JAXB - Hello World

We'll stick with the tradition and use a sort of "Hello World" XML document to illustrate the typical scenario for creating the Java classes and their use to marshal a document. We'll not discuss any details in this subsection; it's just here to give you the overall picture.

The XML Schema on

hello.xsd

defines the structure of our document, which is to contain a series of salutations, each of which contains a greeting (such as "Hello world") and an attribute for registering the language of the salutation.

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:jxb="http://java.sun.com/xml/ns/jaxb" jxb:version="2.0">
<xsd:element name="Greetings" type="GreetingListType"/>
<xsd:complexType name="GreetingListType">
<xsd:sequence>
<xsd:element name="Greeting" type="GreetingType" maxOccurs="unbounded"/>
</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="GreetingType">
<xsd:sequence>
<xsd:element name="Text" type="xsd:string"/>
</xsd:sequence>
<xsd:attribute name="language" type="xsd:language"/>
</xsd:complexType>
</xsd:schema>

Now we can call the JAXB schema compiler, defining the package name

hello

for the generated classes.

xjc -p hello hello.xsd

This generates several classes in the subdirectory

hello

. The class

Hello

shows how to use them.

import java.util.*;
import javax.xml.bind.*;
import hello.*;

public class Hello {

private ObjectFactory of;
private GreetingListType grList;

public Hello(){
of = new ObjectFactory();
grList = of.createGreetingListType();
}

public void make( String t, String l ){
GreetingType g = of.createGreetingType();
g.setText( t );
g.setLanguage( l );
grList.getGreeting().add( g );
}

public void marshal() {
try {
JAXBElement<GreetingListType> gl =
of.createGreetings( grList );
JAXBContext jc = JAXBContext.newInstance( "hello" );
Marshaller m = jc.createMarshaller();
m.marshal( gl, System.out );
} catch( JAXBException jbe ){
// ...
}
}
}

The constructor uses a method from the object factory to create an object of the document's top level XML element type, i.e.,

GreetingListType

. The

make

method adds another salutation with its text element and the language attribute. Finally, with a call to

marshal

, the list is wrapped in its XML element, and the resulting XML document is written to the standard output stream. Here's a sequence of these calls:

Hello h = new Hello();
h.make( "Bonjour, madame", "fr" );
h.make( "Hey, you", "en" );
h.marshal();

The output is shown below, formatted, for better readability.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Greetings>
<Greeting language="fr">
<Text>Bonjour, madame</Text>
</Greeting>
<Greeting language="en">
<Text>Hey, you</Text>
</Greeting>
</Greetings>