0.10/xmlps/src/main/java/org/apache/oodt/xmlps/product/XMLPSProductHandler.java - oodt - Git at Google

 /**
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
  * The ASF licenses this file to You 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.apache.oodt.xmlps.product;

 //OODT imports
 import org.apache.oodt.product.ProductException;
 import org.apache.oodt.product.QueryHandler;
 import org.apache.oodt.xmlps.mapping.DatabaseTable;
 import org.apache.oodt.xmlps.mapping.FieldScope;
 import org.apache.oodt.xmlps.mapping.Mapping;
 import org.apache.oodt.xmlps.mapping.MappingField;
 import org.apache.oodt.xmlps.mapping.MappingReader;
 import org.apache.oodt.xmlps.mapping.funcs.MappingFunc;
 import org.apache.oodt.xmlps.queryparser.Expression;
 import org.apache.oodt.xmlps.queryparser.HandlerQueryParser;
 import org.apache.oodt.xmlps.structs.CDEResult;
 import org.apache.oodt.xmlps.structs.CDEValue;
 import org.apache.oodt.xmlps.util.XMLQueryHelper;
 import org.apache.oodt.xmlquery.QueryElement;
 import org.apache.oodt.xmlquery.XMLQuery;

 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
 import java.util.Stack;
 import java.util.Vector;
 import java.util.logging.Level;
 import java.util.logging.Logger;

 /**
  *
  * <p>
  * An XML configurable version of a Product Server that requires no code
  * to be written to plug into a local site's relational backend DBMS.
  * </p>.
  */
 public class XMLPSProductHandler implements QueryHandler {

     /* our log stream */
     private static final Logger LOG = Logger
             .getLogger(XMLPSProductHandler.class.getName());

     protected Mapping mapping;

     private DBMSExecutor executor;

     protected XMLPSProductHandler(String phony) {
         /* this is to get around invoking the default constructor in sub-classes */
     }

     public XMLPSProductHandler() throws InstantiationException {
         String MappingFilePath = System
                 .getProperty("org.apache.oodt.xmlps.xml.mapFilePath");

         if (MappingFilePath == null) {
             throw new InstantiationException(
                     "Need to specify path to xml mapping file!");
         }

         try {
             mapping = MappingReader.getMapping(MappingFilePath);
         } catch (Exception e) {
             throw new InstantiationException(
                     "Unable to parse mapping xml file: ["
                             + MappingFilePath + "]: reason: "
                             + e.getMessage());
         }

         /* load the db properties file */
         /*
          * if one exists: otherwise, don't bother and just print out the SQL to
          * the console.
          */
         String dbPropFilePath = System
                 .getProperty("org.apache.oodt.xmlps.xml.dbPropFilePath");
         if (dbPropFilePath != null) {
             try {
                 System.getProperties()
                         .load(new FileInputStream(dbPropFilePath));
             } catch (FileNotFoundException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             } catch (IOException e) {
                 e.printStackTrace();
                 throw new InstantiationException(e.getMessage());
             }

             executor = new DBMSExecutor();
         }
     }

     /*
      * (non-Javadoc)
      *
      * @see org.apache.oodt.product.QueryHandler#query(org.apache.oodt.xmlquery.XMLQuery)
      */
     public XMLQuery query(XMLQuery query) throws ProductException {
         List<QueryElement> whereSet = query.getWhereElementSet();
         List<QueryElement> selectSet = query.getSelectElementSet();
         try {
             translateToDomain(selectSet, true);
             translateToDomain(whereSet, false);
         } catch (Exception e) {
             LOG.severe(e.getMessage());
             throw new ProductException(e.getMessage());
         }

         queryAndPackageResults(query);

         return query;
     }

     public static void main(String[] args) throws Exception {
         String usage = "XMLPSProductHandler <query>\n";

         if (args.length != 1) {
             System.err.println(usage);
             System.exit(1);
         }

         XMLPSProductHandler handler = new XMLPSProductHandler();
         XMLQuery q = handler.query(XMLQueryHelper
                 .getDefaultQueryFromQueryString(args[0]));
         System.out.println(q.getXMLDocString());
     }

     protected List<QueryElement> getElemNamesFromQueryElemSet(
             List<QueryElement> origSet) {
         if (origSet == null || (origSet != null && origSet.size() == 0))
             return Collections.emptyList();

