org.geotools.data
Class Query

Object
  extended by Query
Direct Known Subclasses:
DefaultQuery, JoiningQuery

public class Query
extends Object

Encapsulates a request for data, typically as:


 Query query = ...
 myFeatureSource.getFeatures(query);
 
The query class is based on the Web Feature Server specification and offers a few interesting capabilities such as the ability to sort results and use a filter (similar to the WHERE clause in SQL).

Additional capabilities:

Vendor specific: Joins:

The Query class supports the concepts of joins in that a query can result in a join of the feature type to other feature types in the same datastore. For example, the following would be a spatial join that selected the country that contain a particular city.


 Query query = new Query("countries");
 Join join = new Join("cities", CQL.toFilter("CONTAINS(geometry, b.geometry)"));
 join.setAlias("b");
 join.setFilter(CQL.toFilter("CITY_NAME = 'Canmore'"))
 query.getJoins().add(join);
 

Example:

 Filter filter = CQL.toFilter("NAME like '%land'");
 Query query = new Query( "countries", filter );

 FeatureCollection features = featureSource.getFeatures( query );
 

Author:
Chris Holmes

Field Summary
protected  String alias
          The optional alias for type name
static Query ALL
          Implements a query that will fetch all features from a datasource.
static String[] ALL_NAMES
          A constant (value null) that can be used with setPropertyNames(String[]) to indicate that all properties are to be retrieved.
static List<PropertyName> ALL_PROPERTIES
          A constant (value null) that can be used with #setProperties(Collection) to indicate that all properties are to be retrieved.
protected  CoordinateReferenceSystem coordinateSystem
          Coordinate System associated with this query
protected  CoordinateReferenceSystem coordinateSystemReproject
          Reprojection associated associated with this query
static int DEFAULT_MAX
          So getMaxFeatures does not return null we use a very large number.
static Query FIDS
          Implements a query that will fetch all the FeatureIDs from a datasource.
protected  Filter filter
          The filter to constrain the request.
protected  String handle
          The handle associated with this query.
protected  Hints hints
          The hints to be used during query execution
static Hints.Key INCLUDE_MANDATORY_PROPS
          When specifying properties to select, setting this hint flag true tells the datastore to include mandatory properties (i.e. properties with minOccurs >= 1) in the end result, irrespective of whether they are not included in the list of properties.
protected  List<Join> joins
          join clauses for this query
protected  int maxFeatures
          The maximum numbers of features to fetch
protected  URI namespace
          The namespace to get
static String[] NO_NAMES
          A constant (empty String array) that can be used with setPropertyNames(String[]) to indicate that no properties are to be retrieved.
static URI NO_NAMESPACE
          Constant (actually null) used to represent no namespace restrictions on the returned result, should be considered ANY_URI
static List<PropertyName> NO_PROPERTIES
          A constant (empty String array) that can be used with #setProperties(Collection) to indicate that no properties are to be retrieved.
protected  List<PropertyName> properties
          The properties to fetch
protected  SortBy[] sortBy
          Sorting for the query
protected  Integer startIndex
          The index of the first feature to process
protected  String typeName
          The typeName to get
protected  String version
          The version according to WFS 1.0 and 1.1 specs
 
Constructor Summary
Query()
          Default constructor.
Query(Query query)
          Copy contructor.
Query(String typeName)
          Constructor.
Query(String typeName, Filter filter)
          Constructor.
Query(String typeName, Filter filter, int maxFeatures, List<PropertyName> properties, String handle)
          Constructor.
Query(String typeName, Filter filter, int maxFeatures, String[] propNames, String handle)
          Constructor.
Query(String typeName, Filter filter, List<PropertyName> properties)
          Constructor.
Query(String typeName, Filter filter, String[] properties)
          Constructor.
Query(String typeName, URI namespace, Filter filter, int maxFeatures, List<PropertyName> propNames, String handle)
          Constructor.
Query(String typeName, URI namespace, Filter filter, int maxFeatures, String[] propNames, String handle)
          Constructor.
 
