org.datanucleus.query.expression

Class Expression

java.lang.Object

org.datanucleus.query.expression.Expression

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

ArrayExpression, CaseExpression, ClassExpression, CreatorExpression, DyadicExpression, InvokeExpression, JoinExpression, Literal, OrderExpression, ParameterExpression, PrimaryExpression, SubqueryExpression, VariableExpression

public abstract class Expression
extends Object
implements Serializable

A Scalar expression in a Query. Used to compute values with a resulting type.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Expression.DyadicOperator "Dyadic" operator performs operation on one or two operands.
static class	Expression.MonadicOperator "Monadic" operator performs a function on one operand.
static class	Expression.Operator Representation of an Operator.

Field Summary

Fields

Modifier and Type	Field and Description
protected String	alias
protected Expression	left
protected static Localiser	LOCALISER Localiser for messages
protected Expression.Operator	op
static Expression.DyadicOperator	OP_ADD ADD
static Expression.DyadicOperator	OP_AND AND
static Expression.DyadicOperator	OP_CAST IS
static Expression.MonadicOperator	OP_COM COM
static Expression.DyadicOperator	OP_CONCAT CONCAT
static Expression.MonadicOperator	OP_DISTINCT DISTINCT
static Expression.DyadicOperator	OP_DIV DIV
static Expression.DyadicOperator	OP_EQ EQ
static Expression.DyadicOperator	OP_GT GT
static Expression.DyadicOperator	OP_GTEQ GTEQ
static Expression.DyadicOperator	OP_IN IN
static Expression.DyadicOperator	OP_IS IS
static Expression.DyadicOperator	OP_ISNOT ISNOT
static Expression.DyadicOperator	OP_LIKE LIKE
static Expression.DyadicOperator	OP_LT LT
static Expression.DyadicOperator	OP_LTEQ LTEQ
static Expression.DyadicOperator	OP_MOD MOD
static Expression.DyadicOperator	OP_MUL MUL
static Expression.MonadicOperator	OP_NEG NEG
static Expression.MonadicOperator	OP_NOT NOT
static Expression.DyadicOperator	OP_NOTEQ NOTEQ
static Expression.DyadicOperator	OP_NOTIN NOTIN
static Expression.DyadicOperator	OP_OR OR
static Expression.DyadicOperator	OP_SUB SUB
protected Expression	parent Parent of this expression in the tree (if any).
protected Expression	right
protected Symbol	symbol

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Expression() Constructor.
protected	Expression(Expression.MonadicOperator op, Expression operand) Perform a function op on operand
protected	Expression(Expression operand1, Expression.DyadicOperator op, Expression operand2) Performs a function on two arguments.

Method Summary

Methods

Modifier and Type	Method and Description
abstract Symbol	bind(SymbolTable symtbl) Method to bind the expression to the symbol table as appropriate.
Object	evaluate(ExpressionEvaluator eval) Method to evaluate this expression, using the passed evaluator.
String	getAlias()
Expression	getLeft() Accessor for the left hand expression.
Expression.Operator	getOperator() The operator to be performed by this expression.
Expression	getParent() Accessor for the parent expression where this expression is access from.
Expression	getRight() Accessor for the right hand expression.
Symbol	getSymbol() Accessor for the symbol for this expression (if set).
void	setAlias(String alias)
void	setLeft(Expression expr)
void	setRight(Expression expr)

Methods inherited from class java.lang.Object

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

Field Detail

LOCALISER

protected static final Localiser LOCALISER

Localiser for messages

parent

protected Expression parent

Parent of this expression in the tree (if any).

op

protected Expression.Operator op

left

protected Expression left

right

protected Expression right

symbol

protected Symbol symbol

alias

protected String alias

OP_OR

public static final Expression.DyadicOperator OP_OR

OR

OP_AND

public static final Expression.DyadicOperator OP_AND

AND

OP_NOT

public static final Expression.MonadicOperator OP_NOT

NOT

OP_EQ

public static final Expression.DyadicOperator OP_EQ

EQ

OP_NOTEQ

public static final Expression.DyadicOperator OP_NOTEQ

NOTEQ

OP_LT

public static final Expression.DyadicOperator OP_LT

LT

OP_LTEQ

public static final Expression.DyadicOperator OP_LTEQ

LTEQ

OP_GT

public static final Expression.DyadicOperator OP_GT

GT

OP_GTEQ

public static final Expression.DyadicOperator OP_GTEQ

GTEQ

OP_LIKE

public static final Expression.DyadicOperator OP_LIKE

LIKE

OP_IS

public static final Expression.DyadicOperator OP_IS

IS

OP_ISNOT

public static final Expression.DyadicOperator OP_ISNOT

ISNOT

OP_CAST

public static final Expression.DyadicOperator OP_CAST

IS

OP_IN

public static final Expression.DyadicOperator OP_IN

IN

OP_NOTIN

public static final Expression.DyadicOperator OP_NOTIN

NOTIN

OP_ADD

public static final Expression.DyadicOperator OP_ADD

ADD

OP_SUB

public static final Expression.DyadicOperator OP_SUB

SUB

OP_CONCAT

public static final Expression.DyadicOperator OP_CONCAT

CONCAT

OP_MUL

public static final Expression.DyadicOperator OP_MUL

MUL

OP_DIV

public static final Expression.DyadicOperator OP_DIV

DIV

OP_MOD

public static final Expression.DyadicOperator OP_MOD

MOD

OP_NEG

public static final Expression.MonadicOperator OP_NEG

NEG

OP_COM

public static final Expression.MonadicOperator OP_COM

COM

OP_DISTINCT

public static final Expression.MonadicOperator OP_DISTINCT

DISTINCT

Constructor Detail

Expression

protected Expression()

Constructor.

Expression

protected Expression(Expression.MonadicOperator op,
          Expression operand)

Perform a function op on operand

Parameters:

op - operator

operand - operand

Expression

protected Expression(Expression operand1,
          Expression.DyadicOperator op,
          Expression operand2)

Performs a function on two arguments. op(operand1,operand2) operand1 op operand2

Parameters:

operand1 - the first expression

op - the operator between operands

operand2 - the second expression

Method Detail

getParent

public Expression getParent()

Accessor for the parent expression where this expression is access from.

Returns:

Parent expression

setLeft

public void setLeft(Expression expr)

setRight

public void setRight(Expression expr)

getOperator

public Expression.Operator getOperator()

The operator to be performed by this expression. See the OP_{name} final static properties of this class.

Returns:

Operator

getLeft

public Expression getLeft()

Accessor for the left hand expression.

Returns:

Left expression

getRight

public Expression getRight()

Accessor for the right hand expression.

Returns:

Right expression

getSymbol

public Symbol getSymbol()

Accessor for the symbol for this expression (if set).

Returns:

The symbol

setAlias

public void setAlias(String alias)

getAlias

public String getAlias()

evaluate

public Object evaluate(ExpressionEvaluator eval)

Method to evaluate this expression, using the passed evaluator.

Parameters:

eval - Evaluator

Returns:

The result

bind

public abstract Symbol bind(SymbolTable symtbl)

Method to bind the expression to the symbol table as appropriate.

Parameters:

symtbl - Symbol table

Returns:

The symbol for this expression