Abstract:
The present invention is a method, system, and computer program product enabling multiple versions/releases of a J2EE application to be served to clients from a single application server. One or more JNDI proxies are situated between each client and the application server. The JNDI proxies allow a same public “service name” to be utilized by different clients to access different programs/services on the application server. The JNDI proxies do this by translating the service name into a non-public “alias name” on behalf of the client. The alias name is a private name that the service provider who administers the application server understands and uses to locate the specific version of programs/services that the clients need.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of, and claims priority to, U.S. application Ser. No. 10/804,644, filed Mar. 19, 2004, which contents are incorporated fully herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of computer systems and, more particularly to the field of application version management in a J2EE environment. 
     BACKGROUND OF THE INVENTION 
     A J2EE application is a multi-tiered, distributed application that commonly comprises a web-tier that interacts with a business-tier and an enterprise information systems (EIS) tier. It is also possible for a J2EE application to consist only of a business tier and an EIS tier components; there is no web component. These non-web J2EE applications are referred to as being “system-oriented,” where their clients are also applications systems or computers and not end-users or human beings. In order for intersystem communications to take place, application stubs, the software that resides on the client&#39;s end, must be distributed to the client systems. 
     As any software user knows, as time progresses, enhancements and bug fixes are added to applications. These changes may result in a new application version or release (the terms “version” and “release” are used interchangeably herein to refer to a particular embodiment of a program/application/service). With a web-based J2EE application, clients can be redirected to the new application version in an easy, seamless fashion with minimal system downtime through the use of hardware load balancers and additional hardware (e.g., additional machines or computers). For a system-oriented J2EE application, however, migrating clients to the new application version is much more complicated, as new versions of the application stubs must be generated and distributed to client systems themselves. The changes take effect only when the clients switch to using the new application stub. This switching action must be performed in a synchronous fashion between the client and the server applications; otherwise, it may result in incompatibility errors in the binary code of the software. This complexity is further compounded if the server application is a service provider that provides an array of services co-shared by multiple clients. 
     As an example, consider clients X and Y sharing a service, “Service A” on a machine M1. Client X requests updates for Service A when they are issued. Deploying the new version of Service A (Service A, version 2) for Client X on M1 requires Client Y to also upgrade to avoid binary incompatibility errors. This, in itself, may cause a problem, since Client Y may not wish to upgrade to the new version. 
     Further, if the updated version of Service A (Service A, version 2) does not work well and Client X decides to fall back to the old version, Client Y must also execute the fallback procedure or risk having additional binary incompatibility errors. This “synchronous application upgrade” requires tight coupling between clients and in this case, causes unwarranted service discontinuity for Client Y. 
     To avoid tight coupling among clients, the service provider may deploy the new application version (Service A, version 2) on a second machine M2, and have Client X point to M2, thus allowing Client Y to continue to use the old version on machine M1. This strategy, however, incurs additional hardware costs and efforts to configure the new environment. The complexity, cost and risk increases with additional clients and increased frequency of application upgrades. 
     As a result of the above difficulties, application service providers do not attempt to provide multiple versions or releases of the same application to clients from the same machine. Accordingly, it would be desirable to have a method, system, and computer program product for server application management in which multiple, concurrent application versions can be managed with minimal cost, effort and risk, and allow the server application to perform an application upgrade for each client in an isolated, precise fashion without the need for multiple machines or service disruption to other clients. 
     SUMMARY OF THE INVENTION 
     The present invention is a method, system, and computer program product for management and serving of multiple versions/releases of the same program from a single application server. The present invention utilizes one or more JNDI proxies situated between each client and an application server. In additional embodiments, JNDI proxies may also be situated on the application server between related applications. In accordance with the present invention, the JNDI proxies allow a same public “service name” to be utilized by different clients to access to different programs/services on the application server. The JNDI proxies do this by translating the service name into a non-public “alias name” on behalf of the client. The alias name is a private name that the service provider who administers the application server understands and uses to locate the specific version of programs/services that the clients need. Clients refer to programs/services by their service names and the JNDI proxies translate the service names to their corresponding alias names so that the service provider can use the alias names to locate the correct version of program/services for the clients on the application server. The JNDI proxies perform the name translation automatically on behalf of the client. Hence, the clients are not “version aware”. 
