# Interface EJBQLExpression

All Known Subinterfaces:
  `Node`

All Known Implementing Classes:
  `AggregateConditionNode, EJBQLAbs, EJBQLAbstractSchemaName, EJBQLAdd, EJBQLAggregate, EJBQLAggregateColumn, EJBQLAll, EJBQLAnd, EJBQLAny, EJBQLAscending, EJBQLAverage, EJBQLBetween, EJBQLBooleanLiteral, EJBQLClassName, EJBQLConcat, EJBQLConstructor, EJBQLConstructorParameter, EJBQLConstructorParameters, EJBQLCount, EJBQLCurrentDate, EJBQLCurrentTime, EJBQLCurrentTimestamp, EJBQLDbPath, EJBQLDecimalLiteral, EJBQLDelete, EJBQLDescending, EJBQLDistinct, EJBQLDivide, EJBQLEquals, EJBQLEscapeCharacter, EJBQLExists, EJBQLFrom, EJBQLFromItem, EJBQLGreaterOrEqual, EJBQLGreaterThan, EJBQLGroupBy, EJBQLHaving, EJBQLIdentificationVariable, EJBQLIdentifier, EJBQLIn, EJBQLInnerFetchJoin, EJBQLInnerJoin, EJBQLIntegerLiteral, EJBQLIsEmpty, EJBQLIsNull, EJBQLJoin, EJBQLLength, EJBQLLessOrEqual, EJBQLLessThan, EJBQLLike, EJBQLLocate, EJBQLLower, EJBQLMax, EJBQLMemberOf, EJBQLMin, EJBQLMod, EJBQLMultiply, EJBQLNamedInputParameter, EJBQLNegative, EJBQLNot, EJBQLNotEquals, EJBQLOr, EJBQLOrderBy, EJBQLOrderByItem, EJBQLOuterFetchJoin, EJBQLOuterJoin, EJBQLPath, EJBQLPatternValue, EJBQLPositionalInputParameter, EJBQLSelect, EJBQLSelectClause, EJBQLSelectExpression, EJBQLSelectExpressions, EJBQLSize, EJBQLSqrt, EJBQLStringLiteral, EJBQLSubselect, EJBQLSubstring, EJBQLSubtract, EJBQLSum, EJBQLTok, EJBQLTrim, EJBQLTrimBoth, EJBQLTrimCharacter, EJBQLTrimLeading, EJBQLTrimSpecification, EJBQLTrimTrailing, EJBQLUpdate, EJBQLUpdateField, EJBQLUpdateItem, EJBQLUpdateValue, EJBQLUpper, EJBQLWhere, SimpleNode`

public interface EJBQLExpression
An abstract EJBQL expression interface.

Since:
  3.0

- ## Method Summary

  Modifier and Type
  Method
  Description
  `EJBQLExpression`
  `getChild(int index)`
  Returns a child expression node at the specified index.
  `int`
  `getChildrenCount()`
  Returns a number of child operands of this expression node.
  `String`
  `getText()`
  Returns a text property of the node.
  `boolean`
  `isNegated()`
  Returns an optional boolean flag that negates the value of the expression.
  `void`
  `visit(EJBQLExpressionVisitor visitor)`
  Accepts a visitor, calling appropriate visitor method.

- ## Method Details

  - ### visit

    void visit(EJBQLExpressionVisitor visitor)
    Accepts a visitor, calling appropriate visitor method. If the visitor method returns true, visits all children, otherwise stops.

  - ### getChildrenCount

    int getChildrenCount()
    Returns a number of child operands of this expression node.

  - ### getChild

    EJBQLExpression getChild(int index)
    Returns a child expression node at the specified index.

  - ### getText

    String getText()
    Returns a text property of the node.

  - ### isNegated

    boolean isNegated()
    Returns an optional boolean flag that negates the value of the expression.