Abstract:
A system, computer program product and method of narrowing an enterprise Java bean (EJB) object reference to a home implementation class name are provided. To obtain the class name, the location of the EJB in a network is first obtained by performing a JNDI lookup. Using the location, an IOR of the EJB is obtained. The IOR is then processed to obtain the home implementation class name of the object. Processing the IOR includes decomposing the IOR to arrive at a typeId string stored therein. The typeId string is further processed to obtain the home implementation class name contained therein.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The present invention is directed to J2EE software applications. More specifically, the present invention is directed to a system, computer program product and method of narrowing an EJB object reference to a home implementation class name.  
         [0003]     2. Description of Related Art  
         [0004]     Java™, an object-oriented programming language developed by Sun Microsystems, Inc., is platform-independent, and networking/distributed-computing friendly. As a distributed-computing friendly programming language, Java provides for naming and directory services. A naming service provides a mechanism for giving names to objects so they can be used without knowing their storage location. A directory service, on the other hand, associates names with objects. Some directory services may provide additional information by associating attributes with the objects.  
         [0005]     Java provides for naming and directory services through Java Naming and Directory Interface (JNDI). JNDI is a Java application program interface (API) for accessing naming and directory Services. That is, JNDI is an API and not, in itself, a naming and directory service. To use JNDI, an implementation of a naming and directory service, such as Lightweight Directory Access Protocol (LDAP), Domain Name System (DNS), Novell Directory Services (NDS), Network Information Service (NIS) etc. must also be available. JNDI also supports more specialized naming systems such as the Common Object Request Broker Architecture (CORBA) and the Remote Method Invocation (RMI). CORBA is an open distributed object computing infrastructure that is being standardized by the Object Management Group (OMG). CORBA automates many common network programming tasks such as object registration, location, activation et cetera. RMI allows an object running in one Java Virtual Machine (JVM) to invoke methods on an object running in another JVM. That is, RMI provides for remote communication between programs written in the Java programming language.  
         [0006]     In its simplest form, JNDI is used to find resources, such as Enterprise Java Beans (EJBs) that have been registered via a Java 2 platform Enterprise Edition (J2EE) server. J2EE is a platform-independent, Java-centric environment for developing, building and deploying Web-based enterprise applications online. The J2EE platform consists of a set of services, APIs, and protocols that provide functionality for developing multi-tiered, Web-based applications. J2EE applications allow for deployment-time binding while maintaining type and link safety by having each component export a list of needed external components and resources. Thus, in a J2EE application, components find other components not via static linking, but through JNDI lookups.  
         [0007]     When a JNDI lookup for an EJB is performed, a lookup( ) method is executed. The lookup( ) method generally returns a reference to the EJB (or an object reference) that in EJB version 1.0 would have to be cast to the home interface of the EJB. Casting is an explicit conversion from one data type to another. A data type is a named category of data that is characterized by a set of values, together with a way to denote those values and a collection of operations that interpret and manipulate the values. However, in EJB version 1.1 casting is not permitted.  
         [0008]     Specifically, the communication between an EJB server and client is based on RMI. RMI, as mentioned above, is a set of protocols that enables Java objects to communicate remotely with other Java objects. Unlike CORBA, which is designed to support objects created in any language, RMI works only with Java objects.  
         [0009]     The underlying protocol that RMI used for the communication is Internet Inter-Orb Protocol (IIOP), which is part of CORBA. IIOP is a protocol developed by the Object Management Group (OMG) to implement CORBA solutions over the World Wide Web. IIOP enables browsers and servers to exchange integers, arrays, and more complex objects. Since IIOP is part of CORBA, it has not been designed for Java, but rather for generic languages, and as such it has some limitations. One of its limitations is that it does not allow for casting.  
         [0010]     Nonetheless, Java RMI-IIOP provides a mechanism to convert an object type received from a lookup( ) method to an appropriate type. This is done through a narrow( ) method. To use the narrow( ) method, however, a remote reference to a home implementation class name of the EJB must be known. This will allow the EJB to be called for instantiation without error. But, in cases where the EJB instance is being treated as an interface implementation, the home implementation class name is not known. An interface defines operations or methods that a class implements (i.e., declares what a class does). A class is used to instantiate or create objects in memory.  
         [0011]     Thus, there is a need for a system, computer program product and method of dynamically determining EJB home implementation class names.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention provides a system, computer program product and method of narrowing an enterprise Java bean (EJB) object reference to a home implementation class name. Generally, when a Java Naming and Directory Interface lookup is performed for an EJB, an object reference is returned. In the case of the invention, an interoperable object reference (IOR) associated with the object is also obtained. The IOR contains information that may lead to the home implementation class name of the object. Once the class name is obtained, the object may be instantiated.  
