identifiergeneratorfactory.java

介绍了hibernate的入门有一些基本常用的事例

//$Id: IdentifierGeneratorFactory.java,v 1.9 2005/03/07 00:19:01 oneovthafew Exp $
package org.hibernate.id;

import java.io.Serializable;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.dialect.Dialect;
import org.hibernate.type.Type;
import org.hibernate.util.ReflectHelper;

/**
 * Factory and helper methods for <tt>IdentifierGenerator</tt> framework.
 *
 * @author Gavin King
 */
public final class IdentifierGeneratorFactory {
	
	private static final Log log = LogFactory.getLog(IdentifierGeneratorFactory.class);

	/**
	 * Get the generated identifier when using identity columns
	 */
	public static Serializable getGeneratedIdentity(ResultSet rs, Type type)
	throws SQLException, HibernateException, IdentifierGenerationException {
		if ( !rs.next() ) {
			throw new HibernateException( "The database returned no natively generated identity value" );
		}
		final Serializable id = IdentifierGeneratorFactory.get( rs, type );

		if ( log.isDebugEnabled() ) log.debug( "Natively generated identity: " + id );
		return id;
	}

	// unhappy about this being public ... is there a better way?
	public static Serializable get(ResultSet rs, Type type) 
	throws SQLException, IdentifierGenerationException {
	
		Class clazz = type.getReturnedClass();
		if ( clazz==Long.class ) {
			return new Long( rs.getLong(1) );
		}
		else if ( clazz==Integer.class ) {
			return new Integer( rs.getInt(1) );
		}
		else if ( clazz==Short.class ) {
			return new Short( rs.getShort(1) );
		}
		else if ( clazz==String.class ) {
			return rs.getString(1);
		}
		else {
			throw new IdentifierGenerationException("this id generator generates long, integer, short or string");
		}
		
	}

	private static final HashMap GENERATORS = new HashMap();

	public static final String SHORT_CIRCUIT_INDICATOR = new String();
	public static final String POST_INSERT_INDICATOR = new String();

	static {
		GENERATORS.put("uuid", UUIDHexGenerator.class);
		GENERATORS.put("hilo", TableHiLoGenerator.class);
		GENERATORS.put("assigned", Assigned.class);
		GENERATORS.put("identity", IdentityGenerator.class);
		GENERATORS.put("select", SelectGenerator.class);
		GENERATORS.put("sequence", SequenceGenerator.class);
		GENERATORS.put("seqhilo", SequenceHiLoGenerator.class);
		GENERATORS.put("increment", IncrementGenerator.class);
		GENERATORS.put("foreign", ForeignGenerator.class);
		GENERATORS.put("guid", GUIDGenerator.class);
		GENERATORS.put("uuid.hex", UUIDHexGenerator.class); //uuid.hex is deprecated
	}

	public static IdentifierGenerator create(String strategy, Type type, Properties params, Dialect dialect) 
	throws MappingException {
		try {
			Class clazz = (Class) GENERATORS.get(strategy);
			if ( "native".equals(strategy) ) clazz = dialect.getNativeIdentifierGeneratorClass();
			if (clazz==null) clazz = ReflectHelper.classForName(strategy);
			IdentifierGenerator idgen = (IdentifierGenerator) clazz.newInstance();
			if (idgen instanceof Configurable) ( (Configurable) idgen).configure(type, params, dialect);
			return idgen;
		}
		catch (Exception e) {
			throw new MappingException("could not instantiate id generator", e);
		}
	}

	public static Number createNumber(long value, Class clazz) throws IdentifierGenerationException {
		if ( clazz==Long.class ) {
			return new Long(value);
		}
		else if ( clazz==Integer.class ) {
			return new Integer( (int) value );
		}
		else if ( clazz==Short.class ) {
			return new Short( (short) value );
		}
		else {
			throw new IdentifierGenerationException("this id generator generates long, integer, short");
		}
	}

	private IdentifierGeneratorFactory() {} //cannot be instantiated

}