replicationmode.java

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

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

import org.hibernate.type.VersionType;

/**
 * Represents a replication strategy.
 *
 * @see Session#replicate(Object, ReplicationMode)
 * @author Gavin King
 */
public abstract class ReplicationMode implements Serializable {
	private final String name;
	private static final Map INSTANCES = new HashMap();

	public ReplicationMode(String name) {
		this.name=name;
	}
	public String toString() {
		return name;
	}
	public abstract boolean shouldOverwriteCurrentVersion(Object entity, Object currentVersion, Object newVersion, VersionType versionType);
	/**
	 * Throw an exception when a row already exists.
	 */
	public static final ReplicationMode EXCEPTION = new ReplicationMode("EXCEPTION") {
		public boolean shouldOverwriteCurrentVersion(Object entity, Object currentVersion, Object newVersion, VersionType versionType) {
			throw new AssertionFailure("should not be called");
		}
	};
	/**
	 * Ignore replicated entities when a row already exists.
	 */
	public static final ReplicationMode IGNORE = new ReplicationMode("IGNORE") {
		public boolean shouldOverwriteCurrentVersion(Object entity, Object currentVersion, Object newVersion, VersionType versionType) {
			return false;
		}
	};
	/**
	 * Overwrite existing rows when a row already exists.
	 */
	public static final ReplicationMode OVERWRITE = new ReplicationMode("OVERWRITE") {
		public boolean shouldOverwriteCurrentVersion(Object entity, Object currentVersion, Object newVersion, VersionType versionType) {
			return true;
		}
	};
	/**
	 * When a row already exists, choose the latest version.
	 */
	public static final ReplicationMode LATEST_VERSION = new ReplicationMode("LATEST_VERSION") {
		public boolean shouldOverwriteCurrentVersion(Object entity, Object currentVersion, Object newVersion, VersionType versionType) {
			if (versionType==null) return true; //always overwrite nonversioned data
			return versionType.getComparator().compare(currentVersion, newVersion) <= 0;
		}
	};

	static {
		INSTANCES.put( LATEST_VERSION.name, LATEST_VERSION );
		INSTANCES.put( IGNORE.name, IGNORE );
		INSTANCES.put( OVERWRITE.name, OVERWRITE );
		INSTANCES.put( EXCEPTION.name, EXCEPTION );
	}

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

}