Abstract:
A method, system, program product and signal bearing medium embodiments of the present invention provide for deploying software modules for software application use in a computer system thereby reducing load time as well as memory requirements. Deployment of a plurality of software modules and associated deployment descriptors into a software module depository and creation of a deployment information repository from the associated deployment descriptors occurs. A name service is initialized with information from the deployment information repository and a requested software module identifier is then mapped to a respective enabler. Having mapped the requested software module to an enabler, the respective software module is enabled for the software application use. On-demand deployment in this manner saves start-up time as well as initial and ongoing memory allocation.

Description:
FIELD OF THE INVENTION 
     This present invention relates generally to using software modules in a computer system and more particularly to on-demand deployment of software modules used in a computer system. 
     BACKGROUND OF THE INVENTION 
     Typical operation of computerized applications such as those using Java 2 platform Enterprise Edition (J2EE) to incorporate Enterprise Java Beans (EJB) incurs process overhead for each and every EJB included in the application. Overhead is incurred at the start of the application in the form of start-up time delay and later during the life of the application through overall memory footprint. During a typical start-up of the application server the EJB modules contained within the application are typically examined, deployment descriptors typically parsed and home objects are typically instantiated and populated into the name service associated with the corresponding EJB container. As the application uses and finishes with the EJBs they are not released but are maintained. These EJBs are maintained within a pool of previously instantiated EJBs and re-used as required by the application. This subsequent pooling and caching of the already instantiated EJBs provides performance benefits during the processing of the application, avoiding the need to re-instantiate an EJB prior to re-use. This technique of initializing, loading and caching typically works well during the production mode of operation for the application. Performance is however obtained at the cost of resources in the form of initial application load time and ongoing memory footprint. Current techniques such as that just described typically load all the EJBs contained within the application at start-up, thereby increasing application start time and memory requirements. 
     An EJB container is usually responsible for registering unique look-up names within a Java Naming and Directory Interface (JNDI) namespace when the server starts and binding those names to home objects within the container. 
     A development environment typically has requirements differing from those of the production environment. In a development environment one needs to typically get a unit of work done as quickly as possible to verify operation of specific code elements of interest within the application. The development environment typically focuses on a smaller number of EJBs relative to the number of EJBs found in the application as a whole. Unfortunately the development environment must usually adhere to the same instantiation and maintenance practices as found in the production environment. Additionally a development environment is usually memory constrained not having access to the same amount of resource afforded the production environment. 
     Therefore what is required is a more effective way to create and operate a development environment using EJBs that allows for faster start-up while maintaining lower memory requirements as compared to that of a production environment. 
     SUMMARY OF THE INVENTION 
     A method, system, program product and signal bearing medium for deploying software modules for software application use in a computer system are provided. Deployment of software modules and associated descriptor information allow for selected requested software modules to be obtained and made available only as needed, resulting in reduced start-up delay and memory consumption as compared to that of a typical production environment. 
     In one aspect of the present invention, there is provided a method of deploying software modules for software application use in a computer system, said method comprising deploying of a plurality of software modules into a software module depository and deploying deployment descriptors associated with each of the plurality of software modules into a deployment information repository. 
     In another aspect of the present invention, there is provided a deployment system for deploying software modules for software application use in a computer system, comprising a first deployer for deploying a plurality of software modules into a software module depository and a second deployer for deploying deployment descriptors associated with each of the plurality of software modules into a deployment information repository. 
     In another aspect of the present invention there is provided a computer program product having a computer readable medium tangibly embodying computer readable program code for instructing a computer to perform the method for deploying of a plurality of software modules into a software module depository and deploying deployment descriptors associated with each of the plurality of software modules into a deployment information repository. 
     In yet another aspect of the present invention there is provided a signal bearing medium having a computer readable signal tangibly embodying computer readable program code for instructing a computer to perform a method for deploying of a plurality of software modules into a software module depository and deploying deployment descriptors associated with each of the plurality of software modules into a deployment information repository. 
