JAXB Overview

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JAXB Overview

• Vladimir Gapeyev

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XML data binding
Java
XML
ObjectFactory f new ObjectFactory() Book
b f.createBook() b.setTitle(Compilers) List
a b.getAuthor() a.add(Aho) a.add(Sethi)
a.add(Ullman) b.setPages(796)
ltbookgt lttitlegtCompilerslt/titlegt
ltauthorgtAholt/authorgt ltauthorgtSethilt/authorgt
ltauthorgtUllmanlt/authorgt ltpagesgt796lt/pagesgt lt/boo
kgt
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Schema-based XML data binding
compile
Schema
Classes
instance of
conforms
unmarshal
Objects
Documents
marshal
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JAXB Java Architecture for XML Binding

• Specification
• Subset of XML Schema
• Default bindings
• XML names ? Java names
• Schema atomic types ? predefined Java types
• Schema structured types ? Java interfaces
• javax.xml.bind framework interfaces
• Language for binding customization
• Reference implementation
• Schema-to-Java compliler
• Generates classes as well

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Mapping for atomic types
xsstring ? java.lang.string
xsdecimal ? java.math.BigDecimal
xsint ? int
xsQName ? javax.xml.namespace.QName
xsdate ? java.util.Calendar
Etc
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Elements with simple content
interface Zip extends javax.xml.bind.Element
int getValue() void setValue(int)
ltxselement namezip typexsint /gt
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Elements with sequence and repetition
ltxselement namebook gt ltxsComplexTypegt
ltxssequencegt ltxselement nametitle
typexsstring/gt ltxselement nameauthor
typexsstring maxOccursunbounded/gt
ltxselement namepages typexsint/gt
lt/xssequencegt lt/xsComplexTypegt lt/xselementgt
interface Book extends BookType,
javax.xml.bind.Element interface BookType
String getTitile() void setTitle(String x)
List getAuthor() int getPages() void
setPages(int x)
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Elements with choice
ltxscomplexType namevolumegt
ltxschoicegt ltxselement
refbook/gt ltxselement
refjournal/gt lt/xschoicegt lt/xscomplexTypegt
interface Volume BookType getBook() void
setBook(BookType) JournalType getJournal()
void setJournal(JournalType)
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Customization isSet() method
ltxsannotationgtltxsappinfogt ltjxbglobalBindings
generateIsSetMethodtrue"/gt lt/xsappinfogtlt/xsan
notationgt
ltxscomplexType namevolumegt
ltxschoicegt ltxselement
refbook/gt ltxselement
refjournal/gt lt/xschoicegt lt/xscomplexTypegt
interface Volume BookType getBook() void
setBook(BookType) boolean isSetBook()
JournalType getJournal() void
setJournal(JournalType) boolean
isSetJournal()
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No roundtripping
interface T getA() setA() getB()
setB()
type t (element a, element b) (element
b, element a)
Type t members lta/gtltb/gt and ltb/gtlta/gt
unmarshal marshal / identity unmarshal
marshal unmarshal unmarshal
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General content style
ltxscomplexType nametgt ltxschoice
maxOccursunboundedgt ltelement refbook/gt
ltelement refjournal/gt lt/xschoicegt lt/xscomple
xTypegt
interface T List getBookOrJournal()

• Plus a constraint
• The only list members are
• Book objects
• Journal objects

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Model groups, by default
ltxsgroup name"bookName"gt ltxssequencegt
ltxselement name"title" type"xsstring"/gt
ltxselement name"author"
type"xsstring/gt lt/xssequencegt lt/xsgroupgt ltx
scomplexType name"bookType"gt ltxssequencegt
ltxsgroup ref"bookName"/gt ltxselement
name"pages" type"xsint"/gt
lt/xssequencegt lt/xscomplexTypegt
interface BookType String getTitle() void
setTitle(String x) String getAuthor() void
setAuthor(String) int getPages() void
setPages(int x)
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Model groups, customized
ltxsgroup name"bookName"gt ltxssequencegt
ltxselement name"title" type"xsstring"/gt
ltxselement name"author"
type"xsstring/gt lt/xssequencegt lt/xsgroupgt ltx
scomplexType name"bookType"gt ltxssequencegt
ltxsgroup ref"bookName"/gt ltxselement
name"pages" type"xsint"/gt
lt/xssequencegt lt/xscomplexTypegt
interface BookName String getTitle() void
setTitle(String x) String getAuthor() void
setAuthor(String) interface BookType
BookName getBookName() void setBookName(BookNam
e) int getPages() void setPages(int x)
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Summary of observations

• Mapping often loses static typing information
  need to employ dynamic constraints
• Complex content models with choice are most
  problematic
• Alternative mapping styles
• No good declarative specifications for the
  mappings

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Opportunities

• Formal specification of mapping styles
• Formulate desired mapping properties
• Verify that the mapping styles enjoy the
  properties
• A toolkit for generating mapping compilers (as
  opposed to a single compiler)