         List<QueryElement> newSet = new Vector<QueryElement>();

         for (Iterator<QueryElement> i = origSet.iterator(); i.hasNext();) {
             QueryElement elem = i.next();
             if (elem.getRole().equals(XMLQueryHelper.ROLE_ELEMNAME)
                     && !mapping.constantField(elem.getValue())) {
                 newSet.add(elem);

             }

         }

         return newSet;

     }

     protected List<QueryElement> getConstElemNamesFromQueryElemSet(
             List<QueryElement> origSet) {
         if (origSet == null || (origSet != null && origSet.size() == 0))
             return Collections.emptyList();

         List<QueryElement> newSet = new Vector<QueryElement>();

         for (Iterator<QueryElement> i = origSet.iterator(); i.hasNext();) {
             QueryElement elem = i.next();
             if (elem.getRole().equals(XMLQueryHelper.ROLE_ELEMNAME)
                     && mapping.constantField(elem.getValue())) {
                 newSet.add(elem);
             }
         }

         return newSet;
     }

     protected void queryAndPackageResults(XMLQuery query) {
         Stack<QueryElement> queryStack = HandlerQueryParser
                 .createQueryStack(query.getWhereElementSet());
         Expression parsedQuery = HandlerQueryParser.parse(queryStack,
                 this.mapping);
         List<QueryElement> selectNames = getElemNamesFromQueryElemSet(query
                 .getSelectElementSet());

         String querySelectNames = toSQLSelectColumns(selectNames);

         StringBuffer sqlBuf = new StringBuffer("SELECT ");
         sqlBuf.append(querySelectNames);
         sqlBuf.append(" FROM ");
         sqlBuf.append(mapping.getDefaultTable());
         sqlBuf.append(" ");

         if (mapping.getNumTables() > 0) {
             List<QueryElement> whereNames = getElemNamesFromQueryElemSet(query.getWhereElementSet());
             Set<DatabaseTable> requiredTables = getRequiredTables(whereNames, selectNames);
             for (DatabaseTable tbl : requiredTables) {
                 sqlBuf.append("INNER JOIN ");
                 sqlBuf.append(tbl.getName());
                 sqlBuf.append(" ON ");
                 sqlBuf.append(tbl.getName());
                 sqlBuf.append(".");
                 sqlBuf.append(tbl.getJoinFieldName());
                 sqlBuf.append(" = ");
                 sqlBuf.append(tbl.getDefaultTableJoin());
                 sqlBuf.append(".");
                 sqlBuf.append(tbl.getDefaultTableJoinFieldName());
                 sqlBuf.append(" ");
             }
         }

         if(parsedQuery != null){
             sqlBuf.append(" WHERE ");
             sqlBuf.append(parsedQuery.evaluate());
         }

         LOG.log(Level.INFO, sqlBuf.toString());

         if (executor != null) {
             try {
                 CDEResult res = executor.executeLocalQuery(sqlBuf.toString());
                 res.setOrderedFields(query.getSelectElementSet());
                 res.setMapping(mapping);
                 res.setConstValues(getConstValuesForQuery(query));
                 query.getResults().add(res);
             } catch (SQLException e) {
                 e.printStackTrace();
                 LOG.log(Level.WARNING, "Error executing sql: ["
                         + sqlBuf.toString() + "]: Message: " + e.getMessage());
             }
         }

     }

     private List<CDEValue> getConstValuesForQuery(XMLQuery query) {
         List<QueryElement> select = query.getSelectElementSet();
         List<QueryElement> constNames = getConstElemNamesFromQueryElemSet(select);
         List<CDEValue> constValues = new ArrayList<CDEValue>();
         if (constNames != null) {
             for (QueryElement qe : constNames) {
                 MappingField fld = mapping.getFieldByLocalName(qe.getValue());
                 if (fld != null) {
                     constValues.add(new CDEValue(fld.getName(), fld.getConstantValue()));
                 }
             }
         }
         return constValues;
     }

     private String toSQLSelectColumns(List<QueryElement> elems) {
         if (elems == null || (elems != null && elems.size() == 0))
             return null;

