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

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# Ensure that you have ANT correctly installed and configured.
 
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==Initializing the Types from XML Schema==
 
==Initializing the Types from XML Schema==

Revision as of 15:20, 19 September 2008

Overview

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

Setup

  1. Ensure that you have EclipseLink correctly installed and configured for your environment. Please see EclipseLink/Installing and Configuring EclipseLink for more information.
  2. Ensure that you have ANT correctly installed and configured.
  3. Unzip the Example ZIP file to a new directory.
  4. Edit the env.properties file in the root directory of the example and specify the path to your EclipseLink jlib directory:
...
# Edit eclipselink.jlib to point to your EclipseLink jlib directory
eclipselink.jlib=C:/EclipseLink-1.0/eclipselink/jlib
...

You can compile and run the Example at any time by typing ant from the Example 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.

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.

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 "sdo:ChangeSummaryType" on our root complex type:

<xs:complexType name="customer-type">
    <xs:sequence>
        ...
        <xs:element name="changeSummary" type="sdo:ChangeSummaryType" minOccurs="0"/>

    </xs:sequence>
</xs:complexType>

Before we start modifying our data, we must enable logging:

customerDO.getChangeSummary().beginLogging();

From this point on, any modifications to the DataObject will be captured in the Change Summary, until logging is deactivated:

customerDO.getChangeSummary().endLogging();

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:

DataObject addressDO = customerDO.getDataObject("contact-info").getDataObject("shipping-address");
addressDO.set("zip-code", "27601");

Adding a new PhoneNumber:

DataObject newPhoneNumberDO = DataFactory.INSTANCE.create("urn:customer-example", "phone-number");
newPhoneNumberDO.set("number-type", "home");
newPhoneNumberDO.set("value", "(613) 555-3333");
customerDO.getList("contact-info/phone-number").add(newPhoneNumberDO); 

Removing all "cell" PhoneNumbers:

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")) {
        phoneNumbersToRemove.add(phoneNumberDO);
    }
}
phoneNumbers.removeAll(phoneNumbersToRemove);

There are general accessors for properties, i.e., get() and set(), 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 documentation for DataObject.

Marshalling the DataObjects

The following code segment demonstrates how to marshal DataObjects wrapped in a commonj.sdo.helper.XMLDocument back to XML. In this example the stream we are saving to is System.out, so the XML text will be printed to the console.

XMLHelper.INSTANCE.save(xmlDocument, System.out, null);

Interpreting the Change Summary

When the document is saved to System.out, we can see the change summary information in the 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>
      </ns1:contact-info>
      <shipping-address sdo:ref="#/ns1:contact-info/shipping-address">
         <zip-code>12345</zip-code>
      </shipping-address>
   </changeSummary>
</ns1:customer>
  • 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.  In our example, we see a "shipping-address" element which references "#/ns1:contact-info/shipping-address" (the element that was modified), along with its old value, "12345".
  • DataObjects which are currently in the data graph, but were not present when logging was started are indicated in the change summary with a "create" 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 "create" attribute indicating that "#/ns1:contact-info/ns1:phone-number\[2\]" (the second phone number in the XML) is the newly created one.
  • DataObjects deleted during logging are flagged with the "delete" 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 "delete" attribute indicating that "#/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.

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