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JAXB - Java Architecture for XML Binding


Introduction

Allows mapping xml files to java classes.

 

Example


Sample schema file:
<?xml version="1.0" ?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:sx="http://www.w3.org/2001/XMLSchema"
           elementFormDefault="qualified">

    <xs:element name="item-configuration" type="itemConfigurationType"/>

    <xs:complexType name="itemConfigurationType">
        <xs:sequence>
            <xs:element name="item-id" type="StringT"/>
            <xs:element name="enabled" type="xs:boolean"/>
            <xs:element name="item-type">
                <xs:complexType>
                    <xs:sequence>
                        <xs:element name="item-type-name" type="itemTypeNameT"/>
                        <xs:element name="item-type-value" type="Base_item_Type"/>
                    </xs:sequence>
                </xs:complexType>
            </xs:element>
            <xs:element name="retry-count" type="xs:integer" minOccurs="0" default="-1"/>
        </xs:sequence>
    </xs:complexType>

    <xs:complexType name="ITEM_1">
        <xs:complexContent>
            <xs:extension base="Base_item_Type">
                <xs:sequence>
                    <xs:element name="dst-model" type="ModelT"/>
                    <xs:element name="dst-model-key" type="StringT"/>
                </xs:sequence>
            </xs:extension>
        </xs:complexContent>
    </xs:complexType>
    <xs:complexType name="ITEM_2">
        <xs:complexContent>
            <xs:extension base="Base_item_Type">
                <xs:sequence>
                    <xs:element name="dst-model" type="ModelT"/>
                    <xs:element name="dst-model-key" type="StringT"/>
                    <xs:element name="dst-dao" type="DaoT"/>
                </xs:sequence>
            </xs:extension>
        </xs:complexContent>
    </xs:complexType>

    <xs:complexType name="Base_item_Type" abstract="true">
        <xs:sequence>
            <xs:element name="src-filter" type="StringT"/>
        </xs:sequence>
  <xs:attribute name="apply" type="ApplyType" default="ALWAYS"/>
    </xs:complexType>
 
 
    <xs:simpleType name="ApplyType">
        <xs:restriction base="xs:string">
            <xs:enumeration value="ALWAYS"/>
            <xs:enumeration value="IFEMPTY"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="ModelT">
        <xs:restriction base="xs:string">
            <xs:pattern value="(\[int\]|\[ext\])\..+"/>
            <xs:pattern value="NONE"/>
        </xs:restriction>
    </xs:simpleType>
 
    <xs:simpleType name="DaoT">
        <xs:restriction base="xs:string">
            <xs:pattern value="(\[int\]|\[ext\])\..+DaoImpl"/>
            <xs:pattern value="NONE"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="StringT">
        <xs:restriction base="xs:string">
            <xs:minLength value="1"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="itemTypeNameT">
        <xs:restriction base="xs:string">
            <xs:enumeration value="ITEM_TYPE_1"/>
            <xs:enumeration value="ITEM_TYPE_2"/>
        </xs:restriction>
    </xs:simpleType>

</xs:schema>


Sample XML file: Sample is to show possible content of xml file having the item.configuration schema.
<?xml version="1.0" ?>
<item-configuration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                    xsi:noNamespaceSchemaLocation="item.configuration.xsd"> <!-- specify schema file -->

    <item>
        <item-id>item-id-1</item-id>
        <enabled>true</enabled>
        <item-type>
            <item-type-name>ITEM_TYPE_1</item-type-name>
            <item-type-value xsi:type="ITEM_1" apply="IFEMPTY"><!-- optional attribute -->
                <src-filter>asd</src-filter>
                <dst-model>[int].Item1Model</dst-model>
                <dst-model-key>key</dst-model-key>
            </item-type-value>
        </item-type>

        <retry-count>1</retry-count> <!-- optional -->
    </item>

    <item>
        <item-id>item-id-2</item-id>
        <enabled>false</enabled>
        <item-type>
            <item-type-name>ITEM_TYPE_2</item-type-name>
            <item-type-value xsi:type="ITEM_2">
                <src-filter>asd</src-filter>
                <dst-model>[int].Item2Model</dst-model>
                <dst-model-key>key</dst-model-key>
                <dst-dao>[int].Item2Impl</dst-dao>
            </item-type-value>
        </item-type>