         StringBuilder buf = new StringBuilder();
         for (QueryElement qe : elems) {
             MappingField fld = this.mapping.getFieldByLocalName(qe.getValue());
             if (fld != null) {
                 buf.append(fld.getLocalName());
                 buf.append(" as ");
                 buf.append(fld.getName());
                 buf.append(",");
             }
         }

         buf.deleteCharAt(buf.length() - 1);

         return buf.toString();
     }

     protected void translateToDomain(List<QueryElement> elemSet,
             boolean selectSet) throws Exception {
         // go through each query element: use the mapping fields
         // to translate the names

         for (Iterator<QueryElement> i = elemSet.iterator(); i.hasNext();) {
             QueryElement elem = i.next();
             if (elem.getRole().equals(XMLQueryHelper.ROLE_ELEMNAME)) {
                 // do the translation
                 String elemValue = elem.getValue();
                 MappingField fld = this.mapping.getFieldByName(elemValue);
                 // make sure fld is not null
                 if (fld == null) {
                     continue;
                 }

                 // make sure scope is null, or if it's not null, then it's
                 // FieldScope.QUERY

                 if (fld.getScope() != null
                         && fld.getScope().equals(FieldScope.RETURN)) {
                     // skip
                     continue;
                 }

                 // check to see if it has a dbname attr, if not, then the name
                 // stays
                 // the same
                 String newFldName = fld.getLocalName();

                 elem.setValue(newFldName);

                 // now translate the domain vocab if there are translate funcs
                 // present and this isn't the select set

                 if (!selectSet && fld.getFuncs() != null
                         && fld.getFuncs().size() > 0) {
                     // the next query element should be
                     // XMLQueryHelper.ROLE_LITERAL
                     if (!i.hasNext())
                         break;
                     QueryElement litElem = i.next();
                     if (!litElem.getRole().equals(XMLQueryHelper.ROLE_LITERAL)) {
                         throw new Exception("next query element not "
                                 + XMLQueryHelper.ROLE_LITERAL + "! role is "
                                 + litElem.getRole() + " instead!");
                     }

                     for (Iterator<MappingFunc> j = fld.getFuncs().iterator(); j
                             .hasNext();) {
                         MappingFunc func = j.next();
                         CDEValue origVal = new CDEValue(fld.getName(),
                                 litElem.getValue());
                         CDEValue newVal = func.inverseTranslate(origVal);
                         litElem.setValue(newVal.getVal());
                     }

                 }

             }
         }

     }

     protected Set<DatabaseTable> getRequiredTables(
             List<QueryElement> whereElemNames, List<QueryElement> selectElemNames) {
         Set<DatabaseTable> tables = new HashSet<DatabaseTable>();
         // add tables from where element set
         if (whereElemNames != null) {
             for (QueryElement qe : whereElemNames) {
                 MappingField fld = mapping.getFieldByLocalName(qe.getValue());
                 if (fld != null) {
                     DatabaseTable t = mapping.getTableByName(fld.getTableName());
                     if (t != null && !tables.contains(t) && !t.getName().equals(mapping.getDefaultTable())) {
                         tables.add(t);
                     }
                 }
             }
         }
         // add tables from select element set
         if (selectElemNames != null) {
             for (QueryElement qe : selectElemNames) {
                 MappingField fld = mapping.getFieldByLocalName(qe.getValue());
                 if (fld != null) {
                     DatabaseTable t = mapping.getTableByName(fld.getTableName());
                     if (t != null && !tables.contains(t) && !t.getName().equals(mapping.getDefaultTable())) {
                         tables.add(t);
                     }
                 }
             }
         }
         // the tables found may be joined on columns from tables we haven't found
         // yet
         // add additional required join tables
         Set<DatabaseTable> moreTables = new HashSet<DatabaseTable>(tables);
         for (DatabaseTable t : tables) {
             DatabaseTable join = mapping.getTableByName(t.getDefaultTableJoin());
             // recursively add all join tables until we get to either
             // (a) the mapping default table (join == null)
             // (b) or a table already found (moreTables.contains(join))
             while (join != null && !moreTables.contains(join) && !join.getName().equals(mapping.getDefaultTable())) {
                 moreTables.add(join);
                 join = mapping.getTableByName(join.getDefaultTableJoin());
             }
         }
         return moreTables;
     }

