How To Generate DDL Scripts from Hibernate, taken from http://jandrewthompson.blogspot.co.uk/2009/10/how-to-generate-ddl-scripts-from.html

SchemaGenerator.java

package com.jandrewthompson;

import java.io.File;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

/**
 * @author john.thompson
 *
 */
public class SchemaGenerator
{
  private AnnotationConfiguration cfg;
 
  public SchemaGenerator(String packageName) throws Exception
  {
    cfg = new AnnotationConfiguration();
    cfg.setProperty("hibernate.hbm2ddl.auto","create");
  
    for(Class<Object> clazz : getClasses(packageName))
    {
      cfg.addAnnotatedClass(clazz);
    }
  }
 
  /**
   * Method that actually creates the file.  
   * @param dbDialect to use
   */
  private void generate(Dialect dialect)
  {
    cfg.setProperty("hibernate.dialect", dialect.getDialectClass());
  
    SchemaExport export = new SchemaExport(cfg);
    export.setDelimiter(";");
    export.setOutputFile("ddl_" + dialect.name().toLowerCase() + ".sql"); 
    export.execute(true, false, false, false);
  }
 
  /**
   * @param args
   */
  public static void main(String[] args) throws Exception
  {
    SchemaGenerator gen = new SchemaGenerator("org.jthompson.myapp.domain");
    gen.generate(Dialect.MYSQL);
    gen.generate(Dialect.ORACLE);
    gen.generate(Dialect.HSQL);
  }

  /**
   * Utility method used to fetch Class list based on a package name.
   * @param packageName (should be the package containing your annotated beans.
   */
  private List<class> getClasses(String packageName) throws Exception
  {
    List<class> classes = new ArrayList<class>();
    File directory = null;
    try 
    {
      ClassLoader cld = Thread.currentThread().getContextClassLoader();
      if (cld == null) {
        throw new ClassNotFoundException("Can't get class loader.");
      }
      String path = packageName.replace('.', '/');
      URL resource = cld.getResource(path);
      if (resource == null) {
        throw new ClassNotFoundException("No resource for " + path);
      }
      directory = new File(resource.getFile());
    } catch (NullPointerException x) {
      throw new ClassNotFoundException(packageName + " (" + directory
          + ") does not appear to be a valid package");
    }
    if (directory.exists()) {
      String[] files = directory.list();
      for (int i = 0; i < files.length; i++) {
        if (files[i].endsWith(".class")) {
          // removes the .class extension
          classes.add(Class.forName(packageName + '.'
              + files[i].substring(0, files[i].length() - 6)));
        }
      }
    } else {
      throw new ClassNotFoundException(packageName
          + " is not a valid package");
    }
  
    return classes;
  }
 
  /**
   * Holds the classnames of hibernate dialects for easy reference.
   */
  private static enum Dialect 
  {
    ORACLE("org.hibernate.dialect.Oracle10gDialect"),
    MYSQL("org.hibernate.dialect.MySQLDialect"),
    HSQL("org.hibernate.dialect.HSQLDialect");
  
    private String dialectClass;
    private Dialect(String dialectClass)
    {
      this.dialectClass = dialectClass;
    }
    public String getDialectClass()
    {
      return dialectClass;
    }
  }
}