sequencegenerator.java

介绍了hibernate的入门有一些基本常用的事例

//$Id: SequenceGenerator.java,v 1.12 2005/02/12 07:19:22 steveebersole Exp $
package org.hibernate.id;

import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
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.exception.JDBCExceptionHelper;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.mapping.Table;
import org.hibernate.type.Type;
import org.hibernate.util.PropertiesHelper;

/**
 * <b>sequence</b><br>
 * <br>
 * Generates <tt>long</tt> values using an oracle-style sequence. A higher
 * performance algorithm is <tt>SequenceHiLoGenerator</tt>.<br>
 * <br>
 * Mapping parameters supported: sequence, parameters.
 *
 * @see SequenceHiLoGenerator
 * @see TableHiLoGenerator
 * @author Gavin King
 */

public class SequenceGenerator implements PersistentIdentifierGenerator, Configurable {

	/**
	 * The sequence parameter
	 */
	public static final String SEQUENCE = "sequence";

	/**
	 * The parameters parameter, appended to the create sequence DDL.
	 * For example (Oracle): <tt>INCREMENT BY 1 START WITH 1 MAXVALUE 100 NOCACHE</tt>.
	 */
	public static final String PARAMETERS = "parameters";

	private String sequenceName;
	private String parameters;
	private Type identifierType;
	private String sql;

	private static final Log log = LogFactory.getLog(SequenceGenerator.class);

	public void configure(Type type, Properties params, Dialect dialect) throws MappingException {
		this.sequenceName = PropertiesHelper.getString(SEQUENCE, params, "hibernate_sequence");
		this.parameters = params.getProperty(PARAMETERS);
		String schemaName = params.getProperty(SCHEMA);
        String catalogName = params.getProperty(CATALOG);

        if (sequenceName.indexOf(dialect.getSchemaSeparator() ) < 0) {
            sequenceName = Table.qualify(catalogName, schemaName, sequenceName, dialect.getSchemaSeparator() );
        }

        this.identifierType = type;
		sql = dialect.getSequenceNextValString(sequenceName);
	}

	public Serializable generate(SessionImplementor session, Object obj) 
	throws HibernateException {
		
		try {

			PreparedStatement st = session.getBatcher().prepareSelectStatement(sql);
			try {
				ResultSet rs = st.executeQuery();
				final Serializable result;
				try {
					rs.next();
					result = IdentifierGeneratorFactory.get(
						rs, identifierType
					);
				}
				finally {
					rs.close();
				}
				if ( log.isDebugEnabled() )
					log.debug("Sequence identifier generated: " + result);
				return result;
			}
			finally {
				session.getBatcher().closeStatement(st);
			}
			
		}
		catch (SQLException sqle) {
			throw JDBCExceptionHelper.convert(
			        session.getFactory().getSQLExceptionConverter(),
			        sqle,
			        "could not get next sequence value",
			        sql
			);
		}

	}

	public String[] sqlCreateStrings(Dialect dialect) throws HibernateException {
		String[] ddl = dialect.getCreateSequenceStrings(sequenceName);
		if ( parameters!=null ) ddl[ddl.length-1] += ' ' + parameters;
		return ddl;
	}

	public String[] sqlDropStrings(Dialect dialect) throws HibernateException {
		return dialect.getDropSequenceStrings(sequenceName);
	}

	public Object generatorKey() {
		return sequenceName;
	}

}