 }
	/**
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You 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.apache.oodt.xmlps.product;

	//OODT imports
	import org.apache.oodt.product.ProductException;
	import org.apache.oodt.product.QueryHandler;
	import org.apache.oodt.xmlps.mapping.DatabaseTable;
	import org.apache.oodt.xmlps.mapping.FieldScope;
	import org.apache.oodt.xmlps.mapping.Mapping;
	import org.apache.oodt.xmlps.mapping.MappingField;
	import org.apache.oodt.xmlps.mapping.MappingReader;
	import org.apache.oodt.xmlps.mapping.funcs.MappingFunc;
	import org.apache.oodt.xmlps.queryparser.Expression;
	import org.apache.oodt.xmlps.queryparser.HandlerQueryParser;
	import org.apache.oodt.xmlps.structs.CDEResult;
	import org.apache.oodt.xmlps.structs.CDEValue;
	import org.apache.oodt.xmlps.util.XMLQueryHelper;
	import org.apache.oodt.xmlquery.QueryElement;
	import org.apache.oodt.xmlquery.XMLQuery;

	import java.io.FileInputStream;
	import java.io.FileNotFoundException;
	import java.io.IOException;
	import java.sql.SQLException;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.HashSet;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Set;
	import java.util.Stack;
	import java.util.Vector;
	import java.util.logging.Level;
	import java.util.logging.Logger;

	/**
	*
	* <p>
	* An XML configurable version of a Product Server that requires no code
	* to be written to plug into a local site's relational backend DBMS.
	* </p>.
	*/
	public class XMLPSProductHandler implements QueryHandler {

	/* our log stream */
	private static final Logger LOG = Logger
	.getLogger(XMLPSProductHandler.class.getName());

	protected Mapping mapping;

	private DBMSExecutor executor;

	protected XMLPSProductHandler(String phony) {
	/* this is to get around invoking the default constructor in sub-classes */
	}

	public XMLPSProductHandler() throws InstantiationException {
	String MappingFilePath = System
	.getProperty("org.apache.oodt.xmlps.xml.mapFilePath");

	if (MappingFilePath == null) {
	throw new InstantiationException(
	"Need to specify path to xml mapping file!");
	}

	try {
	mapping = MappingReader.getMapping(MappingFilePath);
	} catch (Exception e) {
	throw new InstantiationException(
	"Unable to parse mapping xml file: ["
	+ MappingFilePath + "]: reason: "
	+ e.getMessage());
	}

	/* load the db properties file */
	/*
	* if one exists: otherwise, don't bother and just print out the SQL to
	* the console.
	*/
	String dbPropFilePath = System
	.getProperty("org.apache.oodt.xmlps.xml.dbPropFilePath");
	if (dbPropFilePath != null) {
	try {
	System.getProperties()
	.load(new FileInputStream(dbPropFilePath));
	} catch (FileNotFoundException e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
	} catch (IOException e) {
	e.printStackTrace();
	throw new InstantiationException(e.getMessage());
	}

	executor = new DBMSExecutor();
	}
	}

	/*
	* (non-Javadoc)
	*
	* @see org.apache.oodt.product.QueryHandler#query(org.apache.oodt.xmlquery.XMLQuery)
	*/
	public XMLQuery query(XMLQuery query) throws ProductException {
	List<QueryElement> whereSet = query.getWhereElementSet();
	List<QueryElement> selectSet = query.getSelectElementSet();
	try {
	translateToDomain(selectSet, true);
	translateToDomain(whereSet, false);
	} catch (Exception e) {
	LOG.severe(e.getMessage());
	throw new ProductException(e.getMessage());
	}

	queryAndPackageResults(query);

	return query;
	}

	public static void main(String[] args) throws Exception {
	String usage = "XMLPSProductHandler <query>\n";

	if (args.length != 1) {
	System.err.println(usage);
	System.exit(1);
	}

	XMLPSProductHandler handler = new XMLPSProductHandler();
	XMLQuery q = handler.query(XMLQueryHelper
	.getDefaultQueryFromQueryString(args[0]));
	System.out.println(q.getXMLDocString());
	}

	protected List<QueryElement> getElemNamesFromQueryElemSet(
	List<QueryElement> origSet) {
	if (origSet == null \|\| (origSet != null && origSet.size() == 0))
	return Collections.emptyList();

