org.eclipse.persistence.mappings.converters.ClassInstanceConverter Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of eclipselink Show documentation
EclipseLink build based upon Git transaction 346465e
There is a newer version: 5.0.0-B05
/*******************************************************************************
 * Copyright (c) 1998, 2013 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the 
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 
 * which accompanies this distribution. 
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at 
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
 ******************************************************************************/  
package org.eclipse.persistence.mappings.converters;

import java.security.AccessController;
import java.security.PrivilegedActionException;

import org.eclipse.persistence.mappings.*;
import org.eclipse.persistence.internal.helper.*;
import org.eclipse.persistence.mappings.foundation.AbstractDirectMapping;
import org.eclipse.persistence.sessions.*;
import org.eclipse.persistence.exceptions.*;
import org.eclipse.persistence.internal.security.PrivilegedAccessHelper;
import org.eclipse.persistence.internal.security.PrivilegedNewInstanceFromClass;
import org.eclipse.persistence.internal.sessions.AbstractSession;

/**
 * Purpose: Allows a class name to be converted to and from a new instance of the class.
 * 
 * When using a ClassInstanceConverter, the database will store the Class name and the java object
 * model will contain an instance of that class initialized with its default constructor
 *
 * @author James Sutherland
 * @since OracleAS TopLink 10g (10.0.3)
 */
public class ClassInstanceConverter implements Converter {
    protected DatabaseMapping mapping;

    /**
     * PUBLIC:
     * Default constructor.
     */
    public ClassInstanceConverter() {
    }

    /**
     * INTERNAL:
     * Convert the class name to a class, then create an instance of the class.
     */
    public Object convertDataValueToObjectValue(Object fieldValue, Session session) {
        Object attributeValue = null;
        if (fieldValue != null) {
            Class attributeClass = (Class)((AbstractSession)session).getDatasourcePlatform().convertObject(fieldValue, ClassConstants.CLASS);
            try {
                if (PrivilegedAccessHelper.shouldUsePrivilegedAccess()){
                    try {
                        attributeValue = AccessController.doPrivileged(new PrivilegedNewInstanceFromClass(attributeClass));
                    } catch (PrivilegedActionException exception) {
                        throw ConversionException.couldNotBeConverted(fieldValue, attributeClass, exception.getException());
                    }
                } else {
                    attributeValue = PrivilegedAccessHelper.newInstanceFromClass(attributeClass);
                }
            } catch (Exception exception) {
                throw ConversionException.couldNotBeConverted(fieldValue, attributeClass, exception);
            }
        }

        return attributeValue;
    }

    /**
     *  INTERNAL:
     *  Convert to the field class.
     */
    public Object convertObjectValueToDataValue(Object attributeValue, Session session) {
        if (attributeValue == null) {
            return null;
        }
        return attributeValue.getClass().getName();
    }

    /**
     * INTERNAL:
     * Set the mapping.
     */
    public void initialize(DatabaseMapping mapping, Session session) {
        this.mapping = mapping;
        // CR#... Mapping must also have the field classification.
        if (getMapping().isDirectToFieldMapping()) {
            AbstractDirectMapping directMapping = (AbstractDirectMapping)getMapping();

            // Allow user to specify field type to override computed value. (i.e. blob, nchar)
            if (directMapping.getFieldClassification() == null) {
                directMapping.setFieldClassification(ClassConstants.STRING);
            }
        }
    }

    /**
     * INTERNAL:
     * Return the mapping.
     */
    protected DatabaseMapping getMapping() {
        return mapping;
    }

    /**
     * INTERNAL:
     * If the converter converts the value to a non-atomic value, i.e.
     * a value that can have its' parts changed without being replaced,
     * then it must return false, serialization can be non-atomic.
     */
    public boolean isMutable() {
        return false;
    }
}