Coordinator.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package com.sun.xml.internal.bind.v2.runtime;

import java.util.HashMap;

import javax.xml.bind.ValidationEvent;
import javax.xml.bind.ValidationEventHandler;
import javax.xml.bind.ValidationEventLocator;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import javax.xml.bind.helpers.ValidationEventImpl;

import com.sun.xml.internal.bind.v2.ClassFactory;
import com.sun.xml.internal.bind.v2.runtime.unmarshaller.UnmarshallingContext;

import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

/**
 * Object that coordinates the marshalling/unmarshalling.
 *
 * <p>
 * This class takes care of the logic that allows code to obtain
 * {@link UnmarshallingContext} and {@link XMLSerializer} instances
 * during the unmarshalling/marshalling.
 *
 * <p>
 * This is done by using a {@link ThreadLocal}. Therefore one unmarshalling/marshalling
 * episode has to be done from the beginning till end by the same thread.
 * (Note that the same {@link Coordinator} can be then used by a different thread
 * for an entirely different episode.)
 *
 * This class also maintains the user-configured instances of {@link XmlAdapter}s.
 *
 * <p>
 * This class implements {@link ErrorHandler} and propages erros to this object
 * as the {@link ValidationEventHandler}, which will be implemented in a derived class.
 *
 * @author Kohsuke Kawaguchi
 */
public abstract class Coordinator implements ErrorHandler, ValidationEventHandler {

    private final HashMap<Class<? extends XmlAdapter>,XmlAdapter> adapters =
            new HashMap<Class<? extends XmlAdapter>,XmlAdapter>();


    public final XmlAdapter putAdapter(Class<? extends XmlAdapter> c, XmlAdapter a) {
        if(a==null)
            return adapters.remove(c);
        else
            return adapters.put(c,a);
    }

    /**
     * Gets the instance of the adapter.
     *
     * @return
     *      always non-null.
     */
    public final <T extends XmlAdapter> T getAdapter(Class<T> key) {
        T v = key.cast(adapters.get(key));
        if(v==null) {
            v = ClassFactory.create(key);
            putAdapter(key,v);
        }
        return v;
    }

    public <T extends XmlAdapter> boolean containsAdapter(Class<T> type) {
        return adapters.containsKey(type);
    }

    // this much is necessary to avoid calling get and set twice when we push.
    private static final ThreadLocal<Coordinator> activeTable = new ThreadLocal<Coordinator>();

    /**
     * The {@link Coordinator} in charge before this {@link Coordinator}.
     */
    private Coordinator old;

    /**
     * Called whenever an execution flow enters the realm of this {@link Coordinator}.
     */
    protected final void pushCoordinator() {
        old = activeTable.get();
        activeTable.set(this);
    }

    /**
     * Called whenever an execution flow exits the realm of this {@link Coordinator}.
     */
    protected final void popCoordinator() {
        if (old != null)
            activeTable.set(old);
        else
            activeTable.remove();
        old = null; // avoid memory leak
    }

    public static Coordinator _getInstance() {
        return activeTable.get();
    }

//
//
// ErrorHandler implementation
//
//
    /**
     * Gets the current location. Used for reporting the error source location.
     */
    protected abstract ValidationEventLocator getLocation();

    public final void error(SAXParseException exception) throws SAXException {
        propagateEvent( ValidationEvent.ERROR, exception );
    }

    public final void warning(SAXParseException exception) throws SAXException {
        propagateEvent( ValidationEvent.WARNING, exception );
    }

    public final void fatalError(SAXParseException exception) throws SAXException {
        propagateEvent( ValidationEvent.FATAL_ERROR, exception );
    }

    private void propagateEvent( int severity, SAXParseException saxException )
        throws SAXException {

        ValidationEventImpl ve =
            new ValidationEventImpl( severity, saxException.getMessage(), getLocation() );

        Exception e = saxException.getException();
        if( e != null ) {
            ve.setLinkedException( e );
        } else {
            ve.setLinkedException( saxException );
        }

        // call the client's event handler.  If it returns false, then bail-out
        // and terminate the unmarshal operation.
        boolean result = handleEvent( ve );
        if( ! result ) {
            // bail-out of the parse with a SAX exception, but convert it into
            // an UnmarshalException back in in the AbstractUnmarshaller
            throw saxException;
        }
    }
}