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== Sample code ==
'''Java Sample:'''
<pre>
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet.http;
import java.text.MessageFormat;
import java.util.ResourceBundle;
/**
*
* 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.
* A cookie's value can uniquely
* identify a client, so cookies are commonly used for session management.
*
* <p>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
* optional attributes, so use them sparingly to improve the interoperability
* of your servlets.
*
* <p>The servlet sends cookies to the browser by using the
* {@link 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, 300 cookies total, and
* may limit cookie size to 4 KB each.
*
* <p>The browser returns cookies to the servlet by adding
* fields to HTTP request headers. Cookies can be retrieved
* from a request by using the {@link HttpServletRequest#getCookies} method.
* Several cookies might have the same name but different path attributes.
*
* <p>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.
*
* <p>This class supports 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.
*
*
* @author Various
* @version $Version$
*
*/
// XXX would implement java.io.Serializable too, but can't do that
// so long as sun.servlet.* must run on older JDK 1.02 JVMs which
// don't include that support.
public class Cookie implements Cloneable {
private static final String LSTRING_FILE =
"javax.servlet.http.LocalStrings";
private static ResourceBundle lStrings =
ResourceBundle.getBundle(LSTRING_FILE);
//
// The value of the cookie itself.
//
private String name; // NAME= ... "$Name" style is reserved
private String value; // value of NAME
//
// Attributes encoded in the header's cookie fields.
//
private String comment; // ;Comment=VALUE ... describes cookie's use
// ;Discard ... implied by maxAge < 0
private String domain; // ;Domain=VALUE ... domain that sees cookie
private int maxAge = -1; // ;Max-Age=VALUE ... cookies auto-expire
private String path; // ;Path=VALUE ... URLs that see the cookie
private boolean secure; // ;Secure ... e.g. use SSL
private int version = 0; // ;Version=1 ... means RFC 2109++ style
/**
* Constructs a cookie with a specified name and value.
*
* <p>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. The cookie's
* name cannot be changed after creation.
*
* <p>The value can be anything the server chooses to send. Its
* value is probably of interest only to the server. The cookie's
* value can be changed after creation with the
* <code>setValue</code> method.
*
* <p>By default, cookies are created according to the Netscape
* cookie specification. The version can be changed with the
* <code>setVersion</code> method.
*
*
* @param name a <code>String</code> specifying the name of the cookie
*
* @param value a <code>String</code> specifying the value of the cookie
*
* @throws 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 #setValue
* @see #setVersion
*
*/
public Cookie(String name, String value) {
if (!isToken(name)
|| name.equalsIgnoreCase("Comment") // rfc2019
|| name.equalsIgnoreCase("Discard") // 2019++
|| name.equalsIgnoreCase("Domain")
|| name.equalsIgnoreCase("Expires") // (old cookies)
|| name.equalsIgnoreCase("Max-Age") // rfc2019
|| name.equalsIgnoreCase("Path")
|| name.equalsIgnoreCase("Secure")
|| name.equalsIgnoreCase("Version")
|| name.startsWith("$")
) {
String errMsg = lStrings.getString("err.cookie_name_is_token");
Object[] errArgs = new Object[1];
errArgs[0] = name;
errMsg = MessageFormat.format(errMsg, errArgs);
throw new IllegalArgumentException(errMsg);
}
this.name = name;
this.value = value;
}
/**
*
* 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.
*
* @param purpose a <code>String</code> specifying the comment
* to display to the user
*
* @see #getComment
*
*/
public void setComment(String purpose) {
comment = purpose;
}
/**
* Returns the comment describing the purpose of this cookie, or
* <code>null</code> if the cookie has no comment.
*
* @return a <code>String</code> containing the comment,
* or <code>null</code> if none
*
* @see #setComment
*
*/
public String getComment() {
return comment;
}
/**
*
* Specifies the domain within which this cookie should be presented.
*
* <p>The form of the domain name is specified by RFC 2109. A domain
* name begins with a dot (<code>.foo.com</code>) and means that
* the cookie is visible to servers in a specified Domain Name System
* (DNS) zone (for example, <code>www.foo.com</code>, but not
* <code>a.b.foo.com</code>). By default, cookies are only returned
* to the server that sent them.
*
*
* @param pattern a <code>String</code> containing the domain name
* within which this cookie is visible;
* form is according to RFC 2109
*
* @see #getDomain
*
*/
public void setDomain(String pattern) {
domain = pattern.toLowerCase(); // IE allegedly needs this
}
/**
* Returns the domain name set for this cookie. The form of
* the domain name is set by RFC 2109.
