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The establishment of object-oriented database

Print View , by: iSee ,Total views: 4 ,Word Count: 1205 ,Date: Sat, 18 Apr 2009 Time: 9:36 PM

In <envisaged the use of xml and relational database objects into a database> of a text has been elaborated on the relationship between database and object-oriented database of the main differences: the use of foreign keys is recorded through a direct or sub-table foreign key traversal to obtain. And here is another important difference between the face: how to target the release of resources. For object-oriented database, it was the same as directly stored in the database of the serial object, which forms the actual storage in the end is not in accordance with the relationship between the structure of storage is not the most important, it is important to call the program is read into memory an object, rather than the cursor mapping; this way, the use of object-oriented database must exist on an object how to clear the run out of resources; at the same time as a result of object-oriented database language has nothing to do with the inevitable, and therefore it is bound to target the release process can only be made by calling to complete.

XML can be seen as a serialization in the different languages and platforms to exchange the object structure, it actually needs the same: If it is not a simple xml to HTML as the presentation layer as the style, but object stored in the form, then read into the xml object are bound to exist after they set and maintain focus on the issue, and to make the process efficient, it must be completed by the process container, and not by the bean to maintain. Otherwise, the procedure to reduce the amount of the provision of software quality has been out of the question. Containers through the program have shared the next thread, the use of the object is no longer empty, empty out the resources. In fact, j2ee container entity Bean is such a container, but it is through the form of OR mapping, I hope the database reflects the complexity of the relationship between the target entities. Object-oriented database can be simplified to make such mapping table is basically the form of a single, J2EE, as if it to some extent, the maintenance of the same memory object, the most important thing is to empty the memory footprint, you can achieve better than the effect of entity Bean.

J2EE entity bean is basically flat object relationship does not exist between the entity bean bag into the relationship between each other, to which it can not be easily reflected in the practical application of the relations. The use of the reality, closer to the target structure is a tree-like relations of succession. In this structure, there is no need for all the objects to deal with it by the removal of containers. In other words, do not require removal of all objects, the higher target object itself is the lower container, only the need for higher level (top) to remove the object can be achieved, for java is, JVM garbage processor will not top the class call removed a whole.

The combination of XML and object database systems, called the process of object is: top-level container object initialization -> initialize handle sub-object -> need to call the sub-object in the details of this fully loaded Object -> (removal of sub-object) -> do not need to use in the removal of the remaining top-level object and all sub-objects.

Another task of the container is to maintain records and handle the relationship between the actual data structure. In the above-mentioned process, as detailed on the database content, the higher the lower the target to retain only the handle. This calendar, which was equivalent to a structured data record of non-standardized. From this point of view, when the inconsistency of conflict, certainly in the relational database should be based on the record. More satisfactory way is to achieve a number of container object management interface, the container is responsible for maintaining the same object. Here, the object corresponding to the middle layer is the database of the serial memory-mapped object. Therefore, we really want to make XML + relational database structure to form the object must have the efficiency of operation, there must be reasonable and efficient management of container, the completion of a high concentration of the target to repeat the same maintenance work, and the upper application can focus on application specific logic.

To sum up, the use of object-oriented database paradigm of the process, then the need for such a container: it can auto-complete memory of the clean-up targets; to auto-complete consistency with the database operation. In addition, the form of the object class is similar to the procedure, you can provide some automated tools to complete most of the coding, or to enhance the abstract class can inherit the completion of repetitive maintenance methods are basically the same. How to implement specific, general and how high will the changes in 11 SectionBase to be addressed. At present, the first code to the form of BMP, it is estimated that upon completion, we can further the common way to abstract out.

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