javax.xml.bind.JAXBElement Maven / Gradle / Ivy
/*
* Copyright (c) 2004, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package javax.xml.bind;
import javax.xml.namespace.QName;
import java.io.Serializable;
/**
* JAXB representation of an Xml Element.
*
* 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
*
* - element's xml tag {@code name}
* - {@code value} represents the element instance's atttribute(s) and content model
* - element declaration's {@code declaredType} ({@code xs:element @type} attribute)
* - {@code scope} of element declaration
* - boolean {@code nil} property. (element instance's {@code xsi:nil} attribute)
*
*
* The {@code declaredType} and {@code scope} property are the
* JAXB class binding for the xml type definition.
*
*
* {@code Scope} is either {@link GlobalScope} or the Java class representing the
* complex type definition containing the schema element declaration.
*
*
* There is a property constraint that if {@code value} is {@code null},
* then {@code nil} must be {@code true}. The converse is not true to enable
* representing a nil element with attribute(s). If {@code nil} is true, it is possible
* that {@code value} is non-null so it can hold the value of the attributes
* associated with a nil element.
*
*
* @author Kohsuke Kawaguchi, Joe Fialli
* @since 1.6, JAXB 2.0
*/
public class JAXBElement implements Serializable {
/** xml element tag name */
final protected QName name;
/** Java datatype binding for xml element declaration's type. */
final protected Class 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 {}
/**
* Construct an xml element instance.
*
* @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 {@code GlobalScope.class}
* @param value
* Java instance representing xml element's value.
* @see #getScope()
* @see #isTypeSubstituted()
*/
public JAXBElement(QName name,
Class 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 {@code new JAXBElement(name,declaredType,GlobalScope.class,value)}
*/
public JAXBElement(QName name, Class declaredType, T value ) {
this(name,declaredType,GlobalScope.class,value);
}
/**
* Returns the Java binding of the xml element declaration's type attribute.
*/
public Class getDeclaredType() {
return declaredType;
}
/**
* Returns the xml element tag name.
*/
public QName getName() {
return name;
}
/**
* Set the content model and attributes of this xml element.
*
* When this property is set to {@code null}, {@code isNil()} must by {@code true}.
* Details of constraint are described at {@link #isNil()}.
*
* @see #isTypeSubstituted()
*/
public void setValue(T t) {
this.value = t;
}
/**
* Return the content model and attribute values for this element.
*
* See {@link #isNil()} for a description of a property constraint when
* this value is {@code null}
*/
public T getValue() {
return value;
}
/**
* Returns scope of xml element declaration.
*
* @see #isGlobalScope()
* @return {@code GlobalScope.class} if this element is of global scope.
*/
public Class getScope() {
return scope;
}
/**
* Returns {@code true} iff this element instance content model
* is nil.
*
* This property always returns {@code true} when {@link #getValue()} is null.
* Note that the converse is not true, when this property is {@code true},
* {@link #getValue()} can contain a non-null value for attribute(s). It is
* valid for a nil xml element to have attribute(s).
*/
public boolean isNil() {
return (value == null) || nil;
}
/**
* Set whether this element has nil content.
*
* @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;
}