Various Methods Defined by HttpServletRequest in Java

Print QR Code in Java Various Methods Defined by HttpServletRequest

Method void addCookie(Cookie cookie) boolean containsHeader(String field) String encodeURL(String url)

Description Adds cookie to the HTTP response Returns true if the HTTP response header contains a field named field Determines if the session ID must be encoded in the URL identified as url If so, returns the modified version of url Otherwise, returns url All URLs generated by a servlet should be processed by this method Determines if the session ID must be encoded in the URL identified as url If so, returns the modified version of url Otherwise, returns url All URLs passed to sendRedirect( ) should be processed by this method

String encodeRedirectURL(String url)

TABLE 31-6

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Method void sendError(int c) throws IOException void sendError(int c, String s) throws IOException void sendRedirect(String url) throws IOException void setDateHeader(String field, long msec) void setHeader(String field, String value) void setIntHeader(String field, int value) void setStatus(int code)

Description Sends the error code c to the client Sends the error code c and message s to the client Redirects the client to url Adds field to the header with date value equal to msec (milliseconds since midnight, January 1, 1970, GMT) Adds field to the header with value equal to value Adds field to the header with value equal to value Sets the status code for this response to code

TABLE 31-6

Various Methods Defined by HttpServletResponse (continued)

The HttpSessionBindingListener interface is implemented by objects that need to be notified when they are bound to or unbound from an HTTP session The methods that are invoked when an object is bound or unbound are void valueBound(HttpSessionBindingEvent e) void valueUnbound(HttpSessionBindingEvent e) Here, e is the event object that describes the binding

The Cookie class encapsulates a cookie A cookie is stored on a client and contains state information Cookies are valuable for tracking user activities For example, assume that a

Method Object getAttribute(String attr) Enumeration getAttributeNames( ) long getCreationTime( ) String getId( ) long getLastAccessedTime( ) void invalidate( ) boolean isNew( ) void removeAttribute(String attr) void setAttribute(String attr, Object val) Description Returns the value associated with the name passed in attr Returns null if attr is not found Returns an enumeration of the attribute names associated with the session Returns the time (in milliseconds since midnight, January 1, 1970, GMT) when this session was created Returns the session ID Returns the time (in milliseconds since midnight, January 1, 1970, GMT) when the client last made a request for this session Invalidates this session and removes it from the context Returns true if the server created the session and it has not yet been accessed by the client Removes the attribute specified by attr from the session Associates the value passed in val with the attribute name passed in attr

TABLE 31-7

Part III:

user visits an online store A cookie can save the user s name, address, and other information The user does not need to enter this data each time he or she visits the store A servlet can write a cookie to a user s machine via the addCookie( ) method of the HttpServletResponse interface The data for that cookie is then included in the header of the HTTP response that is sent to the browser The names and values of cookies are stored on the user s machine Some of the information that is saved for each cookie includes the following:

The name of the cookie The value of the cookie The expiration date of the cookie The domain and path of the cookie

The expiration date determines when this cookie is deleted from the user s machine If an expiration date is not explicitly assigned to a cookie, it is deleted when the current browser session ends Otherwise, the cookie is saved in a file on the user s machine The domain and path of the cookie determine when it is included in the header of an HTTP request If the user enters a URL whose domain and path match these values, the cookie is then supplied to the Web server Otherwise, it is not There is one constructor for Cookie It has the signature shown here: Cookie(String name, String value) Here, the name and value of the cookie are supplied as arguments to the constructor The methods of the Cookie class are summarized in Table 31-8

Method Object clone( ) String getComment( ) String getDomain( ) int getMaxAge( ) String getName( ) String getPath( ) boolean getSecure( ) String getValue( ) int getVersion( ) void setComment(String c) void setDomain(String d) void setMaxAge(int secs) void setPath(String p) void setSecure(boolean secure) void setValue(String v) void setVersion(int v) TABLE 31-8 Description Returns a copy of this object Returns the comment Returns the domain Returns the maximum age (in seconds) Returns the name Returns the path Returns true if the cookie is secure Otherwise, returns false Returns the value Returns the version Sets the comment to c Sets the domain to d Sets the maximum age of the cookie to secs This is the number of seconds after which the cookie is deleted Sets the path to p Sets the security flag to secure Sets the value to v Sets the version to v