         [0013]     Thus, the invention first determines the location of the EJB in a network by performing a JNDI lookup. Using the location, an IOR of the EJB is obtained. The IOR is then processed to obtain the home implementation class name of the object. Processing the IOR includes decomposing the IOR to arrive at a typeId string stored therein. The typeId string is further processed to obtain the home implementation class name contained therein.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:  
         [0015]      FIG. 1  is an exemplary block diagram illustrating a distributed data processing system according to the present invention.  
         [0016]      FIG. 2  is an exemplary block diagram of a server apparatus according to the present invention.  
         [0017]      FIG. 3  is an exemplary block diagram of a client apparatus according to the present invention.  
         [0018]      FIG. 4  depicts an exemplary stringified interoperable object reference (IOR).  
         [0019]      FIG. 5  is a flowchart of a process that may be used to implement the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]     With reference now to the figures,  FIG. 1  depicts a pictorial representation of a network of data processing systems in which the present invention may be implemented. Network data processing system  100  is a network of computers in which the present invention may be implemented. Network data processing system  100  contains a network  102 , which is the medium used to provide communications links between various devices and computers connected together within network data processing system  100 . Network  102  may include connections, such as wire, wireless communication links, or fiber optic cables.  
         [0021]     In the depicted example, server  104  is connected to network  102  along with storage unit  106 . In addition, clients  108 ,  110 , and  112  are connected to network  102 . These clients  108 ,  110 , and  112  may be, for example, personal computers or network computers. In the depicted example, server  104  provides data, such as boot files, operating system images, and applications to clients  108 ,  110  and  112 . Clients  108 ,  110  and  112  are clients to server  104 . Network data processing system  100  may include additional servers, clients, and other devices not shown. In the depicted example, network data processing system  100  is the Internet with network  102  representing a worldwide collection of networks and gateways that use the TCP/IP suite of protocols to communicate with one another. At the heart of the Internet is a backbone of high-speed data communication lines between major nodes or host computers, consisting of thousands of commercial, government, educational and other computer systems that route data and messages. Of course, network data processing system  100  also may be implemented as a number of different types of networks, such as for example, an intranet, a local area network (LAN), or a wide area network (WAN).  FIG. 1  is intended as an example, and not as an architectural limitation for the present invention.  
         [0022]     Referring to  FIG. 2 , a block diagram of a data processing system that may be implemented as a server, such as server  104  in  FIG. 1 , is depicted in accordance with a preferred embodiment of the present invention. Data processing system  200  may be a symmetric multiprocessor (SMP) system including a plurality of processors  202  and  204  connected to system bus  206 . Alternatively, a single processor system may be employed. Also connected to system bus  206  is memory controller/cache  208 , which provides an interface to local memory  209 . I/O bus bridge  210  is connected to system bus  206  and provides an interface to I/O bus  212 . Memory controller/cache  208  and I/O bus bridge  210  may be integrated as depicted.  
         [0023]     Peripheral component interconnect (PCI) bus bridge  214  connected to I/O bus  212  provides an interface to PCI local bus  216 . A number of modems may be connected to PCI local bus  216 . Typical PCI bus implementations will support four PCI expansion slots or add-in connectors. Communications links to network computers  108 ,  110  and  112  in  FIG. 1  may be provided through modem  218  and network adapter  220  connected to PCI local bus  216  through add-in boards.  
         [0024]     Additional PCI bus bridges  222  and  224  provide interfaces for additional PCI local buses  226  and  228 , from which additional modems or network adapters may be supported. In this manner, data processing system  200  allows connections to multiple network computers. A memory-mapped graphics adapter  230  and hard disk  232  may also be connected to I/O bus  212  as depicted, either directly or indirectly.  
         [0025]     Those of ordinary skill in the art will appreciate that the hardware depicted in  FIG. 2  may vary. For example, other peripheral devices, such as optical disk drives and the like, also may be used in addition to or in place of the hardware depicted. The depicted example is not meant to imply architectural limitations with respect to the present invention.  
         [0026]     The data processing system depicted in  FIG. 2  may be, for example, an IBM e-Server pSeries system, a product of International Business Machines Corporation in Armonk, N.Y., running the Advanced Interactive Executive (AIX) operating system or LINUX operating system.  
         [0027]     With reference now to  FIG. 3 , a block diagram illustrating a data processing system is depicted in which the present invention may be implemented. Data processing system  300  is an example of a client computer. Data processing system  300  employs a peripheral component interconnect (PCI) local bus architecture. Although the depicted example employs a PCI bus, other bus architectures such as Accelerated Graphics Port (AGP) and Industry Standard Architecture (ISA) may be used. Processor  302  and main memory  304  are connected to PCI local bus  306  through PCI bridge  308 . PCI bridge  308  also may include an integrated memory controller and cache memory for processor  302 . Additional connections to PCI local bus  306  may be made through direct component interconnection or through add-in boards. In the depicted example, local area network (LAN) adapter  310 , SCSI host bus adapter  312 , and expansion bus interface  314  are connected to PCI local bus  306  by direct component connection. In contrast, audio adapter  316 , graphics adapter  318 , and audio/video adapter  319  are connected to PCI local bus  306  by add-in boards inserted into expansion slots. Expansion bus interface  314  provides a connection for a keyboard and mouse adapter  320 , modem  322 , and additional memory  324 . Small computer system interface (SCSI) host bus adapter  312  provides a connection for hard disk drive  326 , tape drive  328 , and CD-ROM/DVD drive  330 . Typical PCI local bus implementations will support three or four PCI expansion slots or add-in connectors.  
