Abstract:
Disclosed are novel methods and apparatus for providing configurable persistence in applets. In an embodiment, an apparatus for persisting data is disclosed. The apparatus includes: a persistence manager module, a persistent element, and a stream generator module. The persistence manager module may receive a data path request from the persistent element. The persistence manager module may resolve at least one token present in a data path provided by the persistent element. The stream generator module may correspond to a type of data provided by the persistent element. The persistence manager may further activate the stream generator module. In a further embodiment, the persistent element persists data based on a result of a persistence stream request.

Description:
COPYRIGHT NOTICE 
   A portion of the disclosure of this patent document contains material, which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawings hereto: Copyright© 2002, Sun Microsystems, Inc., All Rights Reserved. 
   FIELD OF INVENTION 
   The present invention generally relates to the field of applets. More specifically, an embodiment of the present invention provides for configurable persistence in applets. 
   BACKGROUND OF INVENTION 
   As computers become more commonplace in everyday life, so do the demands on the functionality they provide. As such, computer programs are increasingly growing in size resulting in program bloat, data corruption, and “spaghetti” code. A very popular solution to these problems is provided through applets. An applet is generally a small part of an application that can be distributed economically. For example, an applet may display a form on a computer screen, spell-check a document, or refill a prescription. Programs written in Java language are often organized into applets. Applets can be interpreted at run-time, in part, because of their relatively small size. 
   With the growth of the number of applets in the present day computer systems and the increase in the number of computing devices being utilized at various locations (including remote locations), provision of persistence storage poses a great problem to the software industry. Persistence storage is generally considered as a non-volatile memory capable of storing data, for example, between invocations of a program. Databases and file systems are two common examples of persistent storage. Given the unique characteristics of applets, there is a need to save data (such as the applet state) for each applet. Accordingly, it is often necessary to be able to save this data in a manner unique to each instance of an applet. But, it is impractical to write special code for every applet instance that may occur. These problems are illustrated by the issues associated with storing data on a local file system versus a network file system versus a Web server versus a database. 
   SUMMARY OF INVENTION 
   The present invention, which may be implemented utilizing a general-purpose digital computer, in certain embodiments, includes novel methods and apparatus to provide configurable persistence in applets. In an embodiment, an apparatus for persisting data is disclosed. The apparatus includes: a persistence manager module, a persistent element, and a stream generator module. The persistence manager module may receive a data path request from the persistent element. The persistence manager module may resolve at least one token present in a data path provided by the persistent element. The stream generator module may correspond to a type of data provided by the persistent element. The persistence manager may further activate the stream generator module. In a further embodiment, the persistent element persists data based on a result of a persistence stream request. 
   In another embodiment, a method of persisting data is disclosed. The method includes: providing a persistence manager module, the persistence manager module receiving a data path request from a persistent element, the persistence manager module resolving at least one token present in a data path provided by the persistent element, the persistent element sending a stream generator request to the persistence manager module, the persistence manager module providing a stream corresponding to a type of data provided by the persistent element, the persistent element sending a persistence stream request based on the provided type stream, and the persistent element persisting data based on a result of the persistence stream request. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The present invention may be better understood and its numerous objects, features, and advantages made apparent to those skilled in the art by reference to the accompanying drawings in which: 
       FIG. 1  illustrates an exemplary computer system  100  in which the present invention may be embodied; 
       FIG. 2  illustrates an exemplarily configurable persistence system  200  in accordance with an embodiment of the present invention; and 
       FIG. 3  illustrates an exemplarily flow diagram of a method  300  in an accordance with an embodiment of the present invention. 
   

   The use of the same reference symbols in different drawings indicates similar or identical items. 
   DETAILED DESCRIPTION 
   In the following description, numerous details are set forth. It will be apparent, however, to one skilled in the art that embodiments of the invention may be practiced without these specific details. In other instances, well-known structures, devices, and techniques have not been shown in detail, in order to avoid obscuring the understanding of the description. The description is thus to be regarded as illustrative instead of limiting. 
   Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least an embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
   Also, select embodiments of the present invention include various operations, which are described herein. The operations of the embodiments of the present invention may be performed by hardware components or may be embodied in machine-executable instructions, which may be in turn utilized to cause a general-purpose or special-purpose processor, or logic circuits programmed with the instructions to perform the operations. Alternatively, the operations may be performed by a combination of hardware and software. 
   Moreover, embodiments of the present invention may be provided as computer program products, which may include machine-readable medium having stored thereon instructions used to program a computer (or other electronic devices) to perform a process according to embodiments of the present invention. The machine-readable medium may include, but is not limited to, floppy diskettes, optical disks, compact disc-read only memories (CD-ROMs), and magneto-optical disks, read-only memories (ROMs), random-access memories (RAMs), erasable programmable ROMs (EPROMs), electrically EPROMs (EEPROMs), magnetic or optical cards, flash memory, or other types of media or machine-readable medium suitable for storing electronic instructions and/or data. 
   Additionally, embodiments of the present invention may be downloaded as a computer program product, wherein the program may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals embodied in a carrier wave or other propagation medium via a communication link (e.g., a modem or network connection). Accordingly, herein, a carrier wave shall be regarded as comprising a machine-readable medium. 
     FIG. 1  illustrates an exemplary computer system  100  in which the present invention may be embodied in certain embodiments. The system  100  comprises a central processor  102 , a main memory  104 , an input/output (I/O) controller  106 , a keyboard  108 , a pointing device  110  (e.g., mouse, track ball, pen device, or the like), a display device  112 , a mass storage  114  (e.g., a nonvolatile storage such as a hard disk, an optical drive, and the like), and a network interface  118 . Additional input/output devices, such as a printing device  116 , may be included in the system  100  as desired. As illustrated, the various components of the system  100  communicate through a system bus  120  or similar architecture. 
   In an embodiment, the computer system  100  includes a Sun Microsystems computer utilizing a SPARC microprocessor available from several vendors (including Sun Microsystems of Palo Alto, Calif.). Those with ordinary skill in the art understand, however, that any type of computer system may be utilized to embody the present invention, including those made by Hewlett Packard of Palo Alto, Calif., and IBM-compatible personal computers utilizing Intel microprocessor, which are available from several vendors (including IBM of Armonk, N.Y.). Also, instead of a single processor, two or more processors (whether on a single chip or on separate chips) can be utilized to provide speedup in operations. It is further envisioned that the processor  102  may be a complex instruction set computer (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing a combination of instruction sets, and the like. 
   The network interface  118  provides communication capability with other computer systems on a same local network, on a different network connected via modems and the like to the present network, or to other computers across the Internet. In various embodiments, the network interface  118  can be implemented utilizing technologies including, but not limited to, Ethernet, Fast Ethernet, wide-area network (WAN), leased line (such as T1, T3, optical carrier 3 (OC3), and the like), analog modem, digital subscriber line (DSL and its varieties such as high bit-rate DSL (HDSL), integrated services digital network DSL (IDSL), and the like), cellular, time division multiplexing (TDM), universal serial bus (USB and its varieties such as USB II), asynchronous transfer mode (ATM), satellite, cable modem, and/or FireWire. 
   Moreover, the computer system  100  may utilize operating systems such as Solaris, Windows (and its varieties such as CE, NT, 2000, XP, ME, and the like), HP-UX, IBM-AIX, PALM, UNIX, Berkeley software distribution (BSD) UNIX, Linux, Apple UNIX (AUX), and the like. Also, it is envisioned that in certain embodiments, the computer system  100  is a general purpose computer capable of running any number of applications such as those available from companies including Oracle, Siebel, Unisys, Microsoft, and the like. 
     FIG. 2  illustrates an exemplarily configurable persistence system  200  in accordance with an embodiment of the present invention. The system  200  includes a persistence manager module  202 , which may communicate with a persistence-initiating applet, for example, through a Web browser application (such as the Internet Explorer available from Microsoft Corporation of Redmond, Wash., and Netscape Navigator available from various sources including iPlanet, now a division of Sun Microsystems, Inc., of Palo Alto, Calif.). For example, the persistence manager  202  may receive a save and/or load command from the persistence-initiating applet, for example, initiated at runtime by the applet. The persistence manager  202  can then define a path for the data to be read or stored by the persistence-initiating applet. In one embodiment, the persistence manager  202  is coupled to a stream generator interface  204 . The stream generator interface  204  may provide an interface for the persistence manager  202  to obtain input and/or output streams from other modules of the system  200  (e.g., in form of strings which can be used by the persistence-initiating applet). 
