com.mckoi.database
Class FunctionFactory

java.lang.Object
  extended by com.mckoi.database.FunctionFactory
All Implemented Interfaces:
FunctionLookup

public abstract class FunctionFactory
extends java.lang.Object
implements FunctionLookup

A factory that generates Function objects given a function name and a set of expression's that represent parameters. A developer may create their own instance of this class and register the factory with the DatabaseSystem. When the SQL grammer comes across a function, it will try and resolve the function name against the registered function factories.

Author:
Tobias Downer

Nested Class Summary
protected  class FunctionFactory.FF_FunctionInfo
          An implementation of FunctionInfo.
 
Field Summary
static Expression[] GLOB_LIST
          Represents a function argument * for glob's such as 'count(*)'
 
Constructor Summary
FunctionFactory()
          Constructs the FunctionFactory.
 
Method Summary
protected  void addFunction(java.lang.String fun_name, java.lang.Class fun_class)
          Adds a new static function to this factory.
protected  void addFunction(java.lang.String fun_name, java.lang.Class fun_class, int fun_type)
          Adds a new function to this factory.
protected  boolean functionDefined(java.lang.String fun_name)
          Returns true if the function name is defined in this factory.
 Function generateFunction(FunctionDef function_def)
          Creates a Function object for the function with the given name with the given arguments.
 FunctionInfo[] getAllFunctionInfo()
          Returns the list of all function names that this FunctionFactory manages.
 FunctionInfo getFunctionInfo(java.lang.String fun_name)
          Returns a FunctionInfo instance of the function with the given name that this FunctionFactory manages.
abstract  void init()
          Initializes this FunctionFactory.
 boolean isAggregate(FunctionDef function_def)
          Returns true if the function defined by FunctionDef is an aggregate function, or false otherwise.
protected  void removeFunction(java.lang.String fun_name)
          Removes a static function from this factory.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

GLOB_LIST

public static final Expression[] GLOB_LIST
Represents a function argument * for glob's such as 'count(*)'

Constructor Detail

FunctionFactory

public FunctionFactory()
Constructs the FunctionFactory.

Method Detail

addFunction

protected void addFunction(java.lang.String fun_name,
                           java.lang.Class fun_class,
                           int fun_type)
Adds a new function to this factory. Takes a function name and a class that is the Function implementation. When the 'generateFunction' method is called, it looks up the class with the function name and returns a new instance of the function.

Parameters:
fun_name - the name of the function (eg. 'sum', 'concat').
fun_class - the Function class that we instantiate for this function.
fun_type - that type of function (either FunctionInfo.STATIC, FunctionInfo.AGGREGATE, FunctionInfo.STATE_BASED).

addFunction

protected void addFunction(java.lang.String fun_name,
                           java.lang.Class fun_class)
Adds a new static function to this factory.


removeFunction

protected void removeFunction(java.lang.String fun_name)
Removes a static function from this factory.


functionDefined

protected boolean functionDefined(java.lang.String fun_name)
Returns true if the function name is defined in this factory.


init

public abstract void init()
Initializes this FunctionFactory. This is an abstract method that needs to be implemented. (It doesn't need to do anything if a developer implements their own version of 'generateFunction').


generateFunction

public Function generateFunction(FunctionDef function_def)
Creates a Function object for the function with the given name with the given arguments. If this factory does not handle a function with the given name then it returns null.

Specified by:
generateFunction in interface FunctionLookup

isAggregate

public boolean isAggregate(FunctionDef function_def)
Returns true if the function defined by FunctionDef is an aggregate function, or false otherwise.

Specified by:
isAggregate in interface FunctionLookup

getFunctionInfo

public FunctionInfo getFunctionInfo(java.lang.String fun_name)
Returns a FunctionInfo instance of the function with the given name that this FunctionFactory manages. If 'generateFunction' is reimplemented then this method should be rewritten also.


getAllFunctionInfo

public FunctionInfo[] getAllFunctionInfo()
Returns the list of all function names that this FunctionFactory manages. This is used to compile information about the function factories. If 'generateFunction' is reimplemented then this method should be rewritten also.