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The SDO Java project is a subproject of the Apache Tuscany incubator project
is intended to provide a Java implementation of the SDO 2 specification.
The project's code base includes the following:
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Dynamic data object support
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Basic static code generation (generator patterns still subject to
change)
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Most Helper classes either partially or fully implemented
(XMLHelper, XSDHelper, DataFactory, CopyHelper, EqualityHelper)
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Minimal ChangeSummary support (only in DataGraph context)
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Limited example programs
The Tuscany wiki contains an area for raw thoughts and clarifications on SDO that
will eventually make it into well crafted documentation.
Build Environment
Setup
Tuscany Build
Environment Setup
SDO 2 is a subproject of the Tuscany project. If you check out and
build the whole Tuscany Java project, you will have also built the SDO 2
subproject. If you want to work with the SDO 2 project, without the rest
of Tuscany, skip to the next section.
To build the whole Tuscany project follow these instructions.
SDO Java Build
Environment Setup
There are two motivations for building SDO from source and two well tested approches to doing so.
You may be wanting to build a binary release distribution from source code. Alternatively you may be
wishing to establish a development environment in order to futher the development of the code. The two
tested approaches are either to use maven 2 commandline builds or to java source code create projects
in the Eclipse SDK.
If you simply want to create a source code distribution, then even if you are an Eclipse user
its best to just follow the instructions in the BUILDING.txt file at the top of the source code distribution
and run a maven command line build (since the route to establishing an Eclipse environment requires installing maven anyway).
Note that SDO for Java is distributed as two source code distributions. You'll need to
download
two archives, one for the SDO API, and one for the Tuscany implementation of that API.
If you want to work with the SDO projects alone, without the rest of
Tuscany, proceed with the following steps.
-
Set up your environment using the instructions for building the whole of Tuscany,
but only download and install Java 5, Maven and Svn
(note that only one file, Interface2JavaGenerator.java, has a Java 5
dependency, if you want to work with Java 1.4.2 then just delete this
file before building).
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Make sure 'mvn' and 'svn' commands are in your PATH environment
variable.
-
Check out the SDO open source projects from Apache.
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Run "mvn" under <local tuscany dir>/java directory to install
POM files from the root project to the local repository
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Build, or rebuild, the individual SDO projects
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sdo.spec project
Commands:
sdo.impl project
Commands:
sdo.tools project
Commands:
sdo.samples project
Commands:
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Notes:
-
You can all of the sdo.impl, sdo.tools and sdo.sample projects in one step by running
mvn in <local tuscany dir>/java/sdo.
-
If the mvn command completed successfully, you will see BUILD
SUCCESSFUL in the output and the results of compilation will be available in jar files created under
directories named "target" directly under the root directories of the projects. These jar files are also
installed into your local maven repository ($HOME/.m2/repository) and are available as inputs to later build
operations.
-
Maven fetches external resources required for a build process from the internet.
These resources are at times unavailable. It may be necessary to
run "mvn" again at a later time.
-
If you are taking time to reply to firewall prompts, this can cause
some requests to time out. Set up the firewall to permit the action
without prompting.
SDO Project
Structure
The SDO project is divided into five parts:
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sdo.spec contains the SDO (commonj) interfaces
defined and provided by the SDO 2 specification.
-
sdo.impl provides the runtime implementation of the
SDO interfaces.
-
sdo.tools contains import and generator tools.
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sdo.sample contains sample sdo code.
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sdo.plugin contains code to configure the way in which SDO is build by maven.
The main source code in each of these subprojects is located in the
directory src/main/java, and if applicable, test (example) classes are
located in src/test/java. The directory src/test/resources contains any
data files needed by the test programs.
sdo.spec
(
https://svn.apache.org/repos/asf/incubator/tuscany/java/spec/sdo-api)
This project contains the interfaces provided with the SDO 2
specification. It is essentially an unzipped copy of the SDO Java API
sources zip file available at
http://ftpna2.bea.com/pub/downloads/SDO_20_Source.zip, but with some
errata corrections and a Tuscany-specific implementation of class
HelperProvider.
The abstract class, HelperProvider, is used to obtain specific
default helpers and other implementation-specific objects used by the
Java implementation of SDO. In the Tuscany implementation of this class,
there are two ways to specify the implementation of the HelperProvider
class.