	List<QueryElement> newSet = new Vector<QueryElement>();

	for (Iterator<QueryElement> i = origSet.iterator(); i.hasNext();) {
	QueryElement elem = i.next();
	if (elem.getRole().equals(XMLQueryHelper.ROLE_ELEMNAME)
	&& !mapping.constantField(elem.getValue())) {
	newSet.add(elem);

	}

	}

	return newSet;

	}

	protected List<QueryElement> getConstElemNamesFromQueryElemSet(
	List<QueryElement> origSet) {
	if (origSet == null \|\| (origSet != null && origSet.size() == 0))
	return Collections.emptyList();

	List<QueryElement> newSet = new Vector<QueryElement>();

	for (Iterator<QueryElement> i = origSet.iterator(); i.hasNext();) {
	QueryElement elem = i.next();
	if (elem.getRole().equals(XMLQueryHelper.ROLE_ELEMNAME)
	&& mapping.constantField(elem.getValue())) {
	newSet.add(elem);
	}
	}

	return newSet;
	}

	protected void queryAndPackageResults(XMLQuery query) {
	Stack<QueryElement> queryStack = HandlerQueryParser
	.createQueryStack(query.getWhereElementSet());
	Expression parsedQuery = HandlerQueryParser.parse(queryStack,
	this.mapping);
	List<QueryElement> selectNames = getElemNamesFromQueryElemSet(query
	.getSelectElementSet());

	String querySelectNames = toSQLSelectColumns(selectNames);

	StringBuffer sqlBuf = new StringBuffer("SELECT ");
	sqlBuf.append(querySelectNames);
	sqlBuf.append(" FROM ");
	sqlBuf.append(mapping.getDefaultTable());
	sqlBuf.append(" ");

	if (mapping.getNumTables() > 0) {
	List<QueryElement> whereNames = getElemNamesFromQueryElemSet(query.getWhereElementSet());
	Set<DatabaseTable> requiredTables = getRequiredTables(whereNames, selectNames);
	for (DatabaseTable tbl : requiredTables) {
	sqlBuf.append("INNER JOIN ");
	sqlBuf.append(tbl.getName());
	sqlBuf.append(" ON ");
	sqlBuf.append(tbl.getName());
	sqlBuf.append(".");
	sqlBuf.append(tbl.getJoinFieldName());
	sqlBuf.append(" = ");
	sqlBuf.append(tbl.getDefaultTableJoin());
	sqlBuf.append(".");
	sqlBuf.append(tbl.getDefaultTableJoinFieldName());
	sqlBuf.append(" ");
	}
	}

	if(parsedQuery != null){
	sqlBuf.append(" WHERE ");
	sqlBuf.append(parsedQuery.evaluate());
	}

	LOG.log(Level.INFO, sqlBuf.toString());

	if (executor != null) {
	try {
	CDEResult res = executor.executeLocalQuery(sqlBuf.toString());
	res.setOrderedFields(query.getSelectElementSet());
	res.setMapping(mapping);
	res.setConstValues(getConstValuesForQuery(query));
	query.getResults().add(res);
	} catch (SQLException e) {
	e.printStackTrace();
	LOG.log(Level.WARNING, "Error executing sql: ["
	+ sqlBuf.toString() + "]: Message: " + e.getMessage());
	}
	}

	}

	private List<CDEValue> getConstValuesForQuery(XMLQuery query) {
	List<QueryElement> select = query.getSelectElementSet();
	List<QueryElement> constNames = getConstElemNamesFromQueryElemSet(select);
	List<CDEValue> constValues = new ArrayList<CDEValue>();
	if (constNames != null) {
	for (QueryElement qe : constNames) {
	MappingField fld = mapping.getFieldByLocalName(qe.getValue());
	if (fld != null) {
	constValues.add(new CDEValue(fld.getName(), fld.getConstantValue()));
	}
	}
	}
	return constValues;
	}

	private String toSQLSelectColumns(List<QueryElement> elems) {
	if (elems == null \|\| (elems != null && elems.size() == 0))
	return null;

