oracle.toplink.essentials.internal.parsing

Class SelectNode

java.lang.Object

oracle.toplink.essentials.internal.parsing.Node

oracle.toplink.essentials.internal.parsing.MajorNode

oracle.toplink.essentials.internal.parsing.QueryNode

oracle.toplink.essentials.internal.parsing.SelectNode

public class SelectNode
extends QueryNode

INTERNAL

Purpose: Represent a SELECT

Responsibilities:

• Hold the distinct status
• Modify a query based on the contents The SELECT statement determines the return type of an EJBQL query. The SELECT may also determine the distinct state of a query A SELECT can be one of the following: 1. SELECT OBJECT(someObject)... This query will return a collection of objects 2. SELECT anObject.anAttribute ... This will return a collection of anAttribute 3. SELECT <aggregateFunction> ... This will return a single value The allowable aggregateFunctions are: AVG, COUNT, MAX, MIN, SUM SELECT AVG(emp.salary)... Returns the average of all the employees salaries SELECT COUNT(emp)... Returns a count of the employees SELECT COUNT(emp.firstName)... Returns a count of the employee's firstNames SELECT MAX(emp.salary)... Returns the maximum employee salary SELECT MIN(emp.salary)... Returns the minimum employee salary SELECT SUM(emp.salary)... Returns the sum of all the employees salaries

Since:

TopLink 5.0

Author:

Jon Driscoll

Field Summary

Fields inherited from class oracle.toplink.essentials.internal.parsing.Node

left, right, shouldGenerateExpression

Constructor Summary

Constructors

Constructor and Description
SelectNode()

Method Summary

Modifier and Type	Method and Description
void	applyToQuery(DatabaseQuery theQuery, GenerationContext context) INTERNAL Apply this node to the passed query
DatabaseQuery	createDatabaseQuery(ParseTreeContext context) INTERNAL Returns a DatabaseQuery instance representing the owning ParseTree.
Expression	generateExpression(GenerationContext context) INTERNAL Return a TopLink expression generated using the left node
java.lang.Class	getReferenceClass(GenerationContext context) Compute the Reference class for this query
java.util.List	getSelectExpressions()
boolean	hasOneToOneSelected(GenerationContext context) INTERNAL
boolean	isSelected(java.lang.String variableName) Answer true if the variable name given as argument is SELECTed.
boolean	isSelectNode()
boolean	isVariableInINClauseSelected(GenerationContext context) INTERNAL Answer true if a variable in the IN clause is SELECTed
boolean	nodeRefersToObject(Node node, GenerationContext context) INTERNAL Answer true if this node refers to an object described later in the EJBQL True: SELECT p FROM Project p False: SELECT p.id FROM Project p
Node	qualifyAttributeAccess(ParseTreeContext context) INTERNAL Check the select expression nodes for a path expression starting with a unqualified field access and if so, replace it by a qualified field access.
java.lang.Class	resolveClass(GenerationContext context) resolveClass: Answer the class associated with my left node.
void	setDistinct(boolean distinct)
void	setSelectExpressions(java.util.List exprs)
boolean	usesDistinct()
void	validate(ParseTreeContext context) INTERNAL Validate node.
void	verifySelectedAlias(GenerationContext context) Verify that the selected alias is a valid alias.

Methods inherited from class oracle.toplink.essentials.internal.parsing.QueryNode

getParseTree, isDeleteNode, isUpdateNode, setParseTree

Methods inherited from class oracle.toplink.essentials.internal.parsing.MajorNode

getContext, setContext

Methods inherited from class oracle.toplink.essentials.internal.parsing.Node

addToExpression, appendExpression, applyToQuery, getAsString, getColumn, getLeft, getLine, getRight, getType, hasLeft, hasRight, isAggregateNode, isAttributeNode, isConstructorNode, isCountNode, isDivideNode, isDotNode, isEscape, isLiteralNode, isMinusNode, isMultiplyNode, isNotNode, isParameterNode, isPlusNode, isSubqueryNode, isVariableNode, resolveAttribute, resolveClass, resolveMapping, resolveMapping, setColumn, setLeft, setLine, setRight, setType, toString, toString, toStringDisplayName, toStringIndent, validateParameter

Methods inherited from class java.lang.Object

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

Constructor Detail

SelectNode

public SelectNode()

Method Detail

getSelectExpressions

public java.util.List getSelectExpressions()

setSelectExpressions

public void setSelectExpressions(java.util.List exprs)

usesDistinct

public boolean usesDistinct()

setDistinct

public void setDistinct(boolean distinct)

createDatabaseQuery

public DatabaseQuery createDatabaseQuery(ParseTreeContext context)

INTERNAL Returns a DatabaseQuery instance representing the owning ParseTree. This implementation returns a ReadAllQuery for simple SELECT queries and a ReportQuery otherwise.

Specified by:

createDatabaseQuery in class QueryNode

applyToQuery

public void applyToQuery(DatabaseQuery theQuery,
                         GenerationContext context)

INTERNAL Apply this node to the passed query

Specified by:

applyToQuery in class QueryNode

hasOneToOneSelected

public boolean hasOneToOneSelected(GenerationContext context)

INTERNAL

verifySelectedAlias

public void verifySelectedAlias(GenerationContext context)

Verify that the selected alias is a valid alias. If it's not valid, an Exception will be thrown, likely EJBQLException.aliasResolutionException. Valid: SELECT OBJECT(emp) FROM Employee emp WHERE ... Invalid: SELECT OBJECT(badAlias) FROM Employee emp WHERE ...

isSelected

public boolean isSelected(java.lang.String variableName)

Answer true if the variable name given as argument is SELECTed. True: "SELECT OBJECT(emp) ...." & variableName = "emp" False: "SELECT OBJECT(somethingElse) ..." & variableName = "emp"

isSelectNode

public boolean isSelectNode()

Overrides:

isSelectNode in class QueryNode

qualifyAttributeAccess

public Node qualifyAttributeAccess(ParseTreeContext context)

INTERNAL Check the select expression nodes for a path expression starting with a unqualified field access and if so, replace it by a qualified field access.

Overrides:

qualifyAttributeAccess in class Node

validate

public void validate(ParseTreeContext context)

INTERNAL Validate node.

Overrides:

validate in class Node

resolveClass

public java.lang.Class resolveClass(GenerationContext context)

resolveClass: Answer the class associated with my left node.

Specified by:

resolveClass in class QueryNode

generateExpression

public Expression generateExpression(GenerationContext context)

INTERNAL Return a TopLink expression generated using the left node

Specified by:

generateExpression in class QueryNode

getReferenceClass

public java.lang.Class getReferenceClass(GenerationContext context)

Compute the Reference class for this query

Overrides:

getReferenceClass in class QueryNode

Parameters:

context -

Returns:

the class this query is querying for

isVariableInINClauseSelected

public boolean isVariableInINClauseSelected(GenerationContext context)

INTERNAL Answer true if a variable in the IN clause is SELECTed

nodeRefersToObject

public boolean nodeRefersToObject(Node node,
                                  GenerationContext context)

INTERNAL Answer true if this node refers to an object described later in the EJBQL True: SELECT p FROM Project p False: SELECT p.id FROM Project p