groupingfunctions.java

JoSQL 1.5的源代码。JoSQL(SQL for Java Objects)为Java开发者提供运用SQL语句来操作Java对象集的能力.利用JoSQL可以像操作数据库中的数据一样对任何Java

/*
 * Copyright 2004-2005 Gary Bentley 
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may 
 * not use this file except in compliance with the License. 
 * You may obtain a copy of the License at 
 *    http://www.apache.org/licenses/LICENSE-2.0 
 *
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * See the License for the specific language governing permissions and 
 * limitations under the License.
 */
package org.josql.functions;

import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;

import com.gentlyweb.utils.Getter;

import org.josql.QueryExecutionException;

import org.josql.internal.Utilities;

import org.josql.expressions.Expression;

import org.josql.Query;

public class GroupingFunctions extends AbstractFunctionHandler
{

    public static final String VALUE = "value";

    public static final String HANDLER_ID = "_internal_grouping";

    public Object least (List       allobjs,
			 Expression exp,
			 String     saveValueName)
                         throws     QueryExecutionException
    {

	if (saveValueName != null)
	{

	    Object o = this.q.getSaveValue (saveValueName);

	    if (o != null)
	    {

		return o;

	    }

	}

	if (allobjs.size () == 0)
	{

	    return null;

	}

	Object g = null;

	int s = allobjs.size ();

	for (int i = 0; i < s; i++)
	{

	    Object o = allobjs.get (i);

	    Object v = null;

	    try
	    {

		v = exp.getValue (o,
				  this.q);

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to get value from expression: " + 
						   exp +
						   " for maximum value" +
						   e);

	    }	    

	    if (g == null)
	    {

		g = v;

	    } else {

		int c = Utilities.compare (v,
					   g);

		if (c < 0)
		{

		    g = v;

		}

	    }

	}

	if ((saveValueName != null)
	    &&
	    (q != null)
	   )
	{

	    q.setSaveValue (saveValueName,
			    g);

	}

	return g;

    }

    public Object minObject (Expression exp)
	                     throws     QueryExecutionException
    {

	return this.minObject ((List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME),
			       exp);

    }    

    public Object minObject (List       allobjs,
			     Expression exp)
                             throws     QueryExecutionException
    {

	return this.leastObject (allobjs,
				 exp);

    }

    public Object leastObject (List       allobjs,
			       Expression exp)
                               throws     QueryExecutionException
    {

	if (allobjs.size () == 0)
	{

	    return null;

	}

	Object l = null;
	Object lo = null;

	int s = allobjs.size ();

	for (int i = 0; i < s; i++)
	{

	    Object o = allobjs.get (i);

	    Object v = null;

	    try
	    {

		v = exp.getValue (o,
				  this.q);

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to get value from expression: " + 
						   exp +
						   " for maximum value" +
						   e);

	    }	    

	    if (l == null)
	    {

		l = v;
		lo = o;

	    } else {

		int c = Utilities.compare (v,
					   l);

		if (c < 0)
		{

		    l = v;
		    lo = o;

		}

	    }

	}

	return lo;

    }

    public Object maxObject (List       allobjs,
			     Expression exp)
                             throws     QueryExecutionException
    {

	return this.greatestObject (allobjs,
				    exp);

    }

    public Object maxObject (Expression exp)
	                     throws     QueryExecutionException
    {

	return this.maxObject ((List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME),
			       exp);

    }    

    public Object greatestObject (List       allobjs,
				  Expression exp)
                                  throws     QueryExecutionException
    {

	if (allobjs.size () == 0)
	{

	    return null;

	}

	Object g = null;
	Object go = null;

	int s = allobjs.size ();

	for (int i = 0; i < s; i++)
	{

	    Object o = allobjs.get (i);

	    Object v = null;

	    try
	    {

		v = exp.getValue (o,
				  this.q);

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to get value from expression: " + 
						   exp +
						   " for maximum value" +
						   e);

	    }	    

	    if (g == null)
	    {

		g = v;
		go = o;

	    } else {

		int c = Utilities.compare (v,
					   g);

		if (c > 0)
		{

		    g = v;
		    go = o;

		}

	    }

	}

	return go;

    }

    public Object least (List       allobjs,
			 Expression exp)
                         throws     QueryExecutionException
    {

	return this.least (allobjs,
			   exp,
			   null);

    }

    public Object min (Expression exp)
	               throws     QueryExecutionException
    {

	return this.min ((List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME),
			 exp);

    }    

    public Object min (List       allobjs,
		       Expression exp)
                       throws     QueryExecutionException
    {

	return this.least (allobjs,
			   exp,
			   null);