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Set a System Property named "commonj.sdo.impl.HelperProvider" equal
to the fully qualified class name of the implementation class (e.g.
"commonj.sdo.impl.HelperProvider=org.apache.tuscany.sdo.help.HelperProviderImpl").
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In your own jar file, create a text file called
"META-INF/services/commonj.sdo.impl.HelperProvider". In this text file,
specify the fully qualified custom HelperProvider implementation class
(e.g. org.apache.tuscany.sdo.help.HelperProviderImpl).
In the event that both 1 and 2 are specified, the System Property
will take precedence over the text file.
The Tuscany default helper provider implementation class is
org.apache.tuscany.sdo.helper.HelperProviderImpl (in the sdo.impl
project) and is registered using the second technique (services file),
as described in the following section.
sdo.impl
(
https://svn.apache.org/repos/asf/incubator/tuscany/java/sdo/impl)
The sdo.impl subproject contains a test package under src/test/java
(see the section below entitled Static
Code Generator for details) and the following implementation
packages under src/main/java:
package org.apache.tuscany.sdo
package org.apache.tuscany.sdo.helper
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This package contains implementations of the "helper" interfaces
defined in the commonj.sdo.helper package (in the sdo.spec project).
Each helper interface in commonj.sdo.helper has a corresponding
implementation class in this package. The name of each helper class is
the same as the corresponding interface, only with the suffix "Impl"
appended. For example class
org.apache.tuscany.sdo.helper.TypeHelperImpl implements the interface
commonj.sdo.TypeHelper.
The implementation class
org.apache.tuscany.sdo.helper.HelperProviderImpl is used to bootstrap
an implementation of the default INSTANCEs of the SDO helper (see class
commonj.sdo.impl.HelperProvider in sdo.spec). This implementation
creates instances of the other helper implementation classes in this
package and is registered using the services file
src/main/resources/META-INF/services/commonj.sdo.impl.HelperProvider.
package org.apache.tuscany.sdo.impl
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This package contains the majority of the SDO runtime implementation
code. This includes implementations of all of the commonj.sdo
interfaces (see sdo.spec), including several implementations of the
DataObject interface. The design and implementation of the most
important classes in this package are described below).
package org.apache.tuscany.sdo.util
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Contains some utility classes used by the implementation. One class,
SDOUtil, is particularly important. It provides some useful static
utility functions which are not included in the SDO specification
itself. Although these are not "standard" APIs, use of them is
recommended, as opposed to resorting to low-level
implementation-specific APIs. The intent of this class is to
encapsulate, in a relatively clean way, common functions that are
needed, and can potentially be proposed for addition to the
specification in a future version of SDO.
sdo.tools
This project will contain (command line) tools, such as SDO model
importers and generators (Java code, XML schema, etc.). Currently
however, there is only a single tool, a Java code generator implemented
in class org.apache.tuscany.sdo.generate.XSD2JavaGenerator. This
generator can be used to generate static SDO data objects and is
described in more detail in below.
The sdo.tools project also contains a test program and sample
generated model located in src/test/java and src/test/resources
respectively (see the tests
section below for more details).
Dependency Jars
The sdo.impl project requires the following EMF (Eclipse Modeling
Framework - www.eclipse.org/emf) runtime jars to build:
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emf-common-2.2.1-SNAPSHOT.jar - some common framework utility and
base classes
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emf-ecore-2.2.1-SNAPSHOT.jar - the EMF core runtime implementation
classes (the Ecore metamodel)
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emf-ecore-change-2.2.1-SNAPSHOT.jar - the EMF change recorder and
framework
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emf-ecore-xmi-2.2.1-SNAPSHOT.jar - EMF's default XML (and XMI)
serializer and loader
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xsd-2.2.1-SNAPSHOT.jar - the XML Schema model
The sdo.tools project also requires the EMF code generator framework
jars:
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emf-codegen-2.2.1-SNAPSHOT.jar - template-based codegen framework
(JET - Java Emitter Templates)
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emf-codegen-ecore-2.2.1-SNAPSHOT.jar - the EMF code generator
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emf-common-2.2.1-SNAPSHOT.jar - some common framework utility and
base classes
-
emf-ecore-2.2.1-SNAPSHOT.jar - the EMF core runtime implementation
classes (the Ecore metamodel)
-
emf-ecore-change-2.2.1-SNAPSHOT.jar - the EMF change recorder and
framework
-
emf-ecore-xmi-2.2.1-SNAPSHOT.jar - EMF's default XML (and XMI)
serializer and loader
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xsd-2.2.1-SNAPSHOT.jar - the XML Schema model
These are simply Maven-friendly versions of corresponding jar
files/plugins obtained from Eclipse. SNAPSHOT maps to an EMF weekly
integration build (for example, I200602160000). Note that if you are building
SDO for a released source code distribution then the dependency jars will not be
snapshot jars, but will instead themselves be released versions of the dependencies.
