Patent Application
20050289212
Embodiments of the invention generally relate to the field of client/server systems and, more particularly, to a system and method for a non-transactional resource reference.
Conventional client/server systems may include the use of transactions in program operations. The operations may include both local transactions, in which a local object generally will control the operation, and global transactions, in which a global transaction manager may be needed.
In a server, a resource adapter object may be utilized for operations of an application with an external resource. The resource adapter may be associated with a transaction, with may be either a local transaction or a global transaction.
However, in conventional operations the resource adapter may not be capable of establishing or associating with a local transaction if a global transaction is in place. The application may not support nested transactions, in which a global transaction and one or more local transactions are in place concurrently at least in part. Instead, the application may only support flat transactions, in which a single transaction is in place, and such transaction is either completed or rolled back before another transaction is commenced. In the conventional operation, the resource adapter will be associated with the global transaction, if any, even if the resource adapter could otherwise operate without connection to the global transaction.
A system and method for a non-transactional resource reference are described.
Under a first embodiment of the invention, a method comprises establishing a program object, the program object containing information regarding creation of a connection between a computer application and a resource; and establishing a local transaction and associating the computer application with the local transaction, a global transaction being active at the time of association; the local transaction being uninvolved with the global transaction.
Under a second embodiment of the invention, a server system comprises an application server, the application server including an application; and an interface to an external resource, the server system to establish a connection between the application and the external resource; the connection to be associated with a local transaction, the local transaction to be concurrent at least in part with a global transaction.
Under a third embodiment of the invention, a server system comprises means for establishing a connection between an application and an external resource; means for establishing a local transaction; and means for associating the application with the local transaction, a global transaction being active at the time of association, the local transaction and global transaction operating concurrently at least in part.
Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements.
Embodiments of the invention are generally directed to a system and method for providing a non-transactional resource reference.
Under an embodiment of the invention, a program object carries information for tuning up an underlying resource system for a server system. Under embodiment of the invention, the object acts in a manner to provide that requested connections are not involved in an existing global transaction, if any. Under an embodiment of the invention, nested transactions may be implemented, with a nested transaction including a global transaction and one or more local transactions.
An embodiment of the invention may operate in a Java environment, such described in the Java 2 enterprise edition (J2EE) environment provided under the J2EE specification, J2EE (Java 2 Platform, Enterprise Edition), including version 1.4, Nov. 24, 2003. Under an embodiment of the invention, an application may include an Enterprise JavaBean (EJB) program object, including those described in the Enterprise JavaBeans specification, version 2.1, Nov. 12, 2003. Under an embodiment of the invention, connections for a server include those implemented in conformity with the J2EE Connector Architecture Specification (JCA), including version 1.5, Nov. 24, 2003. Under an embodiment of the invention, directory and naming functionality includes that made pursuant to the Java Naming and Directory Interface (JNDI), including version 1.2, Jul. 14, 1999.
Further, the Java Transaction API (JTA) (version 1.0.1B, Nov. 1, 2002) specifies certain local Java interfaces between a transaction manager and the parties involved in a distributed transaction system, such parties being the application, the resource manager, and the application server. The Java Transaction Service (version 1.0, Dec. 1, 1999) specifies a certain implementation of a transaction manager that supports the JTA at high-level and implements Java mapping of the Object Management Group (OMG) Object Transaction Service (OTS), current version 1.4, September 2003, at low-level.
Under an embodiment of the invention, a server system may provide for communications between multiple containers on a server and connectors to resource services, such as external enterprise information services (EIS). Under an embodiment of the invention, containers may include EJB (enterprise Java bean) and WEB containers. Under an embodiment of the invention, connectors include JDBC (Java Database Connectivity), JMS (Java message service) connectors, and JCA (Java connector architecture) services. The JDBC connector service provides for creation and deployment of JDBC adaptors. The JMS connector service provides for creation and deployment of adaptors to the JMS system. The JCA container service may provide for deploying arbitrary resource adaptors.
A transaction is generally an atomic work unit that modifies data. A transaction consists of one or more statements. After completion, all of the statements are either committed or rolled back. In the simplest case, when a commit method (indicating completion of the transaction) or a rollback method (indicating a failure of the transaction, and thus a reversal, or roll back, of all actions taken by the transaction) is called, the current transaction ends and another transaction may begin.
