Package com.mckoi.database

Class FunctionDef

java.lang.Object

com.mckoi.database.FunctionDef

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

public final class FunctionDef
extends java.lang.Object
implements java.io.Serializable, java.lang.Cloneable

A definition of a function including its name and parameters. A FunctionDef can easily be transformed into a Function object via a set of FunctionFactory instances.

NOTE: This object is NOT immutable or thread-safe. A FunctionDef should not be shared among different threads.

Author:

Tobias Downer

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
FunctionDef(java.lang.String name, Expression[] params)	Constructs the FunctionDef.

Method Summary

Modifier and Type	Method	Description
java.lang.Object	clone()	Performs a deep clone of this object.
Function	getFunction(QueryContext context)	Returns a Function object from this FunctionDef.
java.lang.String	getName()	The name of the function.
Expression[]	getParameters()	The list of parameters that are passed to the function.
boolean	isAggregate(QueryContext context)	Returns true if this function is an aggregate, or the parameters are aggregates.
java.lang.String	toString()	Human understandable string, used for the column title.

Methods inherited from class java.lang.Object

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

Constructor Detail

FunctionDef

public FunctionDef(java.lang.String name,
                   Expression[] params)

Constructs the FunctionDef.

Method Detail

getName

public java.lang.String getName()

The name of the function. For example, 'MIN' or 'CONCAT'.

getParameters

public Expression[] getParameters()

The list of parameters that are passed to the function. For example, a concat function may have 7 parameters ('There', ' ', 'are', ' ', 10, ' ', 'bottles.')

isAggregate

public boolean isAggregate(QueryContext context)

Returns true if this function is an aggregate, or the parameters are aggregates. It requires a QueryContext object to lookup the function in the function factory database.

getFunction

public Function getFunction(QueryContext context)

Returns a Function object from this FunctionDef. Note that two calls to this method will produce the same Function object, however the same Function object will not be produced over multiple instances of FunctionDef even when they represent the same thing.

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Performs a deep clone of this object.

Overrides:

clone in class java.lang.Object

Throws:

java.lang.CloneNotSupportedException

toString

public java.lang.String toString()

Human understandable string, used for the column title.

Overrides:

toString in class java.lang.Object