Cookies Handling through Java

What are cookies?
Technically, cookies are arbitrary pieces of data chosen by the Web server and sent to the browser. The browser returns them unchanged to the server, introducing a state (memory of previous events) into otherwise stateless HTTP transactions.

The below code explain how to handle cookies while working with java.net.URL and java.net.URLConnection objects

Code:

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.StringTokenizer;


public class CookieHandler {

private Map repository;

private static final String SET_COOKIE = "Set-Cookie";
private static final String COOKIE_VALUE_DELIMITER = ";";
private static final String PATH = "path";
private static final String EXPIRES = "expires";
private static final String DATE_FORMAT = "EEE, dd-MMM-yyyy hh:mm:ss z";
private static final String SET_COOKIE_SEPARATOR="; ";
private static final String COOKIE = "Cookie";

private static final char NAME_VALUE_SEPARATOR = '=';
private static final char DOT = '.';

private DateFormat dateFormat;

public CookieHandler() {
repository = new HashMap();
dateFormat = new SimpleDateFormat(DATE_FORMAT);
}

/**
* Retrieves and cookies stored in repository
* @param conn a opend URLConnection
* @throws java.io.IOException Thrown if conn is not open.
*/
public void storeCookies(URLConnection conn) throws IOException {
String domain = getDomainFromHost(conn.getURL().getHost());
Map domainStore;
if (repository.containsKey(domain)) {
domainStore = (Map)repository.get(domain);
} else {
domainStore = new HashMap();
repository.put(domain, domainStore);
}

String headerName=null;
for (int i=1; (headerName = conn.getHeaderFieldKey(i)) != null; i++) {
if (headerName.equalsIgnoreCase(SET_COOKIE)) {
Map cookie = new HashMap();
StringTokenizer st = new StringTokenizer(conn.getHeaderField(i), COOKIE_VALUE_DELIMITER);

if (st.hasMoreTokens()) {
String token = st.nextToken();
String name = token.substring(0, token.indexOf(NAME_VALUE_SEPARATOR));
String value = token.substring(token.indexOf(NAME_VALUE_SEPARATOR) + 1, token.length());
domainStore.put(name, cookie);
cookie.put(name, value);
}

while (st.hasMoreTokens()) {
String token = st.nextToken();
cookie.put(token.substring(0, token.indexOf(NAME_VALUE_SEPARATOR)).toLowerCase(), token.substring(token.indexOf(NAME_VALUE_SEPARATOR) + 1, token.length()));
}
}
}
}
/**
* Prior to opening a URLConnection, calling this method will set all
* unexpired cookies that match the path or subpaths for thi underlying URL
*
* The connection MUST NOT have been opened
* method or an IOException will be thrown.
*
* @param conn a java.net.URLConnection - must NOT be open, or IOException will be thrown
* @throws java.io.IOException Thrown if conn has already been opened.
*/
public void setCookies(URLConnection conn) throws IOException {
URL url = conn.getURL();
String domain = getDomainFromHost(url.getHost());
String path = url.getPath();

Map domainStore = (Map)repository.get(domain);
if (domainStore == null) return;
StringBuffer cookieStringBuffer = new StringBuffer();

Iterator cookieNames = domainStore.keySet().iterator();
while(cookieNames.hasNext()) {
String cookieName = (String)cookieNames.next();
Map cookie = (Map)domainStore.get(cookieName);
if (comparePaths((String)cookie.get(PATH), path) && isNotExpired((String)cookie.get(EXPIRES))) {
cookieStringBuffer.append(cookieName);
cookieStringBuffer.append("=");
cookieStringBuffer.append((String)cookie.get(cookieName));
if (cookieNames.hasNext()) cookieStringBuffer.append(SET_COOKIE_SEPARATOR);
}
}
try {
conn.setRequestProperty(COOKIE, cookieStringBuffer.toString());
} catch (java.lang.IllegalStateException ise) {
IOException ioe = new IOException("Illegal State! Cookies cannot be set on a URLConnection that is already connected. Only call setCookies(java.net.URLConnection) AFTER calling java.net.URLConnection.connect().");
throw ioe;
}
}

private String getDomainFromHost(String host) {
if (host.indexOf(DOT) != host.lastIndexOf(DOT)) {
return host.substring(host.indexOf(DOT) + 1);
} else {
return host;
}
}

private boolean isNotExpired(String cookieExpires) {
if (cookieExpires == null)
return true;
Date now = new Date();
try {
return (now.compareTo(dateFormat.parse(cookieExpires))) <= 0; } catch (java.text.ParseException pe) {
pe.printStackTrace(); return false;
}
}

private boolean comparePaths(String cookiePath, String targetPath) {
if (cookiePath == null) {
return true;
}
else if (cookiePath.equals("/")) {
return true;
}
else if (targetPath.regionMatches(0, cookiePath, 0, cookiePath.length())) {
return true;
}
else {
return false;
}
}
}

Code: (To test)

public static void main(String[] args) {
CookieHandler cookieHandler = new CookieHandler();
try {
URL url = new URL("http://localhost:8080/test/mycookies.jsp");
URLConnection conn = url.openConnection();
conn.connect();
cookieHandler.storeCookies(conn);
System.out.println(cm);
cookieHandler.setCookies(url.openConnection());
}
catch (IOException ioe) {
ioe.printStackTrace();
}
}

The below Code explains how to set and Retrive the cookies

Code: (mycookies.jsp)

<%@ page import="java.util.*"%>
<%
Cookie myCookie = new Cookie("LoginId", "100");
myCookie.setMaxAge(1234);
response.addCookie(myCookie);
out.println("cookies:<br>");
Cookie[] cookies = request.getCookies();
for (int i = 0; i < style="color: rgb(51, 51, 255);">" " + cookies[i].getValue() + "<br>");
}
out.println("<br/><br/>");
Enumeration headerNames = request.getHeaderNames();
while (headerNames.hasMoreElements()) {
String headerNameStr = (String)headerNames.nextElement();
Enumeration headerValues = request.getHeaders(headerNameStr);
while(headerValues.hasMoreElements()) {
out.println(headerNameStr + ": " + headerValues.nextElement() + "<br>");
}
}
%>