Coding in an absurd reality

Today I had to use JAXB for XML-object binding. While searching for an introduction, I noted that most articles handling JAXB seemed to be overly long and concerned with all kinds of asides that detracted from the basics, which were all I needed. Therefore I now present: an ultrashort JAXB tutorial.

I will expect you know:

• What XML-object binding is and why you would want to use it.
• How to use Java and solve classpath issues and such
• How to use Linux (or translate the instructions to Windows).
• How to determine intermediate steps I left out (like 'extract the zip')

Requirements:

• An XML file that you wish to 'unmarshal' into an object tree. Example:
  XML:
  

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  <?xml version="1.0" encoding="UTF-8"?> <rootElement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     xmlns="http://some.sensible.url/foo"     xsi:schemaLocation="http://some.sensible.url/foo foo.xsd">     <subElement>         <foo>1</foo>         <baz>2</baz>     </subElement>     <subElement>         <foo>2</foo>         <baz>4</baz>     </subElement>      </rootElement>

• An XML Schema description of the structure of the XML. Example:
  
  XML:
  

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  <?xml version="1.0" encoding="UTF-8"?> <schema xmlns="http://www.w3.org/2001/XMLSchema"      targetNamespace="http://some.sensible.url/foo"      xmlns:f="http://some.sensible.url/foo"      elementFormDefault="qualified">     <element name="rootElement">         <complexType>             <sequence>                 <element name="subElement" type="f:subElement"  maxOccurs="unbounded" />             </sequence>         </complexType>     </element>          <complexType name="subElement">         <sequence>             <element name="foo" type="int" />             <element name="baz" type="int" />         </sequence>     </complexType> </schema>

Tutorial

1. Use a Java 6 SDK (which has JAXB) or download JAXB (and use a Java 5+ JDK)
2. Generate the objects from the xml schema by issuing
   

   jaxb-ri/bin/xjc.sh -p com.company.app.pakkage.of.objects \
   -d /path/to/com/company/app/pakkage/of/objects \
   /path/to/xml-structure.xsd

3. Assuming the root element of your xml is named 'rootElement' (and available as com.company.app.pakkage.of.objects.RootElement):
   
   Java:
   

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   package com.company.app; import java.io.File; import javax.xml.bind.*; import com.company.app.pakkage.of.objects.*; public class Example {     public static void main(String[] args) throws JAXBException {                  final JAXBContext jaxbContext =             JAXBContext.newInstance("com.company.app.pakkage.of.objects");         final Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();         final RootElement rootElement =             (RootElement) unmarshaller.unmarshal(new File("/path/to/xml.xml"));     } }

4. Profit.