TupleTupleMarshalledBinding.java   [plain text]

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2000,2008 Oracle.  All rights reserved.
 *
 * $Id: TupleTupleMarshalledBinding.java,v 12.8 2008/02/07 17:12:25 mark Exp $
 */

package com.sleepycat.bind.tuple;

import com.sleepycat.util.RuntimeExceptionWrapper;

/**
 * A concrete <code>TupleTupleBinding</code> that delegates to the
 * <code>MarshalledTupleEntry</code> and
 * <code>MarshalledTupleKeyEntity</code> interfaces of the entity class.
 *
 * <p>This class calls the methods of the {@link MarshalledTupleEntry}
 * interface to convert between the data entry and entity object.  It calls the
 * methods of the {@link MarshalledTupleKeyEntity} interface to convert between
 * the key entry and the entity object.  These two interfaces must both be
 * implemented by the entity class.</p>
 *
 * @author Mark Hayes
 */
public class TupleTupleMarshalledBinding extends TupleTupleBinding {

    private Class cls;

    /**
     * Creates a tuple-tuple marshalled binding object.
     *
     * <p>The given class is used to instantiate entity objects using
     * {@link Class#forName}, and therefore must be a public class and have a
     * public no-arguments constructor.  It must also implement the {@link
     * MarshalledTupleEntry} and {@link MarshalledTupleKeyEntity}
     * interfaces.</p>
     *
     * @param cls is the class of the entity objects.
     */
    public TupleTupleMarshalledBinding(Class cls) {

        this.cls = cls;

        // The entity class will be used to instantiate the entity object.
        //
        if (!MarshalledTupleKeyEntity.class.isAssignableFrom(cls)) {
            throw new IllegalArgumentException(cls.toString() +
                        " does not implement MarshalledTupleKeyEntity");
        }
        if (!MarshalledTupleEntry.class.isAssignableFrom(cls)) {
            throw new IllegalArgumentException(cls.toString() +
                        " does not implement MarshalledTupleEntry");
        }
    }

    // javadoc is inherited
    public Object entryToObject(TupleInput keyInput, TupleInput dataInput) {

        // This "tricky" binding returns the stored data as the entity, but
        // first it sets the transient key fields from the stored key.
        MarshalledTupleEntry obj;
        try {
            obj = (MarshalledTupleEntry) cls.newInstance();
        } catch (IllegalAccessException e) {
            throw new RuntimeExceptionWrapper(e);
        } catch (InstantiationException e) {
            throw new RuntimeExceptionWrapper(e);
        }
        if (dataInput != null) { // may be null if used by key extractor
            obj.unmarshalEntry(dataInput);
        }
        MarshalledTupleKeyEntity entity = (MarshalledTupleKeyEntity) obj;
        if (keyInput != null) { // may be null if used by key extractor
            entity.unmarshalPrimaryKey(keyInput);
        }
        return entity;
    }

    // javadoc is inherited
    public void objectToKey(Object object, TupleOutput output) {

        MarshalledTupleKeyEntity entity = (MarshalledTupleKeyEntity) object;
        entity.marshalPrimaryKey(output);
    }

    // javadoc is inherited
    public void objectToData(Object object, TupleOutput output) {

        MarshalledTupleEntry entity = (MarshalledTupleEntry) object;
        entity.marshalEntry(output);
    }
}