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JAXB Overview

JAXB Overview. Vladimir Gapeyev. 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);. <book>

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JAXB Overview

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  1. JAXB Overview Vladimir Gapeyev

  2. 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); <book> <title>Compilers</title> <author>Aho</author> <author>Sethi</author> <author>Ullman</author> <pages>796</pages> </book> JAXB Overview

  3. Schema-based XML data binding compile Schema Classes instance of conforms unmarshal Objects Documents marshal JAXB Overview

  4. 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 JAXB Overview

  5. Mapping for atomic types Etc… JAXB Overview

  6. Elements with simple content interface Zip extends javax.xml.bind.Element { int getValue(); void setValue(int); } <xs:element name=“zip” type=“xs:int” /> JAXB Overview

  7. Elements with sequence and repetition <xs:element name=“book” > <xs:ComplexType> <xs:sequence> <xs:element name=“title” type=“xs:string”/> <xs:element name=“author” type=“xs:string” maxOccurs=“unbounded”/> <xs:element name=“pages” type=“xs:int”/> </xs:sequence> </xs:ComplexType> </xs:element> interface Book extends BookType, javax.xml.bind.Element {} interface BookType { String getTitile(); void setTitle(String x); List getAuthor(); int getPages(); void setPages(int x); } JAXB Overview

  8. Elements with choice <xs:complexType name=“volume”> <xs:choice> <xs:element ref=“book”/> <xs:element ref=“journal”/> </xs:choice> </xs:complexType> interface Volume { BookType getBook(); void setBook(BookType); JournalType getJournal(); void setJournal(JournalType); } JAXB Overview

  9. Customization: isSet() method <xs:annotation><xs:appinfo> <jxb:globalBindings generateIsSetMethod=“true"/> </xs:appinfo></xs:annotation> <xs:complexType name=“volume”> <xs:choice> <xs:element ref=“book”/> <xs:element ref=“journal”/> </xs:choice> </xs:complexType> interface Volume { BookType getBook(); void setBook(BookType); boolean isSetBook(); JournalType getJournal(); void setJournal(JournalType); boolean isSetJournal(); } JAXB Overview

  10. No roundtripping interface T { getA(); setA(); getB(); setB(); } type t { (element a, element b) | (element b, element a) } Type t members:<a/><b/>and<b/><a/> unmarshal; marshal =/= identity unmarshal; marshal; unmarshal = unmarshal JAXB Overview

  11. “General content style” <xs:complexType name=“t”> <xs:choice maxOccurs=“unbounded”> <element ref=“book”/> <element ref=“journal”/> </xs:choice> </xs:complexType> interface T { List getBookOrJournal() } • Plus a constraint: • The only list members are • Book objects • Journal objects JAXB Overview

  12. Model groups, by default <xs:group name="bookName"> <xs:sequence> <xs:element name="title" type="xs:string"/> <xs:element name="author" type="xs:string“/> </xs:sequence> </xs:group> <xs:complexType name="bookType"> <xs:sequence> <xs:group ref="bookName"/> <xs:element name="pages" type="xs:int"/> </xs:sequence> </xs:complexType> interface BookType { String getTitle(); void setTitle(String x); String getAuthor(); void setAuthor(String); int getPages(); void setPages(int x); } JAXB Overview

  13. Model groups, customized <xs:group name="bookName"> <xs:sequence> <xs:element name="title" type="xs:string"/> <xs:element name="author" type="xs:string“/> </xs:sequence> </xs:group> <xs:complexType name="bookType"> <xs:sequence> <xs:group ref="bookName"/> <xs:element name="pages" type="xs:int"/> </xs:sequence> </xs:complexType> interface BookName { String getTitle(); void setTitle(String x); String getAuthor(); void setAuthor(String); } interface BookType { BookName getBookName(); void setBookName(BookName); int getPages(); void setPages(int x); } JAXB Overview

  14. 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 JAXB Overview

  15. 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) JAXB Overview

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