Method Summary
 boolean equals(Object obj)
          Equality based on all query parameters other than the handle.
 String getAlias()
          An alias substitutable for getTypeName().
 CoordinateReferenceSystem getCoordinateSystem()
          Get the coordinate system that applies to features retrieved by this Query.
 CoordinateReferenceSystem getCoordinateSystemReproject()
          If reprojection has been requested, this returns the coordinate system that features retrieved by this Query will be reprojected into.
 Filter getFilter()
          Gets the filter used to define constraints on the features that will be retrieved by this Query.
 String getHandle()
          Get the handle (mnemonic name) that will be associated with this Query.
 Hints getHints()
          Get hints that have been set to control the query execution.
 List<Join> getJoins()
          The list of joins for this query.
 int getMaxFeatures()
          Get the maximum number of features that will be retrieved by this Query.
 URI getNamespace()
          Get the namespace of the feature type to be queried.
 List<PropertyName> getProperties()
          Get the names of the properties that this Query will retrieve values for as part of the returned FeatureCollection.
 String[] getPropertyNames()
          Get the names of the properties that this Query will retrieve as part of the returned FeatureCollection.
 SortBy[] getSortBy()
          SortBy results according to indicated property and order.
 Integer getStartIndex()
          Get the index of the first feature to retrieve.
 String getTypeName()
          Get the name of the feature type to be queried.
 String getVersion()
          Defines version or version range requested.
 int hashCode()
          Hashcode based on all parameters other than the handle.
 boolean isMaxFeaturesUnlimited()
          Check if this query allows an unlimited number of features to be returned.
 boolean retrieveAllProperties()
          Convenience method to determine if the query should retrieve all properties defined in the schema of the feature data source.
 void setAlias(String alias)
          Sets the type name alias.
 void setCoordinateSystem(CoordinateReferenceSystem system)
          Set the coordinate system to apply to features retrieved by this Query.
 void setCoordinateSystemReproject(CoordinateReferenceSystem system)
          Request that features retrieved by this Query be reprojected into the given coordinate system.
 void setFilter(Filter filter)
          Sets the filter to constrain the features that will be retrieved by this Query.
 void setHandle(String handle)
          Set the handle (mnemonic name) that will be associated with this Query.
 void setHints(Hints hints)
          Set hints to control the query execution.
 void setMaxFeatures(int maxFeatures)
          Sets the maximum number of features that should be retrieved by this query.
 void setNamespace(URI namespace)
          Set the namespace of the feature type to be queried.
 void setProperties(List<PropertyName> propNames)
          Set the names of the properties that this Query should retrieve as part of the returned FeatureCollection.
 void setPropertyNames(List<String> propNames)
          Set the names of the properties that this Query should retrieve as part of the returned FeatureCollection.
 void setPropertyNames(String[] propNames)
          Set the names of the properties that this Query should retrieve as part of the returned FeatureCollection.
 void setSortBy(SortBy[] sortBy)
          Sets the sort by information.
 void setStartIndex(Integer startIndex)
          Set the index of the first feature to retrieve.
 void setTypeName(String typeName)
          Sets the name of the feature type to be queried.
 void setVersion(Date date)
           
 void setVersion(Date startTime, Date endTime)
           
 void setVersion(int index)
           
 void setVersion(ResourceId history)
           
 void setVersion(String version)
          Set the version of features to retrieve where this is supported by the data source being queried.
 void setVersion(Version.Action action)
           
 String toString()
          Return a string representation of this Query.
 
