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package javax.xml.bind;
import javax.xml.namespace.QName;
import java.io.Serializable;
/**
* <p>JAXB representation of an Xml Element.</p>
*
* <p>This class represents information about an Xml Element from both the element
* declaration within a schema and the element instance value within an xml document
* with the following properties
* <ul>
* <li>element's xml tag <b><tt>name</tt></b></li>
* <li><b><tt>value</tt></b> represents the element instance's atttribute(s) and content model</li>
* <li>element declaration's <b><tt>declaredType</tt></b> (<tt>xs:element @type</tt> attribute)</li>
* <li><b><tt>scope</tt></b> of element declaration</li>
* <li>boolean <b><tt>nil</tt></b> property. (element instance's <tt><b>xsi:nil</b></tt> attribute)</li>
* </ul>
*
* <p>The <tt>declaredType</tt> and <tt>scope</tt> property are the
* JAXB class binding for the xml type definition.
* </p>
*
* <p><b><tt>Scope</tt></b> is either {@link GlobalScope} or the Java class representing the
* complex type definition containing the schema element declaration.
* </p>
*
* <p>There is a property constraint that if <b><tt>value</tt></b> is <tt>null</tt>,
* then <tt>nil</tt> must be <tt>true</tt>. The converse is not true to enable
* representing a nil element with attribute(s). If <tt>nil</tt> is true, it is possible
* that <tt>value</tt> is non-null so it can hold the value of the attributes
* associated with a nil element.
* </p>
*
* @author Kohsuke Kawaguchi, Joe Fialli
* @since JAXB 2.0
*/
public class JAXBElement<T> implements Serializable {
/** xml element tag name */
final protected QName name;
/** Java datatype binding for xml element declaration's type. */
final protected Class<T> declaredType;
/** Scope of xml element declaration representing this xml element instance.
* Can be one of the following values:
* - {@link GlobalScope} for global xml element declaration.
* - local element declaration has a scope set to the Java class
* representation of complex type defintion containing
* xml element declaration.
*/
final protected Class scope;
/** xml element value.
Represents content model and attributes of an xml element instance. */
protected T value;
/** true iff the xml element instance has xsi:nil="true". */
protected boolean nil = false;
/**
* Designates global scope for an xml element.
*/
public static final class GlobalScope {}
/**
* <p>Construct an xml element instance.</p>
*
* @param name Java binding of xml element tag name
* @param declaredType Java binding of xml element declaration's type
* @param scope
* Java binding of scope of xml element declaration.
* Passing null is the same as passing <tt>GlobalScope.class</tt>
* @param value
* Java instance representing xml element's value.
* @see #getScope()
* @see #isTypeSubstituted()
*/
public JAXBElement(QName name,
Class<T> declaredType,
Class scope,
T value) {
if(declaredType==null || name==null)
throw new IllegalArgumentException();
this.declaredType = declaredType;
if(scope==null) scope = GlobalScope.class;
this.scope = scope;
this.name = name;
setValue(value);
}
/**
* Construct an xml element instance.
*
* This is just a convenience method for <tt>new JAXBElement(name,declaredType,GlobalScope.class,value)</tt>
*/
public JAXBElement(QName name, Class<T> declaredType, T value ) {
this(name,declaredType,GlobalScope.class,value);
}
/**
* Returns the Java binding of the xml element declaration's type attribute.
*/
public Class<T> getDeclaredType() {
return declaredType;
}
/**
* Returns the xml element tag name.
*/
public QName getName() {
return name;
}
/**
* <p>Set the content model and attributes of this xml element.</p>
*
* <p>When this property is set to <tt>null</tt>, <tt>isNil()</tt> must by <tt>true</tt>.
* Details of constraint are described at {@link #isNil()}.</p>
*
* @see #isTypeSubstituted()
*/
public void setValue(T t) {
this.value = t;
}
/**
* <p>Return the content model and attribute values for this element.</p>
*
* <p>See {@link #isNil()} for a description of a property constraint when
* this value is <tt>null</tt></p>
*/
public T getValue() {
return value;
}
/**
* Returns scope of xml element declaration.
*
* @see #isGlobalScope()
* @return <tt>GlobalScope.class</tt> if this element is of global scope.
*/
public Class getScope() {
return scope;
}
/**
* <p>Returns <tt>true</tt> iff this element instance content model
* is nil.</p>
*
* <p>This property always returns <tt>true</tt> when {@link #getValue()} is null.
* Note that the converse is not true, when this property is <tt>true</tt>,
* {@link #getValue()} can contain a non-null value for attribute(s). It is
* valid for a nil xml element to have attribute(s).</p>
*/
public boolean isNil() {
return (value == null) || nil;
}
/**
* <p>Set whether this element has nil content.</p>
*
* @see #isNil()
*/
public void setNil(boolean value) {
this.nil = value;
}
/* Convenience methods
* (Not necessary but they do unambiguously conceptualize
* the rationale behind this class' fields.)
*/
/**
* Returns true iff this xml element declaration is global.
*/
public boolean isGlobalScope() {
return this.scope == GlobalScope.class;
}
/**
* Returns true iff this xml element instance's value has a different
* type than xml element declaration's declared type.
*/
public boolean isTypeSubstituted() {
if(value==null) return false;
return value.getClass() != declaredType;
}
private static final long serialVersionUID = 1L;
}
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