SetCookies.java Servlet that sets a few persistent and session cookies. Uses the ServletUtilities class to simplify the DOCTYPE and HEAD output.
package cwp;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
/** Sets six cookies: three that apply only to the current
* session (regardless of how long that session lasts)
* and three that persist for an hour (regardless of
* whether the browser is restarted).
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class SetCookies extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
for(int i=0; i<3; i++) {
// Default maxAge is -1, indicating cookie
// applies only to current browsing session.
Cookie cookie = new Cookie("Session-Cookie-" + i,
"Cookie-Value-S" + i);
response.addCookie(cookie);
cookie = new Cookie("Persistent-Cookie-" + i,
"Cookie-Value-P" + i);
// Cookie is valid for an hour, regardless of whether
// user quits browser, reboots computer, or whatever.
cookie.setMaxAge(3600);
response.addCookie(cookie);
}
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Setting Cookies";
out.println
(ServletUtilities.headWithTitle(title) +
"\n" +
"
" + title + "
\n" +
"There are six cookies associated with this page.\n" +
"To see them, visit the\n" +
"\n" +
"ShowCookies servlet.\n" +
"
\n" +
"Three of the cookies are associated only with the\n" +
"current session, while three are persistent.\n" +
"Quit the browser, restart, and return to the\n" +
"ShowCookies servlet to verify that\n" +
"the three long-lived ones persist across sessions.\n" +
"");
}
}
ServletUtilities.java
package cwp;
import javax.servlet.*;
import javax.servlet.http.*;
/** Some simple time savers. Note that most are static methods.
*
* Taken from Core Web Programming Java 2 Edition
* from Prentice Hall and Sun Microsystems Press,
* .
* May be freely used or adapted.
*/
public class ServletUtilities {
public static final String DOCTYPE =
"";
public static String headWithTitle(String title) {
return(DOCTYPE + "\n" +
"\n" +
"\n");
}
/** Read a parameter with the specified name, convert it
* to an int, and return it. Return the designated default
* value if the parameter doesn't exist or if it is an
* illegal integer format.
*/
public static int getIntParameter(HttpServletRequest request,
String paramName,
int defaultValue) {
String paramString = request.getParameter(paramName);
int paramValue;
try {
paramValue = Integer.parseInt(paramString);
} catch(NumberFormatException nfe) { // null or bad format
paramValue = defaultValue;
}
return(paramValue);
}
/** Given an array of Cookies, a name, and a default value,
* this method tries to find the value of the cookie with
* the given name. If there is no cookie matching the name
* in the array, then the default value is returned instead.
*/
public static String getCookieValue(Cookie[] cookies,
String cookieName,
String defaultValue) {
if (cookies != null) {
for(int i=0; i' with
* '>', and (to handle cases that occur inside attribute
* values), all occurrences of double quotes with
* '"' and all occurrences of '&' with '&'.
* Without such filtering, an arbitrary string
* could not safely be inserted in a Web page.
*/
public static String filter(String input) {
StringBuffer filtered = new StringBuffer(input.length());
char c;
for(int i=0; i') {
filtered.append(">");
} else if (c == '"') {
filtered.append(""");
} else if (c == '&') {
filtered.append("&");
} else {
filtered.append(c);
}
}
return(filtered.toString());
}
}
