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Difference between revisions of "EclipseLink/UserGuide/SDO/Introduction to EclipseLink SDO (ELUG)"
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SDO <code>Type</code> acts similarly to a Class in Java, and provides much of the same metadata as the Java Reflection API provides for Java classes. | SDO <code>Type</code> acts similarly to a Class in Java, and provides much of the same metadata as the Java Reflection API provides for Java classes. | ||
− | In EclipseLink, a <code>Type<code> wraps an object-XML mapping (OXM) descriptor (see ...). | + | In EclipseLink, a <code>Type</code> wraps an object-XML mapping (OXM) descriptor (see ...). |
A <code>Type</code> can have supertypes, which corresponds to the EclipseLink concept of an inheritance policy (see ...). | A <code>Type</code> can have supertypes, which corresponds to the EclipseLink concept of an inheritance policy (see ...). | ||
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====What You May Need to Know About DataObject Types for Data Types==== | ====What You May Need to Know About DataObject Types for Data Types==== | ||
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===Using Property=== | ===Using Property=== |
Revision as of 11:17, 23 April 2009
Information pending
This section introduces EclipseLink implementation of Service Data Objects (SDO) specification, as well as provides information on how you can use it in your application development.
Contents
Using SDO Metadata
SDO metadata is represented as Type
and Property
objects. You define the metadata at run time either programmatically, or from an XML schema.
Using Type
SDO Type
acts similarly to a Class in Java, and provides much of the same metadata as the Java Reflection API provides for Java classes.
In EclipseLink, a Type
wraps an object-XML mapping (OXM) descriptor (see ...).
A Type
can have supertypes, which corresponds to the EclipseLink concept of an inheritance policy (see ...).
For more information, see Type API.
What You May Need to Know About Open Sequenced Type
...
What You May Need to Know About DataObject Types for Data Types
...
Using Property
SDO Property
acts similarly to a property in Java and provides much of the same metadata as the Java Reflection API provides for Java fields or methods.
In EclipseLink, a Property
wraps an object-XML mapping (see ...) in the following way:
- DataType=true + isMany=false (see OXM Direct Mapping (or an OXM Binary Mapping))
- DataType=true + isMany=true (see OXM Direct Collection Mapping (or an OXM Binary Collection Mapping))
- DataType=false + isMany=false + containment=true (see OXM Composite Object Mapping)
- DataType=false + isMany=true + containment=true (see OXM Composite Collection Mapping)
- DataType=false + isMany=false + containment=false (see OXM Reference Mapping)
- DataType=false + isMany=true + containment=false (see OXM Collection Reference Mapping)
For more information, see Property API.
Defining Metadata
You can use the following EclipseLink helper classes to define SDO metadata (information pending: document how the underlying EclipseLink metadata can be accessed and modified).
How to Define Metadata with EclipseLink XSDHelper
You use the XSDHelper
to do the following:
- Define SDO metadata, where SDO metadata is derived from XML schemas.
- Generate XML schemas from SDO types.
You can customize metadata using the following annotations that you apply to the XML schema:
- Standard annotations (information pending: list them).
- EclipseLink annotations.
You can also use various APIs to determine the XML representation about the SDO metadata.
How to Define Metadata with EclipseLink TypeHelper
You use the TypeHelper
to do the following:
- Look up SDO metadata.
- Programmatically define SDO metadata (note that this is not the typical usage for the
TypeHelper
).
Using Data
...
Using DataObject (see 17.2.6 “Mapping converters and transformers” in JITDG/ELUG)
DataObject
in SDO corresponds to a Java Object (POJO).
To define object-XML mappings, you map the DataObject
to XML.
You can create your DataObject
as either dynamic (see Dynamic DataObject Examples), or static by applying a type-safe interface to it (see Static DataObject Examples).
The DataObject
provides an XPath-like (see ...) means of data access. For example, the following code is valid in SDO:
customerDO.getDataObject("contact-info/phone-number[2]");
The standard JAXB, however, would require the following:
customer.getContactInfo().getPhoneNumbers().get(1);
For more information, see DataObject API
What You May Need to Know About Serialization in SDO (see 17.2.6.1 in JITDG/ELUG)
SDO has its own Java serialization format.
Using XMLDocument
When you marshall (save) to, or unmarshall (load from) XML a DataObject
, the XMLDocument
class contains information about the root of the XML document.
What You May Need to Know About Sequence, ChangeSummary, and DataGraph
The following SDO classes... :(information pending)
-
Sequence
-
ChangeSummary
-
DataGraph
-- essentially deprecated.