|
|
CXXXV. SDO Functions
Service Data Objects (SDOs) enable PHP applications to work with
data from different sources (like a database query, an XML file,
and a spreadsheet) using a single interface.
Each different kind of data source requires a Data Access Service
(DAS) to provide access to the data in the data source.
In your PHP application, you use a DAS to create an SDO
instance that represents some data in the data source. You can then
set and get values in the SDO instance using the standard SDO
interface. Finally, you use a DAS to write the modified data back
to a data source, typically the same one.
See the
list of Data Access Services
for details on those
currently available. In addition to the provided DASs, SDO also
provides interfaces to enable others to be implemented
(see the section on SDO Data
Access Services Interface for more details).
This extension is derived from concepts taken from the
Service Data Objects specification.
It includes a version of the
Apache Tuscany SDO 2.0 for C++ project.
A Service Data Object instance is made up of a tree of data objects.
The tree is defined by containment relationships between the data
objects. For example, a Company data object might consist of a number
of Department data objects and therefore the Company would have
a containment relationship to the Departments.
An SDO may also have non-containment references between data objects in the
tree. For example, one Employee data object might reference another Employee to
identify a career mentor.
As well as data objects referencing each other, they can also have
primitive properties. For example, the Company data object might
have a property called "name" of type string, for holding the name
of the company (for example, "Acme").
Each of these properties of a data object - containment relationships,
non-containment references, or primitive properties - may be many-valued or
single-valued. In the above examples, Departments is many-valued and
the Company name is single-valued.
In PHP, each SDO data object is represented as a PHP object. The properties of the
data object can be accessed using either object syntax or associative array syntax.
We'll see some examples of this later.
The SDO extension requires PHP 5.1 or higher. It also requires the libxml2 library.
Normally libxml2 will already be installed, but if not, it can be downloaded from
http://www.xmlsoft.org/.
Unix systems You can download and install the latest stable release of all three SDO
components - the SDO core, the XML DAS and the Relational DAS - with the command:
This command will build the SDO and XML shared libraries as well as installing
the PHP files that make the Relational DAS.
If you want to use the latest beta version, then instead run:
The
pecl command automatically installs the SDO and SDO_DAS_XML
modules into your PHP extensions directory. To enable the SDO extensions you must add
the following lines to php.ini:
extension=sdo.so
extension=sdo_das_xml.so |
For more information about building PECL packages, consult the
PECL installation section of the manual.
Windows
The latest DLLs for the SDO core and the XML DAS can be
downloaded from
php_sdo.dll and
php_sdo_das_xml.dll respectively.
Note that currently the pecl4win site does not provide
these binaries at the current release level; you can only download the latest level.
The
pecl command automatically installs the SDO and SDO_DAS_XML
modules into your PHP extensions directory. To enable the SDO extensions you must add
the following lines to php.ini:
extension=php_sdo.dll
extension=php_sdo_das_xml.dll |
The Relational DAS can be downloaded and installed with the command:
The Relational DAS is written in PHP. You may need to update your
include_path in php.ini to point to
the directory that contains
sdo/DAS/Relational.
Building SDO on Linux This section describes how to build the SDO core and XML DAS on Linux. You would
only need to know how to do this if you wish to build a recent version that you have checked
out of CVS.
Change to the main extension directory:
cd < wherever your sdo code is >
Run phpize, which will set up the environment to
compile both SDO and the XML Data Access Service.
Next, run ./configure; make; make install.
Please note, you may need to login as root to install the extension.
Make sure that these modules are loaded by PHP, by adding
extension=sdo.so and
extension=sdo_das_xml.so to your
php.ini file in the same order.
The table below lists the currently provided SDO Data Access Services:
Implementation Limitations
The following are limitations in the current SDO implementation:
There is no support for multi-byte character sets.
This will be considered, depending on community requirements,
in the Unicode-enabled version of PHP.
See Unicode Functions.
