Java tutorial
/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. * * Copyright (c) 2004-2017 Oracle and/or its affiliates. All rights reserved. * * The contents of this file are subject to the terms of either the GNU * General Public License Version 2 only ("GPL") or the Common Development * and Distribution License("CDDL") (collectively, the "License"). You * may not use this file except in compliance with the License. You can * obtain a copy of the License at * https://oss.oracle.com/licenses/CDDL+GPL-1.1 * or LICENSE.txt. See the License for the specific * language governing permissions and limitations under the License. * * When distributing the software, include this License Header Notice in each * file and include the License file at LICENSE.txt. * * GPL Classpath Exception: * Oracle designates this particular file as subject to the "Classpath" * exception as provided by Oracle in the GPL Version 2 section of the License * file that accompanied this code. * * Modifications: * If applicable, add the following below the License Header, with the fields * enclosed by brackets [] replaced by your own identifying information: * "Portions Copyright [year] [name of copyright owner]" * * Contributor(s): * If you wish your version of this file to be governed by only the CDDL or * only the GPL Version 2, indicate your decision by adding "[Contributor] * elects to include this software in this distribution under the [CDDL or GPL * Version 2] license." If you don't indicate a single choice of license, a * recipient has the option to distribute your version of this file under * either the CDDL, the GPL Version 2 or to extend the choice of license to * its licensees as provided above. However, if you add GPL Version 2 code * and therefore, elected the GPL Version 2 license, then the option applies * only if the new code is made subject to such option by the copyright * holder. */ 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>{@code name}</b></li> * <li><b>{@code value}</b> represents the element instance's atttribute(s) and content model</li> * <li>element declaration's <b>{@code declaredType}</b> ({@code xs:element @type} attribute)</li> * <li><b>{@code scope}</b> of element declaration</li> * <li>boolean <b>{@code nil}</b> property. (element instance's <b>{@code xsi:nil}</b> attribute)</li> * </ul> * * <p>The {@code declaredType} and {@code scope} property are the * JAXB class binding for the xml type definition. * </p> * * <p><b>{@code Scope}</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>{@code value}</b> 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. * </p> * * @author Kohsuke Kawaguchi, Joe Fialli * @since 1.6, 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 {@code GlobalScope.class} * @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 {@code new JAXBElement(name,declaredType,GlobalScope.class,value)} */ 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 {@code null}, {@code isNil()} must by {@code true}. * 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 {@code null}</p> */ 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; } /** * <p>Returns {@code true} iff this element instance content model * is nil.</p> * * <p>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).</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; }