1. Data Modeling II XML Schema & JAXB Marc Dumontier May 4, 2004
Lecture 2.1
(c) 2004 CGDN

2. Outline Introduction to XML Schema XML Schema components & structure
Marc Dumontier
May 4, 2004
Outline
Introduction to XML Schema
XML Schema components & structure
XML Schema datatypes
Representing and Modeling data
Introduction to Java Architecture for XML Binding (JAXB)
JAXB Architecture
Lecture 2.1
(c) 2004 CGDN

3. Marc Dumontier
May 4, 2004
DTDs and XML Schema
Document Type Definition (DTD): A DTD defines the elements that can appear in an XML document, the order in which they can appear, how they can be nested inside each other, and other basic details of XML document structure. DTDs are part of the original XML specification.
XML Schema: A schema can define all of the document structures that you can put in a DTD, and it can also define data types and more complicated rules than a DTD can. The W3C developed the XML Schema specification.
Lecture 2.1
(c) 2004 CGDN

4. XML Schema http://www.w3.org/XML/Schema
Marc Dumontier
May 4, 2004
XML Schema
XML Schemas are well-formed XML documents.
Can be parsed by XML parser
Can be referenced using XPath
XML Schemas share similar characteristics to classes in object oriented programming languages; and an XML document which conforms to that schema is said to be an ‘instance document’
XML Schema also has object oriented features such as inheritance, and type definitions.
Ideal for transitioning XML to programming languages.
Lecture 2.1
(c) 2004 CGDN

5. Marc Dumontier
May 4, 2004
XML Schema
Lecture 2.1
(c) 2004 CGDN

6. Outline Introduction to XML Schema XML Schema components & structure
Marc Dumontier
May 4, 2004
Outline
Introduction to XML Schema
XML Schema components & structure
XML Schema datatypes
Representing and Modeling data
Introduction to Java Architecture for XML Binding (JAXB)
JAXB Architecture
Lecture 2.1
(c) 2004 CGDN

7. Marc Dumontier
May 4, 2004
XML Schema - Structure
The <schema> element: The root element of an XML Schema.
Has many attributes to specify general information about the schema such as default values for attributes, and target namespace.
Customary to use ‘xs’ or ‘xsd’ as the namespace prefix in an XML Schema.
Components are the structures which outline the constraints placed on instance documents.
Lecture 2.1
(c) 2004 CGDN

8. XML Schema - Components
Marc Dumontier
May 4, 2004
XML Schema - Components
Primary Components
Simple type definitions
Complex type definitions
Element declarations
Attribute declarations
Secondary Components
Attribute group definitions
Identity-constraint definitions
Model group definitions
Notation declarations
Lecture 2.1
(c) 2004 CGDN

9. XML Schema - Components
Marc Dumontier
May 4, 2004
XML Schema - Components
Helper Components
Annotations
Model groups
Particles
Wildcards
Attribute uses
Lecture 2.1
(c) 2004 CGDN

10. XML Schema – Type Definitions
Marc Dumontier
May 4, 2004
XML Schema – Type Definitions
There are 2 types of type definitions: simple and complex.
They are used to define datatypes which may act as global type definitions or be applied to other components, such as element declarations and attribute declarations.
All types are derived from anyType.
Lecture 2.1
(c) 2004 CGDN

11. XML Schema – Simple Types
Marc Dumontier
May 4, 2004
XML Schema – Simple Types
A simple type is a restriction on a primitive type or another user-defined simple type.
Can be defined anywhere in the schema (named), or used anonymously within an element declaration.
Use the <simpleType> tag.
Lecture 2.1
(c) 2004 CGDN

12. XML Schema – Simple Types
Marc Dumontier
May 4, 2004
XML Schema – Simple Types
Lecture 2.1
(c) 2004 CGDN

13. XML Schema – Simple Types
Marc Dumontier
May 4, 2004
XML Schema – Simple Types
Lecture 2.1
(c) 2004 CGDN

14. XML Schema – Complex Types
Marc Dumontier
May 4, 2004
XML Schema – Complex Types
Complex types can be restrictions or extensions.
Can be a restriction on a complex type.
Can be a restriction on some other complex type.
Can be an extension of a simple type.
Can be an extension of another complex type.
Declared either globally or locally.
Lecture 2.1
(c) 2004 CGDN

