org.geotools.filter

Class Filters

Object

Filters

public class Filters
extends Object

Utility class for working with Filters & Expression.

To get the full benefit you will need to create an instanceof this Object (supports your own custom FilterFactory!). Additional methods to help create expressions are available.

Example use:

 Filters filters = new Filters( factory );
 filters.duplicate( original );
 

The above example creates a copy of the provided Filter, the factory provided will be used when creating the duplicated content.

Expression

Expressions form an interesting little semi scripting language, intended for queries. A interesting Feature of Filter as a language is that it is not strongly typed. This utility class many helper methods that ease the transition from Strongly typed Java to the more relaxed setting of Expression where most everything can be a string.

 double sum = Filters.number( Object ) + Filters.number( Object );
 

The above example will support the conversion of many things into a format suitable for addition - the complete list is something like:

• Any instance of Number
• "1234" - aka Integer
• "#FFF" - aka Integer
• "123.0" - aka Double

A few things (like Geometry and "ABC") will not be considered addative. In general the scope of these functions should be similar to that allowed by the XML Atomic Types, aka those that can be seperated by whitespace to form a list.

We do our best to be forgiving, any Java class which takes a String as a constructor can be tried, and toString() assumed to be the inverse. This lets many things (like URL and Date) function without modification.

Since:

GeoTools 2.2

Author:

Jody Garnett (LISAsoft)

Field Summary

Fields

Modifier and Type	Field and Description
static int	NOTFOUND NOTFOUND indicates int value was unavailable

Constructor Summary

Constructors

Constructor and Description
Filters() Create Filters helper object using global FilterFactory provided by CommonFactoryFinder
Filters(FilterFactory2 factory) Create a Filters helper using the provided FilterFactory

Method Summary

Modifier and Type	Method and Description
static Filter	and(FilterFactory ff, Filter filter1, Filter filter2) Safe version of FilterFactory *and* that is willing to combine filter1 and filter2 correctly in the even either of them is already an And filter.
static Filter	and(FilterFactory ff, List<Filter> filters) Safe and combiner for filters, will build an and filter around them only if there is at least two filters
static double	asDouble(Expression expr) Obtain the provided Expression as a double.
static int	asInt(Expression expr) Obtain the provided Expression as an integer.
static String	asString(Expression expr) Obtain the provided Expression as a String.
Set<String>	attributeNames(Filter filter) Uses FilterAttributeExtractor to return the list of all mentioned attribute names.
static String[]	attributeNames(Filter filter, SimpleFeatureType featureType) Traverses the filter and returns any encountered property names.
static ArrayList<Filter>	children(Filter filter) List of child filters.
static ArrayList<Filter>	children(Filter filter, boolean all) List of child filters.
Filter	duplicate(Filter filter) Deep copy the filter.
static String	findPropertyName(Filter filter) Given a filter which contains a term which is a PropertyName, returns the name of the property.
static short	getExpressionType(Expression experssion) Convert expression to a constant for use in switch statements.
static <T> T	gets(String text, Class<T> TYPE) Used to upcovnert a "Text Value" into the provided TYPE.
static boolean	hasChildren(Filter filter) Check if the provided filter has child filters of some sort.
static double	number(Object value) Treat provided value as a Number, used for math opperations.
static Filter	or(FilterFactory ff, Filter filter1, Filter filter2) Safe version of FilterFactory *or* that is willing to combine filter1 and filter2 correctly in the even either of them is already an Or filter.
static Filter	or(FilterFactory ff, List<Filter> filters) Safe or combiner for filters, will build an and filter around them only if there is at least two filters
static Set<PropertyName>	propertyNames(Expression expression) Traverses the expression and returns any encountered property names.
static Set<PropertyName>	propertyNames(Expression expression, SimpleFeatureType featureType) Traverses the expression and returns any encountered property names.
static Set<PropertyName>	propertyNames(Filter filter) Traverses the filter and returns any encountered property names.
static Set<PropertyName>	propertyNames(Filter filter, SimpleFeatureType featureType) Traverses the filter and returns any encountered property names.
static String	puts(Color color) Inverse of eval, used to softly type supported types into Text for use as literals.
static String	puts(double number) Convert provided number to a suitable text representation Examples: Filters.puts( 3.14 ) => "3.14" Filters.puts( 1.0 ) => "1"
static String	puts(Object obj) Inverse of eval, used to softly type supported types into Text for use as literals.
Filter	remove(Filter baseFilter, Filter targetFilter) Removes the targetFilter from the baseFilter if the baseFilter is a group filter (And or Or),recursing into any sub-logic filters to find the targetFilter if necessary.
Filter	remove(Filter baseFilter, Filter targetFilter, boolean recurse) Removes the targetFilter from the baseFilter if the baseFilter is a group filter (And or Or).
static Filter	removeFilter(Filter baseFilter, Filter targetFilter)
static Filter	removeFilter(Filter baseFilter, Filter targetFilter, boolean recurse)
static <T extends Filter> T	search(Filter filter, Class<T> filterType, String propertyName) Find the first child-filter (or the base filter itself) that is of the given type and uses the specified property.
void	setFilterFactory(FilterFactory2 factory)