SDO Limitations
The following SDO 2.0 concepts are not supported in the current
PHP implementation.
It is not necessarily the case that these will all be added over time.
Their inclusion will depend on community requirements.
Bi-directional relationships.
Type and property alias names.
Read-only properties.
The Helper classes defined in SDO 2.0 are not directly implemented.
However equivalent function is provided in a more natural way for PHP.
For example the function of CopyHelper::copy()
is provided by applying the PHP
clone keyword to a data object.
The examples below assume an SDO created with the schema
and instance information shown below, using the XML Data Access Service.
The instance document below describes a single company,
called 'MegaCorp', which contains a single department,
called 'Advanced Technologies'.
The Advanced Technologies department contains three employees.
The company employeeOfTheMonth is referencing the second employee,
'Jane Doe'.
<?xml version="1.0" encoding="UTF-8" ?>
<company xmlns="companyNS" name="MegaCorp"
employeeOfTheMonth="E0003">
<departments name="Advanced Technologies" location="NY" number="123">
<employees name="John Jones" SN="E0001"/>
<employees name="Jane Doe" SN="E0003"/>
<employees name="Al Smith" SN="E0004" manager="true"/>
</departments>
</company> |
The root element of the schema is a company. The company contains departments, and
each department contains employees. Each element has a number of attributes to store
things like name, serial number, and so on. Finally, the company also has an IDREF
attribute which identifies one of the employees as the 'employeeOfTheMonth'.
<xsd:schema
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:sdo="commonj.sdo"
xmlns:sdoxml="commonj.sdo/xml"
xmlns:company="companyNS"
targetNamespace="companyNS">
<xsd:element name="company" type="company:CompanyType"/>
<xsd:complexType name="CompanyType">
<xsd:sequence>
<xsd:element name="departments" type="company:DepartmentType"
maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute name="name" type="xsd:string"/>
<xsd:attribute name="employeeOfTheMonth" type="xsd:IDREF"
sdoxml:propertyType="company:EmployeeType"/>
</xsd:complexType>
<xsd:complexType name="DepartmentType">
<xsd:sequence>
<xsd:element name="employees" type="company:EmployeeType"
maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute name="name" type="xsd:string"/>
<xsd:attribute name="location" type="xsd:string"/>
<xsd:attribute name="number" type="xsd:int"/>
</xsd:complexType>
<xsd:complexType name="EmployeeType">
<xsd:attribute name="name" type="xsd:string"/>
<xsd:attribute name="SN" type="xsd:ID"/>
<xsd:attribute name="manager" type="xsd:boolean"/>
</xsd:complexType>
</xsd:schema> |
The XML Data Access Service maps the schema to an SDO. Attributes such as "name"
become primitive properties, the sequence of employees becomes a many-valued
containment relationship, and so on. Note that the containment relationships are
expressed as one complex type within another, whereas non-containment references are
expressed in terms of ID and IDREF, with a special
sdoxml:propertyType attribute specifying the type of the
non-containment reference.
The following examples assume
$company is the root of a tree of data objects created from the
schema and instance document shown above.
Example 1. Access via property name
Data object properties can be accessed using the object property
access syntax. The following sets the company name to 'Acme'.
<?php
$company->name = 'Acme';
?> |
|
Example 2. Access via property name as array index We can also access properties using associative array syntax. The simplest
form of this uses the property name as the array index. For example, the following sets
the company name and gets the employeeOfTheMonth.
<?php
$company['name'] = 'UltraCorp';
$eotm = $company['employeeOfTheMonth'];
?> |
|
Example 3. Data Object iteration
We can iterate over the properties of a data object using foreach.
The following iterates over the properties of the employee of the month.
<?php
$eotm = $company->employeeOfTheMonth;
foreach ($eotm as $name => $value) {
echo "$name: $value\n";
}
?> |
which will output:
The 'manager' property is not output, because it has not been set.
|
Example 4. Access many-valued property by name Many-valued data object properties can also be accessed using the object
property name syntax. The following gets the list of departments.