15. XML Schema – Complex Types
Marc Dumontier
May 4, 2004
XML Schema – Complex Types
Lecture 2.1
(c) 2004 CGDN

16. Element Declarations Created with the <element> tag.
Marc Dumontier
May 4, 2004
Element Declarations
Created with the <element> tag.
Child elements can be <simpleType>, <complexType>, <simpleContent>, and <complexContent> to specify specify details about the content model for that element.
Can specify default or fixed values.
Can manage the relationship between related elements.
Lecture 2.1
(c) 2004 CGDN

17. Constraining Elements with Attributes
Marc Dumontier
May 4, 2004
Constraining Elements with Attributes
name – specify the name of the element.
default – specify a default value for the element.
fixed – forces the instance document to include information.
maxOccurs – Specifies how many times an element may appear in the document or content model. 0,1,…n or unbounded.
minOccurs – see above.
Lecture 2.1
(c) 2004 CGDN

18. Marc Dumontier
May 4, 2004
Content Models
Describes what content is allowable in an element. If the content consists of only text and no child elements, then the content is said to be simple. Otherwise, it is said to be complex or mixed.
The <element> tag can contain the following elements
<annotation>
<simpleType>
<complexType>
Lecture 2.1
(c) 2004 CGDN

19. Marc Dumontier
May 4, 2004
Content Models
XML Schema has built in datatypes such as integer, decimal, date, boolean, and string.
If element has no restrictions, use the built-in datatypes directly in the element tag.
Lecture 2.1
(c) 2004 CGDN

20. Marc Dumontier
May 4, 2004
Content Models
Lecture 2.1
(c) 2004 CGDN

21. Content Models - simpleType
Marc Dumontier
May 4, 2004
Content Models - simpleType
<simpleType> allows you to create simple content as well, in addition to adding restrictions (or constraints).
Lecture 2.1
(c) 2004 CGDN

22. Content Models - complexType
Marc Dumontier
May 4, 2004
Content Models - complexType
<complexType> is used to create content models which consist of element content or mixed content.
Valid children of this tag are
<simpleContent>
<complexContent>
<sequence>
<choice>
<all>
<group>
Lecture 2.1
(c) 2004 CGDN

23. Content Models - complexType
Marc Dumontier
May 4, 2004
Content Models - complexType
<simpleContent> is used to describe data with only text and no child elements.
It can be a restriction or extension.
Lecture 2.1
(c) 2004 CGDN

24. Content Models - complexType
Marc Dumontier
May 4, 2004
Content Models - complexType
<complexContent> can be used to represent either a complex content model, or a mixed one either as a restriction or an extension.
Lecture 2.1
(c) 2004 CGDN

25. Content Models - complexType
Marc Dumontier
May 4, 2004
Content Models - complexType
Lecture 2.1
(c) 2004 CGDN

26. Attribute Declarations
Marc Dumontier
May 4, 2004
Attribute Declarations
Attributes are declared with the <attribute> tag.
Can have global or local scope.
Can have a default or fixed value.
Attribute groups can be created using the <attributeGroup> tag.
Enumerations can be created using the <enumeration> tag as a restriction.
Lecture 2.1
(c) 2004 CGDN

27. Attribute Declarations
Marc Dumontier
May 4, 2004
Attribute Declarations
Lecture 2.1
(c) 2004 CGDN

28. Attribute Declarations
Marc Dumontier
May 4, 2004
Attribute Declarations
Lecture 2.1
(c) 2004 CGDN

29. Attribute Declarations
Marc Dumontier
May 4, 2004
Attribute Declarations
Lecture 2.1
(c) 2004 CGDN

30. Marc Dumontier
May 4, 2004
Model Groups
Particles: A list of the individual particles in the model group, such as elements.
Compositor: Maybe be all, choice, or sequence, which specify how that model group will be used.
Annotation: Comments or description about the model group.
Lecture 2.1
(c) 2004 CGDN

31. Model Groups - choice Marc Dumontier May 4, 2004 Lecture 2.1
(c) 2004 CGDN

32. Model Groups - sequence
Marc Dumontier
May 4, 2004
Model Groups - sequence
Lecture 2.1
(c) 2004 CGDN

33. Outline Introduction to XML Schema XML Schema components & structure
Marc Dumontier
May 4, 2004
Outline
Introduction to XML Schema
XML Schema components & structure
XML Schema datatypes
Representing and Modeling data
Introduction to Java Architecture for XML Binding (JAXB)
JAXB Architecture
Lecture 2.1
(c) 2004 CGDN

