org.geotools.expr
Class LiteralExpr

java.lang.Object
  org.geotools.expr.AbstractExpr
      org.geotools.expr.LiteralExpr

All Implemented Interfaces:

Expr, ResolvedExpr

public class LiteralExpr

extends org.geotools.expr.AbstractExpr

implements ResolvedExpr

Provides a literal for use with Expr.

This is a start of an Expr chain - I would rather setup Expr.literal( value ) if I can figure out how. Maybe Chain.literal( value ), or Statement.literal( value )

Note many expression have constructors that take values directly allowing us to cut down the use of this class and increase readability.

Field Summary

protected FilterFactory

factory

Constructor Summary

LiteralExpr(boolean b)

LiteralExpr(java.lang.Object value)

Method Summary

Expr	and(Expr expr) Explicit Expr chain extention - required for custom Expressions.
Expr	bbox(com.vividsolutions.jts.geom.Envelope bbox) Convience method for: geom().disjoint( geom( bbox )).not()
Expr	between(Expr min, Expr max) min <= expr <= max
Expr	eq(Expr expr) expr == expr
Expr	eval() Evaludate Expr - with LiteralExpr as a goal.
Expression	expression(FeatureType schema) Turns a Filter into an a logical true/false expression.
Expr	fid(java.util.Set fids) expr.filter( fids ) Restruct current Expr to provided featureId(s).
Expr	fid(java.lang.String featureID) Convience method for accessing a single fid
Filter	filter(FeatureType schema) Useful super class that casts expressions into a Filter.
Expr	fn(java.lang.String name) name( expr )
Expr	fn(java.lang.String name, Expr expr) name( expr, expr )
Expr	fn(java.lang.String name, Expr[] expr) name( expr[0], expr[0], ... )
java.lang.Object	getValue() Value of this LiteralExpr.
Expr	gt(Expr expr) expr > expr
Expr	gte(Expr expr) expr >= expr
Expr	lt(Expr expr) expr < expr
Expr	lte(Expr expr) expr <= expr
Expr	ne(Expr expr) expr !
Expr	not() !
Expr	notNull() expr !
Expr	or(Expr expr) Expr Disjunction
Expr	reduce(java.lang.String bind) Reduce attributes matching "bind/x" to "x".
Expr	resolve(org.opengis.catalog.MetadataEntity metadata) Bind all meta entries according to provided metadata.
Expr	resolve(java.lang.String bind, Feature feature) Bind attributes matching "bind/x" to feature.getAttribute("x").

Methods inherited from class java.lang.Object

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

Field Detail

factory

protected FilterFactory factory

Constructor Detail

LiteralExpr

public LiteralExpr(boolean b)

LiteralExpr

public LiteralExpr(java.lang.Object value)

Method Detail

expression

public Expression expression(FeatureType schema)

Description copied from class: org.geotools.expr.AbstractExpr

Turns a Filter into an a logical true/false expression.

Specified by:

expression in interface Expr

getValue

public java.lang.Object getValue()

Value of this LiteralExpr.

Expr is doing its best to be immutable, Please don't duck around this idea.

Specified by:

getValue in interface ResolvedExpr

Returns:

value of literal Expr

eval

public Expr eval()

Evaludate Expr - with LiteralExpr as a goal.

By default this method simply returns the current Expr.

Specified by:

eval in interface Expr

resolve

public Expr resolve(org.opengis.catalog.MetadataEntity metadata)

Bind all meta entries according to provided metadata.

 Feature
 

Specified by:

resolve in interface Expr

Parameters:

metadata -

Returns:

Expr with all meta( xpath ) Exprs resolved

reduce

public Expr reduce(java.lang.String bind)

Reduce attributes matching "bind/x" to "x".

This may be used to reduce an Expr as part of an otter join, to something simple that can be passed off to an DataStore by way of filter( FeatureType ).