Methods inherited from class Object

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

Field Detail

NOTFOUND

public static final int NOTFOUND

NOTFOUND indicates int value was unavailable

See Also:

Constant Field Values

Constructor Detail

Filters

public Filters()

Create Filters helper object using global FilterFactory provided by CommonFactoryFinder

Filters

public Filters(FilterFactory2 factory)

Create a Filters helper using the provided FilterFactory

Method Detail

setFilterFactory

public void setFilterFactory(FilterFactory2 factory)

and

public static Filter and(FilterFactory ff,
                         List<Filter> filters)

Safe and combiner for filters, will build an and filter around them only if there is at least two filters

Parameters:

ff - The filter factory used to combine filters

filters - The list of filters to be combined

Returns:

The combination in AND of the filters, or Filter.EXCLUDE if filters is null or empty, or the one filter found in the list, in case it has only one element

and

public static Filter and(FilterFactory ff,
                         Filter filter1,
                         Filter filter2)

Safe version of FilterFactory *and* that is willing to combine filter1 and filter2 correctly in the even either of them is already an And filter.

Returns:

And

or

public static Filter or(FilterFactory ff,
                        List<Filter> filters)

Safe or combiner for filters, will build an and filter around them only if there is at least two filters

Parameters:

ff - The filter factory used to combine filters

filters - The list of filters to be combined

Returns:

The combination in OR of the filters, or Filter.EXCLUDE if filters is null or empty, or the one filter found in the list, in case it has only one element

or

public static Filter or(FilterFactory ff,
                        Filter filter1,
                        Filter filter2)

Safe version of FilterFactory *or* that is willing to combine filter1 and filter2 correctly in the even either of them is already an Or filter.

duplicate

public Filter duplicate(Filter filter)

Deep copy the filter.

Filter objects are mutable, when copying a rich data structure (like SLD) you will need to duplicate the Filters referenced therein.

getExpressionType

public static short getExpressionType(Expression experssion)

Convert expression to a constant for use in switch statements. This is an alternative to performing instanceof checks. p> This utility method for those upgrading to a newer version of GeoTools, instance of checks are preferred as they will take into account new kinds of expressions as the filter specification grows over time. Example:

 
 BEFORE: expression.getType() == ExpressionType.MATH_ADD
 QUICK:  Filters.getExpressionType( expression ) == ExpressionType.MATH_ADD
 AFTER: expression instanceof Add
 
 

Returns:

ExpressionType constant.

See Also:

ExpressionType

asInt

public static int asInt(Expression expr)

Obtain the provided Expression as an integer.

This method is quickly used to safely check Literal expressions.

Returns:

int value of first Number, or NOTFOUND

asString

public static String asString(Expression expr)

Obtain the provided Expression as a String.

This method only reliably works when the Expression is a Literal.

Returns:

Expression as a String, or null

asDouble

public static double asDouble(Expression expr)

Obtain the provided Expression as a double.

Returns:

int value of first Number, or Double.NaN

number

public static double number(Object value)

Treat provided value as a Number, used for math opperations.

This function allows for the non stongly typed Math Opperations favoured by the Expression standard.

Able to hanle:

• null - to NaN
• Number
• String - valid Integer and Double encodings

Returns:

double or Double.NaN;

Throws:

IllegalArgumentException - For non numerical among us -- like Geometry

gets

public static <T> T gets(String text,
                         Class<T> TYPE)
                  throws Throwable

Used to upcovnert a "Text Value" into the provided TYPE.

Used to tread softly on the Java typing system, because Filter/Expression is not strongly typed. Values in in Expression land are often not the the real Java Objects we wish they were - it is reall a small, lax, query language and Java objects need a but of help getting through.

A couple notes:

• Usual trick of reflection for a Constructors that supports a String parameter is used as a last ditch effort.
• will do its best to turn Object into the indicated Class
• will be used for ordering literals against attribute values are calculated at runtime (like Date.)

Remember Strong typing is for whimps who know what they are doing ahead of time. Real programmers let their program learn at runtime... :-)

Throws:

open - set of Throwable reflection for TYPE( String )

Throwable

puts

public static String puts(double number)

Convert provided number to a suitable text representation

Examples:

• Filters.puts( 3.14 ) => "3.14"
• Filters.puts( 1.0 ) => "1"

Returns:

text representation

puts

public static String puts(Object obj)

Inverse of eval, used to softly type supported types into Text for use as literals.