When a single connection to a database exists, a local program object, such as a resource manager for a connection to an EIS, may directly control the transaction and may be capable of calling commit or rollback methods for the connection. A transaction that operates in this manner is referred to as a local transaction.
In contrast, a global transaction, or distributed transaction, is a set of two or more related transactions that are managed in a coordinated manner. The transactions that constitute a distributed transaction may involve a single database or multiple databases, and may involve multiple locations. Each individual transaction of a distributed transaction is referred to as a transaction branch.
In operations for a global transaction, all database connections are registered with a global transaction service, such as a transaction manager, which controls the transaction. In a global transaction, an EJB will not make calls directly on a database connection. This is in contrast to a local transaction, in which the EJB will make calls directly on the database connection. The local transaction is limited in scope to a single EIS system, and the EIS resource manager may manage the transaction. A global transaction may span multiple resource managers and requires global control. In a global transaction, each resource manager acts to manage resources in conjunction with the transaction manager. A transaction manager is the element responsible for creation of a transaction and its context. To handle global transactions, a transaction manager may utilize a two-phase commit protocol (2PC) to manage a transaction that spans multiple resource managers (with multiple EISs), in which there is first a call to determine whether each resource manager is ready to commit and then a second call to either commit, if all resource managers are ready to commit, or a second call to roll back, if one or more resource managers are not ready to commit. A one-phase commit optimization may be utilized if only one resource manager is participating in a transaction.
Each global transaction is associated with one transaction object when a transaction is created. The transaction object can be used to enlist the transactional resources in use by the application, register for transaction synchronization callbacks, commit or rollback the transaction, and obtain the status of the transaction.
A resource adapter is responsible for opening or initializing a resource manager when the connection to the resource manager is established. The resource manager is then closed by the resource adapter as a result of destroying the transactional resource. The J2EE Connector Architecture defines a transaction management contract between an application server and a resource adapter and its underlying resource manager. The transaction management contract extends the connection management contract and provides support for management of both local and global transactions. The transaction management contract has two parts depending on the type of transaction, either a contract between a transaction manager and an EIS resource manager (in a global transaction) or a local transaction management contract.
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Embodiments of the invention may be utilized in various environments. For example,
In addition to the concepts of local and global transactions, there is also a question of concurrent operations of separate transactions. A flat transaction comprises a basic transaction, with the flat transaction being either completed or rolled back. In a J2EE environment, the flat transaction may be either a local transaction or a global transaction. In either case, at most either a single local transaction or a single global transaction is in place at any time.
In a nested transaction, operations may be more complex. In general, a nested transaction includes a high level transaction and lower level sub-transactions. In theory, each sub-transaction may comprise one or more flat transactions, one or more sub-transactions, or a combination of each. The transactions in a nested transaction operate concurrently at least in part. For example, an embodiment of the invention may include a nested transaction with a global transaction and one or more local transactions.
A nested transaction may provide advantages in operation. Multiple transactions are possible without association of each connection with a global transaction. By isolating a local transaction, the control of the transaction may then be local. The local transaction thus can be committed or rolled back as a separate entity, and not be required to be part of a roll back or commitment of a global transaction.
However, in general, an Enterprise JavaBean container supports flat transactions, but does not support nested transactions. For example, the EJB specification indicates that the architecture supports flat transactions, with enhancement required for nested transactions. In such environment, either a local transaction or a global transaction (which may comprise multiple co-managed transactions) is in place, but, if a global transaction is in place, a resource adapter will be required to be associated with the global transaction for operations during the pendency of the global transaction.
The XAResource (javax.transaction.xa.XAResource) interface is a Java mapping of the standard XA interface based on the X/Open CAE Specification (Distributed Transaction Processing: The XA Specification). The XAResource may define a contract between a resource manager and a transaction manager in a distributed transaction processing (DTP) environment. A resource adapter for a resource manager implements the XAResource to support association of a global transaction to a transaction resource. In this context, a global transaction is a unit of work performed by one or more resource managers in a distributed transaction processing system. The system relies on an external transaction manager, such as a transaction manager under the Java Transaction Service, to coordinate transactions.