Example:

 FeatureType RIVER = river.getSchema();
 FeatureType HAZZARD = hazard.getSchema();
 
 Expr joinExpr = Exprs.attribute("river/name").eq( Exprs.attribute("hazzard/river") );
 
 FeatureReader outer = river.getFeatures().reader();
 while( reader.hasNext() ){
   Feature aRiver = outer.next();
 
   Expr inner = joinExpr.resolve( "river", aRiver ).reduce( "hazzard" );
   FeatureReader inner = district.getFeatures( inner.filter( HAZZARD ) );
 	 while( inner.hasNext() ){
      Feature aHazzard = inner.next();
 
 		// code here has access to both aRiver and aHazzard 
   } 
   inner.close();
 }
 outer.close();
 

Specified by:

reduce in interface Expr

resolve

public Expr resolve(java.lang.String bind,
                    Feature feature)

Bind attributes matching "bind/x" to feature.getAttribute("x").

This may be used to reduce an Expr as part of an otter join, to something simple that can be passed off to an DataStore by way of filter( FeatureType ).

Specified by:

resolve in interface Expr

Parameters:

bind -

feature -

Returns:

filter

public Filter filter(FeatureType schema)
              throws java.io.IOException

Useful super class that casts expressions into a Filter.

To turn Expression into a Filter I am going to follow the usual Perl defaults of "true".

• Boolean.TRUE is true
• Non empty String is true
• Non zero is true
• Non zero length array is true
• Non isEmpty Collection/Map is true
• Non isNull Envelope is true

Where true means that the generated Filter will accept the results.

Specified by:

filter in interface Expr

Throws:

java.io.IOException

bbox

public Expr bbox(com.vividsolutions.jts.geom.Envelope bbox)

Convience method for: geom().disjoint( geom( bbox )).not()

Specified by:

bbox in interface Expr

fid

public Expr fid(java.lang.String featureID)

Convience method for accessing a single fid

Specified by:

fid in interface Expr

Returns:

fid

public Expr fid(java.util.Set fids)

Description copied from interface: Expr

expr.filter( fids )

Restruct current Expr to provided featureId(s).

Specified by:

fid in interface Expr

not

public Expr not()

Description copied from interface: Expr

!expr

Invert of logical TRUTH value. Can be used to test for non contained fitler contents or FALSE Expressions

Specified by:

not in interface Expr

Returns:

Invert of Logical TRUETH value

and

public Expr and(Expr expr)

Description copied from interface: Expr

Explicit Expr chain extention - required for custom Expressions.

Specified by:

and in interface Expr

Parameters:

expr -

Returns:

Explicit chain extention.

or

public Expr or(Expr expr)

Description copied from interface: Expr

Expr Disjunction

Specified by:

or in interface Expr

eq

public Expr eq(Expr expr)

Description copied from interface: Expr

expr == expr

Specified by:

eq in interface Expr

gt

public Expr gt(Expr expr)

Description copied from interface: Expr

expr > expr

Specified by:

gt in interface Expr

gte

public Expr gte(Expr expr)

Description copied from interface: Expr

expr >= expr

Specified by:

gte in interface Expr

lt

public Expr lt(Expr expr)

Description copied from interface: Expr

expr < expr

Specified by:

lt in interface Expr

lte

public Expr lte(Expr expr)

Description copied from interface: Expr

expr <= expr

Specified by:

lte in interface Expr

ne

public Expr ne(Expr expr)

Description copied from interface: Expr

expr != expr

Specified by:

ne in interface Expr

between

public Expr between(Expr min,
                    Expr max)

Description copied from interface: Expr

min <= expr <= max

Specified by:

between in interface Expr

notNull

public Expr notNull()

Description copied from interface: Expr

expr != null

Specified by:

notNull in interface Expr

fn

public Expr fn(java.lang.String name)

Description copied from interface: Expr

name( expr )

Specified by:

fn in interface Expr

fn

public Expr fn(java.lang.String name,
               Expr expr)

Description copied from interface: Expr

name( expr, expr )

Specified by:

fn in interface Expr

fn

public Expr fn(java.lang.String name,
               Expr[] expr)

Description copied from interface: Expr

name( expr[0], expr[0], ... )

Specified by:

fn in interface Expr