34. Datatypes Datatypes are essential to model data properly.
Marc Dumontier
May 4, 2004
Datatypes
Datatypes are essential to model data properly.
Datatypes are a mechanism for us to agree on the representation of the data in our data set.
XML Schema provides two type of datatypes: primitive and derived.
Lecture 2.1
(c) 2004 CGDN

35. Marc Dumontier
May 4, 2004
Lecture 2.1
(c) 2004 CGDN

36. Marc Dumontier
May 4, 2004
Primitive Datatypes
Primitive datatypes are those that are not defined in terms of other datatypes; they exist ab initio.
Derived datatypes are those that are defined in terms of other datatypes.
Lecture 2.1
(c) 2004 CGDN

37. Datatypes – Facets Constraining facets length minLength maxLength
Marc Dumontier
May 4, 2004
Datatypes – Facets
Constraining facets
length
minLength
maxLength
pattern
enumeration
whitespace
minInclusive/minExclusive
maxInclusive/maxExclusive
totalDigits/fractionDigits
Lecture 2.1
(c) 2004 CGDN

38. Marc Dumontier
May 4, 2004
Datatypes
Lecture 2.1
(c) 2004 CGDN

39. XML Schema Questions? Marc Dumontier May 4, 2004 Lecture 2.1
(c) 2004 CGDN

40. Outline Introduction to XML Schema XML Schema components & structure
Marc Dumontier
May 4, 2004
Outline
Introduction to XML Schema
XML Schema components & structure
XML Schema datatypes
Representing and Modeling data
Introduction to Java Architecture for XML Binding (JAXB)
JAXB Architecture
Lecture 2.1
(c) 2004 CGDN

41. Java Architecture for XML Binding (JAXB)
Marc Dumontier
May 4, 2004
Java Architecture for XML Binding (JAXB)
A framework for automating the process of mapping XML documents to java data objects.
Provides a compiler which takes in an XML Schema as input, and auto-generates the Java code for the data structures.
Provides a runtime library to unmarshal XML documents to Java representation, marshall the Java objects to XML, and validates the Java objects against the XML Schema.
Lecture 2.1
(c) 2004 CGDN

42. Marc Dumontier
May 4, 2004
Why use JAXB?
Simplifies using XML by generating objects specific to your model instead of working with SAX or DOM which is very general.
Provides a high level API for working with XML documents.
Allows customization.
Very useful for large data specifications. Eg. BIND has 2,200 individual fields which generated ~3000 classes.
Lecture 2.1
(c) 2004 CGDN

43. Marc Dumontier
May 4, 2004
Availability
The JAXB Reference Implementation was produced by SUN Microsystems.
Version 1.0
Part of the Java Web Services Developer Pack (JWSDP)
Lecture 2.1
(c) 2004 CGDN

44. Outline Introduction to XML Schema XML Schema components & structure
Marc Dumontier
May 4, 2004
Outline
Introduction to XML Schema
XML Schema components & structure
XML Schema datatypes
Representing and Modeling data
Introduction to Java Architecture for XML Binding (JAXB)
JAXB Architecture
Lecture 2.1
(c) 2004 CGDN

45. Marc Dumontier
May 4, 2004
JAXB Architecture
The binding compiler transforms a source schema to a set of content classes in Java.
The binding runtime framework provides the interfaces for the functionality of unmarshalling, marshalling and validation for content classes.
The binding language is an XML-based language that describes the binding of a source schema to a java representation.
Lecture 2.1
(c) 2004 CGDN

46. JAXB Architecture SOURCE: java.sun.com Marc Dumontier May 4, 2004
Lecture 2.1
(c) 2004 CGDN

47. Marc Dumontier
May 4, 2004
Binding Compiler
Binding a schema means generating a set of Java classes that represents the schema. All JAXB implementations provide a tool called a binding compiler to bind a schema (the way the binding compiler is invoked can be implementation-specific). For example, the JAXB Reference Implementation provides a binding compiler that you can invoke through scripts.
Lecture 2.1
(c) 2004 CGDN