     Configuration information for each client, which identifies the alias name to be used to serve specific versions of applications/services to the clients, is provided to the proxies so that a proper link can be made between the public service name and the non-public alias name for each client. Thus, the client always accesses the desired version of an application or a service in a transparent manner with respect to the client. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating the architecture and operation of a typical JNDI naming service being used to provide access to Enterprise Java Beans (EJBs); 
         FIG. 2  illustrates the architecture and operation of a typical JNDI naming service being used to provide access to multiple versions of a particular service; 
         FIG. 3  illustrates a first embodiment of the present invention; 
         FIG. 4  illustrates the present invention utilized in a delegation-of-service environment; 
         FIG. 5  illustrates the a delegation-of-service environment in which services are redirected across different versions of a service; 
         FIG. 6  illustrates the use of the present invention in connection with JMS queues; 
         FIG. 7  is a flowchart illustrating an example of the basic steps performed in order to utilize the JNDI proxy server to enable multiple versioning in accordance with the present invention; and 
         FIGS. 8 and 9  illustrate the use of the present invention in connection with a JDBC DataSource. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     To understand the present invention, it helps to have an understanding of the Java Naming and Directory Interface (JNDI); JNDI is a naming service that allows a program or container to register a name for an object (service). This name is commonly referred to as the JNDI name. The JNDI naming service provides a list of services identified by JNDI names, organized in a “tree” structure, that are hosted on an J2EE application server. Clients then obtain a service by connecting to the application server and looking up the bound JNDI name of the service. The JNDI names are alias names in the context of the present invention. 
       FIG. 1  is a block diagram illustrating the architecture and operation of a typical JNDI naming service being used to provide access to, in this example, Enterprise Java Beans (EJBs). Referring to  FIG. 1 , a first client  110  (client X) and a second client  120  (client Y) access an application server  130 . An EJB  134  is shown. This EJB has a JNDI (alias) name of “Service A”. Since there is only a single application with a single name, client  110  and client  120  each can request Service A using the same service name, e.g., a service name such as “Lotus Notes” or a service name that is the same as the alias name used by the application server, that is, Service A. Since both clients  110  and  120  are accessing the same program, there is no concern about which application will be served to the clients; there is only one choice. 
     Referring now to  FIG. 2 , a situation is illustrated where there are two available versions of Service A, a first version called Service A, version 1 and a second version called Service A, version 2. Since both clients  110  and  120  are accessing the program using a single service name (e.g., Lotus Notes or Service A), both clients must access the same version, since prior art systems have no way of binding the same service name to different alias names. Thus, if EJB  134 , which corresponds to version 1 of Service A, is identified by the service name “Lotus Notes”, then when each client requests access to the service name Lotus Notes, they will be directed to EJB  134 . If one of the clients, for example client  110 , decides to switch to use the Service A, version 2, designated by EJB  244 , then either both clients will have to access the same version (since EJB  244  will now have a pointer associated with the service name Lotus Notes so that anyone requesting Lotus Notes is directed to EJB  244 ), or clients  110  and  120  will have to be “version aware”, meaning that distinct service names will have to be designated for each of EJB  134  and EJB  234  (e.g., Lotus Notes v.1 and Lotus Notes v.2) and then each client will have to be configured so that they access the different versions (client  110  will access Lotus Notes v.2 while client  120  will access Lotus Notes v.1). This alternate path is illustrated by the dotted line extending from client  110  to EJB  244 . 
     As noted above, it is undesirable to require the clients to be version aware or to require that they all use the same version of a particular program or service. 
       FIG. 3  illustrates a first embodiment of the present invention. Referring to  FIG. 3 , JNDI proxy servers  350  and  352  are interposed between each client and the application server  130 . 
     In the case where only a single application version is available on the application server (e.g., if, in  FIG. 3 , there was only a single version of Service A, identified as EJB  134 , more specifically Service A, version 1), then JNDI proxy  350  would bind the service name (a public name) used by client  110  to EJB  134 , and JNDI proxy  352  would bind the service name used by client  120  to the same EJB  134 . Presumably, the service name for each would be identical; however, with the binding process performed by the proxies, it is not necessary that they be the same. 
     In the case where there are multiple versions as shown in  FIG. 3 , if, for example, client  110  wishes to utilize the second version, Service A, version 2 illustrated by EJB  244 , then proxy server  350  will bind the service name used by client  110  (which can be the same service name used by client  120  to access version 1) to EJB  244  instead of to EJB  134 . In this manner, while on the surface each client may be “asking” for the same application/service (since they are using, for example, the same service name to make the request) the proxy servers will correctly serve the appropriate version to each client. 