         [0028]     An operating system runs on processor  302  and is used to coordinate and provide control of various components within data processing system  300  in  FIG. 3 . The operating system may be a commercially available operating system, such as Windows XP™, which is available from Microsoft Corporation. An object oriented programming system such as Java may run in conjunction with the operating system and provide calls to the operating system from Java programs or applications executing on data processing system  300 . “Java” is a trademark of Sun Microsystems, Inc. Instructions for the operating system, the object-oriented operating system, and applications or programs are located on storage devices, such as hard disk drive  326 , and may be loaded into main memory  304  for execution by processor  302 .  
         [0029]     Those of ordinary skill in the art will appreciate that the hardware in  FIG. 3  may vary depending on the implementation. Other internal hardware or peripheral devices, such as flash ROM (or equivalent nonvolatile memory) or optical disk drives and the like, may be used in addition to or in place of the hardware depicted in  FIG. 3 . Also, the processes of the present invention may be applied to a multiprocessor data processing system.  
         [0030]     As another example, data processing system  300  may be a stand-alone system configured to be bootable without relying on some type of network communication interface, whether or not data processing system  300  comprises some type of network communication interface. As a further example, data processing system  300  may be a Personal Digital Assistant (PDA) device, which is configured with ROM and/or flash ROM in order to provide non-volatile memory for storing operating system files and/or user-generated data.  
         [0031]     The depicted example in  FIG. 3  and above-described examples are not meant to imply architectural limitations. For example, data processing system  300  may also be a notebook computer or hand held computer in addition to taking the form of a PDA. Data processing system  300  also may be a kiosk or a Web appliance.  
         [0032]     The present invention provides a system, computer program product and method of dynamically determining EJB home implementation class names for narrowing purposes. The invention may be local to client systems  108 ,  110  and  112  of  FIG. 1  or to the server  104  or to both the server  104  and clients  108 ,  110  and  112 . Further, the present invention may reside on any data storage medium (i.e., floppy disk, compact disk, hard disk, ROM, RAM, etc.) used by a computer system.  
         [0033]     Generally, objects publish their identities and locations via object references. In CORBA, object references are exchanged over IIOP in the form of interoperable object reference (IOR). An IOR is a data structure associated with an object that contains enough information to locate the object from anywhere on a network. Put simply, an IOR allows an application to make remote method calls on an object. To do so, an IOR usually contains one or more profiles. A profile describes how a client can contact and send requests to the object using a particular protocol. The profile contains the Internet address of the object&#39;s server and a key value used by the server to find the specific object described by the reference.  
         [0034]     Typically, the application that creates a CORBA object produces a file containing a stringified IOR. To use a CORBA object, an application has to obtain the stringified IOR from the file in which it is stored, and call the object request broker&#39;s (ORB&#39;s) string_to_object method( ). This method will convert the string to a real CORBA object reference for use.  
         [0035]      FIG. 4  depicts an exemplary stringified IOR. As can be seen, the stringified IOR is in the form of IOR:###. Within the IOR is a “typeId string.” The “typeId string contains, among other information, the class name of the object. Using the class name, the returned object reference can be narrowed to an appropriate specific class that enables the create() method to be called without error.  
         [0036]     Thus, in operation, if server  104  is a J2EE server with which an EJB is registered. And, if an application on one of the clients  108 ,  110  and  112  wants to dynamically link to the EJB, the application may perform a JNDI lookup for the EJB. As mentioned before, an object reference to the EJB will be returned to the application. Further, the application may use a utility method to retrieve the IOR of the RMI/IIOP CORBA object. Once the IOR is obtained, it may be decomposed to isolate the “typeId string.” From the “typeId string,” the class name of the object may be obtained. Using the class name of the object, the application may call the object for instantiation.  
         [0037]      FIG. 5  is a flowchart of a process that may be used to implement the invention. The process starts when a JNDI lookup is performed (step  500 ). After the JNDI lookup has been initiated, the process waits for an object reference to the object to be returned (step  502 ). Once the object reference is returned, the IOR of the object is obtained (step  504 ) and decomposed to get to the typeId string (step  506 ). The typeId string is processed to obtain a particular class name of the object (step  508 ). The class is then called to instantiate the object (step  510 ) before the process ends (step  512 ).  
         [0038]     The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.