476 words

javax.persistence.criteria.Expression - JPA interface

javax.persistence.criteria
Interface Expression<T>

Superinterfaces:
Selection<T>, TupleElement<T>
Subinterfaces:
CollectionJoin, Case, Coalesce, In, SimpleCase, From, Join, ListJoin, MapJoin, ParameterExpression, Path, PluralJoin, Predicate, Root, SetJoin, Subquery
Type for query expressions.
Since:
JPA 2.0
Learn how to use JPA Criteria API's Expression in Chapter 4 of the ObjectDB/JPA manual.
Selection<X> alias(String name)
Assigns an alias to the selection item.
Assigns an alias to the selection item. Once assigned, an alias cannot be changed or reassigned. Returns the same selection item.
Parameters:
name - alias
Returns:
selection item
Since:
JPA 2.0
Expression<X> as(Class<X> type)
Perform a typecast upon the expression, returning a new expression object.
Perform a typecast upon the expression, returning a new expression object. This method does not cause type conversion: the runtime type is not changed. Warning: may result in a runtime failure.
Parameters:
type - intended type of the expression
Returns:
new expression of the given type
Since:
JPA 2.0
String getAlias()
Return the alias assigned to the tuple element or null, if no alias has been assigned.
Return the alias assigned to the tuple element or null, if no alias has been assigned.
Returns:
alias
Since:
JPA 2.0
Return the selection items composing a compound selection.
Return the selection items composing a compound selection. Modifications to the list do not affect the query.
Returns:
list of selection items
Throws:
IllegalStateException - if selection is not a compound selection
Since:
JPA 2.0
Class<?> getJavaType()
Return the Java type of the tuple element.
Return the Java type of the tuple element.
Returns:
the Java type of the tuple element
Since:
JPA 2.0
Predicate in(Object... values)
Create a predicate to test whether the expression is a member of the argument list.
Create a predicate to test whether the expression is a member of the argument list.
Parameters:
values - values to be tested against
Returns:
predicate testing for membership
Since:
JPA 2.0
Predicate in(Collection<?> values)
Create a predicate to test whether the expression is a member of the collection.
Create a predicate to test whether the expression is a member of the collection.
Parameters:
values - collection of values to be tested against
Returns:
predicate testing for membership
Since:
JPA 2.0
Create a predicate to test whether the expression is a member of the collection.
Create a predicate to test whether the expression is a member of the collection.
Parameters:
values - expression corresponding to collection to be tested against
Returns:
predicate testing for membership
Since:
JPA 2.0
Create a predicate to test whether the expression is a member of the argument list.
Create a predicate to test whether the expression is a member of the argument list.
Parameters:
values - expressions to be tested against
Returns:
predicate testing for membership
Since:
JPA 2.0
Whether the selection item is a compound selection.
Whether the selection item is a compound selection.
Returns:
boolean indicating whether the selection is a compound selection
Since:
JPA 2.0
Create a predicate to test whether the expression is not null.
Create a predicate to test whether the expression is not null.
Returns:
predicate testing whether the expression is not null
Since:
JPA 2.0
Create a predicate to test whether the expression is null.
Create a predicate to test whether the expression is null.
Returns:
predicate testing whether the expression is null
Since:
JPA 2.0

This documentation page is derived (with some adjustments) from the open source JPA 2 RI (EclipseLink)
and is available under the terms of the Eclipse Public License, v. 1.0 and Eclipse Distribution License, v. 1.0.
Object Relational Mapping (ORM) JPA 2 providers include Hibernate, EclipseLink, TopLink, OpenJPA and DataNucleus.
Object DB is not an ORM JPA implementation but an Object Database for Java with built in JPA 2 support.