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|Creating
Custom Java Objects
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| Creating
Custom Java Objects |
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This is a
very brief description of how to customize zeroCode. You can
create your own custom objects that give better control over
run-time behavior. The basic idea is to create your own classes
that implement the DataPort-related interfaces. zeroCode enables
this by allowing each UDM tree node to have its own designated
DataPort.
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Let us start with
an e.g. to understand where the need for writing custom Java
objects is felt:
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A custom UDM named
company can have a vector node called Stock prices. The stock
prices may vary by date. If you want to list the stock prices
based on date and weather conditions, you may not have the
temperature value and the weather chart of a particular place
in your database. In this case you can write your own set
of Java objects with Dataports. These objects should be written
in such a way that they should go and link up with the database
of other resources which may have the required weather report.
These objects can capture the data and can list the stock
prices based on date and weather conditions.
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Company
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-----Stock price
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Date
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Price
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Weather
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Another example
where the usage of custom java objects takes place is displaying
the latest(current) news headlines in the site. A news media
site in India can give the instant news from anywhere in the
world by capturing the news from other resourceful sites of
the respective place throughout the world. Writing Java Objects
to perform the above function is more powerful.
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There are several of
Dataport interfaces:
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List of interfaces supported |
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If a node is allowed to retrieve data (i.e., it isn't
insert-only), then its data port must be a Java class that implements
the SingleValueDataSource interface if it is a non-vector node,
and the MultiValueDataSource interface if it is a vector node.
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If a node is allowed to store data, its data port must
implement the DataStore interface. |
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that the DbObjectStore class implements all of these interfaces,
and so it can be used as data port for any UDM tree node. |
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To get the machinery
to work correctly, every DataPort class must have a corresponding
DataPortDescriptor class (one that implements the DataPortDescriptor
interface). The latter class is used at design time, by the zDE, to determine the properties of the DataPort class.
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