This method has been superseeded by Converters which offers a more general and open ended solution.

Returns:

String representation of provided object

puts

public static String puts(Color color)

Inverse of eval, used to softly type supported types into Text for use as literals.

This method has been superseeded by Converters which offers a more general and open ended solution.

Returns:

String representation of provided color.

remove

public Filter remove(Filter baseFilter,
                     Filter targetFilter)

Removes the targetFilter from the baseFilter if the baseFilter is a group filter (And or Or),recursing into any sub-logic filters to find the targetFilter if necessary.

• If the targetFilter equals the baseFilter, then Filter.INCLUDE is returned to indicate that no filters are left.
• If the targetFilter does not equal the base filter, no change is made and the baseFilter is returned.
• If removing the targetFilter would leave only a single term within the baseFilter, then the single remaining term is returned instead of the (now invalid) baseFilter. If the last item is removed from an Or statement then Filter.EXCLUDE is return If the last item is removed from an And statement then Filter.INCLUDE is returned

removeFilter

public static Filter removeFilter(Filter baseFilter,
                                  Filter targetFilter)

remove

public Filter remove(Filter baseFilter,
                     Filter targetFilter,
                     boolean recurse)

Removes the targetFilter from the baseFilter if the baseFilter is a group filter (And or Or). See removeFilter(org.opengis.filter.Filter, org.opengis.filter.Filter) for details, except this method includes the option to not recurse into child filters.

Parameters:

recurse - true if the method should descend into child group filters looking for the target

removeFilter

public static Filter removeFilter(Filter baseFilter,
                                  Filter targetFilter,
                                  boolean recurse)

attributeNames

public Set<String> attributeNames(Filter filter)

Uses FilterAttributeExtractor to return the list of all mentioned attribute names.

You can use this method to quickly build up the set of any mentioned attribute names.

Returns:

Set of propertyNames

attributeNames

public static String[] attributeNames(Filter filter,
                                      SimpleFeatureType featureType)

Traverses the filter and returns any encountered property names.

The feature type is supplied as contexts used to lookup expressions in cases where the attributeName does not match the actual name of the type.

propertyNames

public static Set<PropertyName> propertyNames(Filter filter,
                                              SimpleFeatureType featureType)

Traverses the filter and returns any encountered property names.

The feature type is supplied as contexts used to lookup expressions in cases where the attributeName does not match the actual name of the type.

propertyNames

public static Set<PropertyName> propertyNames(Filter filter)

Traverses the filter and returns any encountered property names.

propertyNames

public static Set<PropertyName> propertyNames(Expression expression,
                                              SimpleFeatureType featureType)

Traverses the expression and returns any encountered property names.

The feature type is supplied as contexts used to lookup expressions in cases where the attributeName does not match the actual name of the type.

propertyNames

public static Set<PropertyName> propertyNames(Expression expression)

Traverses the expression and returns any encountered property names.

hasChildren

public static boolean hasChildren(Filter filter)

Check if the provided filter has child filters of some sort.

Where a child filter is considered:

• Not: has a single child filter being negated
• And: has a list of child filters
• Or: has a list of child filters

Any other filter will return false.

Returns:

list of child filters

children

public static ArrayList<Filter> children(Filter filter)

List of child filters.

Where a child filter is considered:

• Not: has a single child filter being negated
• And: has a list of child filters
• Or: has a list of child filters

Any other filters will return false.

This represents the space covered by a number of the search functions.

The returned list is a mutable copy that can be used with filter factory to construct a new filter when you are ready. To make that explicit I am returning an ArrayList so it is clear that the result can be modified.

Returns:

are belong to us

children

public static ArrayList<Filter> children(Filter filter,
                                         boolean all)

List of child filters.

Where a child filter is considered:

• Not: has a single child filter being negated
• And: has a list of child filters
• Or: has a list of child filters

Any other filters will return false.

This represents the space covered by a number of the search functions, if *all* is true this function will recursively search for additional child filters beyond those directly avaialble from your filter.

The returned list is a mutable copy that can be used with filter factory to construct a new filter when you are ready. To make that explicit I am returning an ArrayList so it is clear that the result can be modified.

Parameters:

all - true to recurse into the filter and retrieve all children; false to only return the top level children

Returns:

are belong to us

search

public static <T extends Filter> T search(Filter filter,
                                          Class<T> filterType,
                                          String propertyName)

Find the first child-filter (or the base filter itself) that is of the given type and uses the specified property.

Parameters:

filterType - - class of the filter to look for

propertyName - - name of the property to look for

findPropertyName

public static String findPropertyName(Filter filter)

Given a filter which contains a term which is a PropertyName, returns the name of the property. Returns null if no PropertyName is passed