<?php
$departments = $company->departments;
?> |
|
Example 5. Many-valued element access
We can access individual elements of many-valued properties using array
syntax. The following accesses the first department in the company.
<?php
$ad_tech_dept = $company->departments[0];
?> |
|
Example 6. Many-valued property iteration
Many-valued properties can also be iterated over using
foreach. The following iterates over the company's departments.
<?php
foreach ($company->departments as $department) {
// ...
}
?> |
Each iteration will assign the next department in the
list to the variable $department.
|
Example 7. Chained property access We can chain property references on a single line.
The following sets and gets the name of the first department.
<?php
$company->departments[0]->name = 'Emerging Technologies';
$dept_name = $company->departments[0]->name;
?> |
Using the associative array syntax, this is equivalent to <?php
$company['departments'][0]['name'] = 'Emerging Technologies';
$dept_name = $company['departments'][0]['name'];
?> |
In either case, the dept_name variable is set to 'Emerging Technologies'.
|
Example 8. XPath navigation The associative array index can be an XPath-like expression. Valid
expressions are defined by an augmented sub-set of XPath.
Two forms of indexing into many-valued properties are supported.
The first is the standard XPath array syntax with the indexing
starting at one, the second is an SDO extension to XPath with an index
starting at zero. The standard syntax is:
<?php
$jane_doe = $company["departments[1]/employees[2]"];
?> |
and the SDO XPath extension syntax is: <?php
$jane_doe = $company["departments.0/employees.1"];
?> |
Both these examples get the second employee from the first department.
|
Example 9. XPath querying
We can use XPath to query and identify parts of a data object based
on instance data. The following retrieves the manager from the
'Advanced Technologies' department.
<?php
$ad_tech_mgr =
$company["departments[name='Advanced Technologies']/employees[manager=true]"];
?> |
|
Example 10. Creating child data objects
A data object can be a factory for its child data objects.
A child data object is automatically part of the data graph.
The following add a new employee to the 'Advanced Technologies'
department.
<?php
$ad_tech_dept = $company["departments[name='Advanced Technologies']"];
$new_hire = $ad_tech_dept->createDataObject('employees');
$new_hire->name = 'John Johnson';
$new_hire->SN = 'E0005';
$new_hire->manager = false;
?> |
|
Example 11. Unset a primitive property
We can use the isset() and
unset() functions to test and remove items
from the data object.
The following clears the name of the first department.
<?php
unset($company->departments[0]->name);
?> |
|
Example 12. Unset a data object
unset can also be used to remove a data object from the tree.
The following example shows John Jones leaving the company.
<?php
unset($company->departments[0]->employees[0]);
?> |
|
Example 13. Unset a referenced data object
The following removes the 'employeeOfTheMonth' from the company.
If this were a containment relationship then the
employee would be removed from the company
(probably not a good idea to sack your best employee each month!),
but since this is a non-containment reference,
the employee being referenced will remain in the
department in the company,
but will no longer be accessible via the employeeOfTheMonth property.
<?php
if (isset($company->employeeOfTheMonth)) {
unset($company->employeeOfTheMonth);
}
?> |
|
Example 14. Access via property index Data object properties can be accessed via their property index using array
syntax. The property index is the position at which the property's definition
appears in the model (in this case the xml schema). We can see from the schema listing
above that the company name attribute is the second company property (the SDO
interface makes no distinction between XML attributes and elements). The following
sets the company name to 'Acme', with the same result as
Access via property name
<?php
$company[1] = 'Acme';
?> |
Using the index directly in this way is likely to be fragile. Normally the
property name syntax should be preferred, but the property index may be required
in special cases.
|
Sequenced data objects are SDOs which can track property
ordering across the properties of a data object. They can also
contain unstructured text elements (text element which do not
belong to any of the SDO's properties). Sequenced data objects are
useful for working with XML documents which allow unstructured text (i.e.
mixed=true) or if the elements can be interleaved (
<A/><B/><A/>). This can occur for example when
the schema defines maxOccurs>1 on a
element which is a complexType with a choice order indicator.
