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 <div class="sect1"><!-- infolevel="all" infotype="General" -->
 <h1 class="sect1"><font face="arial, helvetica, sans-serif" color="#330099">Using an XmlAdapter</font></h1>
 <p>Some Java classes may not be well suited for use with JAXB and at first glance may seem "unmappable" &ndash; for example, classes that do not have a default <code>no-arg</code> constructor, or classes for which an XML representation cannot be automatically determined. Using JAXB's <code>XmlAdapter</code>, you can define custom code to convert the unmappable class into something that JAXB can handle. Then, you can use the <code>@XmlJavaTypeAdapter</code> annotation to indicate that your adapter should be used when working with the unmappable class.</p>
 <p><code>XmlAdapter</code> uses the following terminology:</p>
 <ul>
 <li>
 <p><code>ValueType</code> &ndash; The type that JAXB knows how to handle out of the box.</p>
 </li>
 <li>
 <p><code>BoundType</code> &ndash; The type that JAXB doesn't know how to handle. An adapter is written to allow this type to be used as an in-memory representation through the ValueType.</p>
 </li>
 </ul>
 <p>The outline of an XmlAdapter class is as follows:</p>
 <div class="example"><a id="TLJAX419" name="TLJAX419"></a><a id="sthref178" name="sthref178"></a>
 <p><strong><em><font face="arial, helvetica, sans-serif">Example 8-32 XmlAdapter Class Outline</font></em></strong></p>
 <pre xml:space="preserve" class="oac_no_warn">
 public class AdapterName extends XmlAdapter&lt;ValueType, BoundType&gt; {

    public BoundType unmarshal(ValueType value) throws Exception {
       ...
    }

    public ValueType marshal(BoundType value) throws Exception {
       ...
    }

 }

 </pre></div>
 <!-- class="example" -->
 <a id="TLJAX420" name="TLJAX420"></a>
 <div class="sect2"><a id="sthref179" name="sthref179"></a>
 <h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Using java.util.Currency</font></h2>
 <p>Our first example will use the following domain class:</p>
 <div class="example"><a id="TLJAX421" name="TLJAX421"></a><a id="sthref180" name="sthref180"></a>
 <p><strong><em><font face="arial, helvetica, sans-serif">Example 8-33 Sample Domain Class</font></em></strong></p>
 <pre xml:space="preserve" class="oac_no_warn">
 package example;

 import java.util.Currency;

 import javax.xml.bind.annotation.*;

 @XmlRootElement
 @XmlAccessorType(XmlAccessType.FIELD)
 public class PurchaseOrder {

    private Double amount;

    private Currency currency;

    ...
 }

 </pre></div>
 <!-- class="example" -->
 <p>Here, the <strong>Currency</strong> cannot be automatically mapped with JAXB because it does not contain a no-argument constructor. However, we can write an adapter that will convert the <strong>Currency</strong> into something that JAXB does know how to handle &ndash; a simple <code>String</code>. Luckily, in this case the <strong>Currency's</strong> <code>toString()</code> method returns the currency code, which can also be used to create a new <strong>Currency</strong>:</p>
 <div class="example"><a id="TLJAX422" name="TLJAX422"></a><a id="sthref181" name="sthref181"></a>
 <p><strong><em><font face="arial, helvetica, sans-serif">Example 8-34 Using an Adapter</font></em></strong></p>
 <pre xml:space="preserve" class="oac_no_warn">
 package example;

 import java.util.Currency;

 import javax.xml.bind.annotation.adapters.XmlAdapter;

 public class CurrencyAdapter extends XmlAdapter&lt;String, Currency&gt; {

    /*
     * Java =&gt; XML
     * Given the unmappable Java object, return the desired XML representation.
     */
    public String marshal(Currency val) throws Exception {
       return val.toString();
    }

    /*
     * XML =&gt; Java
     * Given an XML string, use it to build an instance of the unmappable class.
     */
    public Currency unmarshal(String val) throws Exception {
       return Currency.getInstance(val);
    }

 }

 </pre></div>
 <!-- class="example" -->
 <p>To indicate that our adapter should be used for the <strong>Currency</strong> property, we annotate it with <code>@XmlJavaTypeAdapter</code> and provide the class name of our adapter:</p>
 <div class="example"><a id="TLJAX423" name="TLJAX423"></a><a id="sthref182" name="sthref182"></a>
 <p><strong><em><font face="arial, helvetica, sans-serif">Example 8-35 Using the @XmlJavaTypeAdapter Annotation</font></em></strong></p>
 <pre xml:space="preserve" class="oac_no_warn">
 package example;

 import java.util.Currency;

 import javax.xml.bind.annotation.*;

 @XmlRootElement
 @XmlAccessorType(XmlAccessType.FIELD)
 public class PurchaseOrder {

    private Double amount;