    }

    public Object min (List       allobjs,
		       Expression exp,
		       String     saveValueName)
                       throws     QueryExecutionException
    {

	return this.least (allobjs,
			   exp,
			   saveValueName);

    }

    public Map.Entry maxEntry (Map    m,
			       String type)
    {

	int t = 0;

	if (type.equals (GroupingFunctions.VALUE))
	{

	    t = 1;

	}

	Map.Entry r = null;
	Map.Entry le = null;

	Iterator iter = m.entrySet ().iterator ();

	while (iter.hasNext ())
	{

	    r = (Map.Entry) iter.next ();

	    if (le != null)
	    {

		if (t == 0)
		{

		    if (Utilities.isGTEquals (r.getKey (),
					      le.getKey ()))
		    {

			le = r;

		    }

		} else {

		    if (Utilities.isGTEquals (r.getValue (),
					      le.getValue ()))
		    {

			le = r;

		    }

		}

	    } else {

		le = r;

	    }

	}

	return le;

    }

    public Map.Entry minEntry (Object m,
			       String type)
	                       throws QueryExecutionException
    {

	if (!(m instanceof Map))
	{

	    throw new QueryExecutionException ("Only instances of: " +
					       Map.class.getName () + 
					       " are supported, passed: " +
					       m.getClass ().getName ());

	}

	return this.minEntry ((Map) m,
			      type);

    }

    public Map.Entry minEntry (Map    m,
			       String type)
    {

	int t = 0;

	if (type.equals (GroupingFunctions.VALUE))
	{

	    t = 1;

	}

	Map.Entry r = null;
	Map.Entry le = null;

	Iterator iter = m.entrySet ().iterator ();

	while (iter.hasNext ())
	{

	    r = (Map.Entry) iter.next ();

	    if (le != null)
	    {

		if (t == 0)
		{

		    if (Utilities.isLTEquals (r.getKey (),
					      le.getKey ()))
		    {

			le = r;

		    }

		} else {

		    if (Utilities.isLTEquals (r.getValue (),
					      le.getValue ()))
		    {

			le = r;

		    }

		}

	    } else {

		le = r;

	    }

	}

	return le;

    }

    public Object max (List       allobjs,
		       Expression exp,
		       String     saveValueName)
                       throws     QueryExecutionException
    {

	return this.greatest (allobjs,
			      exp,
			      saveValueName);

    }

    public Object greatest (List       allobjs,
			    Expression exp,
			    String     saveValueName)
                            throws     QueryExecutionException
    {

	if (saveValueName != null)
	{

	    Object o = this.q.getSaveValue (saveValueName);

	    if (o != null)
	    {

		return (Double) o;

	    }

	}

	if (allobjs.size () == 0)
	{

	    return null;

	}

	Object g = null;

	int s = allobjs.size ();

	for (int i = 0; i < s; i++)
	{

	    Object o = allobjs.get (i);

	    Object v = null;

	    try
	    {

		v = exp.getValue (o,
				  this.q);

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to get value from expression: " + 
						   exp +
						   " for maximum value" +
						   e);

	    }	    

	    if (g == null)
	    {

		g = v;

	    } else {

		int c = Utilities.compare (v,
					   g);

		if (c > 0)
		{

		    g = v;

		}

	    }

	}

	if (saveValueName != null)
	{

	    this.q.setSaveValue (saveValueName,
				 g);

	}

	return g;

    }

    public Object greatest (List       allobjs,
			    Expression exp)
                            throws     QueryExecutionException
    {

	return this.greatest (allobjs,
			      exp,
			      null);

    }

    public Object max (Expression exp)
	               throws     QueryExecutionException
    {

	return this.max ((List) this.q.getVariable (Query.ALL_OBJS_VAR_NAME),
			 exp);

    }    

    public Object max (List       allobjs,
		       Expression exp)
                       throws     QueryExecutionException
    {

	return this.greatest (allobjs,
 			      exp,
			      null);

    }

    private double getTotal (List       allobjs,
			     Expression exp)
	                     throws     QueryExecutionException
    {

	Object currObj = this.q.getCurrentObject ();

	double total = 0;

	int size = allobjs.size ();

	for (int i = 0; i < size; i++)
	{

	    Object o = allobjs.get (i);

	    this.q.setCurrentObject (o);

	    Number n = null;

	    try
	    {

		n = (Number) exp.getValue (o,
					   this.q);

	    } catch (Exception e) {

		throw new QueryExecutionException ("Unable to get value from expression: " +
						   exp + 
						   " for item: " + 
						   i +
						   " from the list of objects.",
						   e);

	    }

	    total += n.doubleValue ();

	}

	this.q.setCurrentObject (currObj);

	return total;