     In another aspect of the present invention there is provided a computer program product having a computer readable medium tangibly embodying computer readable program code for instructing a computer system to provide the means of a first deployer for deploying a plurality of software modules into a software module depository and a second deployer for deploying deployment descriptors associated with each of the plurality of software modules into a deployment information repository. 
     In another aspect of the present invention there is provided a signal bearing medium having a computer readable signal tangibly embodying computer readable program code for instructing a computer to provide the means for first deployer for deploying a plurality of software modules into a software module depository and a second deployer for deploying deployment descriptors associated with each of the plurality of software modules into a deployment information repository. 
     Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. The illustrative embodiments of the present invention incorporate the use of Enterprise Java Beans. Those skilled in the art may appreciate that EJBs are but one form of software module which may be within the scope of the embodiments of the present invention. In the examples which follow one is reminded of the following relationships. 
     Enterprise Java Beans are but one embodiment of software modules and in general should not be taken as limiting applicability to use of the subject matter to Enterprise Java Beans. 
     Deployment descriptors associated with the EJBs may also be found in relationship to other implementations of software modules as a means of providing descriptive information regarding attributes of the particular software module type. 
     A software enabler is discussed within the following examples as a home object associated with an EJB. It is used to instantiate an EJB for software application use and may have a counterpart in other software implementations such as stub code for performing operations. 
     A name service as in the examples is referred to as a mapper providing mapping between the JNDI name space and home object implementation classes. Other techniques are available for this service as well such as a simple look up table or database table. Any suitable means for quickly resolving an input identifier to an out identifier is useful. 
     A property file is one form of resource used to provide extrinsic information regarding a software module or EJB. It may be replaced by another technique providing programmatic access to attribute information related to the software module or EJB as in the examples. Functionality could also be provided by way of lists, tables, arrays and objects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a hardware overview of a computer system, in support of embodiments of the present invention; 
         FIGS. 2 ,  3  and  4  are block diagrams showing typical EJB deployment into a production environment as supported in the computer system of  FIG. 1 ; 
         FIG. 5  is a flow diagram of a typical process of deploying an EJB into a production environment as suggested in  FIGS. 2 ,  3  and  4 ; 
         FIGS. 6 ,  7  and  8  are block diagrams showing an EJB deployment into a development environment in an embodiment of the present invention; 
         FIG. 9  is a flow diagram showing a process of an EJB deployment into a development environment in an embodiment of the invention as suggested in  FIGS. 6 ,  7  and  8 ; 
         FIG. 10  is a flow diagram showing an embodiment of the present invention as shown in  FIG. 9  with designated home objects; 
         FIG. 11  is a flow diagram showing an embodiment of the present invention as shown in  FIG. 10  with prioritized home objects. 
     
    
    
     Like reference numerals refer to corresponding components and steps throughout the drawings. It is to be expressly understood that the description and the drawings are only for the purpose of illustration and as an aid to understanding, and are not intended as a definition of the limits of the invention. 
     DETAILED DESCRIPTION 
       FIG. 1  depicts, in a simplified block diagram, a computer system  100  suitable for implementing embodiments of the present invention. Computer system  100  has processor  110 , which is a programmable processor for executing programmed instructions stored in memory  108 . Memory  108  can also include hard disk, tape or other storage media. While a single CPU is depicted in  FIG. 1 , it is understood that other forms of computer systems can be used to implement embodiments of the invention. It is also, appreciated that embodiments of the present invention can be implemented in a distributed computing environment having a plurality of computers communicating via a suitable network  119 . 
     CPU  110  is connected to memory  108  either through a dedicated system bus  105  and/or a general system bus  106 . Memory  108  can be a random access semiconductor memory for storing application data for processing such as that in a database partition. Memory  108  is depicted conceptually as a single monolithic entity but it is well known that memory  108  can be arranged in a hierarchy of caches and other memory devices.  FIG. 1  illustrates that operating system  120  may reside in memory  108 . 
