fetchmode.java

hibernate 开源框架的代码 jar包希望大家能喜欢

//$Id: FetchMode.java 5060 2004-12-24 03:11:05Z oneovthafew $
package org.hibernate;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

/**
 * Represents an association fetching strategy. This is used
 * together with the <tt>Criteria</tt> API to specify runtime
 * fetching strategies.<br>
 * <br>
 * For HQL queries, use the <tt>FETCH</tt> keyword instead.
 *
 * @see Criteria#setFetchMode(java.lang.String, FetchMode)
 * @author Gavin King
 */
public final class FetchMode implements Serializable {
	private final String name;
	private static final Map INSTANCES = new HashMap();

	private FetchMode(String name) {
		this.name=name;
	}
	public String toString() {
		return name;
	}
	/**
	 * Default to the setting configured in the mapping file.
	 */
	public static final FetchMode DEFAULT = new FetchMode("DEFAULT");

	/**
	 * Fetch using an outer join. Equivalent to <tt>fetch="join"</tt>.
	 */
	public static final FetchMode JOIN = new FetchMode("JOIN");
	/**
	 * Fetch eagerly, using a separate select. Equivalent to
	 * <tt>fetch="select"</tt>.
	 */
	public static final FetchMode SELECT = new FetchMode("SELECT");

	/**
	 * Fetch lazily. Equivalent to <tt>outer-join="false"</tt>.
	 * @deprecated use <tt>FetchMode.SELECT</tt>
	 */
	public static final FetchMode LAZY = SELECT;
	/**
	 * Fetch eagerly, using an outer join. Equivalent to
	 * <tt>outer-join="true"</tt>.
	 * @deprecated use <tt>FetchMode.JOIN</tt>
	 */
	public static final FetchMode EAGER = JOIN;
	
	static {
		INSTANCES.put( JOIN.name, JOIN );
		INSTANCES.put( SELECT.name, SELECT );
		INSTANCES.put( DEFAULT.name, DEFAULT );
	}

	private Object readResolve() {
		return INSTANCES.get(name);
	}

}