Methods inherited from class Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

INCLUDE_MANDATORY_PROPS

public static Hints.Key INCLUDE_MANDATORY_PROPS
When specifying properties to select, setting this hint flag true tells the datastore to include mandatory properties (i.e. properties with minOccurs >= 1) in the end result, irrespective of whether they are not included in the list of properties. Datastores may implement adding all mandatory properties to the end result when this flag is set to true. For example: Object includeProps = query.getHints().get(Query.INCLUDE_MANDATORY_PROPS); if (includeProps instanceof Boolean && ((Boolean)includeProps).booleanValue()) { query.setProperties (DataUtilities.addMandatoryProperties(type, query.getProperties())); }


NO_NAMESPACE

public static final URI NO_NAMESPACE
Constant (actually null) used to represent no namespace restrictions on the returned result, should be considered ANY_URI


DEFAULT_MAX

public static final int DEFAULT_MAX
So getMaxFeatures does not return null we use a very large number.

See Also:
Constant Field Values

ALL

public static final Query ALL
Implements a query that will fetch all features from a datasource. This query should retrieve all properties, with no maxFeatures, no filtering, and the default featureType.


FIDS

public static final Query FIDS
Implements a query that will fetch all the FeatureIDs from a datasource. This query should retrieve no properties, with no maxFeatures, no filtering, and the a featureType with no attribtues.


NO_NAMES

public static final String[] NO_NAMES
A constant (empty String array) that can be used with setPropertyNames(String[]) to indicate that no properties are to be retrieved.

Note the query will still return a result - limited to FeatureIDs.


ALL_NAMES

public static final String[] ALL_NAMES
A constant (value null) that can be used with setPropertyNames(String[]) to indicate that all properties are to be retrieved.


NO_PROPERTIES

public static final List<PropertyName> NO_PROPERTIES
A constant (empty String array) that can be used with #setProperties(Collection) to indicate that no properties are to be retrieved.

Note the query will still return a result - limited to FeatureIDs.


ALL_PROPERTIES

public static final List<PropertyName> ALL_PROPERTIES
A constant (value null) that can be used with #setProperties(Collection) to indicate that all properties are to be retrieved.


properties

protected List<PropertyName> properties
The properties to fetch


maxFeatures

protected int maxFeatures
The maximum numbers of features to fetch


startIndex

protected Integer startIndex
The index of the first feature to process


filter

protected Filter filter
The filter to constrain the request.


typeName

protected String typeName
The typeName to get


alias

protected String alias
The optional alias for type name


namespace

protected URI namespace
The namespace to get


handle

protected String handle
The handle associated with this query.


coordinateSystem

protected CoordinateReferenceSystem coordinateSystem
Coordinate System associated with this query


coordinateSystemReproject

protected CoordinateReferenceSystem coordinateSystemReproject
Reprojection associated associated with this query


sortBy

protected SortBy[] sortBy
Sorting for the query


version

protected String version
The version according to WFS 1.0 and 1.1 specs


hints

protected Hints hints
The hints to be used during query execution


joins

protected List<Join> joins
join clauses for this query

Constructor Detail

Query

public Query()
Default constructor. Use setter methods to configure the Query before use (the default Query will retrieve all features).


Query

public Query(String typeName)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve

Query

public Query(String typeName,
             Filter filter)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve.
filter - the OGC filter to constrain the request.

Query

public Query(String typeName,
             Filter filter,
             String[] properties)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve.
filter - the OGC filter to constrain the request.
properties - an array of the properties to fetch.

Query

public Query(String typeName,
             Filter filter,
             List<PropertyName> properties)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve.
filter - the OGC filter to constrain the request.
properties - a list of the properties to fetch.

Query

public Query(String typeName,
             Filter filter,
             int maxFeatures,
             String[] propNames,
             String handle)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve.
filter - the OGC filter to constrain the request.
maxFeatures - the maximum number of features to be returned.
propNames - an array of the properties to fetch.
handle - the name to associate with this query.

Query

public Query(String typeName,
             Filter filter,
             int maxFeatures,
             List<PropertyName> properties,
             String handle)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve.
filter - the OGC filter to constrain the request.
maxFeatures - the maximum number of features to be returned.
properties - a list of the properties to fetch.
handle - the name to associate with this query.