    </item>


</item-configuration>

Creating Java Files: As simple as typing the following command.
xjc item.configuration.xsd
Java files will be generated into a folder called “generated”. Sample test method can something like below. Following code reads items.xml file, parses according to item.configuration.xsd and maps toItemConfiguration object.
public class Main{

    private static final String ITEM_CONFIGURATION_SCHEMA_LOCATION_FILE = "item.configuration.xsd";
 
 public static void main(String[] args){
 
   try {
   File file = new File("items.xml");
            SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
            Schema schema = schemaFactory.newSchema(ClassLoader.getSystemResource(ITEM_CONFIGURATION_SCHEMA_LOCATION_FILE));

            JAXBContext jaxbContext = JAXBContext.newInstance(ItemConfigurationType.class);
            Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();// create unmarshaller
            jaxbUnmarshaller.setSchema(schema); // set schema file

            JAXBElement element = (JAXBElement) jaxbUnmarshaller.unmarshal(file);// unmarshal file
            ItemConfigurationType itemConfiguration = element.getValue();
   
   //work on itemConfiguration object
   // ....
   // ....
   
        } catch (JAXBException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        }
 
 }
}


Example Cases:



Inheritance Relationship

XML:
<item-type>
            <item-type-name>ITEM_TYPE_1</item-type-name>
            <item-type-value xsi:type="ITEM_1" apply="IFEMPTY"><!-- optional attribute -->
                <src-filter>asd</src-filter>


XSD:

    <xs:complexType name="Base_item_Type" abstract="true">
        <xs:sequence>
            <xs:element name="src-filter" type="StringT"/>
        </xs:sequence>
        <xs:attribute name="apply" type="ApplyType" default="ALWAYS"/>
    </xs:complexType>
               
    <xs:complexType name="ITEM_1">
        <xs:complexContent>
            <xs:extension base="Base_item_Type">
                <xs:sequence>


Java File:
BaseItemType.java
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "Base_item_Type", propOrder = {
    "srcFilter"
})
@XmlSeeAlso({
    ITEM1 .class,
    ITEM2 .class
})
public abstract class BaseItemType {

    @XmlElement(name = "src-filter", required = true)
    protected String srcFilter;
    @XmlAttribute(name = "apply")
    protected ApplyType apply;

    …

}

ITEM1.java
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "ITEM_1", propOrder = {
    "dstModel",
    "dstModelKey"
})
public class ITEM1
    extends BaseItemType
{

    @XmlElement(name = "dst-model", required = true)
    protected String dstModel;
    @XmlElement(name = "dst-model-key", required = true)
    protected String dstModelKey;

    …

}

Attributes

XML:
<item-type-value xsi:type="ITEM_1" apply="IFEMPTY">

XSD:
    <xs:complexType name="Base_item_Type" abstract="true">
        <xs:sequence>
            <xs:element name="src-filter" type="StringT"/>
        </xs:sequence>
        <xs:attribute name="apply" type="ApplyType" default="ALWAYS"/>
    </xs:complexType>

Java File:
@XmlAttribute(name = "apply")
      protected ApplyType apply;



Enumeration Type

XML:
<item-type-name>ITEM_TYPE_2</item-type-name>

XSD:

    <xs:simpleType name="itemTypeNameT">
        <xs:restriction base="xs:string">
            <xs:enumeration value="ITEM_TYPE_1"/>
            <xs:enumeration value="ITEM_TYPE_2"/>
        </xs:restriction>
    </xs:simpleType>

Java File:
ItemTypeNameT.java
@XmlType(name = "itemTypeNameT")
@XmlEnum
public enum ItemTypeNameT {
    ITEM_TYPE_1,
    ITEM_TYPE_2;

    public String value() {
        return name();
    }

    public static ItemTypeNameT fromValue(String v) {
        return valueOf(v);
    }
}


Regular Expression Types

XML:
<xs:element name="dst-dao" type="DaoT"/>

XSD:
   
    <xs:simpleType name="DaoT">
        <xs:restriction base="xs:string">
            <xs:pattern value="(\[int\]|\[ext\])\..+DaoImpl"/>
            <xs:pattern value="NONE"/>
        </xs:restriction>
    </xs:simpleType>


Java File:
    @XmlElement(name = "dst-dao", required = true)
    protected String dstDao;


Summary


JAXB is a great tool while working with XML files. It is easy to use yet powerful. Complete file listing can be download from this link.

Feel free to share your comments to http://el-harezmi.blogspot.com on design and any typos, incorrect or inaccurate expressions you see.

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