org.geotools.expr
Class Exprs

java.lang.Object
  org.geotools.expr.Exprs

public class Exprs

extends java.lang.Object

Filter/Expression construction kit - this class starts off chains.

I can't take Filter anymore, the turning point was the fact that I needed a FeatureType to make a AttributeExpression. Simply *no*, I cannot expect customer code to have to jump through hoops so that my impmentation is easier. Late binding is required.

The answer - while not completely forcing DataStores away from Expression/Filter is to make a class that captures all the same information and can do the late binding.

On the way there we are not going to have the difference between Filter/Expression. Expr can make an Expression, and Expr can make a Filter.

Example Expr:
Exprs.bbox( extent ).and( Exprs.attribute("cost").lt( 50 ) )

Example Filter:

 Expression extentExpression = factory.createBBoxExpression( bbox );
 Expression geomExpression = factory.createAttributeExpression( featureType, featureType.getDefaultGeometry().getName() );	    
 GeometryFilter disjointExpression = factory.createGeometryFilter( GeometryFilter.GEOMETRY_DISJOINT );
 disjointExpression.addLeftGeometry( geomExpression );
 disjointExpression.addRightGeometry( extentExpression );	    
 Filter bboxFilter = disjointExpression.not();	    
 AttributeExpression costExpression = factory.createAttributeExpression( featureType, "cost" );
 CompareFilter lessThanFilter = factory.createCompareFilter( CompareFilter.COMPARE_LESS_THAN );
 lessThanFilter.addLeftValue( costExpression );
 lessThanFilter.addRightValue( factory.createLiteralExpression( 50 ) );	    
 LogicFilter filter = factory.createLogicFilter( bboxFilter, lessThanFilter, LogicFilter.LOGIC_AND);	    
 

BTW: just so we can have everything make sense

• Expr is immutable
• I don't care if Expr trees simplfy themselves during construction
• Allow user to type less by using '.' to mean AND -
  Exprs.bbox( extent ).fids( fidSet) == Exprs.bbox( extent ).and( Exprs.fids( fidSet ) )
• There are convience methods that make sense -
Exprs.bbox( extent ) == geom().disjoint( Expr.literal( extent)).not()
• "Or" you have to do by hand -
Exprs.fid( "road.1234" ).or( Exprs.fid("road.4321) )

Wild idea time: chaining parameters

• Fid expr above with param chainging?
  Expr.fid( "road.1234" ).param( "road.4321" )
  Of course this idea is really lame given 1.5 new features - kill it :-(
• Of course something like this may be Extactly whtat is needed to make those nasty As FeatureView/Opperation chains work....
  repository.view("road").as("name", "CUSTOMER_NAME").as( "addresss", "ADDRESS" )
  Still does not look right - sigh.

  Author:

  Jody Garnett

  Field Summary

  protected static FilterFactory

  factory

  Constructor Summary

  Exprs()
  

  Method Summary

  static MathExpr	add(MathExpr[] expr)
  static Expr	and(Expr[] expr)
  static Expr	attribute(java.lang.String attribute) Attribute access.
  static MathExpr	divide(MathExpr[] expr)
  static Expr	fid(java.util.Set fids)
  static Expr	fid(java.lang.String featureID) Convience method for accessing a single fid
  static Expr	fn(java.lang.String name, Expr expr)
  static Expr	fn(java.lang.String name, Expr[] expr)
  static Expr	fn(java.lang.String name, Expr expr1, Expr expr2)
  static GeometryExpr	geom() Default Geometry access.
  static GeometryExpr	geom(java.lang.String attribute) Geometry attribute access.
  static Expr	literal(boolean b)
  static MathExpr	literal(double number)
  static GeometryExpr	literal(com.vividsolutions.jts.geom.Envelope extent) Literal Geometry access.
  static GeometryExpr	literal(com.vividsolutions.jts.geom.Geometry geom) Literal Geometry access.
  static MathExpr	literal(int number)
  static MathExpr	literal(java.lang.Number number)
  static Expr	literal(java.lang.Object literal)
  static MathExpr	math(java.lang.String attribute)
  static Expr	meta(java.lang.String xpath) Metadata element access.
  static Expr	multiply(MathExpr[] expr)
  static Expr	or(Expr[] expr)
  static MathExpr	subtract(MathExpr[] expr)

  Methods inherited from class java.lang.Object

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

  Field Detail

  factory

  protected static FilterFactory factory

  Constructor Detail

  Exprs

  public Exprs()

  Method Detail

  fid

  public static Expr fid(java.lang.String featureID)

  Convience method for accessing a single fid

  Returns:

  fid

  public static Expr fid(java.util.Set fids)

  and

  public static Expr and(Expr[] expr)

  or

  public static Expr or(Expr[] expr)

  literal

  public static Expr literal(boolean b)

  literal

  public static MathExpr literal(int number)

  literal

  public static MathExpr literal(double number)

  literal

  public static MathExpr literal(java.lang.Number number)

  literal

  public static Expr literal(java.lang.Object literal)

  literal

  public static GeometryExpr literal(com.vividsolutions.jts.geom.Envelope extent)

  Literal Geometry access.

  literal

  public static GeometryExpr literal(com.vividsolutions.jts.geom.Geometry geom)

  Literal Geometry access.

  add

  public static MathExpr add(MathExpr[] expr)

  subtract

  public static MathExpr subtract(MathExpr[] expr)

  divide

  public static MathExpr divide(MathExpr[] expr)

  multiply

  public static Expr multiply(MathExpr[] expr)

  attribute

  public static Expr attribute(java.lang.String attribute)

  Attribute access.

  Allows access to chained opperations.

  Parameters:

  attribute - xpath expression to attribute

  Returns:

  Expr

  meta

  public static Expr meta(java.lang.String xpath)

  Metadata element access.

  Allows access to chained opperations.

  Returns:

  Expr

  geom

  public static GeometryExpr geom()

  Default Geometry access.

  geom

  public static GeometryExpr geom(java.lang.String attribute)

  Geometry attribute access.

  Allows access to chained spatial opperations.

  Parameters:

  attribute - xpath expression to attribute

  Returns:

  GeometryAttribtue

  math

  public static MathExpr math(java.lang.String attribute)

  fn

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

  fn

  public static Expr fn(java.lang.String name,
                        Expr expr1,
                        Expr expr2)

  fn

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