Query

public Query(String typeName,
             URI namespace,
             Filter filter,
             int maxFeatures,
             String[] propNames,
             String handle)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve.
namespace - Namespace for provided typeName, or null if unspecified
filter - the OGC filter to constrain the request.
maxFeatures - the maximum number of features to be returned.
propNames - an array of the properties to fetch.
handle - the name to associate with the query.

Query

public Query(String typeName,
             URI namespace,
             Filter filter,
             int maxFeatures,
             List<PropertyName> propNames,
             String handle)
Constructor.

Parameters:
typeName - the name of the featureType to retrieve.
namespace - Namespace for provided typeName, or null if unspecified
filter - the OGC filter to constrain the request.
maxFeatures - the maximum number of features to be returned.
properties - a list of the property names to fetch.
handle - the name to associate with the query.

Query

public Query(Query query)
Copy contructor.

Parameters:
query - the query to copy
Method Detail

getPropertyNames

public String[] getPropertyNames()
Get the names of the properties that this Query will retrieve as part of the returned FeatureCollection.

Returns:
the attributes to be used in the returned FeatureCollection.
See Also:
retrieveAllProperties()
TODO:
REVISIT: make a FidProperties object, instead of an array size 0. I think Query.FIDS fills this role to some degree. Query.FIDS.equals( filter ) would meet this need?

setPropertyNames

public void setPropertyNames(String[] propNames)
Set the names of the properties that this Query should retrieve as part of the returned FeatureCollection. As well as an array of names, the following constants can be used: The available properties can be determined with FeatureSource.getSchema(). If properties that are not part of the source's schema are requested an exception will be thrown.

Parameters:
propNames - the names of the properties to retrieve or one of ALL_NAMES or NO_NAMES.

getProperties

public List<PropertyName> getProperties()
Get the names of the properties that this Query will retrieve values for as part of the returned FeatureCollection.

Returns:
the xpath expressions to be used in the returned FeatureCollection.
See Also:
retrieveAllProperties()

setProperties

public void setProperties(List<PropertyName> propNames)
Set the names of the properties that this Query should retrieve as part of the returned FeatureCollection. As well as an array of names, the following constants can be used: The available properties can be determined with FeatureSource.getSchema(). If properties that are not part of the source's schema are requested an exception will be thrown.

Parameters:
propNames - the names of the properties to retrieve or one of ALL_PROPERTIES or NO_PROPERTIES.

setPropertyNames

public void setPropertyNames(List<String> propNames)
Set the names of the properties that this Query should retrieve as part of the returned FeatureCollection.

The available properties can be determined with FeatureSource.getSchema(). If properties that are not part of the source's schema are requested an exception will be thrown.

Parameters:
propNames - the names of the properties to retrieve or ALL_NAMES; an empty List can be passed in to indicate that only feature IDs should be retrieved
TODO:
REVISIT: This syntax is really obscure. Consider having an fid or featureID propertyName that datasource implementors look for instead of looking to see if the list size is 0.

retrieveAllProperties

public boolean retrieveAllProperties()
Convenience method to determine if the query should retrieve all properties defined in the schema of the feature data source. This is equivalent to testing if getPropertyNames() returns ALL_NAMES.

Returns:
true if all properties will be retrieved by this Query; false otherwise

getMaxFeatures

public int getMaxFeatures()
Get the maximum number of features that will be retrieved by this Query.

Note: This is the only method that is not directly out of the Query element in the WFS specification. It is instead a part of a GetFeature request, which can hold one or more queries. But each of those in turn will need a maxFeatures, so it is needed here.

If the value returned here is max integer then the number of features should not be limited.

Returns:
the maximum number of features that will be retrieved by this query

isMaxFeaturesUnlimited

public boolean isMaxFeaturesUnlimited()
Check if this query allows an unlimited number of features to be returned.