	StringBuilder buf = new StringBuilder();
	for (QueryElement qe : elems) {
	MappingField fld = this.mapping.getFieldByLocalName(qe.getValue());
	if (fld != null) {
	buf.append(fld.getLocalName());
	buf.append(" as ");
	buf.append(fld.getName());
	buf.append(",");
	}
	}

	buf.deleteCharAt(buf.length() - 1);

	return buf.toString();
	}

	protected void translateToDomain(List<QueryElement> elemSet,
	boolean selectSet) throws Exception {
	// go through each query element: use the mapping fields
	// to translate the names

	for (Iterator<QueryElement> i = elemSet.iterator(); i.hasNext();) {
	QueryElement elem = i.next();
	if (elem.getRole().equals(XMLQueryHelper.ROLE_ELEMNAME)) {
	// do the translation
	String elemValue = elem.getValue();
	MappingField fld = this.mapping.getFieldByName(elemValue);
	// make sure fld is not null
	if (fld == null) {
	continue;
	}

	// make sure scope is null, or if it's not null, then it's
	// FieldScope.QUERY

	if (fld.getScope() != null
	&& fld.getScope().equals(FieldScope.RETURN)) {
	// skip
	continue;
	}

	// check to see if it has a dbname attr, if not, then the name
	// stays
	// the same
	String newFldName = fld.getLocalName();

	elem.setValue(newFldName);

	// now translate the domain vocab if there are translate funcs
	// present and this isn't the select set

	if (!selectSet && fld.getFuncs() != null
	&& fld.getFuncs().size() > 0) {
	// the next query element should be
	// XMLQueryHelper.ROLE_LITERAL
	if (!i.hasNext())
	break;
	QueryElement litElem = i.next();
	if (!litElem.getRole().equals(XMLQueryHelper.ROLE_LITERAL)) {
	throw new Exception("next query element not "
	+ XMLQueryHelper.ROLE_LITERAL + "! role is "
	+ litElem.getRole() + " instead!");
	}

	for (Iterator<MappingFunc> j = fld.getFuncs().iterator(); j
	.hasNext();) {
	MappingFunc func = j.next();
	CDEValue origVal = new CDEValue(fld.getName(),
	litElem.getValue());
	CDEValue newVal = func.inverseTranslate(origVal);
	litElem.setValue(newVal.getVal());
	}

	}

	}
	}

	}

	protected Set<DatabaseTable> getRequiredTables(
	List<QueryElement> whereElemNames, List<QueryElement> selectElemNames) {
	Set<DatabaseTable> tables = new HashSet<DatabaseTable>();
	// add tables from where element set
	if (whereElemNames != null) {
	for (QueryElement qe : whereElemNames) {
	MappingField fld = mapping.getFieldByLocalName(qe.getValue());
	if (fld != null) {
	DatabaseTable t = mapping.getTableByName(fld.getTableName());
	if (t != null && !tables.contains(t) && !t.getName().equals(mapping.getDefaultTable())) {
	tables.add(t);
	}
	}
	}
	}
	// add tables from select element set
	if (selectElemNames != null) {
	for (QueryElement qe : selectElemNames) {
	MappingField fld = mapping.getFieldByLocalName(qe.getValue());
	if (fld != null) {
	DatabaseTable t = mapping.getTableByName(fld.getTableName());
	if (t != null && !tables.contains(t) && !t.getName().equals(mapping.getDefaultTable())) {
	tables.add(t);
	}
	}
	}
	}
	// the tables found may be joined on columns from tables we haven't found
	// yet
	// add additional required join tables
	Set<DatabaseTable> moreTables = new HashSet<DatabaseTable>(tables);
	for (DatabaseTable t : tables) {
	DatabaseTable join = mapping.getTableByName(t.getDefaultTableJoin());
	// recursively add all join tables until we get to either
	// (a) the mapping default table (join == null)
	// (b) or a table already found (moreTables.contains(join))
	while (join != null && !moreTables.contains(join) && !join.getName().equals(mapping.getDefaultTable())) {
	moreTables.add(join);
	join = mapping.getTableByName(join.getDefaultTableJoin());
	}
	}
	return moreTables;
	}

	}