48. Binding Compiler SOURCE: java.sun.com Marc Dumontier May 4, 2004
Lecture 2.1
(c) 2004 CGDN

49. Marc Dumontier
May 4, 2004
Java Representation
Set of interfaces which models the XML Schema hierarchy.
Like JavaBeans, uses get and set methods for properties
Implementation classes also generated.
Lecture 2.1
(c) 2004 CGDN

50. Binding Framework 3 primary operations
Marc Dumontier
May 4, 2004
Binding Framework
3 primary operations
Unmarshalling: Reading of the XML document and translation to tree of content objects.
Marshalling: inverse of unmarshalling; traversal of content tree and writing an XML document that reflects the tree’s content.
Validation: validating data in content tree against XML Schema.
Lecture 2.1
(c) 2004 CGDN

51. Binding Declarations Allows for the customization of the mapping.
Marc Dumontier
May 4, 2004
Binding Declarations
Allows for the customization of the mapping.
A set of binding declarations are writing in a binding language which itself is XML.
Each binding declaration can occur in the <appinfo> tag of a schema or the set can be aggregated in a separate file.
Binding declarations allow the developer to override the default binding rules
Lecture 2.1
(c) 2004 CGDN

52. Marc Dumontier
May 4, 2004
Types of validation
A type constraint imposes requirements upon the values that may be provided by constraint facets in simple type definitions.
A local structural constraint imposes requirements upon every instance of a given element. (eg. Required attributes have values)
A global structural constraint imposes requirements upon an entire document.
Lecture 2.1
(c) 2004 CGDN

53. Marc Dumontier
May 4, 2004
The Binding Framework
The API which provides access to unmarshalling, marshalling, and validation.
Root package is javax.xml.bind
The JAXBContext class is the entry point into the API. This class allows for the initialization of classes for a particular content tree.
Lecture 2.1
(c) 2004 CGDN

54. Marc Dumontier
May 4, 2004
JAXBContext
Lecture 2.1
(c) 2004 CGDN

55. General Validation Processing
Marc Dumontier
May 4, 2004
General Validation Processing
Unmarshal-time validation: Validation errors and warnings detected while unmarshalling an instance document.
On-demand validation: An application can validate it’s content tree against schema constraints at any time.
Fail-fast validation: An application gets notified about validation errors and warnings upon a modification to the content tree.
Lecture 2.1
(c) 2004 CGDN

56. Marc Dumontier
May 4, 2004
Validator
Lecture 2.1
(c) 2004 CGDN

57. Marc Dumontier
May 4, 2004
Unmarshaller
Lecture 2.1
(c) 2004 CGDN

58. Unmarshalling SOURCE: java.sun.com Marc Dumontier May 4, 2004
Lecture 2.1
(c) 2004 CGDN

59. Marc Dumontier
May 4, 2004
Marshaller
Lecture 2.1
(c) 2004 CGDN

60. Marshalling SOURCE: java.sun.com Marc Dumontier May 4, 2004
Lecture 2.1
(c) 2004 CGDN

61. Marc Dumontier
May 4, 2004
Default Bindings
Lecture 2.1
(c) 2004 CGDN

62. Marc Dumontier
May 4, 2004
Java Representation
A package containts an ObjectFactory class, a jaxb.properties files, a set of interfaces for each content model, a set of interfaces for each element declaration, and the implementation classes.
Lecture 2.1
(c) 2004 CGDN

63. Java Representation Marc Dumontier May 4, 2004 Lecture 2.1
(c) 2004 CGDN

64. Marc Dumontier
May 4, 2004
Lecture 2.1
(c) 2004 CGDN

65. Creating Content Trees
Marc Dumontier
May 4, 2004
Creating Content Trees
You don’t need an XML document as input
Static factory class (ObjectFactory) to instantiate implementations of interfaces.
Use mutator (get/set) methods to set content.
Lecture 2.1
(c) 2004 CGDN

66. Marc Dumontier
May 4, 2004
Not Covered
Details about default bindings such as lists (sequence) , and model groups.
Custom bindings
Lecture 2.1
(c) 2004 CGDN

67. Marc Dumontier
May 4, 2004
JAXB
Questions?
Lecture 2.1
(c) 2004 CGDN