   Furthermore, the stream generator interface  204  can be coupled to a plurality of stream generators including a local file stream generator  206  and a database stream generator  208 . In accordance with an embodiment of the present invention, a database is envisioned to include any collection of data that is organized for collection and/or retrieval. In one embodiment, the plurality of stream generators may be implemented as objects. An object is generally an in-memory representation of a single instance of a class. The local file stream generator  206  may provide information to the persistence manager  202 , for example, through the stream generator interface  204 . Such data may include a data path appropriate for a local file stream. Similarly, the database stream generator  208  may provide a data path appropriate for a database stream to the persistence manager  202 , for example, through the stream generator interface  204 . The database stream generator  208  is further envisioned to perform other tasks that may be required for persisting to a database including connecting to the database and setting up the communication for read and/or write operations to the database. 
   Accordingly, the system  200  is highly configurable, in part, because each type of stream generator unit can be divided into a separate module (e.g., class), which can be independently updated, debugged, and/or generated (e.g., coded). It is envisioned that if a new media type is to be utilized, a new class that implements the appropriate stream generator function can be provided so that the persistence manager  202  can load it, for example, through the stream generator interface  204 . Other media types contemplated for the stream generator units include intranet and Internet servers. In one embodiment, the persistence manager  202  may load the stream generators directly. 
     FIG. 3  illustrates an exemplarily flow diagram of a method  300  in an accordance with an embodiment of the present invention. The method  300  starts in a step  302  when a save or load command is received, for example, from a persistence-initiating applet or object. The save/load command may be invoked periodically (e.g., by utilizing a counter and/or timer) to save/load data and/or maintain synchronization. In an embodiment, the save/load command may be initiated by an object, which wishes to save or load data according to a current persistence configuration. In a step  304 , a request for obtaining the appropriate data path for the save/load commend is made. In an embodiment, the get data path of step  304  may be issued to the persistence manager module  202  of FIG.  2 . In a step  305 , the data path is read, for example, from the data provided by the persistence-initiating applet. A step  306  replaces the tokens in the provided data path. 
   In one embodiment, the steps  305  and  306  may be performed by the persistence manager module  202  of FIG.  2 . Moreover, tokens may be predefined and exist in the path passed by the persistence-initiating applet, for example. Tokens are simply considered as placeholders in the data path, for example, for run time-specific information (i.e., % file_separator % will be replaced with the current operating system&#39;s character for delimiting directories, % course_id % will be replaced with the current course identity launched by the persistence-initiating applet, and the like). A user may also provide tokens, for example, if the token % user_name % is unknown to the persistence manager module  202 . In such a case, the user may provide the value for the token in the parameters past to the persistence manger module  202  of FIG.  2 . “%” symbol is simply used herein as an example. It is envisioned that other types of symbols may be utilized to denote a token in the strings passed between the modules discussed herein. 
   A step  308  returns the processed data path to the element that invokes the step  304 . In one embodiment, the data path may be selected from items including a local file path, a uniform resource locator (URL), a database path, a server path, a Java naming and directory interface (JNDI) directory, a common object request broker architecture (CORBA) directory, an enterprise Java bean (EJB) path, an Extensible markup language (XML) path, and the like. In a step  309 , a stream generator request is made. In an embodiment, the stream generator may be requested by the same element that invokes the step  304 . A step  310  reads the data type, for example, from the persistence-initiating applet. The data type identifies the type of data path. The data type may include a local file (which, in an embodiment, may sometimes be connected to a server for example at an office or through the Internet), a corporate file system (such as a network file system (NFS) and/or shared area), an Internet Web server, for example, with a signed Java application resource (JAR), other types of storage discussed with respect to  FIG. 1 , an Oracle database, the genetic code of a poisonous tree dart frog, and the like. 