Runtime
Implementation
The primary SDO runtime implementation classes are located in the
package org.apache.tuscany.sdo.impl and consist of the following:
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DataObject implementation classes
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Implementation of the SDO metamodel interfaces: Type and Property
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ChangeSummary and DataGraph implementations
The implementation of the SDO runtime is based on and leverages the
EMF runtime model (i.e., EObject and the Ecore metamodel - refer to
documentation at www.eclipse.org/emf). It subclasses and specializes the
Ecore metamodel, and provides its own DataObject-tuned implementation(s)
of the EObject interface. The design is described in more detail in the
following sections.
DataObject
implementation classes
SDO provides several DataObject implementation classes as shown in
the following diagram:
Class DataObjectImpl is the most important. It provides a complete
base implementation of the SDO DataObject interface. It extends from the
EMF base class BasicEObjectImpl, which provides the "scaffolding" needed
to easily implement an EObject, but without allocating any storage
itself.
DataObjectImpl provides the DataObject implementation while
allocating only the minimum storage overhead needed to be a data object
(e.g., container pointer and feature, change recorder). It does not,
however, allocate any storage for the actual properties of the data
object. It instead requires subclasses for this purpose. For example,
statically generated SDOs (see the generator
section below) directly or indirectly extend from this class, providing
their own storage in generated instance variables.
The subclass, DynamicDataObjectImpl serves as a concrete
implementation class for dynamic data objects. It is the default
implementation class used when creating dynamic data objects using the
DataFactory.create() method, for example. DynamicDataObjectImpl provides
efficient data storage using a dynamically allocated settings array.
StoreDataObjectImpl and DynamicStoreDataObjectImpl provide a
delegating implementations for DataObjects that implement their own
storage management using a store (see EMF's EStore interface)
implementation class. StoreDataObjectImpl is used in conjuction with the
"-storePattern" generator option (see section 4), while
DynamicStoreDataObjectImpl, as its name implies, is used for dynamic
store-based instances.
Type and Property
implementation classes
The SDO implementation provides three implementations of the
interface Type, one for each of the following three kinds of types:
classes, simple data types, and enumerations.
-
class ClassImpl extends EClassImpl implements Type
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class DataTypeImpl extends EDataTypeImpl implements Type
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class EnumImpl extends EEnumImpl implements Type
For example, class org.apache.tuscany.sdo.impl.ClassImpl extends form
the corresponding Ecore class, EClassImpl, and mixes in the SDO
interface commonj.sdo.Type. All the Type methods are implemented by
calls to super.
With this approach, a data object's Type, returned from
DataObjectImpl.getType(), and its EClass, returned by
DataObjectImpl.eClass(), are the same underlying meta object. This
allows the SDO implementation to leverage any appropriate base
functionality without any performance overhead. The arrangement is shown
in the following diagram:
The implementation of the SDO Property interface follows a similar
pattern. Two implementation classes, subclasses of corresponding Ecore
classes, mix in the Property interface:
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class AttributeImpl extends EAttributeImpl implements Property
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class ReferenceImpl extends EReferenceImpl implements Property
As with the Type implementation classes, these classes call methods
on super to implement the mixed-in Property methods.
The following diagram illustrates the design:
As shown, the getProperties() method in ClassImpl (i.e., of the SDO
Type interface) returns a set of properties whose implementation classes
also implement EAttribute or EReference, and since ClassImpl, extends
EClassImpl (as shown in the previous diagram), these are in fact the
same objects as those returned by the EClass.getEAllStructuralFeatures()
method. The two metamodels are one and the same, making the
implementation of many of the SDO APIs trivial calls to the base class.