    <strong>@XmlJavaTypeAdapter</strong>(CurrencyAdapter.class)
    private Currency currency;

    ...
 }

 </pre></div>
 <!-- class="example" --></div>
 <!-- class="sect2" -->
 <a id="TLJAX424" name="TLJAX424"></a>
 <div class="sect2"><a id="sthref183" name="sthref183"></a>
 <h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Using java.awt.Point</font></h2>
 <p>Sometimes the best way to handle an unmappable class is to write a "stand-in" class which <em>can</em> be mapped with JAXB, and convert between the two classes in the <code>XmlAdapter</code>. In this example, we want to use the <strong>Point</strong> class. Because of that class' <code>getLocation()</code> method (which JAXB will pickup automatically and map), an infinite loop will occur during marshalling. Because we cannot change the <strong>Point</strong> class, we will write a new class, <strong>MyPoint</strong>, and use it in the adapter.</p>
 <div class="example"><a id="TLJAX425" name="TLJAX425"></a><a id="sthref184" name="sthref184"></a>
 <p><strong><em><font face="arial, helvetica, sans-serif">Example 8-36 Using java.awt.Point</font></em></strong></p>
 <pre xml:space="preserve" class="oac_no_warn">
 package example;

 public class MyPoint {

    private int x, y;

    public MyPoint() {
       this(0, 0);
    }

    public MyPoint(int x, int y) {
       this.x = x;
       this.y = y;
    }

    public int getX() {
       return x;
    }

    ...
 }

 package example;

 import java.awt.Point;

 import javax.xml.bind.annotation.adapters.XmlAdapter;

 public class MyPointAdapter extends XmlAdapter&lt;MyPoint, Point&gt; {

    /*
     * Java =&gt; XML
     */
    public MyPoint marshal(Point val) throws Exception {
       return new MyPoint((int) val.getX(), (int) val.getY());
    }

    /*
     * XML =&gt; Java
     */
    public Point unmarshal(MyPoint val) throws Exception {
       return new Point(val.getX(), val.getY());
    }

 }

 </pre></div>
 <!-- class="example" -->
 <p>Finally, our <strong>Point</strong> properties are marked with <code>@XmlJavaTypeAdapter</code>:</p>
 <div class="example"><a id="CHDBBDAC" name="CHDBBDAC"></a><a id="TLJAX426" name="TLJAX426"></a>
 <p><strong><em><font face="arial, helvetica, sans-serif">Example 8-37 Using the @XmlJavaTypeAdapter Annotation</font></em></strong></p>
 <pre xml:space="preserve" class="oac_no_warn">
 package example;

 import java.awt.Point;

 import javax.xml.bind.annotation.*;

 @XmlRootElement
 @XmlAccessorType(XmlAccessType.FIELD)
 public class Zone {

    private String name;

    <strong>@XmlJavaTypeAdapter</strong>(MyPointAdapter.class)
    private Point startCoord;

    <strong>@XmlJavaTypeAdapter</strong>(MyPointAdapter.class)
    private Point endCoord;

    ...
 }
 </pre></div>
 <!-- class="example" --></div>
 <!-- class="sect2" -->
 <a id="TLJAX427" name="TLJAX427"></a>
 <div class="sect2"><a id="sthref185" name="sthref185"></a>
 <h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Specifying Package-Level Adapters</font></h2>
 <p>In <a href="#CHDBBDAC">Example 8-37</a>, we annotated both <strong>Point</strong> properties with the <code>@XmlJavaTypeAdapter</code> annotation. If you have many of these types of properties &ndash; for example, in other domain classes &ndash; it can be more convenient to specify the <strong>@XmlJavaTypeAdapters</strong> at the package level.</p>
 <p>We could define both of the adapter classes in <strong>package-info.java</strong>, and would no longer have to annotate any further <strong>Currency</strong> or <strong>Point</strong> properties:</p>
 <pre xml:space="preserve" class="oac_no_warn">
 @XmlJavaTypeAdapters({
    @XmlJavaTypeAdapter(value=CurrencyAdapter.class,type=Currency.class),
    @XmlJavaTypeAdapter(value=MyPointAdapter.class,type=Point.class)
 })
 package example;

 </pre></div>
 <!-- class="sect2" -->
 <a id="TLJAX428" name="TLJAX428"></a>
 <div class="sect2"><a id="sthref186" name="sthref186"></a>
 <h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Specifying Class-Level @XmlJavaTypeAdapters</font></h2>
 <p>If you have a Java class and you would like to always use an <code>XmlAdapter</code> during marshalling and unmarshalling, then you can specify the <code>@XmlJavaTypeAdapter</code> directly at the class level:</p>
 <pre xml:space="preserve" class="oac_no_warn">
 package example;

 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

 @XmlJavaTypeAdapter(DataStructureAdapter.class)
 public class DataStructure {

    ...

