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/*******************************************************************************
 * Copyright (c) 2015 LegSem.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * 
 * Contributors:
 *     LegSem - initial API and implementation
 ******************************************************************************/
package com.legstar.coxb.util;

import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlSchema;
import javax.xml.bind.annotation.XmlType;

import com.legstar.coxb.CobolBindingException;

/**
 * This immutable class holds the parameters that describe the relationship
 * between an XML element and a corresponding JAXB object. This same information
 * can be derived from a JAXB object XmlType annotation or XmlRootElement
 * annotation.
 */
public class JAXBElementDescriptor {

    /** The JAXB package name. */
    private String mJaxbPackageName;

    /** The JAXB type name. */
    private String mJaxbTypeName;

    /** The JAXB class. */
    private Class < ? > mJaxbClass;

    /** Element name extracted from XmlRootElement or XmlType annotation. */
    private String mElementName;

    /** The XML Schema namespace. */
    private String mNamespace;

    /**
     * Inferred from the presence of an XmlRootElement annotation on the JAXB
     * type.
     */
    private boolean mIsXmlRootElement;

    /** JAXB Object factory for the JAXB package. */
    private Object mObjectFactory;

    /**
     * Create the element descriptor.
     * 
     * @param jaxbPackageName the JAXB package name
     * @param jaxbTypeName the JAXB type name
     * @throws JAXBAnnotationException if JAXB annotations are incomplete
     */
    public JAXBElementDescriptor(
            final String jaxbPackageName, final String jaxbTypeName)
            throws JAXBAnnotationException {
        try {
            mJaxbPackageName = jaxbPackageName;
            mJaxbTypeName = jaxbTypeName;
            mObjectFactory = BindingUtil.newJaxbObjectFactory(jaxbPackageName);
            mJaxbClass = ClassUtil.loadClass(jaxbPackageName, jaxbTypeName);
            mElementName = extractElementName();
            mNamespace = extractNamespace();
            mIsXmlRootElement = extractIsXmlRootElement();
        } catch (ClassNotFoundException e) {
            throw new JAXBAnnotationException(e);
        } catch (CobolBindingException e) {
            throw new JAXBAnnotationException(e);
        }
    }

    /**
     * @return the element name is given either by the XmlRootElement
     *         annotation or the XmlType annotation.
     * @throws JAXBAnnotationException if element name cannot be retrieved
     *             from JAXB annotations
     */
    private String extractElementName() throws JAXBAnnotationException {
        XmlRootElement xmlRootElement =
                getJaxbClass().getAnnotation(XmlRootElement.class);
        if (xmlRootElement != null) {
            String name = xmlRootElement.name();
            if (name != null && !name.equals("##default")) {
                return name;
            }
        }
        XmlType xmlType = getJaxbClass().getAnnotation(XmlType.class);
        if (xmlType != null) {
            String name = xmlType.name();
            if (name != null && !name.equals("##default")) {
                return name;
            }
        }
        throw new JAXBAnnotationException("Object " + getJaxbTypeName()
                + " in package " + getJaxbPackageName()
                + " does not have an XmlRootElement or XmlType annotation");
    }

    /**
     * Extract the XML Schema namespace associated with the JAXB package.
     * 
     * When there was no namespace and no package name when the JAXB class was
     * generated, it ends in a package called 'generate' and there is no
     * package-info. So if we don't finf package-info, we assume there was no
     * namespace to start with.
     * 
     * @return the XML Schema namespace
     */
    private String extractNamespace() {
        try {
            Class < ? > packageInfoClass = ClassUtil
                    .loadClass(getJaxbPackageName()
                            + ".package-info");
            XmlSchema xmlSchema = packageInfoClass
                    .getAnnotation(XmlSchema.class);
            return xmlSchema.namespace();
        } catch (ClassNotFoundException e) {
            return null;
        }
    }

    /**
     * @return true if the JAXB element is marked as XmlRootElement which
     *         means it does not need to be encapsulated in a JAXBElement.
     * @throws JAXBAnnotationException if class is not found
     */
    private boolean extractIsXmlRootElement() throws JAXBAnnotationException {
        XmlRootElement xmlRootElement =
                getJaxbClass().getAnnotation(XmlRootElement.class);
        if (xmlRootElement != null) {
            return true;
        }
        return false;
    }

    /**
     * @return the JAXB package name
     */
    public String getJaxbPackageName() {
        return mJaxbPackageName;
    }

    /**
     * @return the JAXB class name
     */
    public String getJaxbTypeName() {
        return mJaxbTypeName;
    }

    /**
     * @return the element name is given either by the XmlRootElement
     *         annotation or the XmlType annotation.
     *         from JAXB annotations
     */
    public String getElementName() {
        return mElementName;
    }

    /**
     * @return true if the JAXB element is marked as XmlRootElement which
     *         means it does not need to be encapsulated in a JAXBElement.
     */
    public boolean isXmlRootElement() {
        return mIsXmlRootElement;
    }

    /**
     * Returns the JAXB package Object factory.
     * 
     * @return the object factory
     */
    public Object getObjectFactory() {
        return mObjectFactory;
    }

    /** {@inheritDoc} */
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("JAXB package=");
        sb.append(getJaxbPackageName());
        sb.append(", ");
        sb.append("JAXB type=");
        sb.append(getJaxbTypeName());
        sb.append(", ");
        sb.append("XML namespace=");
        sb.append(getNamespace());
        sb.append(", ");
        sb.append("XML element=");
        sb.append(getElementName());
        sb.append(", ");
        sb.append("is XmlRootElement=");
        sb.append(isXmlRootElement());
        return sb.toString();
    }

    /**
     * @return the XML Schema namespace
     */
    public String getNamespace() {
        return mNamespace;
    }

    /**
     * @return the The JAXB class
     */
    public Class < ? > getJaxbClass() {
        return mJaxbClass;
    }

}