net.sf.jec.namedop
Class OrderByOperator

java.lang.Object
  net.sf.jec.Operator
      net.sf.jec.namedop.GroupOperator
          net.sf.jec.namedop.OrderByOperator

public class OrderByOperator

extends GroupOperator

OrderByOperator sorts a Collection of elements by applying the argument operator to each element and comparing between the resulting values. The sort mode can be ascendent (by default) or descendent. You can specify a sort mode for each argument operator by writting it just after the argument operator.

Syntax: orderby(argOperator, [sortMode], [argOperator, [sortMode]])

Examples:

1. This one orders ascending by the accessor operators customerNumber (primary field) and customerAge (secondary field).

orderby(customerNumber, customerAge)

2. This one orders by the same criteria but descending. This example ilustrates where to specify the sort mode when you want to apply the same for all the argument operators. You must place it as the last argument.

orderby(customerNumber, customerAge, 'desc')

3. This one orders the primary field descending and the secondary ascending.

orderby(customerNumber, 'desc', customerAge, 'asc')

4. A given sort mode applies to all of the operator arguments preceeding it until another sort mode is found. In this example, the two last argOperators are sorted ascending and the first is sorted descending.
Think that the tuple is processed from the right to the left and the sort modes are switches that fix the current sort mode.

orderby(customerNumber, 'desc', customerAge, customerWeight, 'asc')

In this case we could remove the last 'asc' argument because this is the default sort mode. The result would be the same:

orderby(customerNumber, 'desc', customerAge, customerWeight)

But you should always specify explicitly the desired order.

Author:

mballesteros

Field Summary

Fields inherited from class net.sf.jec.Operator

argOps, nestedOp, showFunctionString

Constructor Summary

OrderByOperator()
Creates a new OrderByOperator

Method Summary

protected java.lang.Object	directMap(java.lang.Object rootCtx, java.lang.Object ctx) Returns the associated value to the given context and root context
java.lang.String	toExpressionString() Returns an expression String representation for this operator
java.lang.String	toFunctionString() Returns a function representation String for this operator

Methods inherited from class net.sf.jec.namedop.GroupOperator

applyToGroup

Methods inherited from class net.sf.jec.Operator

apply, setArgumentOperators, setNestedOperator, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

OrderByOperator

public OrderByOperator()

Creates a new OrderByOperator

Method Detail

toFunctionString

public java.lang.String toFunctionString()

Returns a function representation String for this operator

Specified by:

toFunctionString in class Operator

Returns:

representation String for this operator

toExpressionString

public java.lang.String toExpressionString()

Returns an expression String representation for this operator

Specified by:

toExpressionString in class Operator

Returns:

String representation for this operator

directMap

protected java.lang.Object directMap(java.lang.Object rootCtx,
                                     java.lang.Object ctx)
                              throws EvaluationException

Returns the associated value to the given context and root context

Specified by:

directMap in class Operator

Parameters:

rootCtx - The root context, needed for operators that require expression evaluation from root point. Example: Indexer operators

ctx - The current context where the operator will work over

Returns:

The result of applying THIS Operator to the given context.

Throws:

EvaluationException - when the operator can not be applied to the given context.