Returns:
true maxFeatures is less then zero, or equal to Integer.MAX_VALUE.

setMaxFeatures

public void setMaxFeatures(int maxFeatures)
Sets the maximum number of features that should be retrieved by this query. The default is to retrieve all features.

Parameters:
maxFeatures - the maximum number of features to retrieve

getStartIndex

public Integer getStartIndex()
Get the index of the first feature to retrieve.

Returns:
the index of the first feature to retrieve or null if no start index is defined.

setStartIndex

public void setStartIndex(Integer startIndex)
Set the index of the first feature to retrieve. This can be used in conjuction with setMaxFeatures(int) to 'page' through a feature data source.

Parameters:
startIndex - index of the first feature to retrieve or null to indicate no start index
Throws:
IllegalArgumentException - if startIndex is less than 0

getFilter

public Filter getFilter()
Gets the filter used to define constraints on the features that will be retrieved by this Query.

Returns:
The filter that defines constraints on the query.

setFilter

public void setFilter(Filter filter)
Sets the filter to constrain the features that will be retrieved by this Query. If no filter is set all features will be retrieved (taking into account any bounds set via setMaxFeatures(int) and setStartIndex(java.lang.Integer)).

The default is Filter.INCLUDE.

Parameters:
filter - the OGC filter which features must pass through to be retrieved by this Query.

getTypeName

public String getTypeName()
Get the name of the feature type to be queried.

Returns:
the name of the feature type to be returned with this query.

setTypeName

public void setTypeName(String typeName)
Sets the name of the feature type to be queried. If no typename is specified, then the data source's default type will be used. When working with sources such as shapefiles that only support one feature type this method can be ignored.

Parameters:
typeName - the name of the featureType to retrieve.

getAlias

public String getAlias()
An alias substitutable for getTypeName().

This value is typically used in a join query in which the join filter requires disambiguation due to property name overlaps between joined types.

Since:
8.0

setAlias

public void setAlias(String alias)
Sets the type name alias.

Since:
8.0
See Also:
getAlias()

getNamespace

public URI getNamespace()
Get the namespace of the feature type to be queried.

Returns:
the gml namespace of the feature type to be returned with this query

setNamespace

public void setNamespace(URI namespace)
Set the namespace of the feature type to be queried.


getHandle

public String getHandle()
Get the handle (mnemonic name) that will be associated with this Query. The handle is used in logging and error reporting.

Returns:
the name to refer to this query.

setHandle

public void setHandle(String handle)
Set the handle (mnemonic name) that will be associated with this Query. The handle is used in logging and error reporting.

Parameters:
handle - the name to refer to this query.

getVersion

public String getVersion()
Defines version or version range requested.

From WFS Spec: The version attribute is included in order to accommodate systems that support feature versioning. A value of ALL indicates that all versions of a feature should be fetched. Otherwise an integer, n, can be specified to return the n th version of a feature. The version numbers start at '1' which is the oldest version. If a version value larger than the largest version is specified then the latest version is return. The default action shall be for the query to return the latest version. Systems that do not support versioning can ignore the parameter and return the only version that they have.

GeoTools employs the following options:

Returns:
the version of the feature to return, or null for LAST.

setVersion

public void setVersion(int index)

setVersion

public void setVersion(Date date)

setVersion

public void setVersion(Version.Action action)

setVersion

public void setVersion(Date startTime,
                       Date endTime)

setVersion

public void setVersion(ResourceId history)

setVersion

public void setVersion(String version)
Set the version of features to retrieve where this is supported by the data source being queried.

Parameters:
version -
Since:
2.4
See Also:
getVersion() for explanation

getCoordinateSystem

public CoordinateReferenceSystem getCoordinateSystem()
Get the coordinate system that applies to features retrieved by this Query. By default this is the coordinate system of the features in the data source but this can be overriden via setCoordinateSystem( CoordinateReferenceSystem ).