ChangeSummary and
DataGraph implementation classes
TBD.
Static Code
Generator
The SDO static code generator is a command line tool for generating
Java source code (static SDOs) for DataObjects defined in an XML Schema.
It is implemented by the class
org.apache.tuscany.sdo.generate.XSD2JavaGenerator in the sdo.tools
project. The generator is used as follows:
Usage arguments:
[ -targetDirectory <target-root-directory> ]
[ -javaPackage <base-package-name> ]
[ -prefix <prefix-string> ]
[ -sparsePattern | -storePattern ]
[ -noInterfaces ] [ -noContainment ] [ -noNotification ] [ -arrayAccessors ] [ -noUnsettable ] [-noEMF]
<xsd-file> | <wsdl-file>
For example:
java XSD2JavaGenerator somedir/somefile.xsd
Options:
-
-targetDirectory Generates the Java source code in
the specified directory. By default, the code is generated in the same
directory as the input xsd or wsdl file.
-javaPackage Overrides the Java package for the
generated classes. If not specified, a default package or one specified
with an sdoJava:package annotation on the <schema> element in the
xsd file (see SDO specification for details) is used for the java
package.
-prefix Specifies the prefix string to use for
naming the generated factory. For example "-prefix Foo" will result in
a factory interface with the name "FooFactory".
-sparsePattern For SDO metamodels that have classes
with many properties of which only a few are typically set at runtime,
this option can be used to produce a space-optimized implementation (at
the expense of speed).
-storePattern This option can be used to generate
static classes that work with a Store-based DataObject implementation.
It changes the generator pattern to generate accessors which delegate
to the reflective methods (as opposed to the other way around) and
changes the DataObject base class to
org.apache.tuscany.sdo.impl.StoreDataObjectImpl. Note that this option
generates classes that require a Store implementation to be provided
before they can be run.
-noInterfaces By default, each DataObject generates
both a Java interface and a corresponding implementation class. If an
SDO metamodel does not use multiple inheritance (which is always the
case for XML Schema derived models), then this option can be used to
eliminate the interface and to generate only an implementation class.
-noNotification This option eliminates all change
notification overhead in the generated classes. Changes to DataObjects
generated using this option cannot be recorded, and consequently the
classes cannot be used with an SDO ChangeSummary or DataGraph.
-noContainment Turns off container management for
containment properties. DataObject.getContainer() will always return
null for data objects generated with this option, even if a containment
reference is set. Setting a containment reference will also not
automatically remove the target object from its previous container, if
it had one, so it will need to be explicitly removed by the client. Use
of this option is only recommended for scenarios where this kind of
container movement/management is not necessary.
-arrayAccessors Generates Java array
getters/setters for multiplicity-many properties. Note that
this option is experimental prototype code and is not fully developed
With this option, the
set of "standard" JavaBean array accessor methods (e.g., Foo[]
getFoo(), Foo getFoo(int), int getFooLength(), setFoo(Foo[]), and void
setFoo(int, Foo)) are generated. The normal List-returning accessor is
renamed with the suffix "List" (e.g., List getFooList()). The array
returned by the generated method is not a copy, but instead a pointer
to the underlying storage array, so directly modifying it can have
undesirable consequences and should be avoided.
-noUnsettable By default, some XML constructs
result in SDO property implementations that maintain additional state
information to record when the property has been set to the "default
value", as opposed to being truly unset (see DataObject.isSet() and
DataObject.unset()). The SDO specification allows an implementation to
choose to provide this behavior or not. With this option, all generated
properties will not record their unset state. The generated isSet()
methods simply returns whether the current value is equal to the
property's "default value".
-noEMF By default, the generated java
implementation source files directly import the Eclipse EMF classes
which they depend upon. This can lead to a discrepancy in EMF library
level dependencies between the generated classes and the environment
into which they are deployed. The -noEmf option provides an early level
of function to avoid this situation. Classes generated using this
option access EMF function indirectly via inherited behaviour, thereby
allowing packaging of these generated classes into jar files which do
not directly depend on EMF.
This early implementation of this option is limited in the subset of
XML Schema it is known to handle, and is subject to change. The
generator is known to be able to deal with Complex content (including
content models which map to SDO Sequence), and Mixed content for
example .
