jaxb-ri/core/src/main/java/org/glassfish/jaxb/core/v2/model/core/ElementPropertyInfo.java

/*
 * Copyright (c) 1997, 2021 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 org.glassfish.jaxb.core.v2.model.core;

import java.util.List;

import javax.xml.namespace.QName;

/**
 * Property that maps to an element.
 *
 * @author Kohsuke Kawaguchi
 */
// TODO: there seems to be too much interactions between switches, and that's no good.
public interface ElementPropertyInfo<T,C> extends PropertyInfo<T,C> {
    /**
     * Returns the information about the types allowed in this property.
     *
     * <p>
     * In a simple case like the following, an element property only has
     * one {@link TypeRef} that points to {@link String} and tag name "foo".
     * <pre>
     * &#64;XmlElement
     * String abc;
     * </pre>
     *
     * <p>
     * However, in a general case an element property can be heterogeneous,
     * meaning you can put different types in it, each with a different tag name
     * (and a few other settings.)
     * <pre><code>
     * // list can contain String or Integer.
     * {@literal @}XmlElements({
     *   {@literal @}XmlElement(name="a",type=String.class),
     *   {@literal @}XmlElement(name="b",type=Integer.class),
     * })
     * {@literal List<Object>} abc;
     * </code></pre>
     * <p>
     * In this case this method returns a list of two {@link TypeRef}s.
     *
     *
     * @return
     *      Always non-null. Contains at least one entry.
     *      If {@link #isValueList()}==true, there's always exactly one type.
     */
    List<? extends TypeRef<T,C>> getTypes();

    /**
     * Gets the wrapper element name.
     *
     * @return
     *      must be null if {@link #isCollection()}==false or
     *      if {@link #isValueList()}==true.
     *
     *      Otherwise,
     *      this can be null (in which case there'll be no wrapper),
     *      or it can be non-null (in which case there'll be a wrapper)
     */
    QName getXmlName();

    /**
     * Checks if the wrapper element is required.
     *
     * @return
     *      Always false if {@link #getXmlName()}==null.
     */
    boolean isCollectionRequired();

    /**
     * Returns true if this property is nillable
     * (meaning the absence of the value is treated as nil='true')
     *
     * <p>
     * This method is only used when this property is a collection.
     */
    boolean isCollectionNillable();

    /**
     * Returns true if this property is a collection but its XML
     * representation is a list of values, not repeated elements.
     *
     * <p>
     * If {@link #isCollection()}==false, this property is always false.
     *
     * <p>
     * When this flag is true, {@code getTypes().size()==1} always holds.
     */
    boolean isValueList();

    /**
     * Returns true if this element is mandatory.
     *
     * For collections, this property isn't used.
     * TODO: define the semantics when this is a collection
     */
    boolean isRequired();

    Adapter<T,C> getAdapter();
}