     Operating system  120  provides functions such as device interfaces, memory management, multiple task management, and the like as known in the art. CPU  110  can be suitably programmed to read, load, and execute instructions of operating system  120 . Computer system  100  has the necessary subsystems and functional components to implement on-demand loading of software modules such as Enterprise Java Beans (EJBs) as will be discussed later. Other programs (not shown) include server software applications in which network adapter  118  interacts with the server software application to enable computer system  100  to function as a network server via network  119 . 
     General system bus  106  supports transfer of data, commands, and other information between various subsystems of computer system  100 . While shown in simplified form as a single bus, bus  106  can be structured as multiple buses arranged in hierarchical form. Display adapter  114  supports video display device  115 , which is a cathode-ray tube display or a display based upon other suitable display technology. The Input/output adapter  112  supports devices suited for input and output, such as keyboard or mouse device  113 , and a disk drive unit (not shown). Storage adapter  142  supports one or more data storage devices  144 , which could include a magnetic hard disk drive or CD-ROM, although other types of data storage devices can be used, including removable media. 
     Adapter  117  is used for operationally connecting many types of peripheral computing devices to computer system  100  via bus  106 , such as printers, bus adapters, and other computers using one or more protocols including Token Ring, LAN connections, as known in the art. Network adapter  118  provides a physical interface to a suitable network  119 , such as the Internet. Network adapter  118  includes a modem that can be connected to a telephone line for accessing network  119 . Computer system  100  can be connected to another network server via a local area network using an appropriate network protocol and the network server that can in turn be connected to the Internet.  FIG. 1  is intended as an exemplary representation of computer system  100  by which embodiments of the present invention can be implemented. It is understood that in other computer systems, many variations in system configuration are possible in addition to those mentioned here. 
       FIG. 2  is a simplified view of a typical relationship between pre-deployment software components comprising software modules such as EJB module  200  and deployment descriptor  205  containing attribute information of the associated software module and post deployment software components comprising deployed EJB module  210 , deployed deployment descriptor  215  and deployed code  220  resulting from a deployment operation of EJBs. Deployed deployment descriptor  215  is also kept with deployed EJB module  210  as it will be used later during server initialization. Not all server required information was captured in the deployed EJB module  210 , hence the maintenance of deployed deployment descriptor  215 . 
       FIG. 3  is a block diagram showing the typical components of deployed EJBs of  FIG. 2  after server initialization has completed. Deployed deployment descriptor  215  provides information for the further establishment of name service  230 . All of the EJBs specific to application  240  will be loaded in the form of preloaded home objects  235  and made available for application  240  uses by way of server initialization. Name service  230  provides a lookup service to resolve Java Naming and Directory Interface (JNDI) home object names to the implementation of various classes. Deployed deployment descriptor  215  may be a copy of deployment descriptor  205  in a deployed format. 
     Referring now to  FIG. 4 , EJB container  400  is shown associated with and managing reusable cached and pooled objects  405 . EJBs which have been previously used by application  240  are recycled by means of reusable cached and pooled objects  405 . EJBs once used are not discarded; they are placed in reusable cached and pooled objects  405  to await further use requests. 
     Referring now to  FIG. 5  a typical process inherent in the discussion of  FIGS. 2 ,  3  and  4  is shown. Beginning with operation  500  the EJB module and its associated descriptor are deployed into a production environment of the previous examples. Having completed deployment, processing moves to operation  505  during which the server is initialized. Having initialized the server processing moves to operation  510  during which the name service to be used for resolving named home object requests is created. The name service is required for object retrieval. During operation  515  all of the EJBs used in the application are found for which are created home objects. All of the home objects created during operation  515  are then used to populate the naming service during operation  520 . Having finished populating the name service, processing moves to operation  525  during which a storage pool is created. The storage pool is used to maintain previously used EJBs pending their further use. During operation  526  a request for a home object is received and the home object requested is then retrieved during operation  530 . A home object acts as a software enabler, making a requested EJB available for use by a requesting software application. If the home object requested was previously used it has an associated EJB that was cached in the pool and that EJB will then be retrieved during operation  545 . If the application has completed use of a home object it will release the EJB associated with the home object during operation  535 . Having released an EJB from the home object during operation  535 , the associated EJB is then moved to the pool during operation  540  where it resides awaiting further use, where it may again be retrieved by way of operation  545  as before. 
