org.deegree.io.datastore.sql
Class QueryHandler

java.lang.Object
  org.deegree.io.datastore.sql.AbstractRequestHandler
      org.deegree.io.datastore.sql.FeatureFetcher
          org.deegree.io.datastore.sql.QueryHandler

public class QueryHandler
extends FeatureFetcher

Handles Query requests to SQL backed datastores.

Version:

$Revision: 20808 $, $Date: 2009-11-16 14:03:13 +0100 (Mo, 16. Nov 2009) $

Author:

Markus Schneider , last edited by: $Author: mschneider $

See Also:

FeatureFetcher, AbstractSQLDatastore, QueryTableTree

Field Summary

Fields inherited from class org.deegree.io.datastore.sql.FeatureFetcher

featureMap, featuresInGeneration, fidToPropertyMap, vcProvider

Fields inherited from class org.deegree.io.datastore.sql.AbstractRequestHandler

aliasGenerator, conn, datastore, FT_COLUMN, FT_PREFIX

Constructor Summary

QueryHandler(AbstractSQLDatastore ds, TableAliasGenerator aliasGenerator, Connection conn, MappedFeatureType[] rootFts, Query query)
Creates a new instance of QueryHandler from the given parameters.

Method Summary

protected StatementBuffer	buildInitialSelect(SelectManager selectManager) Builds the initial SELECT statement.
FeatureCollection	performQuery() Performs the associated Query against the datastore.

Methods inherited from class org.deegree.io.datastore.sql.FeatureFetcher

appendQualifiedContentList, buildResultPosMap, determineFetchContents, extractFeature, extractFeatureId

Methods inherited from class org.deegree.io.datastore.sql.AbstractRequestHandler

appendColumnsList, appendFeatureIdColumns, appendFeatureIdConstraint, appendFeatureIdConstraint, appendJoinCondition, appendJoins, appendQualifiedColumn, appendQualifiedColumnsList, determineAffectedAndModifiableFIDs, determineAffectedFIDs, determineSubFeatures, determineSuperFeatures, extractFeatureId, extractFeatureIds, extractFeatureIdsForceUnique

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

QueryHandler

public QueryHandler(AbstractSQLDatastore ds,
                    TableAliasGenerator aliasGenerator,
                    Connection conn,
                    MappedFeatureType[] rootFts,
                    Query query)
             throws DatastoreException

Creates a new instance of QueryHandler from the given parameters.

Parameters:

ds - datastore that spawned this QueryHandler

aliasGenerator - used to generate unique aliases for the tables in the SELECT statements

conn - JDBCConnection to execute the generated SELECT statements against

rootFts - the root feature types that are queried, more than one type means that the types are joined

query - query to perform

Throws:

DatastoreException

Method Detail

performQuery

public FeatureCollection performQuery()
                               throws SQLException,
                                      DatastoreException,
                                      UnknownCRSException

Performs the associated Query against the datastore.

Returns:

collection of requested features

Throws:

SQLException - if a JDBC error occurs

DatastoreException

UnknownCRSException

buildInitialSelect

protected StatementBuffer buildInitialSelect(SelectManager selectManager)
                                      throws DatastoreException

Builds the initial SELECT statement.

This statement determines all feature ids that are affected by the filter, but also SELECTs all properties that are stored in the root feature types' tables (to improve efficiency).

The statement is structured like this:

• SELECT
• comma-separated list of qualified columns/functions to fetch from root tables
• FROM
• comma-separated list of tables and their aliases (this is needed to constrain the paths to selected XPath-PropertyNames)
• WHERE
• SQL representation of the filter expression
• ORDER BY
• qualified sort criteria columns/functions

Parameters:

selectManager - associated SelectManager

Returns:

initial select statement

Throws:

DatastoreException