org.proteios.core.query
Interface Expression

All Superinterfaces:

QueryElement

All Known Implementing Classes:

AddExpression, CountExpression, DivideExpression, FloatExpression, HqlElementsExpression, HqlEntityExpression, HqlIndexExpression, HqlPropertyExpression, IntegerExpression, LogExpression, MaxExpression, MeanExpression, MinExpression, MultiplyExpression, NegateExpression, ParameterExpression, SelectedExpression, SqrtExpression, SubtractExpression, SumExpression

public interface Expression
extends QueryElement

An expression query element. This is a query element that can appear almost anywhere in a query. For example a Select is usually an expression together with an alias, a Restriction is a comparison of two or more expressions, etc.

There are many types of expressions. The simplest ones just insert a constant value: Expressions.integer(int) or Expressions.aFloat(float).

Other expressions create a reference to a property or database column: Hql.property(String, String).

Expressions can also be combined to form other expressions: Expressions.add(Expression, Expression) or Expressions.divide(Expression, Expression)

Thus it is possible to form a complex tree of expressions:

// The log ratio of foreground intensities: LOG(ch1fg) / LOG(ch2fg)
Expression logRatio = Expressions.divide(
  Expressions.log(Hql.property("ch1fg")),
  Expressions.log(Hql.property("ch2fg"))
);

The expressions can then be used to create restrictions:

// Return only data with log ratio greater than 2.0 
Restrictions.gt(logRatio, Expressions.aFloat(2.0));

The Expressions, Hql, Annotations and Annotations are factory classes that create expressions.

Version:

2.0

Author:

Nicklas

Last modified

$Date: 2009-04-09 08:48:11 +0200 (Thu, 09 Apr 2009) $

Method Summary

Methods inherited from interface org.proteios.core.query.QueryElement

toQl