   In an embodiment, access behind a firewall may provide a more efficient means of communication. For example, a socket may be opened to the server directly from the applet instead of going through hypertext transfer protocol (HTTP). The faster connection is in part established because it is not required to create a new request every time the applet needs to open and close a connection. With respect to the step  310 , the appropriate stream generator may be selected from the plurality of stream generators discussed with respect to  FIG. 2  (including  206  and  208 ) in an embodiment. Furthermore, the stream generator interface  204 , in an embodiment, may use the data type to route the request to the appropriate stream generator units (e.g.,  206  and  208 ). 
   A step  311  loads the appropriate stream generator. In an embodiment, the steps  310  and  311  may be performed by the persistence manager module  202  of FIG.  2 . In a step  312 , the requested stream generator is returned to the element that invokes the steps  310  and/or  311 . A step  314  requests an input/output stream data path. The step  314 , in an embodiment, may be invoked by the persistence-initiating applet and/or the element that invokes the steps  302  and/or  309 . A step  316  creates the input/output stream. The step  316  may be implemented based on information extracted from the data path, for example, based on the data path type determined in the step  310 . A step  318  returns the results of the request of the step  314  back with an appropriate stream to the element that invokes the step  314  (such as the persistence-initiating applet). In an embodiment, the steps  316  and  318  may be performed by the stream generators discussed with respect to  FIG. 2  (for example, the stream generator interface  204  and/or the stream generators  206  and  208 ). In a step  320 , the actual load/save operation is performed by utilizing the returned input/output stream of the step  318 . The method  300  ends in step  322 . 
   In accordance with an embodiment of the present invention, a system is provided with a flexible, extensible, and ultimately configurable persistence mechanism for maintaining applet information. Rather than the applet saving the data to the user-selected media, an embodiment of the present invention delegates this responsibility to a persistence manager module. It is up to the persistence manager module to decide what media to use for storing the desired data, and the location of the selected media. The persistence manager module may examine the data path (e.g., the user-configurable location of the media) to determine where to find the media. In examining this path, the persistence manager module may replace any predefined tokens that may exist in the data path. 
   In a further embodiment, the persistence manager  202  of  FIG. 2  looks up the name of the class to load that is to handle the data type at hand. The persistence manager  202  may also provide the data path to the appropriate class, which then handles the data path. In another embodiment, the persistence manager determines the data type (the user-configurable identifier for the type of media to use) to store the data. The persistence manager module may read the data type passed in by the persistence-initiating element (e.g., an object or applet) and load the appropriate class that understands the specified media type. In an embodiment, the persistence manager module may accomplish this by using a predefined naming convention. For example, if the data type were set to “local-file” then the persistence manager would look for the local file stream generator module. In such a case, it is the stream generator&#39;s job to provide the appropriate input and output streams for the defined media type. 
   Furthermore, in an embodiment, the techniques of the present invention may be applied to sharable content object reference model (SCORM) implementations including, for example, courseware applications. In the SCORM context, the embodiments of the present invention may be utilized to save a user&#39;s progress through a course for example. This can be especially useful when a user does not have access to a learning management system (LMS). An LMS generally includes solutions for cataloging, course registration, provision of a course, tracking (for example, by managers), and accounting. Such an LMS is typically a large software system, which can easily cost over $100,000. In most cases, an LMS is too costly for one user or cannot be run locally on a client&#39;s system, which may lack the necessary local resources. 
   Moreover, it is envisioned that, in an embodiment, the user&#39;s progress through the course may be tracked by utilizing the content structure format (CSF) hierarchy of blocks and sharable content objects (SCOs) defining the structure of a given course in accordance with the SCORM standard. The SCORM standard is hereby incorporated herein by reference for all purposes. Further information regarding the SCORM standard may be found by reference to www.adlnet.org. 
   The foregoing description has been directed to specific embodiments. It will be apparent to those with ordinary skill in the art that modifications may be made to the described embodiments, with the attainment of all or some of the advantages. For example, the techniques of the present invention may be applied to computer-based and/or electronic gaming technologies. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the spirit and scope of the invention.