Returns:
The coordinate system to be returned for Features from this Query (override the set coordinate system).

setCoordinateSystem

public void setCoordinateSystem(CoordinateReferenceSystem system)
Set the coordinate system to apply to features retrieved by this Query.

This denotes a request to temporarily override the coordinate system contained in the feature data source being queried. The same coordinate values will be used, but the features retrieved will appear in this Coordinate System.

This change is not persistant and only applies to the features returned by this Query. If used in conjunction with getCoordinateSystemReproject() the reprojection will occur from getCoordinateSystem() to getCoordinateSystemReproject().

Parameters:
system - the coordinate system to apply to features retrieved by this Query

getCoordinateSystemReproject

public CoordinateReferenceSystem getCoordinateSystemReproject()
If reprojection has been requested, this returns the coordinate system that features retrieved by this Query will be reprojected into.

Returns:
the coordinate system that features will be reprojected into (if set)
See Also:
setCoordinateSystemReproject( CoordinateReferenceSystem )

setCoordinateSystemReproject

public void setCoordinateSystemReproject(CoordinateReferenceSystem system)
Request that features retrieved by this Query be reprojected into the given coordinate system.

If used in conjunction with setCoordinateSystem(CoordinateReferenceSystem) the reprojection will occur from the overridden coordinate system to the system specified here.


getSortBy

public SortBy[] getSortBy()
SortBy results according to indicated property and order.

SortBy is part of the Filter 1.1 specification, it is referenced by WFS1.1 and Catalog 2.0.x specifications and is used to organize results.

The SortBy's are ment to be applied in order:
  • SortBy( year, ascending )
  • SortBy( month, decsending )
Would produce something like:

 [year=2002 month=4],[year=2002 month=3],[year=2002 month=2],
 [year=2002 month=1],[year=2003 month=12],[year=2002 month=4],
 

SortBy should be considered at the same level of abstraction as Filter, and like Filter you may sort using properties not listed in getPropertyNames.

At a technical level the interface SortBy2 is used to indicate the additional requirements of a GeoTools implementation. The pure WFS 1.1 specification itself is limited to SortBy.

Returns:
SortBy array or order of application

setSortBy

public void setSortBy(SortBy[] sortBy)
Sets the sort by information.


getHints

public Hints getHints()
Get hints that have been set to control the query execution.

Returns:
hints that are set (may be empty)
See Also:
setHints(Hints) for more explanation

setHints

public void setHints(Hints hints)
Set hints to control the query execution.

Hints can control such things as:

  • the GeometryFactory to be used
  • a generalization distance to be applied
  • the fetch size to be used in JDBC queries
The set of hints supported can be found by calling FeatureSource.getSupportedHints().

Note: Data sources may ignore hints (depending on their values) and no mechanism currently exists to discover which hints where actually used during the query's execution.

Parameters:
hints - the hints to apply
See Also:
Hints.FEATURE_DETACHED, Hints.JTS_GEOMETRY_FACTORY, Hints.JTS_COORDINATE_SEQUENCE_FACTORY, Hints.JTS_PRECISION_MODEL, Hints.JTS_SRID, Hints.GEOMETRY_DISTANCE, Hints.FEATURE_2D

hashCode

public int hashCode()
Hashcode based on all parameters other than the handle.

Overrides:
hashCode in class Object
Returns:
hascode for this Query

equals

public boolean equals(Object obj)
Equality based on all query parameters other than the handle.

Overrides:
equals in class Object
Parameters:
obj - Other object to compare against
Returns:
true if this Query matches the other object; false otherwise

toString

public String toString()
Return a string representation of this Query.

Overrides:
toString in class Object
Returns:
a string representation of this Query

getJoins

public List<Join> getJoins()
The list of joins for this query.

Each Join object specifies a feature type to join to. The join may only reference a feature type from within the same datastore.

See Also:
Join


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