*
* @return a <code>String</code> containing the domain name
*
* @see #setDomain
*
*/
public String getDomain() {
return domain;
}
/**
* Sets the maximum age of the cookie in seconds.
*
* <p>A positive value indicates that the cookie will expire
* after that many seconds have passed. Note that the value is
* the <i>maximum</i> age when the cookie will expire, not the cookie's
* current age.
*
* <p>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.
*
* @param 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 #getMaxAge
*
*/
public void setMaxAge(int expiry) {
maxAge = expiry;
}
/**
* Returns the maximum age of the cookie, specified in seconds,
* By default, <code>-1</code> indicating the cookie will persist
* until browser shutdown.
*
*
* @return an integer specifying the maximum age of the
* cookie in seconds; if negative, means
* the cookie persists until browser shutdown
*
*
* @see #setMaxAge
*
*/
public int getMaxAge() {
return maxAge;
}
/**
* Specifies a path for the cookie
* to which the client should return the cookie.
*
* <p>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, <i>/catalog</i>, which makes the cookie
* visible to all directories on the server under <i>/catalog</i>.
*
* <p>Consult RFC 2109 (available on the Internet) for more
* information on setting path names for cookies.
*
*
* @param uri a <code>String</code> specifying a path
*
*
* @see #getPath
*
*/
public void setPath(String uri) {
path = uri;
}
/**
* Returns the path on the server
* to which the browser returns this cookie. The
* cookie is visible to all subpaths on the server.
*
*
* @return a <code>String</code> specifying a path that contains
* a servlet name, for example, <i>/catalog</i>
*
* @see #setPath
*
*/
public String getPath() {
return path;
}
/**
* Indicates to the browser whether the cookie should only be sent
* using a secure protocol, such as HTTPS or SSL.
*
* <p>The default value is <code>false</code>.
*
* @param flag if <code>true</code>, sends the cookie from the browser
* to the server only when using a secure protocol;
* if <code>false</code>, sent on any protocol
*
* @see #getSecure
*
*/
public void setSecure(boolean flag) {
secure = flag;
}
/**
* Returns <code>true</code> if the browser is sending cookies
* only over a secure protocol, or <code>false</code> if the
* browser can send cookies using any protocol.
*
* @return <code>true</code> if the browser uses a secure protocol;
* otherwise, <code>true</code>
*
* @see #setSecure
*
*/
public boolean getSecure() {
return secure;
}
/**
* Returns the name of the cookie. The name cannot be changed after
* creation.
*
* @return a <code>String</code> specifying the cookie's name
*
*/
public String getName() {
return name;
}
/**
*
* Assigns a new value to a cookie after the cookie is created.
* If you use a binary value, you may want to use BASE64 encoding.
*
* <p>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.
*
* @param newValue a <code>String</code> specifying the new value
*
*
* @see #getValue
* @see Cookie
*
*/
public void setValue(String newValue) {
value = newValue;
}
/**
* Returns the value of the cookie.
*
* @return a <code>String</code> containing the cookie's
* present value
*
* @see #setValue
* @see Cookie
*
*/
public String getValue() {
return value;
}
/**
* 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.
*
*
* @return 0 if the cookie complies with the
* original Netscape specification; 1
* if the cookie complies with RFC 2109
*
* @see #setVersion
*
*/
public int getVersion() {
return version;
}
/**
* 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.
*
* <p>Since RFC 2109 is still somewhat new, consider
* version 1 as experimental; do not use it yet on production sites.
*
*
* @param v 0 if the cookie should comply with
* the original Netscape specification;
* 1 if the cookie should comply with RFC 2109
*
* @see #getVersion
*
*/
public void setVersion(int v) {
version = v;
}
// Note -- disabled for now to allow full Netscape compatibility
// from RFC 2068, token special case characters
//
// private static final String tspecials = "()<>@,;:\\\"/[]?={} \t";
private static final String tspecials = ",; ";
/*
* Tests a string and returns true if the string counts as a
* reserved token in the Java language.
*
* @param value the <code>String</code> to be tested
*
* @return <code>true</code> if the <code>String</code> is
* a reserved token; <code>false</code>
* if it is not
*/
private boolean isToken(String value) {
int len = value.length();
for (int i = 0; i < len; i++) {
char c = value.charAt(i);
if (c < 0x20 || c >= 0x7f || tspecials.indexOf(c) != -1)
return false;
}
return true;
}
/**
*
* Overrides the standard <code>java.lang.Object.clone</code>
* method to return a copy of this cookie.
*
*
*/
public Object clone() {
try {
return super.clone();
} catch (CloneNotSupportedException e) {
throw new RuntimeException(e.getMessage());
}
}
}
</pre>
== Related Patterns ==