The examples below assume an SDO created with the following schema
and instance information, using the XML Data Access Service.
The schema below describes the format of a letter. The letter can
optionally contain three properties; date, firstName, and lastName.
The schema states mixed="true" which means that
unstructured text can be interspersed between the three properties.
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:letter="http://letterSchema"
targetNamespace="http://letterSchema">
<xsd:element name="letters" type="letter:FormLetter"/>
<xsd:complexType name="FormLetter" mixed="true">
<xsd:sequence>
<xsd:element name="date" minOccurs="0" type="xsd:string"/>
<xsd:element name="firstName" minOccurs="0" type="xsd:string"/>
<xsd:element name="lastName" minOccurs="0" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:schema> |
The following is an instance letter document. It contains the
three letter properties; date, firstName and lastName, and has
unstructured text elements for the address and letter body.
<letter:letters xmlns:letter="http://letterSchema">
<date>March 1, 2005</date>
Mutual of Omaha
Wild Kingdom, USA
Dear
<firstName>Casy</firstName>
<lastName>Crocodile</lastName>
Please buy more shark repellent.
Your premium is past due.
</letter:letters> |
When loaded, the letter data object will have the sequence and
property indices shown in the table below:
To ensure sequence indices are maintained, sequenced data objects
should be manipulated through the SDO_Sequence interface.
This allows the data object's instance data to be manipulated
in terms of the sequence index as opposed to the property index
(shown in the table above).
The following examples assume the letter instance has been
loaded into a data object referenced by the variable
$letter.
Example 15. Getting the SDO_Sequence interface
We obtain a data object's sequence using the
getSequence()
method. The follow gets the
sequence for the letter data object.
<?php
$letter_seq = $letter->getSequence();
?> |
|
All subsequent examples assume that the
$letter_seq
variable has been assigned the sequence for the letter data object.
Example 16. Get/set sequence values
We can get and set individual values (including unstructured text)
using the sequence index.
The following sets the firstName to 'Snappy' and gets the last
sequence values (the unstructured text, 'Your premium is past due.').
<?php
$letter_seq[4] = 'Snappy';
$text = $letter_seq[count($letter_seq) - 1];
?> |
|
Example 17. Sequence iteration
We can iterate through the individual sequence values using foreach.
The following runs through the individual values in sequence order.
<?php
foreach ($letter->getSequence() as $value) {
// ...
}
?> |
|
Example 18. Sequence versus Data Object
Setting values through the data object interface may result in the
value not being part of the sequence. A value set through the data
object will only be accessible through the sequence if the property was
already part of the sequence. The following example sets the
lastName through the data object and gets it through the sequence.
This is fine because lastName already exists in the sequence. If
it had not previously been set, then lastName would be set to
'Smith', but would not be part of the sequence.
<?php
$letter[2] = 'Smith';
$last_name = $letter_seq[5];
?> |
|
Example 19. Adding to a sequence
We can add new values to a sequence using the
SDO_Sequence::insert()
method. The following examples assume that the 'firstName' and
'lastName' properties are initially unset.
<?php
// Append a firstName value to the sequence
// value: 'Smith'
// sequence index: NULL (append)
// propertyIdentifier: 1 (firtName property index)
$letter_seq->insert('Smith', NULL, 1);
// Append a lastName value to the sequence
// value: 'Jones'
// sequence index: NULL (append)
// propertyIdentifier: 'lastName' (lastName property name)
$letter_seq->insert('Jones', NULL, 'lastName');
// Append unstructured text
// value: 'Cancel Subscription.'
