Java developers for the db4o Guide: Beyond Simple Object
Class: Junior
Ted Neward (ted@tedneward.com), Principal, Neward & Associates
July 9, 2007
So far, we have created and operated db4o Object seem relatively simple - in fact, even be a bit too simplistic. In this paper, enthusiastic in the Ted Neward db4o will go beyond these simple object, he will demonstrate simple structure of the object (the object invoked object) in the operation. In addition, he also expounded on the infinite recursive including, layering, as well as consistency, cited some topic.
For some time now, in the face of the db4o Java developers in the guide, I read a variety of Java objects using db4o storage methods, these methods do not rely on mapping file. Use the original object database which can be avoided is one of the advantages of object-relational mapping (perhaps this is not focused), but I have to object on the merits of this model is too simple, the vast majority of enterprises operating system requirements and the creation of a complex object, called structural object, this paper will discuss the structure of the object creation.
Basically, the structure of the object can be used as an object of other objects. Despite db4o allow for the implementation of all the structure of objects commonly used CRUD operations, but users have to endure a certain complexity. This article will explore some of the major complications (such as infinite recursion, layering behavior and cited consistency), then the article will explore in depth the structure of the more advanced object deal with the problem. As a supplement, I will also introduce detectors testing (exploration test): A less well known to test db4o API class libraries and the testing technology.
Java developers for the open source db4o Guide to db4o database was introduced, db4o can take full advantage of the current object-oriented languages, systems and concepts. Home visits db4o face, immediately download db4o. You need to use it to complete the examples given in this paper.
Think about, including the terrible implied. Although one can imagine how to avoid OODBMS is infinitely recursive scenes, the problem is more terror, it is envisaged that an object has on dozens of other, the use of thousands of objects, each object and invoke its own share of the other objects are cited. May wish to consider the model that children, parents and other scenarios. Just removed from the database would lead to a Person dating back to the source of all human beings. This means that transmit large amounts of objects on the network!
Fortunately, apart from the most primitive of OODBMS, almost all OODBMS have solved the problem, db4o is no exception.
"Java developers for the db4o Guide: For enquiries, update and consistency"), it will not the same object twice storage.
Retrieving structure of objects makes me shudder. To retrieve the object (whether by QBE or original enquiries) with large object reference, and each cited the object also has a large number of objects used, and so on. It's a bit like the worst Ponzi model, is not it?
original English text.
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Ted Neward Neward & Associates is the supervisor in charge of the Java,. NET, XML and other platforms advice, guidance, training and promotion. He now lives in Washington state near Seattle.
Tags: java object, Object