propertyaccessorfactory.java

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//$Id: PropertyAccessorFactory.java 8451 2005-10-24 08:45:37Z maxcsaucdk $
package org.hibernate.property;

import java.util.Map;

import org.hibernate.MappingException;
import org.hibernate.EntityMode;
import org.hibernate.type.Type;
import org.hibernate.engine.SessionFactoryImplementor;
import org.hibernate.mapping.Property;
import org.hibernate.util.ReflectHelper;
import org.hibernate.util.StringHelper;

/**
 * A factory for building/retrieving PropertyAccessor instances.
 *
 * @author Gavin King
 * @author Steve Ebersole
 */
public final class PropertyAccessorFactory {

	private static final PropertyAccessor BASIC_PROPERTY_ACCESSOR = new BasicPropertyAccessor();
	private static final PropertyAccessor DIRECT_PROPERTY_ACCESSOR = new DirectPropertyAccessor();
	private static final PropertyAccessor MAP_ACCESSOR = new MapAccessor();
	private static final PropertyAccessor NOOP_ACCESSOR = new NoopAccessor();
	private static final PropertyAccessor EMBEDDED_PROPERTY_ACCESSOR = new EmbeddedPropertyAccessor();

	//TODO: ideally we need the construction of PropertyAccessor to take the following:
	//      1) EntityMode
	//      2) EntityMode-specific data (i.e., the classname for pojo entities)
	//      3) Property-specific data based on the EntityMode (i.e., property-name or dom4j-node-name)
	// The easiest way, with the introduction of the new runtime-metamodel classes, would be the
	// the following predicates:
	//      1) PropertyAccessorFactory.getPropertyAccessor() takes references to both a
	//          org.hibernate.metadata.EntityModeMetadata and org.hibernate.metadata.Property
	//      2) What is now termed a "PropertyAccessor" stores any values needed from those two
	//          pieces of information
	//      3) Code can then simply call PropertyAccess.getGetter() with no parameters; likewise with
	//          PropertyAccessor.getSetter()

    /**
     * Retrieves a PropertyAccessor instance based on the given property definition and
     * entity mode.
     *
     * @param property The property for which to retrieve an accessor.
     * @param mode The mode for the resulting entity.
     * @return An appropriate accessor.
     * @throws MappingException
     */
	public static PropertyAccessor getPropertyAccessor(Property property, EntityMode mode) throws MappingException {
		//TODO: this is temporary in that the end result will probably not take a Property reference per-se.
	    if ( null == mode || EntityMode.POJO.equals( mode ) ) {
		    return getPojoPropertyAccessor( property.getPropertyAccessorName() );
	    }
	    else if ( EntityMode.MAP.equals( mode ) ) {
		    return getDynamicMapPropertyAccessor();
	    }
	    else if ( EntityMode.DOM4J.equals( mode ) ) {
	    	//TODO: passing null here, because this method is not really used for DOM4J at the moment
	    	//      but it is still a bug, if we don't get rid of this!
		    return getDom4jPropertyAccessor( property.getAccessorPropertyName( mode ), property.getType(), null );
	    }
	    else {
		    throw new MappingException( "Unknown entity mode [" + mode + "]" );
	    }
	}	/**
	 * Retreives a PropertyAccessor specific for a PojoRepresentation with the given access strategy.
	 *
	 * @param pojoAccessorStrategy The access strategy.
	 * @return An appropriate accessor.
	 */
	private static PropertyAccessor getPojoPropertyAccessor(String pojoAccessorStrategy) {
		if ( StringHelper.isEmpty( pojoAccessorStrategy ) || "property".equals( pojoAccessorStrategy ) ) {
			return BASIC_PROPERTY_ACCESSOR;
		}
		else if ( "field".equals( pojoAccessorStrategy ) ) {
			return DIRECT_PROPERTY_ACCESSOR;
		}
		else if ( "embedded".equals( pojoAccessorStrategy ) ) {
			return EMBEDDED_PROPERTY_ACCESSOR;
		}
		else if ( "noop".equals(pojoAccessorStrategy) ) {
			return NOOP_ACCESSOR;
		}
		else {
			return resolveCustomAccessor( pojoAccessorStrategy );
		}
	}

	public static PropertyAccessor getDynamicMapPropertyAccessor() throws MappingException {
		return MAP_ACCESSOR;
	}

	public static PropertyAccessor getDom4jPropertyAccessor(String nodeName, Type type, SessionFactoryImplementor factory) 
	throws MappingException {
		//TODO: need some caching scheme? really comes down to decision 
		//      regarding amount of state (if any) kept on PropertyAccessors
		return new Dom4jAccessor( nodeName, type, factory );
	}

	private static PropertyAccessor resolveCustomAccessor(String accessorName) {
		Class accessorClass;
		try {
			accessorClass = ReflectHelper.classForName(accessorName);
		}
		catch (ClassNotFoundException cnfe) {
			throw new MappingException("could not find PropertyAccessor class: " + accessorName, cnfe);
		}
		try {
			return (PropertyAccessor) accessorClass.newInstance();
		}
		catch (Exception e) {
			throw new MappingException("could not instantiate PropertyAccessor class: " + accessorName, e);
		}
	}

	private PropertyAccessorFactory() {}

	// todo : this eventually needs to be removed
	public static PropertyAccessor getPropertyAccessor(Class optionalClass, String type) throws MappingException {
		if ( type==null ) type = optionalClass==null || optionalClass==Map.class ? "map" : "property";
		return getPropertyAccessor(type);
	}

	// todo : this eventually needs to be removed
	public static PropertyAccessor getPropertyAccessor(String type) throws MappingException {
		if ( type==null || "property".equals(type) ) return BASIC_PROPERTY_ACCESSOR;
		if ( "field".equals(type) ) return DIRECT_PROPERTY_ACCESSOR;
		if ( "map".equals(type) ) return MAP_ACCESSOR;
		if ( "embedded".equals(type) ) return EMBEDDED_PROPERTY_ACCESSOR;
		if ( "noop".equals(type)) return NOOP_ACCESSOR;
		
		return resolveCustomAccessor(type);
	}
}