// sequence index: absent (append)
// propertyIdentifier: absent (unstructured text)
$letter_seq->insert('Cancel Subscription.');
// Insert new unstructured text. Subsequent sequence values
// are shifted up.
// value: 'Care of:'
// sequence index: 1 (insert as second element)
// propertyIdentifier: absent (unstructured text)
$letter_seq->insert('Care of:', 1);
?> |
|
Example 20. Removing from a sequence
We can use the isset() and
unset() functions to test and remove items
from the sequence (Note: unset() currently
leaves the values in the data object, but this behaviour is
likely to change to also remove the data from the data object).
A sequence behaves like a contiguous list; therefore, removing
items from the middle will shift entries at higher indices
down. The following example tests to see if the first sequence
element is set and unsets it if is.
<?php
if (isset($letter_seq[0])) {
unset($letter_seq[0]);
}
?> |
|
SDOs have a knowledge of the structure they have been created to
represent (the model). For example, a Company SDO created using
the Company XML schema above
would only be permitted to contain DepartmentType data objects
which in turn could only contain EmployeeType data objects.
Sometimes it is useful to be able to access this model information at
runtime. For example, this could be used to automatically generate
a user interface for populating a data object. The model information
is accessed using reflection.
Example 21. Reflecting on a Data Object
The following example shows how we can reflect on an empty Employee
data object.
<?php
// Create the employee data object (e.g. from an XML Data Access Service)
$employee = ...;
$reflection = new SDO_Model_ReflectionDataObject($employee);
print($reflection);
?> |
The above example will output: object(SDO_Model_ReflectionDataObject)#4 { - ROOT OBJECT - Type {
companyNS:EmployeeType[3] { commonj.sdo:String $name;
commonj.sdo:String $SN; commonj.sdo:Boolean $manager; } } |
Using print on the SDO_Model_ReflectionDataObject writes out the data
object's model. We can see from the output how the type
companyNS:EmployeeType has three properties and we can see the names
of the properties along with their types. Note, the primitive types
are listed as SDO types (e.g. commonj.sdo namespace, String type).
It is worth noting that this is the SDO model and when these are
surfaced to an application they can be treated as the PHP equivalent
types (e.g. string and boolean).
|
Example 22. Accessing the type information
We can query the type information of a data object using reflection.
The following example checks the type corresponds to a data object
rather than a primitive and then iterates through the properties of
the type, writing out the name of each property ($type and $property
are SDO_Model_Type and SDO_Model_Property objects, respectively).
<?php
// Create the employee data object (e.g. from an XML Data Access Service)
$employee = ...;
$reflection = new SDO_Model_ReflectionDataObject($employee);
$type = $reflection->getType();
if (! $type->isDataType()) {
foreach ($type->getProperties() as $property) {
print $property->getName() . "\n";
}
}
?> |
The above example will output: |
SDO consists of three sets of interfaces. The first set covers those
interfaces for use by typical SDO applications. These are identified
by the package prefix 'SDO_'. The second set is those used to reflect
on, and work with, the model of a data object. These are identified
by the package prefix 'SDO_Model_'. Finally, the third set are those
use by Data Access Service implementations and are identified by the
package prefix 'SDO_DAS_'. The majority of SDO users will not need to
use or understand the 'SDO_Model_' and 'SDO_DAS_' interfaces.
The main interface through which data objects are manipulated. In
addition to the methods below, SDO_DataObject extends the
ArrayAccess, SDO_PropertyAccess (defines __get() /
__set() methods for property access overloading),
Iterator, and Countable interfaces.
The interface through which sequenced data objects can be accessed
to preserve ordering across a data object's properties and
to allow unstructured text.
SDO_Sequence preserves contiguous indices and therefore inserting
or removing elements may shift other elements up or
down. In addition to the methods below, SDO_Sequence extends the
ArrayAccess, Iterator and Countable interface.
getProperty
- get the property for a given sequence index
move
- move an element from one property index to another
insert
- insert a new value into the sequence
The interface through which many-valued properties are manipulated.
