compositequeryitem.java

一个工作流设计及定义的系统,可以直接与数据库结合进行系统工作流程的定义及应用.

/*
 * Copyright (c) 2005, John Mettraux, OpenWFE.org
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 * . Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.  
 * 
 * . Redistributions in binary form must reproduce the above copyright notice, 
 *   this list of conditions and the following disclaimer in the documentation 
 *   and/or other materials provided with the distribution.
 * 
 * . Neither the name of the "OpenWFE" nor the names of its contributors may be
 *   used to endorse or promote products derived from this software without
 *   specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * $Id: CompositeQueryItem.java,v 1.13 2005/05/17 16:41:06 jmettraux Exp $
 */

//
// CompositeQueryItem.java
//
// [e-mail]
//
// generated with 
// jtmpl 1.1.00 16.08.2003 John Mettraux ([e-mail])
//

package openwfe.org.xdbc.query;

import openwfe.org.sql.SqlUtils;
import openwfe.org.xdbc.XdbcException;


/**
 * no comment
 *
 * <p><font size=2>CVS Info :
 * <br>$Author: jmettraux $
 * <br>$Id: CompositeQueryItem.java,v 1.13 2005/05/17 16:41:06 jmettraux Exp $ </font>
 *
 * @author [e-mail]
 */
public abstract class CompositeQueryItem

    implements QueryItem

{

    static org.apache.log4j.Logger log = org.apache.log4j.Logger
        .getLogger(CompositeQueryItem.class.getName());

    //
    // CONSTANTS & co

    public static String XML_ELT_NAME = "composite";
        // this is not a real constant... It's not final

    //
    // FIELDS

    protected java.util.List items = new java.util.ArrayList();

    //
    // CONSTRUCTORS

    //
    // METHODS from QueryItem

    public IdSet query (String clientIdLike, java.sql.Connection con)
        throws XdbcException
    {
        //
        // is it an homogeneous composite ?
        
        Class firstClass = getFirstClass();
        boolean isHomogeneous = false;
        if (firstClass != null) isHomogeneous = isHomogeneous(firstClass);

        //
        // it's an homogeneous composite
        
        if (isHomogeneous)
        {
            StringBuffer sb = new StringBuffer();

            sb.append("SELECT ");
            sb.append(DOCUMENT_ID);
            sb.append(", ");
            sb.append(CLIENT_ID);
            sb.append(" FROM ");

            if (firstClass.equals(AttributeQueryItem.class))
                sb.append(ATTRIBUTES);
            else
                sb.append(ELEMENTS);
            sb.append(", ");
            sb.append(DOCUMENTS);

            sb.append(" WHERE ");

            if (firstClass.equals(AttributeQueryItem.class))
                sb.append(ATTRIBUTES);
            else
                sb.append(ELEMENTS);
            sb.append("."); sb.append(DOCUMENT_ID);
            sb.append(" = ");
            sb.append(DOCUMENTS); sb.append("."); sb.append("id");

            sb.append(" AND ");
            sb.append(CLIENT_ID);
            sb.append(" LIKE ");
            sb.append(SqlUtils.prepareString(clientIdLike));

            sb.append(" AND ");
            sb.append(getQueryString());
            //sb.append(";");

            String query = sb.toString();

            log.debug("query() >\n"+query+"\n<");

            //
            // execute query

            return AtomicQueryItem.executeQuery(con, query);
        }

        //
        // it's an heterogeneous composite
        
        /*
         * this is NOT optimized... 
         * to optimized, homogeneous groups should be detected,
         * because there is one select per homongeneous group...
         */
        
        IdSet result = new IdSet();

        java.util.Iterator it = this.items.iterator();
        while (it.hasNext())
        {
            QueryItem next = (QueryItem)it.next();

            if (it.hasNext())
                result = combineResults(result, next.query(clientIdLike, con));
        }

        return result;
    }

    public org.jdom.Element encode ()
    {
        org.jdom.Element result = new org.jdom.Element(XML_ELT_NAME);

        java.util.Iterator it = this.items.iterator();
        while (it.hasNext())
            result.addContent(((QueryItem)it.next()).encode());

        return result;
    }

    //
    // METHODS

    public CompositeQueryItem add (QueryItem qi)
    {
        this.items.add(qi);
        return this;
    }

    public boolean isHomogeneous ()
    {
        if (this.items.size() < 1) return true;

        Class queryItemClass = getFirstClass();

        return isHomogeneous(queryItemClass);
    }

    public Class getFirstClass ()
    {
        if (this.items.size() < 1) return null;

        java.util.Iterator it = this.items.iterator();
        while (it.hasNext())
        {
            Object next = it.next();

            if (next instanceof AttributeQueryItem ||
                next instanceof ElementQueryItem)
            {
                return next.getClass();
            }

            //
            // deep first...

            if (next instanceof CompositeQueryItem)
            {
                Class clazz = ((CompositeQueryItem)next).getFirstClass();
                if (clazz != null) return clazz;
            }
        }

        return null;
    }

    public boolean isHomogeneous (Class queryItemClass)
    {
        java.util.Iterator it = this.items.iterator();
        while (it.hasNext())
        {
            Object next = it.next();

            if (next instanceof OwfeQueryItem)
            {
                //
                // an OwfeQueryItem is never part of an homogeneous
                // query : it is complex itself and cannot mix
                // with other QueryItem in a simple SQL query string.
                //

                return false;
            }

            if (next instanceof CompositeQueryItem)
            {
                if ( ! ((CompositeQueryItem)next).isHomogeneous(queryItemClass))
                    return false;
            }

            Class nextClass = next.getClass();

            if ( ! nextClass.equals(queryItemClass)) return false;
        }

        return true;
    }

    //
    // METHODS that have to be implemented (or overriden if static)

    public static CompositeQueryItem buildNew ()
    {
        return null;
    }

    protected abstract IdSet combineResults (IdSet set1, IdSet set2);

    //
    // non public methods

    protected String combineQueryStrings (String combinationOperator)
    {
        StringBuffer sb = new StringBuffer();

        sb.append("(");

        java.util.Iterator it = this.items.iterator();
        while (it.hasNext())
        {
            QueryItem qi = (QueryItem)it.next();

            sb.append(qi.getQueryString());

            if (it.hasNext())
            {
                sb.append(" ");
                sb.append(combinationOperator);
                sb.append(" ");
            }
        }

        sb.append(")");

        return sb.toString();
    }

}