     Having described a typical production view a different environment having been optimized in accordance with embodiments of the present invention will now be discussed. Referring now to  FIG. 6  there is shown as before EJB module  200  and deployment descriptor  205 . Deploying EJB module  200  and deployment descriptor  205  causes deployed EJB module  210 , deployed code  220  and deployment information repository  225  to be created. Deployment of EJB module  200  and deployment descriptor  205  may be accomplished using a single deployer combining both capabilities or separate deployers as in a first and second deployer established to handle an EJB module and deployment descriptor respectively as part of a deployment system. Deployment information repository  225  contains all of the necessary information needed by the server during initialization at start-up. Creation of deployment information repository  225  eliminates the need for maintaining the copy of deployment descriptor  205  in a post deployment form. Deployment information repository  225  contains parsed input from deployment descriptor  205  eliminating the need to have deployment descriptor  205  parsed yet again during server initialization. Deployment information repository  225  may be implemented in any suitable form as is known in the art. A suitable implementation may be in the form of a property file mapping JNDI home object names to the implementation classes. In a similar manner lookup tables may be used as well as relational tables, arrays, indexed arrays or other means may be used to provide fast efficient resolution. 
     This embodiment will delay the loading of EJBs until they are actually requested by the application typically allowing the application to be ready sooner than otherwise possible. Further a reduction in memory allocation at start-up is typically possible due to the reduced number of EJBs to be loaded into storage as well as on an ongoing basis only having those which are used loaded. 
       FIG. 7  shows in block form a relationship between deployment information repository  225  and name service  245 . Name service  245  is used to resolve the EJB name passed by the application to the proper request-loaded home objects  250  as requested by application  240 . Name service  245  possesses intelligence in order to find the mapping between a requested EJB and on-demand instantiated home object  250  to perform the needed retrieval. On-demand instantiated home objects  250  are created on a call by call basis as EJBs are requested for use by application  240 . No home object is created until a request has been received from application  240 . When application  240  requests name service  245  to find an EJB home object, name service  245  will use information in deployment information repository  225  to locate and instantiate the required home object implementation classes. 
     Referring now to  FIG. 8  EJB container  410  may be seen with application  240 . No additional storage is maintained by EJB container  410  to hold on-demand instantiated home objects  250  as they are released from application  240  after each use. As on-demand instantiated home objects  250  are released they are made available for garbage collection and subsequent disposal. 
     Referring now to  FIG. 9  a typical process of an embodiment of the invention that may be used typically in an environment such as in a development mode using EJBs is shown. Beginning with operation  500  an EJB module and associated deployment descriptor are deployed. As part of the deployment an information repository is created during operation  550  to contain information needed during server initialization. Server initialization is then performed during operation  505 . Processing moves to operation  510  during which a name service is created to resolve mappings between EJBs requested by an application and home objects providing runtime support. During operation  526  a request is received needing a home object. A determination is then made in operation  555  as to whether the home object has been loaded. If the requested home object is found, it is then retrieved during operation  530 , otherwise processing moves to operation  560 . During operation  560  information is retrieved from the deployment information repository for the specific EJB and processing moves to operation  515 , during which the home object is instantiated and made ready for use by the application. Processing moves to operation  530  and as before the home object is retrieved for application use. After application use of the home object, processing moves to operation  535  during which the used home object is discarded as it is no longer required. 
