sdo 3.0 – enhancing the api blaise doughan team lead, oracle toplink oxm/sdo/jaxb team lead,...
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SDO 3.0 – Enhancing the APIBlaise DoughanTeam Lead, Oracle TopLink OXM/SDO/JAXBTeam Lead, Eclipse Persistence Services (EclipseLink) OXM/SDO/JAXB
Java EE – The Competing Technology
XML
DocumentRelational
DBObjectsOXM ORM
JAXB/JAX-WS JPA/EJB
Some vendors are providing extensions to the above specifications to better meet customer needs.
Data
DB
Java EE – The Companion Technology
Java EE
Objects JAXB
Java EE
ObjectsJAXBXML
JPA
SCA
Data
ObjectsSDO
SCA
Data
ObjectsSDO
Data
Graph
Object vs. DataObject
JAXB SDO
Primitive Types Supports all Java primitive types.
Supports some Java primitive types.
Portability Portable across all vendor implementations.
Interfaces are portable, and impl classes are not.
Serialization Easily serializable. Easily serializable only when using static INSTANCE helpers
Property Restrictions
Cannot have a property called “class” due to the Java language.
Cannot have an additional 8 properties due to the DataObject interface.
Bytecode Technologies
Easy to use with byte code manipulation technologies.
Difficult to use at least in a vendor neutral way.
Java SE 5 – DataObject get*/set* APIs
Proposed by Ron Barrack, SAP
We could take advantage of Java SE 5 to reduce the number of methods on the
DataObject interface.
get* (Could reduce 39 methods to 3 methods)• <T> T get(Class<T> targetClass, String path);• <T> T get(Class<T> targetClass, int propertyIndex);• <T> T get(Class<T> targetClass, Property property);
set* (Could reduce 39 methods to 3 methods)• <T> void set(Class<T> targetClass, String path, T value);• <T> void set(Class<T> targetClass, int propertyIndex, T value);• <T> void set(Class<T> targetClass, Property property, T value);
Java SE 5 – DataObject List APIs
Proposed by Ron Barrack, SAP
We could take advantage of Java SE 5 to enhance the List methods on the
DataObject interface.
getList• <T> List<T> getList(Class<T> elementClass, String path);• <T> List<T> getList(Class<T> elementClass, int propertyIndex);• <T> List<T> getList(Class<T> elementClass, Property property);
setList• <T> void setList(Class<T> targetClass, String path, List<T> value);• <T> void setList(Class<T> targetClass, int propertyIndex, List<T> value);• <T> void setList(Class<T> targetClass, Property property, List<T> value);
Performance – DataObject.get*(String)
get*(String path)
This API requires that the String be introspected in order to determine how to execute it.getFirstName() not comparable to get(“firstName”)
Performance – Containment (SDO-186)
Section 3.1.6
“Containment is managed. When a DataObject is set or added to a containment Property, it is removed from any previous containment Property. Containment cannot have cycles. If a set or add would produce a containment cycle, an exception is thrown.”
The above spec defined behaviour can be a big performance hit for deeply nested trees.
isSet – isMany == true
SDO Properties Have an “isSet” ConceptcustomerDO.get(“phone-numbers”); // aList.size() > 0
customerDO.isSet(“phone-numbers”); // return true
SDO Does Not Track an Explicit ClearcustomerDO.get(“phone-numbers”).clear();
customerDO.get(“phone-numbers”); // return empty list
customerDO.isSet(“phone-numbers”); // return false
Read Only Properties
Proposal
Change this to be a hint instead of it actually preventing an update of a property.
Sequence (SDO-274)
The add APIs are not consistent:• public void add(int index, Property property, Object value)• public boolean add(Property property, Object value)
Change to remove API:• public void remove(int index)
Change this method to be consistent with java.util.List and return the Object that was removed.
Eating our own Dog Food
Why aren’t we using SDO to implement SDO?
• DataGraph (commonj.sdo)• Type (commonj.sdo)• Property (commonj.sdo) • XMLDocument (commonj.sdo.helper) • XMLHelper (commonj.sdo.helper) load & save
• The load and save operations take an java.lang.Object parameter to represent options. Why isn’t this parameter a DataObject?
Type & Property as DataObject
SDO-252 – Clarify behavior when storing Type /
Property as a value in a DataObject• If you mark a Property as Type commonj.sdo.Type
can I store an implementation of commonj.sdo.Type on it and/or a DataObject of Type commonj.sdo.Type?
• If you can create a Data Objects for Type and Property should I be able to use the XML representation to populate TypeHelper?
Type & Property as DataObjectsThe Pain Points
• Conflicts between existing API• Property.getType()
• If the property represented a Customer’s first name, this method would probably return the Type commonj.sdo.Type.
• DataObject.getType()• As a DataObject Property would need to return the Type
commonj.sdo.Property.
• Type & Property are currently read-only. They would need to be read/write to work with TypeHelper.
Property – Namespace URIs (SDO-66)
Oracle Requirements:
1. Loading an XML Schema with no target namespace should result in registered global properties.
2. If no Types or Property objetcs are defined the user should be able to create a namespace qualified XML document.
Section 9.10 – XML without Schema
• The algorithm here necessitates a sequenced and open Type with no defined Properties to be used.
• Currently this Type is vendor specific, I propose we add a defined Type to the spec.
Unfinished Items
• Multiple Inheritance• No XML Representation• Cannot be serialized (due to above)
• Helper Context• Added late in SDO 2.1• No standard way to create them• Problems related to serialization
JAXB Runtime vs. SDO Runtime
JAXBContext• Fixed• No programmatic way to
generate XML Schema
Marshaller• Multiple marshal targets• Standard options
Unmarshaller• Multiple unmarshal sources• Standard options
XSDHelper & TypeHelper• Dynamic• Programmatic way to
generate XML Schema
XMLHelper• Limited marshal targets• No standard options
XMLHelper• Limited unmarshal sources• No standard options
Specifying Vendor Implementations
Currently in Java there can only be one SDO implementation
available in a VM.
From commonj.sdo.helper.impl:
public abstract class HelperProvider {
static HelperProvider INSTANCE = getHelperProviderImpl();
static HelperProvider getHelperProviderImpl() {
return (HelperProvider)
Class.forName("commonj.sdo.impl.HelperProviderImpl")
.newInstance();
}
…
}
Expected Behaviour (Example SDO-255)
In my opinion we are not consistent with our handling of error
conditions. In some circumstances we throw an exception, and
in other cases we try to continue. In many cases it is undefined.
Option #1 – Throw Exceptions
For example in the case where an undefined property is asked for throw an Exception.
Option #2 – Avoid Exceptions
If an undefined property is asked for assume the user meant to have a property by this name and create one automatically.
Standard Exceptions (SDO-105)
It is common for Java EE technologies to throw a common exception. Clearly identifying the layer that encountered the problem:• javax.xml.bind.JAXBException (JAXB)• javax.persistence.PersistenceException (JPA)
Many SDO runtime methods necessitate vendor specific
runtime exceptions, others mandate confusing Java SE
exceptions.• java.lang.ClassCastException• java.lang.UnsupportedOperationException