<xsd:complexType mixed="true" name="Sequence">
<xsd:sequence>
<xsd:choice maxOccurs="unbounded" minOccurs="0">
<xsd:element name="a" type="xsd:string" />
<xsd:element name="b" type="xsd:int" />
</xsd:choice>
<xsd:element name="split" type="xsd:string" />
<xsd:choice maxOccurs="unbounded" minOccurs="0">
<xsd:element name="y" type="xsd:string" />
<xsd:element name="z" type="xsd:int" />
</xsd:choice>
</xsd:sequence>
</xsd:complexType>
Generator
Patterns
The DataObject interface generation pattern is as described in the
SDO specification (see Java Interface Specification section). The SDO
specification does not define a factory pattern for efficient
construction of static SDOs, which is however provided by the Tuscany
implementation. The generated SDO Factory interface conforms to the
following pattern:
public interface <prefix>Factory {
<Type1> create<Type1>();
<Type2> create<Type2>();
...
<prefix>Factory INSTANCE = <default_factory_impl>;
}
A generated factory corresponds to an SDO Type namespace uri (see
commonj.sdo.Type.getURI) with one create() method for each SDO Type in
the namespace. The <prefix> of the factory name is derived from
the uri. An instance of the factory is available using the INSTANCE
field in the interface.
Using the static factory, a DataObject might be created as follows:
Quote aQuote = StockFactory.INSTANCE.createQuote();
... // do something with aQuote
The generated implementation of each create() method simply
constructs an instance of the corresponding type like this:
public Quote createQuote() {
QuoteImpl quote = new QuoteImpl();
return quote;
}
In addition to these generated type-specific create<Type>()
methods, the generated factory implementation class also includes a
generated reflective create() method that, given an SDO Type,
efficiently dispatches to the correct type-specific create() method. The
reflective create() method is called by the implementation of the SDO
commonj.sdo.helper.DataFactory interface.
Test/Example
Programs
The SDO project does not include any proper sample programs at this
time (any volunteers?) but it does include a number of JUnit test cases,
some of which serve as good examples of how to use SDO APIs to perform
various tasks.
The following tests are particularly good SDO examples included in
the sdo.impl project:
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SimpleDynamicTestCase This program uses the SDO
XSDHelper.define() method to register a simple XML Schema based model
(simple.xsd). It then instantiates a DataObject instance (type Quote),
initializes several of its properties, and then serializes the instance
to an XML stream.
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MixedTypeTestCase This program shows how to uses
the Sequence API to create an XML instance which mixes arbitrary text
within the DataObject's XML structure. It uses the XML schema
complexType (MixedQuote) in mixed.xsd to define the SDO model.
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OpenTypeTestCase Uses an XML Schema complexType
with a wildcard (xsd:any) to illustrate how to work with and manipulate
an SDO open type. The type OpenQuote in open.xsd is used for this
example.
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SimpleCopyTestCase Uses the SDO CopyHelper to
create shallow and deep copies of the simple Quote model from
SimpleDynamicTest.
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SimpleEqualityTestCase Uses the SDO EqualityHelper
to perform deep and shallow equality checks.
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ChangeSummaryTestCase Creates a data graph with an
instance of type Quote (in simple.xsd) as the root object. It then
turns on change logging and makes a number of changes to the graph.
Finally, it turns off change logging and serializes the data graph.
-
XSDHelperTestCase This program shows how the
XSDHelper.define() method can be called multiple times with the same
schema. The second (and subsequent) call simply returns an empty list
since no new types are defined.
The following is in the sdo.tools project:
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SimpleStaticTestCase - This test performs the same
function as SimpleDynamicTestCase, above, only using a generated
version of the simple.xsd model. The generated model has been
pre-generated (with default options) in the directory src/test, but it
can be regenerated using the XSD2JavaGenerator, possibly with different
generator options (e.g., -noInterfaces or -sparsePattern), if desired.
-
StaticSequenceNoEmfTest This test exercises the
-noEMF generator option with a set of complex types, focussing on
Sequenced behaviour in the generated classes. The generated model has
been pre-generated (with options -noEMF -javaPackage
com.example.noemf.sequences) in the directory src/test, but it can be
regenerated using the XSD2JavaGenerator, possibly with different
generator options (e.g., -noInterfaces or -sparsePattern), if desired.
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