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Difference between revisions of "EclipseLink/Examples/SDO/DynamicAPI"

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The following example will demonstrate how to use EclipseLink's SDO functionality to:
* Define a set of SDO Types from an XML Schema
* Load an XML file and modify its data
* Monitor changes made to the data
* Save the modified data to XML
# Ensure that you have EclipseLink correctly installed and configured for your environment.  Please see [[EclipseLink/Installing and Configuring EclipseLink]] for more information.
# Ensure that you have ANT correctly installed and configured.
# Unzip the Example ZIP file to a new directory.
# Edit the <tt>env.properties</tt> file in the root directory of the example and specify the path to your EclipseLink <tt>jlib</tt> directory:
<source lang="ini">
# Edit eclipselink.jlib to point to your EclipseLink jlib directory
You can compile and run the Example at any time by typing <tt>ant</tt> from the Example directory. 
For Eclipse IDE users, a <tt>.project</tt> file is included in the Example directory.  To setup this project in Eclipse:
# From the "File" menu, choose "Import..."
# In the Import dialog, choose "General > Existing Projects into Workspace", and click "Next".
# Click "Browse" to select a root directory, and point to the folder containing this example.  After selecting the directory, you should see the project name in the "Projects" list.  Click "Finish".
This project is configured to use a classpath variable, <tt>ECLIPSELINK_JLIB</tt>, to point to the required JAR files.  After the project is imported, you should define a variable called <tt>ECLIPSELINK_JLIB</tt> to point to your EclipseLink <tt>jlib</tt> directory.
==Initializing the Types from XML Schema==
The first thing that needs to be done in an SDO application is to set up the metadata for the Types and Properties. This is most commonly done by loading an XML schema, although it may also be done programmatically.
<source lang="java">
FileInputStream xsdInputStream = new FileInputStream("Customer.xsd");
XSDHelper.INSTANCE.define(xsdInputStream, null);
==Unmarshalling the XML Document==
With the SDO Types and Properties defined from the schema, we can now load an XML document based on that schema, and then obtain a DataObject and begin modifying its contents.
<source lang="java">
FileInputStream xmlInputStream = new FileInputStream("Customer-data.xml");
XMLDocument xmlDocument = XMLHelper.INSTANCE.load(xmlInputStream);
DataObject customerDO = xmlDocument.getRootObject();
==Tracking Object Modifications using Change Summary==
SDO's Change Summary provides access to change history information for the DataObjects in a data graph.  A change history covers any modifications that have been made to a data graph starting from the point when logging was activated.
In order to use Change Summary, we have defined an element of type "<tt>sdo:ChangeSummaryType</tt>" on our root complex type:
<source lang="xml">
<xs:complexType name="customer-type">
        <xs:element name="changeSummary" type="sdo:ChangeSummaryType" minOccurs="0"/>
Before we start modifying our data, we must enable logging:
<source lang="java">
From this point on, any modifications to the DataObject will be captured in the Change Summary, until logging is deactivated:
<source lang="java">
==Modifying the DataObjects==
Below are examples of manipulating the DataObjects using the dynamic APIs.  Note how the dynamic accessors take an XPath instead of just a property name.
Modifying the ShippingAddress ZipCode:
<source lang="java">
DataObject addressDO = customerDO.getDataObject("contact-info").getDataObject("shipping-address");
addressDO.set("zip-code", "27601");
Adding a new PhoneNumber:
<source lang="java">
DataObject newPhoneNumberDO = DataFactory.INSTANCE.create("urn:customer-example", "phone-number");
newPhoneNumberDO.set("number-type", "home");
newPhoneNumberDO.set("value", "(613) 555-3333");
Removing all "cell" PhoneNumbers:
<source lang="java">
ArrayList phoneNumbersToRemove = new ArrayList();
List phoneNumbers = customerDO.getDataObject("contact-info").getList("phone-number");
Iterator it = phoneNumbers.iterator();
while (it.hasNext()) {
    DataObject phoneNumberDO = (DataObject) it.next();
    if (phoneNumberDO.get("number-type").equals("cell")) {
There are general accessors for properties, i.e., <tt>get()</tt> and <tt>set()</tt>, as well as specific accessors for the primitive types and commonly used data types like String, Date, List, BigInteger, and BigDecimal.  For more information see the [http://help.eclipse.org/help32/topic/org.eclipse.emf.ecore.sdo.doc/references/javadoc/commonj/sdo/DataObject.html documentation for DataObject].
==Marshalling the DataObjects==
The following code segment demonstrates how to marshal DataObjects wrapped in a <tt>commonj.sdo.helper.XMLDocument</tt> back to XML.  In this example the stream we are saving to is <tt>System.out</tt>, so the XML text will be printed to the console.
<source lang="java">
XMLHelper.INSTANCE.save(xmlDocument, System.out, null);
==Interpreting the Change Summary==
When the document is saved to <tt>System.out</tt>, we can see the change summary information in the XML:
<source lang="xml">
<ns1:customer ...>
  <changeSummary logging="false" create="#/ns1:contact-info/ns1:phone-number[2]"
      delete="#/changeSummary/ns1:contact-info/ns1:phone-number[2]" xmlns:sdo="commonj.sdo">
      <ns1:contact-info sdo:ref="#/ns1:contact-info">
        <ns1:phone-number sdo:ref="#/ns1:contact-info/ns1:phone-number[1]"/>
        <ns1:phone-number number-type="cell">(613) 555-2222</ns1:phone-number>
      <shipping-address sdo:ref="#/ns1:contact-info/shipping-address">
* For DataObjects with modified data type properties, the Change Summary element contains a copy of the DataObject from the data graph, but containing only the properties which have changed, and showing their old values.&nbsp; In our example, we see a "<tt>shipping-address</tt>" element which references "<tt>#/ns1:contact-info/shipping-address</tt>" (the element that was modified), along with its old value, "<tt>12345</tt>".
* DataObjects which are currently in the data graph, but were not present when logging was started are indicated in the change summary with a "<tt>create</tt>" attribute.  If more than one DataObject had been created, the attribute would contain a space-separated list of references, one for each DataObject.  In our example, we see a "<tt>create</tt>" attribute indicating that "<tt>#/ns1:contact-info/ns1:phone-number\[2\]</tt>" (the second phone number in the XML) is the newly created one.
* DataObjects deleted during logging are flagged with the "<tt>delete</tt>" attribute. In this case the change summary also contains a deep copy of the object which was deleted, as it no longer appears in the data graph.  Here, we see a "<tt>delete</tt>" attribute indicating that "<tt>#/changeSummary/ns1:contact-info/ns1:phone-number\[2\]</tt>" (the second phone number in the ''Change Summary'') is the one that was deleted from the XML.
Download the "Examples Zip" from the EclipseLink [http://www.eclipse.org/eclipselink/downloads/ Downloads] page.  Code for this example will be found in the <tt>org.eclipse.persistence.example.sdo.dynamicapi.zip</tt> file.

Revision as of 16:28, 24 February 2009