 }

 </pre>
 <p>Now, any object that has a <strong>DataStructure</strong> property will automatically use the <code>DataStructureAdapter</code>, without the need for an annotation on the property itself.</p>
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	<div class="sect1"><!-- infolevel="all" infotype="General" -->
	<h1 class="sect1"><font face="arial, helvetica, sans-serif" color="#330099">Using an XmlAdapter</font></h1>
	<p>Some Java classes may not be well suited for use with JAXB and at first glance may seem "unmappable" – for example, classes that do not have a default <code>no-arg</code> constructor, or classes for which an XML representation cannot be automatically determined. Using JAXB's <code>XmlAdapter</code>, you can define custom code to convert the unmappable class into something that JAXB can handle. Then, you can use the <code>@XmlJavaTypeAdapter</code> annotation to indicate that your adapter should be used when working with the unmappable class.</p>
	<p><code>XmlAdapter</code> uses the following terminology:</p>
	<ul>
	<li>
	<p><code>ValueType</code> – The type that JAXB knows how to handle out of the box.</p>
	</li>
	<li>
	<p><code>BoundType</code> – The type that JAXB doesn't know how to handle. An adapter is written to allow this type to be used as an in-memory representation through the ValueType.</p>
	</li>
	</ul>
	<p>The outline of an XmlAdapter class is as follows:</p>
	<div class="example"><a id="TLJAX419" name="TLJAX419"></a><a id="sthref178" name="sthref178"></a>
	<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-32 XmlAdapter Class Outline</font></em></strong></p>
	<pre xml:space="preserve" class="oac_no_warn">
	public class AdapterName extends XmlAdapter<ValueType, BoundType> {

	public BoundType unmarshal(ValueType value) throws Exception {
	...
	}

	public ValueType marshal(BoundType value) throws Exception {
	...
	}

	}

	</pre></div>
	<!-- class="example" -->
	<a id="TLJAX420" name="TLJAX420"></a>
	<div class="sect2"><a id="sthref179" name="sthref179"></a>
	<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Using java.util.Currency</font></h2>
	<p>Our first example will use the following domain class:</p>
	<div class="example"><a id="TLJAX421" name="TLJAX421"></a><a id="sthref180" name="sthref180"></a>
	<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-33 Sample Domain Class</font></em></strong></p>
	<pre xml:space="preserve" class="oac_no_warn">
	package example;

	import java.util.Currency;

	import javax.xml.bind.annotation.*;

	@XmlRootElement
	@XmlAccessorType(XmlAccessType.FIELD)
	public class PurchaseOrder {

	private Double amount;

	private Currency currency;

	...
	}

	</pre></div>
	<!-- class="example" -->
	<p>Here, the <strong>Currency</strong> cannot be automatically mapped with JAXB because it does not contain a no-argument constructor. However, we can write an adapter that will convert the <strong>Currency</strong> into something that JAXB does know how to handle – a simple <code>String</code>. Luckily, in this case the <strong>Currency's</strong> <code>toString()</code> method returns the currency code, which can also be used to create a new <strong>Currency</strong>:</p>
	<div class="example"><a id="TLJAX422" name="TLJAX422"></a><a id="sthref181" name="sthref181"></a>
	<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-34 Using an Adapter</font></em></strong></p>
	<pre xml:space="preserve" class="oac_no_warn">
	package example;

	import java.util.Currency;

	import javax.xml.bind.annotation.adapters.XmlAdapter;

	public class CurrencyAdapter extends XmlAdapter<String, Currency> {

	/*
	* Java => XML
	* Given the unmappable Java object, return the desired XML representation.
	*/
	public String marshal(Currency val) throws Exception {
	return val.toString();
	}

	/*
	* XML => Java
	* Given an XML string, use it to build an instance of the unmappable class.
	*/
	public Currency unmarshal(String val) throws Exception {
	return Currency.getInstance(val);
	}

	}

	</pre></div>
	<!-- class="example" -->
	<p>To indicate that our adapter should be used for the <strong>Currency</strong> property, we annotate it with <code>@XmlJavaTypeAdapter</code> and provide the class name of our adapter:</p>
	<div class="example"><a id="TLJAX423" name="TLJAX423"></a><a id="sthref182" name="sthref182"></a>
	<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-35 Using the @XmlJavaTypeAdapter Annotation</font></em></strong></p>
	<pre xml:space="preserve" class="oac_no_warn">
	package example;

	import java.util.Currency;

	import javax.xml.bind.annotation.*;

	@XmlRootElement
	@XmlAccessorType(XmlAccessType.FIELD)
	public class PurchaseOrder {

	private Double amount;

	<strong>@XmlJavaTypeAdapter</strong>(CurrencyAdapter.class)
	private Currency currency;