Pursuant to the JTA, global transactions are associated with a transactional resource via the XAResource.start method and disassociated via the Xaresource.end method. XAResource does not support nested transactions, there being an error for the XAResource to be invoked on a connection that is currently associated with a different transaction. Under the JTA, if a resource adapter supports both local and global transactions and the same connection is used to perform both local and global transactions, any local transaction generally is required to committed or rolled back before starting a global transaction in the connection, and the global transaction is disassociated from the connection before a local transaction is started.
However, the operations of a resource adapter may not actually affect the operations of a global transaction. In such a situation, the operation of a nested transaction, involving a global transaction and one or more unrelated local transactions, may be practical. Under an embodiment of the invention, a resource adapter is not required to become part of a global transaction, if a global transaction exists. Under an embodiment of the invention, it is possible to manage a local transaction over a given connection independently from the global transaction that is place. The environment that is given the adapter by the server is used and the adapter manages the transaction separately from other transactions. Therefore, it is thus possible to start nested transactions that are comprised of one global transaction and one or more local transactions.
Under an embodiment of the invention, a reference object can be imported into a system using JNDI. The reference object carries specified information, which is used by a resource object factory and is used at lookup time for tuning up the underlying resource system. In general, a resource reference is an element in a deployment descriptor that identifies the component's coded name for the resource. Under an embodiment of the invention, it is possible to use a given adapter in a nested transaction by configuring and binding the resource reference or by looking up a currently bound non-transactional resource reference. Under an embodiment of the invention, taking such action will provide for a connection factory configured in the manner needed, a connection factory being an object that produces connection objects that enable a J2EE component to access a resource.
The JNDI contains four packages, one of which is the naming package javax.naming, containing classes and interfaces for accessing naming services. The reference class is object that exists outside of a directory. In general a reference may be used to provide JNDI clients that illusion that objects of arbitrary classes may be bound in naming or directory services that do not have native support for objects in the Java programming language. Under an embodiment of the invention, a reference is used for a non-transactional resource, the reference containing the properties for resource object factory allowing nested transactions. Specifically, an embodiment of the invention includes a reference for a non-transactional resource that will allow for the association of a resource adapter with a local transaction because there will be no requirement for associating with an existing global transaction.
After binding, the non-transactional resource reference can then be obtained and implemented.
The computer 805 further comprises a random access memory (RAM) or other dynamic storage as a main memory 825 to store information and instructions to be executed by the processor 815 through 820. The RAM or other main memory 825 also may be used for storing temporary variables or other intermediate information during execution of instructions by the processors 815 through 820.
A hard drive or other storage device 830 may be used by the computer 805 for storing information and instructions. The storage device 830 may include a magnetic disk or optical disc and its corresponding drive, flash memory or other nonvolatile memory, or other memory device. Such elements may be combined together or may be separate components. The computer 805 may include a read only memory (ROM) 835 or other static storage device for storing static information and instructions for the processors 815 through 820.
A keyboard or other input device 840 may be coupled to the bus 810 for communicating information or command selections to the processors 815 through 820. The input device 840 may include a keyboard, a keypad, a touch-screen and stylus, a voice-activated system, or other input device, or combinations of such devices. The computer may further include a mouse or other cursor control device 845, which may be a mouse, a trackball, or cursor direction keys to communicate direction information and command selections to the processors and to control cursor movement on a display device. The computer 805 may include a computer display device 850, such as a cathode ray tube (CRT), liquid crystal display (LCD), or other display technology, to display information to a user. In some environments, the display device may be a touch-screen that is also utilized as at least a part of an input device. In some environments, the computer display device 850 may be or may include an auditory device, such as a speaker for providing auditory information.
A communication device 850 may also be coupled to the bus 810. The communication device 850 may include a modem, a transceiver, a wireless modem, or other interface device. The computer 805 may be linked to a network or to other device using via an interface 855, which may include links to the Internet, a local area network, or another environment. The computer 805 may comprise a server that connects to multiple devices. In one embodiment the computer 805 comprises a Java compatible server that is connected to user devices and to external resources.
It should be appreciated that reference throughout this 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 one embodiment of the present invention. Therefore, it is emphasized and should be appreciated that two or more references to “an embodiment” or “one embodiment” or “an alternative embodiment” in various portions of this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the invention.
Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