     Referring now to  FIG. 10  a typical process of another embodiment of the invention that may be used typically in an environment such as in a development mode using EJBs is shown. Beginning with operation  500  an EJB module and associated deployment descriptor are deployed. As part of the deployment an information repository is created during operation  550  to contain information needed during server initialization. Server initialization is then performed during operation  505 . Processing moves to operation  510  during which a name service is created to resolve mappings between EJBs requested by an application and home objects providing runtime support. Having completed operation  510 , operation  516  begins during which designated home objects are instantiated. These designated home objects are a number of EJBs which have been determined to be made available prior to execution of the application rather than waiting for eventual requests from the application. Examples of such EJBs may be those dealing typically with housekeeping or security operations or other functions which are commonly used and useful in a variety of environments. Designated home objects may be so chosen for any reason, the reason not being of import rather it is the facility being offered. Locating designated home objects may be performed by way of resource files as used in various programming environments, simple lists, arrays, indexed arrays and tables. Typical numbers of such designated home objects will be small relative to the number available to the related application. Retrieval of such names should be simple and fast to ensure rapid loading of the environment. During operation  526  a request is received having an associated home object. A determination is then made in operation  555  as to whether the home object has been loaded. If the requested home object is found, it is then retrieved during operation  530 , otherwise processing moves to operation  560 . During operation  560 , information is retrieved from the deployment information repository for the specific EJB and processing moves to operation  515 , during which the home object is instantiated and made ready for use by the application. Processing moves to operation  530  and as before the home object is retrieved for application use. After application use of the home object, processing moves to operation  535  during which the used home object is discarded as it is no longer required. 
     Referring now to  FIG. 11  a typical process of yet another embodiment of the invention that may be used typically in an environment such as in a development mode using EJBs is shown. Beginning with operation  500  an EJB module and associated deployment descriptor are deployed. As part of the deployment an information repository is created during operation  550  to contain information needed during server initialization. Server initialization is then performed during operation  505 . Processing moves to operation  510  during which a name service is created to resolve mappings between EJBs requested by an application and home objects providing runtime support. Having completed operation  510 , operation  516  begins during which designated home objects are instantiated. These designated home objects are a number of EJBs which have been determined to be made available prior to execution of the application rather than waiting for eventual requests from the application. Examples of such EJBs may be those dealing typically with housekeeping or security operations or other functions which are commonly used and useful in a variety of environments. Designated home objects may be so chosen for any reason, the reason not being of import rather it is the facility being offered. During operation  526  a request is received having an associated home object. A determination is then made in operation  555  as to whether the home object has been loaded. If the requested home object is found, it is then retrieved during operation  530 , otherwise processing moves to operation  560 . During operation  560 , information is retrieved from the deployment information repository for the specific EJB and processing moves to operation  515 , during which the home object is instantiated and made ready for use by the application. Processing moves to operation  530  and as before the home object is retrieved for application use. After application use of the home object, processing moves to operation  531  during which a determination is made regarding the priority of the used home object. If the home object was required for future processing it would have an entry in a priority list and be retained within the EJB container for subsequent retrieval. On the other hand if it is no longer required it would not be located on a priority list and processing would move to operation  535  during which the home object is discarded. Home objects which would be typical candidates for inclusion on a priority list may be those designated earlier as designated home objects or those which may have been recorded as a result of test conditions. A variety of rationale may be used to determine candidates for prioritization. Prioritized home objects may be so chosen for a number of reasons, the reason not being of import rather it is the facility being offered. Locating designated home objects may be performed by way of resource files as used in various programming environments, simple lists, arrays, indexed arrays and tables. Typically numbers of such prioritized home objects will be small relative to the number available to the related application. Retrieval of such names should be simple and fast to ensure rapid loading of the environment. 
     Although the invention has been described with reference to illustrative embodiments, it is to be understood that the invention is not limited to these precise embodiments and that various changes and modifications may be effected therein by one skilled in the art. All such changes and modifications are intended to be encompassed in the appended claims.