     The application server “knows” which version each client wishes to access because this information is obtained from the client when the client makes a request for a service from the application server. On the client&#39;s end, there is a set up process that identifies the version of the software/program/service that the client will be accessing. In the client&#39;s set up process, each client has a configuration file that identifies which version of a particular application the client intends to use, and if this changes, the information is revised during a subsequent set up process using well-known techniques, for example, as part of the installation process for the new version. This information is stored in a configuration file for each client on the client&#39;s end. At start up, each proxy (located on the client&#39;s machine) reads the configuration file to determine which version the client intends to use, and when the client requests a service from the application server, binds the alias name of that version to the service name used by the client to access that program. Whenever the client changes the version it wishes to use, the proxy server associated with that client binds the newly desired version with the service name, so that the client will always get the right version, while other clients can access different versions using the same service name. 
     In addition to remote clients, the JNDI proxy can also be used by internal application components to perform look up of other J2EE objects, e.g., to handle a delegation-of-services operation. For example, referring to  FIG. 4 , assume that EJB  134  specializes in handling requests such as data validation while EJB  446  specializes in information retrieval. An internal JNDI proxy  454  is situated between EJB  134  and EJB  446  such that EJB  446  is invoked upon request from EJB  134 . This is an example of a delegation-of-services operation. Thus, if EJB  134  determines that a request does not possess all of the required validation information required to access EJB  446  (e.g., a required social security number has not been provided), then EJB  134  will not call the next service, the data retrieval service performed by EJB  446 . Likewise, a second EJB  446  can be delegated by EJB  244  via proxy  456  in the same manner. 
       FIG. 5  illustrates the flexibility available using the system of the present invention. In this example, a second level of delegation is illustrated, whereby client  120  invokes Service A, version 1 represented by EJB  134  and EJB  134  in turn invokes Service B, version 1 represented by EJB  436 . EJB  436  in turn can invoke Service C, version 1, represented by EJB  560  (this invocation is illustrated by the dotted line connection EJB  436  to EJB  560 ). However,  FIG. 5  also illustrates that it is not necessary that the same version be maintained across all service invocations. As shown by the solid arrow from EJB  436  to EJB  562 , Service B, version 1 (EJB  436 ) can be configured to invoke Service C, version 2 (EJB  562 ) instead of Service C, version 1 (EJB  560 ). This illustrates the flexibility of the JNDI proxy to be configured to direct services across different versions as desired. 
     Although described above with respect to providing version management for services provided through EJB resources, there are additional J2EE resources that can be affected by application versioning. For example, the JNDI proxy can be used for application versioning management of JMS resources. JMS resources include queues, queue connection factories, topics, and topic connection factories. Like other J2EE resources, each JMS resource can be bound by a name in the JNDI name service in the application server. These JMS resources can then be acquired and used by external clients or by internal EJBs. Thus, for example, as shown in  FIG. 6 , EJB  632  and EJB  642  are each separately connected, via JNDI proxies  664  and  666 , respectively, to JMS queues  668  and  670 , respectively. Each queue can be associated with the service name used by a particular client so that regardless of the service name used by the client, the information destined for or coming from the queue will always be linked to the correct client. 
       FIG. 7  is a flowchart illustrating an example of the basic steps performed in order to utilize the JNDI proxy server to enable multiple versioning in accordance with the present invention. Referring to  FIG. 7 , at step  702  the process begins, and at step  704 , the client identifies the program/service to be accessed from the application server. Typically this would be performed during the installation of a particular software program on the client, for example, installation of software that will access the application server and retrieve a particular service or software solution from the server. At step  706 , as part of this process, the service provider (the owner of the services provided on the application server) creates a configuration file identifying the program/service and version used by the particular client. 
     At step  708 , the client requests the application using its service name. As discussed above, the service name can be the same for all clients accessing the application server, regardless of which version each client is using. At step  710 , the proxy receives the request from the client, and at step  712 , the proxy determines the version used by the client. The proxy does this by reading the configuration file. The proxy then directs the server to serve the correct version, using the appropriate alias name associated with the service name provided by the client. 
     At step  714 , the server serves the appropriate version of the application to the client, and the process ends at step  716 . 
