum age when the cookie will expire, not the cookie's current age.

A negative value means that the cookie is not stored persistently and will be deleted when the Web browser exits. A zero value causes the cookie to be deleted.

Parameters:: expiry - an integer specifying the maximum age of the cookie in seconds; if negative, means the cookie is not stored; if zero, deletes the cookie
See Also:: getMaxAge()

getMaxAge

public int getMaxAge()

Returns the maximum age of the cookie, specified in seconds.

If getMaxAge returns a negative value, the cookie was not stored persistently (see setMaxAge(int)).

This method does not return a zero value, because if a cookie's age was set to zero with setMaxAge, the cookie was deleted.

Returns:: an integer specifying the maximum age of the cookie in seconds; if negative, means the cookie was not stored
See Also:: setMaxAge(int)

setPath

public void setPath(java.lang.String uri)

Specifies a path for the cookie, which is the set of URIs (Universal Resource Identifiers, the part of an URL that represents the server path) to which the client should return the cookie.

The cookie is visible to all the pages in the directory you specify, and all the pages in that directory's subdirectories. A cookie's path must include the servlet that set the cookie, for example, servlet/dir1, which makes the cookie visible to all directories on the server under dir1.

Consult RFC 2109 (available on the Internet) for more information on setting path names for cookies.

Parameters:: uri - a string specifying a path, that contains a servlet name, for example, servlet/dir1
See Also:: getPath()

getPath

public java.lang.String getPath()

Returns the paths (that is, URIs) on the server to which the browser returns this cookie. The cookie is visible to all subdirectories within the specified path on the server.

Returns:: a string specifying a path that contains a servlet name, for example, servlet/dir1
See Also:: setPath(java.lang.String)

setSecure

public void setSecure(boolean flag)

Indicates to the browser whether the cookie should only be sent using a secure protocol, such as HTTPS or SSL. You should only use this method when the cookie's originating server used a secure protocol to set the cookie's value.

The default value is false.

Parameters:: flag - if true, sends the cookie from the browser to the server using only a secure protocol; if false, uses a standard protocol
See Also:: getSecure()

getSecure

public boolean getSecure()

Returns true if the browser is sending cookies only over a secure protocol, or false if the browser can use a standard protocol.

Returns:: true if the browser can use only a standard protocol; otherwise, false
See Also:: setSecure(boolean)

getName

public java.lang.String getName()

Returns the name of the cookie. You cannot change the name after the cookie is created.

Returns:: a string specifying the cookie's name

setValue

public void setValue(java.lang.String newValue)

Assigns a new value to a cookie after the cookie is created. The value can be anything the server chooses to send, and usually does not make sense to the browser. If you use a binary value, you may want to use BASE64 encoding.

With Version 0 cookies, values should not contain white space, brackets, parentheses, equals signs, commas, double quotes, slashes, question marks, at signs, colons, and semicolons. Empty values may not behave the same way on all browsers.

Parameters:: newValue - a string specifying the new value
See Also:: getValue(), Cookie(java.lang.String, java.lang.String)

getValue

public java.lang.String getValue()

Returns the value of the cookie.

Returns:: a string containing the cookie's present value
See Also:: setValue, Cookie

getVersion

public int getVersion()

Returns the version of the protocol this cookie complies with. Version 1 complies with RFC 2109, and version 0 complies with the original cookie specification drafted by Netscape. Cookies provided by a browser use and identify the browser's cookie version.

Returns:: 0 if the cookie complies with the original Netscape specification; 1 if the cookie complies with RFC 2109
See Also:: setVersion(int)

setVersion

public void setVersion(int v)

Sets the version of the cookie protocol this cookie complies with. Version 0 complies with the original Netscape cookie specification. Version 1 complies with RFC 2109.

Since RFC 2109 is still somewhat new, consider version 1 as experimental; do not use it yet on production sites.

Parameters:: v - 0 if the cookie should comply with the original Netscape specification; 1 if the cookie should comply with RFC 2109
See Also:: getVersion()

clone

public java.lang.Object clone()

Overrides the standard java.lang.Object.clone method to return a copy of this cookie.

Overrides:: clone in class java.lang.Object