In addition to the method defined below, SDO_List extends ArrayAccess,
Iterator and Countable. SDO_List preserves contiguous indices and
therefore inserting or removing elements may shift other elements
up or down.
The interface through which data objects can be created.
A Data Access Service is responsible for populating the model
(i.e. configuring the data factory with the type and structure
information for the data objects it can create.)
for the factory and can then optionally return an instance of,
or implement, the SDO_DataFactory interface.
An SDO_Exception is thrown when the caller's request cannot be completed.
The subclasses of SDO_Exception are:
SDO_PropertyNotSetException -
the property specified exists but has not been set or does not have a
default value
SDO_PropertyNotFoundException -
the property specified is not part of the data object's type
SDO_TypeNotFoundException -
the specified namespace URI or type name is unknown
SDO_InvalidConversionException -
conversion between the types of the assignment is not possible
SDO_IndexOutOfBoundsException -
the numeric index into a data object, sequence or list is not in the
valid range
SDO_UnsupportedOperationException -
the request cannot be completed because it is not allowed,
for example an attempt to set a read-only property.
One method is added to those inherited from the built in
Exception class:
The main interface used to reflect on a data object instance
to obtain its model type and property information.
It is designed to follow the reflection pattern introduced in PHP 5.
export
- get a string describing the data object.
getType
- get the SDO_Model_Type for the data object.
getInstanceProperties
- get the instance properties of the data object.
getContainmentProperty
- get the property which defines the containment relationship to the data object.
The interface through which a data object's type information can be
retrieved. This interface can be used to find out the type name and
namespace URI of the type, whether the type allow open content, and so
on.
The interface through which a data object's property information can
be retrieved. This interface can be used to find out the type of a
property, whether a property has a default value, whether the
property is contained or reference by its parent, its cardinality,
and so on.
getName
- get the name of the property.
getType
- get the type of the property.
isMany
- test to see if the property is many-valued.
isContainment
- test to see if the property describes a containment relationship.
getContainingType
- get the type which contains this property.
getDefault
- get the default value for a property.
The interface through which a Data Access Service can access
a data object's
SDO_DAS_ChangeSummary.
The change summary is used by the Data Access Service to check for
conflicts when applying changes back to a data source.
The interface through which the change history of a data
object is accessed. The change summary holds information for any
modifications on a data object which occurred since logging
was activated. In the case of deletions and modifications, the old
values are also held in the change summary.
If logging is no longer active
then the change summary only holds changes made up to the point when
logging was deactivated.
Reactivating logging clears the change summary.
This is useful when a set of changes have been written out by a
DAS and the data object is to be reused.
The interface through which the old value for a property is
accessed. A list of settings is returned by the change summary method
getOldValues()
.
getPropertyIndex
- get the property index for the changed property
getPropertyName
- get the property name for the changed property
getValue
- get the old value for the changed property
getListIndex
- get the list index for the old value if it was part of a
many-valued property
isSet
- test to see if the property was set prior to being modified
The interface for constructing the model for an SDO_DataObject.
The SDO_DAS_DataFactory is an abstract class providing a static
method which returns a concrete data factory implementation.
The implementation is used by Data Access Services to create an
SDO model from their model.
For example, a Relational Data Access Service might create and populate
an SDO_DAS_DataFactory model based on a schema for a relational
database.
The constants below are defined by this extension, and
will only be available when the extension has either
been compiled into PHP or dynamically loaded at runtime.
- SDO_DAS_ChangeSummary::NONE=0
(integer)
Represents a change type of 'none'.
- SDO_DAS_ChangeSummary::MODIFICATION=1
(integer)
Represents a change type of 'modification'.
- SDO_DAS_ChangeSummary::ADDITION=2
(integer)
Represents a change type of 'addition'.
- SDO_DAS_ChangeSummary::DELETION=3
(integer)
Represents a change type of 'deletion'.
|
|
|