     As is clear, the use of the JNDI proxies enables a great deal of flexibility in delivering and/or routing of programs, services, data, etc. between clients and their ultimate connection points. This invention can find application in application server architecture, email routing, bank transaction management, and any other environment where it is desired to have a client be free from the necessity of being version aware. 
     As described above, using the present invention, control of which version and/or release to deliver to a client from an application server is controlled by the proxy based on configuration information submitted by a particular client. Thus, the service name used to access the application/service does not need to be changed, but merely the binding of that name for a particular client to the particular version/release desired. This simplifies use of the client for the user, who typically does not care to have to specify between various versions, releases, etc.; they simply want to type in a familiar name and receive the application or service requested. This simplifies use of the system by the user, and also simplifies administration of releases and versions by system administrators. 
       FIGS. 8 and 9  illustrate the use of the present invention in connection with a JDBC DataSource. A first example of such a datasource is illustrated in  FIG. 8 . In  FIG. 8 , a client  802  is coupled via a JNDI proxy  804  to EJBs  806  and  808  (each of which, in this example, illustrate delegation-of-services operations described above). Each of EJBs  806  and  808  are connected to JDBC DataSources; in this example EJB  806  is connected to JDBC DataSource  810 , and EJB  808  is connected to JDBC DataSource  812 . Each of the JDBC DataSources is in turn coupled to a database  814 . 
     The JDBC DataSource is a named group containing ready-to-use JDBC connections. It establishes database connections when the connection pool starts up, and eliminates the overhead of establishing database connections on demand at run time. A DataSource object enables JDBC clients to obtain a database connection. Each DataSource object has a unique JNDI name and points to a JDBC connection pool. A client, which can be, for example, a Java application, an EJB, or an MDB, performs a JNDI look up for the DataSource to get a database connection. 
     To support datasources for multiple application versions, different DataSource versions can be configured for different application versions. With this option, datasources will be created for each application version. Each datasource will have a unique JNDI name, different from its peer in another application version. Application code that obtains database connections from datasources such as a Java client, an EJB, or an MDB, will use the similar approach of going through the JNDI proxy to perform a transparent JNDI name translation to access the appropriate datasource intended for that version. For example, in the illustration of  FIG. 8 , database  814  can represent a bank, and datasource  810  can represent a checking account with the bank, while datasource  812  can represent a savings account with the bank. This allows client  802  to direct checking deposits through datasource  810  and savings deposits through datasource  812 , both of which will end up eventually at the bank  814 . 
       FIG. 9  illustrates essentially the same architecture, but in this case, datasource  810 , pertaining to the checking account, has been eliminated, and all data (e.g., electronic deposits) are directed through datasource  812 , pertaining to the savings account. This would allow, for example, a user to decide to direct all deposits, etc. through the savings account if the bank decides to begin charging for use of the checking account. From the client perspective, the user will still designate deposits to go to checking and/or savings, but no apparent changes are made at the client end; all of the redirections are performed via the JNDI proxies as shown and described herein. 
     The above-described steps can be implemented using standard well-known programming techniques. The novelty of the above-described embodiment lies not in the specific programming techniques but in the use of the steps described to achieve the described results. Software programming code which embodies the present invention is typically stored in permanent storage of some type, such as permanent storage associated with the client and/or application server. The software programming code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, or hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users from the memory or storage of one computer system over a network of some type to other computer systems for use by users of such other systems. The techniques and methods for embodying software program code on physical media and/or distributing software code via networks are well known and will not be further discussed herein. 
     It will be understood that each element of the illustrations, and combinations of elements in the illustrations, can be implemented by general and/or special purpose hardware-based systems that perform the specified functions or steps, or by combinations of general and/or special-purpose hardware and computer instructions. 
     These program instructions may be provided to a processor to produce a machine, such that the instructions that execute on the processor create means for implementing the functions specified in the illustrations. The computer program instructions may be executed by a processor to cause a series of operational steps to be performed by the processor to produce a computer-implemented process such that the instructions that execute on the processor provide steps for implementing the functions specified in the illustrations. Accordingly, the figures support combinations of means for performing the specified functions, combinations of steps for performing the specified functions, and program instruction means for performing the specified functions. 
     While there has been described herein the principles of the invention, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation to the scope of the invention. Accordingly, it is intended by the appended claims, to cover all modifications of the invention which fall within the true spirit and scope of the invention.