org.geotools.appschema.filter.expression

Class ToLineStringFunction

Object

ToLineStringFunction

All Implemented Interfaces:

Expression, Function

public class ToLineStringFunction
extends Object
implements Function

This function converts double values to 1D LineString geometry object. This is needed when the data store doesn't have geometry type columns (or they want to use custom CRS). If custom SRS name is used, a 1D CRS will be created. This function expects:

1. Expression: SRS name (could be custom SRS name)
2. Expression: name of column pointing to first double value
3. Expression: name of column pointing to second double value

Author:

Rini Angreani (CSIRO Earth Science and Resource Engineering)

Field Summary

Fields

Modifier and Type	Field and Description
static FunctionName	NAME

Fields inherited from interface Expression

NIL

Constructor Summary

Constructors

Constructor and Description
ToLineStringFunction()
ToLineStringFunction(List<Expression> parameters, Literal fallback)

Method Summary

Modifier and Type	Method and Description
Object	accept(ExpressionVisitor visitor, Object extraData) Accepts a visitor.
Object	evaluate(Object object) Evaluates the given expression based on the content of the given object.
<T> T	evaluate(Object object, Class<T> context) Evaluates the given expressoin based on the content of the given object and the context type.
Literal	getFallbackValue() The value of the fallbackValue attribute is used as a default value, if the SE implementation does not support the function.
FunctionName	getFunctionName() Access to the FunctionName description as used in a FilterCapabilities document.
String	getName() Returns the name of the function to be called.
List<Expression>	getParameters() Returns the list subexpressions that will be evaluated to provide the parameters to the function.

Methods inherited from class Object

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

Field Detail

NAME

public static final FunctionName NAME

Constructor Detail

ToLineStringFunction

public ToLineStringFunction()

ToLineStringFunction

public ToLineStringFunction(List<Expression> parameters,
                            Literal fallback)

Method Detail

getName

public String getName()

Description copied from interface: Function

Returns the name of the function to be called. For example, this might be "cos" or "atan2".

You can use this name to look up the number of required parameters in a FilterCapabilities data structure. For the specific meaning of the required parameters you will need to consult the documentation.

Specified by:

getName in interface Function

getFunctionName

public FunctionName getFunctionName()

Description copied from interface: Function

Access to the FunctionName description as used in a FilterCapabilities document.

Specified by:

getFunctionName in interface Function

Returns:

FunctionName description, if available.

getParameters

public List<Expression> getParameters()

Description copied from interface: Function

Returns the list subexpressions that will be evaluated to provide the parameters to the function.

Specified by:

getParameters in interface Function

getFallbackValue

public Literal getFallbackValue()

Description copied from interface: Function

The value of the fallbackValue attribute is used as a default value, if the SE implementation does not support the function. If the implementation supports the function, then the result value is determined by executing the function.

Specified by:

getFallbackValue in interface Function

Returns:

Optional literal to use if an implementation for this function is not available.

accept

public Object accept(ExpressionVisitor visitor,
                     Object extraData)

Description copied from interface: Expression

Accepts a visitor. Subclasses must implement with a method whose content is the following:

return visitor.visit(this, extraData);

Specified by:

accept in interface Expression

evaluate

public Object evaluate(Object object)

Description copied from interface: Expression

Evaluates the given expression based on the content of the given object.

Specified by:

evaluate in interface Expression

Returns:

computed value

evaluate

public <T> T evaluate(Object object,
                      Class<T> context)

Description copied from interface: Expression

Evaluates the given expressoin based on the content of the given object and the context type.

The context parameter is used to control the type of the result of the expression. A particular expression may not be able to evaluate to an instance of context. Therefore to be safe calling code should do a null check on the return value of this method, and call Expression.evaluate(Object) if neccessary. Example:

  Object input = ...;
  String result = expression.evaluate( input, String.class );
  if ( result == null ) {
     result = expression.evalute( input ).toString();
  }
  ...
 

Implementations that can not return a result as an instance of context should return null.

Specified by:

evaluate in interface Expression

Type Parameters:

T - The type of the returned object.

Parameters:

object - The object to evaluate the expression against.

context - The type of the resulting value of the expression.

Returns:

Evaluates the given expression based on the content of the given object an an instance of context.