org.datanucleus.store.rdbms.sql.expression
Class ObjectExpression

java.lang.Object
  org.datanucleus.store.rdbms.sql.expression.SQLExpression
      org.datanucleus.store.rdbms.sql.expression.ObjectExpression

Direct Known Subclasses:

ObjectLiteral

public class ObjectExpression
extends SQLExpression

Representation of an Object expression in a Query. Typically represents a persistable object, and so its identity, though could be used to represent any Object.

Let's take an example. We have classes A and B, and A contains a reference to B "b". If we do a JDOQL query for class A of "b == value" then "b" is interpreted first and an ObjectExpression is created to represent that object (of type B).

Nested Class Summary

Nested classes/interfaces inherited from class org.datanucleus.store.rdbms.sql.expression.SQLExpression

SQLExpression.ColumnExpressionList

Field Summary

Fields inherited from class org.datanucleus.store.rdbms.sql.expression.SQLExpression

isParameter, LOCALISER, lowestOperator, mapping, st, stmt, subExprs, table

Constructor Summary

ObjectExpression(SQLStatement stmt, SQLTable table, org.datanucleus.store.mapped.mapping.JavaTypeMapping mapping)
Constructor for an SQL expression for a (field) mapping in a specified table.

Method Summary

SQLExpression	cast(SQLExpression expr) Cast operator.
BooleanExpression	eq(SQLExpression expr) Equals operator.
BooleanExpression	in(SQLExpression expr) In expression.
BooleanExpression	is(SQLExpression expr) An "is" (instanceOf) expression, providing a BooleanExpression whether this expression is an instanceof the provided type.
BooleanExpression	ne(SQLExpression expr) Not equals operator.
void	useFirstColumnOnly() Method to change the expression to use only the first column.

Methods inherited from class org.datanucleus.store.rdbms.sql.expression.SQLExpression

add, and, checkForAndCorrectParameterComparison, com, div, encloseInParentheses, eor, ge, getJavaTypeMapping, getNumberOfSubExpressions, getSQLStatement, getSQLTable, gt, invoke, ior, isParameter, le, lt, mod, mul, neg, not, sub, toSQLText

Methods inherited from class java.lang.Object

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

Constructor Detail

ObjectExpression

public ObjectExpression(SQLStatement stmt,
                        SQLTable table,
                        org.datanucleus.store.mapped.mapping.JavaTypeMapping mapping)

Constructor for an SQL expression for a (field) mapping in a specified table.

Parameters:

stmt - The statement

table - The table in the statement

mapping - The mapping for the field

Method Detail

useFirstColumnOnly

public void useFirstColumnOnly()

Method to change the expression to use only the first column. This is used where we want to use the expression with COUNT(...) and that only allows 1 column.

eq

public BooleanExpression eq(SQLExpression expr)

Equals operator. Called when the query contains "obj == value" where "obj" is this object.

Overrides:

eq in class SQLExpression

Parameters:

expr - The expression we compare with (the right-hand-side in the query)

Returns:

Boolean expression representing the comparison.

ne

public BooleanExpression ne(SQLExpression expr)

Not equals operator. Called when the query contains "obj != value" where "obj" is this object.

Overrides:

ne in class SQLExpression

Parameters:

expr - The expression we compare with (the right-hand-side in the query)

Returns:

Boolean expression representing the comparison.

in

public BooleanExpression in(SQLExpression expr)

Description copied from class: SQLExpression

In expression. Return true if this is contained by expr

Overrides:

in in class SQLExpression

Parameters:

expr - the right-hand expression

Returns:

true if the left-hand expression is contained by the right-hand expression. Otherwise the result is false.

cast

public SQLExpression cast(SQLExpression expr)

Cast operator. Called when the query contains "(type)obj" where "obj" is this object.

Overrides:

cast in class SQLExpression

Parameters:

expr - Expression representing the type to cast to

Returns:

Scalar expression representing the cast object.

is

public BooleanExpression is(SQLExpression expr)

An "is" (instanceOf) expression, providing a BooleanExpression whether this expression is an instanceof the provided type.

Overrides:

is in class SQLExpression

Parameters:

expr - The expression representing the type

Returns:

Whether this expression is an instance of the provided type