	...
	}

	</pre></div>
	<!-- class="example" --></div>
	<!-- class="sect2" -->
	<a id="TLJAX424" name="TLJAX424"></a>
	<div class="sect2"><a id="sthref183" name="sthref183"></a>
	<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Using java.awt.Point</font></h2>
	<p>Sometimes the best way to handle an unmappable class is to write a "stand-in" class which <em>can</em> be mapped with JAXB, and convert between the two classes in the <code>XmlAdapter</code>. In this example, we want to use the <strong>Point</strong> class. Because of that class' <code>getLocation()</code> method (which JAXB will pickup automatically and map), an infinite loop will occur during marshalling. Because we cannot change the <strong>Point</strong> class, we will write a new class, <strong>MyPoint</strong>, and use it in the adapter.</p>
	<div class="example"><a id="TLJAX425" name="TLJAX425"></a><a id="sthref184" name="sthref184"></a>
	<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-36 Using java.awt.Point</font></em></strong></p>
	<pre xml:space="preserve" class="oac_no_warn">
	package example;

	public class MyPoint {

	private int x, y;

	public MyPoint() {
	this(0, 0);
	}

	public MyPoint(int x, int y) {
	this.x = x;
	this.y = y;
	}

	public int getX() {
	return x;
	}

	...
	}

	package example;

	import java.awt.Point;

	import javax.xml.bind.annotation.adapters.XmlAdapter;

	public class MyPointAdapter extends XmlAdapter<MyPoint, Point> {

	/*
	* Java => XML
	*/
	public MyPoint marshal(Point val) throws Exception {
	return new MyPoint((int) val.getX(), (int) val.getY());
	}

	/*
	* XML => Java
	*/
	public Point unmarshal(MyPoint val) throws Exception {
	return new Point(val.getX(), val.getY());
	}

	}

	</pre></div>
	<!-- class="example" -->
	<p>Finally, our <strong>Point</strong> properties are marked with <code>@XmlJavaTypeAdapter</code>:</p>
	<div class="example"><a id="CHDBBDAC" name="CHDBBDAC"></a><a id="TLJAX426" name="TLJAX426"></a>
	<p><strong><em><font face="arial, helvetica, sans-serif">Example 8-37 Using the @XmlJavaTypeAdapter Annotation</font></em></strong></p>
	<pre xml:space="preserve" class="oac_no_warn">
	package example;

	import java.awt.Point;

	import javax.xml.bind.annotation.*;

	@XmlRootElement
	@XmlAccessorType(XmlAccessType.FIELD)
	public class Zone {

	private String name;

	<strong>@XmlJavaTypeAdapter</strong>(MyPointAdapter.class)
	private Point startCoord;

	<strong>@XmlJavaTypeAdapter</strong>(MyPointAdapter.class)
	private Point endCoord;

	...
	}
	</pre></div>
	<!-- class="example" --></div>
	<!-- class="sect2" -->
	<a id="TLJAX427" name="TLJAX427"></a>
	<div class="sect2"><a id="sthref185" name="sthref185"></a>
	<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Specifying Package-Level Adapters</font></h2>
	<p>In <a href="#CHDBBDAC">Example 8-37</a>, we annotated both <strong>Point</strong> properties with the <code>@XmlJavaTypeAdapter</code> annotation. If you have many of these types of properties – for example, in other domain classes – it can be more convenient to specify the <strong>@XmlJavaTypeAdapters</strong> at the package level.</p>
	<p>We could define both of the adapter classes in <strong>package-info.java</strong>, and would no longer have to annotate any further <strong>Currency</strong> or <strong>Point</strong> properties:</p>
	<pre xml:space="preserve" class="oac_no_warn">
	@XmlJavaTypeAdapters({
	@XmlJavaTypeAdapter(value=CurrencyAdapter.class,type=Currency.class),
	@XmlJavaTypeAdapter(value=MyPointAdapter.class,type=Point.class)
	})
	package example;

	</pre></div>
	<!-- class="sect2" -->
	<a id="TLJAX428" name="TLJAX428"></a>
	<div class="sect2"><a id="sthref186" name="sthref186"></a>
	<h2 class="sect2"><font face="arial, helvetica, sans-serif" color="#330099">Specifying Class-Level @XmlJavaTypeAdapters</font></h2>
	<p>If you have a Java class and you would like to always use an <code>XmlAdapter</code> during marshalling and unmarshalling, then you can specify the <code>@XmlJavaTypeAdapter</code> directly at the class level:</p>
	<pre xml:space="preserve" class="oac_no_warn">
	package example;

	import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

	@XmlJavaTypeAdapter(DataStructureAdapter.class)
	public class DataStructure {

	...

	}

	</pre>
	<p>Now, any object that has a <strong>DataStructure</strong> property will automatically use the <code>DataStructureAdapter</code>, without the need for an annotation on the property itself.</p>
	</div>
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