.net framework QR Code ISO/IEC18004 for .NET

14.3 Business logic and rule-based computing use none none printer toencode none with nonebarcode create in say Order.enter none for none Order(), on an object Order. The attribute values of this object are populated by the controller using data captured during the entry process.

Note that such an object may contain many nested OrderItem objects, i.e. it may represent many database records that need to be created.

What does enterOrder() do It could for example (i) verify whether the order has been completely entered, such as whether a customer-id has been entered, and whether each order item has a product-id and quantity; (ii) it may compute the total value of the order after adding shipping charges (which may depend on where the order is being shipped to); (iii) it would then prepare and submit all the required data manipulation (SQL) statements to the database as part of a single database transaction. In the process it would also take care to (iv) retrieve the order-id that may have been assigned by the database after inserting the ORDER record for this order, and ensure that this order-id value is also included in each inserted ORDER ITEM record so as to link it to the parent order. In addition, it may be necessary to enter records in other tables, such as an accounting transaction for the order.

This would usually be done by (v) calling methods on other objects (e.g. the OrderAccountingTransaction object).

Clearly similar logic is required when modifying an existing order. Similarly, while retrieving orders and their items against a search criterion, say all orders placed in the past ten days, (vi) complex or possibly multiple SELECT statements may need to be executed; for example retrieving orders and items together in a complex join or fetching orders rst and followed by related items for each order. (The method used will differ depending on whether one is using a traditional relational database, or a more objectoriented cloud database where, while there are no joins, traversing from an order to its items is fast and easy, as we have already seen in 10.

) We can now summarize the tasks a business logic method needs to handle as follows: Functions of business logic: (14.2). 1. Validations (e.g.

verifying whether the order is complete) 2. Computations (e.g.

computing a total) 3. Transaction Management (e.g.

accomplishing all required operations in the scope of a single database transaction) 4. Data Manipulation (e.g.

actually inserting the order and order item records) and Object Relational Mapping (e.g. ensuring that the order items have the correct order id).

c# barcode 128 function CUSTOM ENTERPRISE APPLICATIONS AND DEV 2.0 qr.encode c# 5. Calling othe r Business Logic Methods (e.g.

posting an accounting transaction) 6. Complex Search (e.g.

retrieving a set of orders and their related items) A number of design strategies and architecture frameworks attempt to ease the task of writing the large volume of business logic needed in a typical enterprise application. Object relational mapping (ORM) tools such as Hibernate4 attempt to provide an abstraction that allows users to program using operations on nested objects such as Order and leave the job of translating such operations into multiple SQL statements for the framework to handle. The EJB container of J2EE makes a similar attempt; it also handles transaction management to a certain extent.

Unfortunately all of these approaches are in one way or another lacking: For example, consider ensuring that orders and items are linked by the same foreign key value, which is set only when the order record is actually created in the database; even this simple task remains cumbersome using most ORM frameworks. Cloud databases, such as Google s Datastore, on the other hand, do better; one can link Order and OrderItem objects in memory before persisting them, and exactly the same references are persisted in the Datastore. In the next two sections we consider formally modeling business logic using primitive abstractions such as (1) (6) above.

Rule-based computing uses models based on formal logic, whereas business logic maps are an example of a more informal model loosely based on the MapReduce paradigm.. c# qr code creating library Develop delivery point barcode (dpbc) on .net
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