java.lang.Object
- org.eclipse.persistence.jpa.jpql.parser.AbstractExpression
- - org.eclipse.persistence.jpa.jpql.parser.NullExpression

All Implemented Interfaces:

Expression
```
public final class NullExpression
extends AbstractExpression
```
A null Expression is used instead of a true null, which allows operations to be performed without doing a null check first.

Since:

2.3

Version:

2.5

Author:

Pascal Filion

Field Summary
- Fields inherited from class org.eclipse.persistence.jpa.jpql.parser.AbstractExpression
  COMMA, DOT, DOUBLE_QUOTE, LEFT_CURLY_BRACKET, LEFT_PARENTHESIS, NOT_DEFINED, RIGHT_CURLY_BRACKET, RIGHT_PARENTHESIS, SINGLE_QUOTE, SPACE, UNDERSCORE
- Fields inherited from interface org.eclipse.persistence.jpa.jpql.parser.Expression
  ABS, ALL, AND, ANY, AS, AS_OF, ASC, AVG, BETWEEN, BIT_LENGTH, BOTH, CASE, CAST, CHAR_LENGTH, CHARACTER_LENGTH, CLASS, COALESCE, COLUMN, CONCAT, CONNECT_BY, COUNT, CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP, DELETE, DELETE_FROM, DESC, DIFFERENT, DISTINCT, DIVISION, ELSE, EMPTY, END, ENTRY, EQUAL, ESCAPE, EXCEPT, EXISTS, EXTRACT, FALSE, FETCH, FIRST, FROM, FUNC, FUNCTION, GREATER_THAN, GREATER_THAN_OR_EQUAL, GROUP_BY, HAVING, IN, INDEX, INNER, INNER_JOIN, INNER_JOIN_FETCH, INTERSECT, IS, IS_EMPTY, IS_NOT_EMPTY, IS_NOT_NULL, IS_NULL, JOIN, JOIN_FETCH, KEY, LAST, LEADING, LEFT, LEFT_JOIN, LEFT_JOIN_FETCH, LEFT_OUTER_JOIN, LEFT_OUTER_JOIN_FETCH, LENGTH, LIKE, LOCATE, LOWER, LOWER_THAN, LOWER_THAN_OR_EQUAL, MAX, MEMBER, MEMBER_OF, MIN, MINUS, MOD, MULTIPLICATION, NAMED_PARAMETER, NEW, NOT, NOT_BETWEEN, NOT_EQUAL, NOT_EXISTS, NOT_IN, NOT_LIKE, NOT_MEMBER, NOT_MEMBER_OF, NULL, NULLIF, NULLS, NULLS_FIRST, NULLS_LAST, OBJECT, OF, ON, OPERATOR, OR, ORDER_BY, ORDER_SIBLINGS_BY, OUTER, PLUS, POSITION, POSITIONAL_PARAMETER, QUOTE, REGEXP, SCN, SELECT, SET, SIZE, SOME, SQL, SQRT, START_WITH, SUBSTRING, SUM, TABLE, THEN, TIMESTAMP, TRAILING, TREAT, TRIM, TRUE, TYPE, UNION, UNKNOWN, UPDATE, UPPER, VALUE, WHEN, WHERE

Constructor Summary

Constructors
Constructor Description

NullExpression(AbstractExpression parent)
Creates a new NullExpression.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`accept(ExpressionVisitor visitor)`	Visits this `Expression` by the given `visitor`.
`void`	`acceptChildren(ExpressionVisitor visitor)`	Visits the children of this `Expression`.
`JPQLQueryBNF`	`findQueryBNF(Expression expression)`	Retrieves the `JPQLQueryBNF` that represents the fragment of this `Expression` that was used when parsing the given `Expression`.
`JPQLQueryBNF`	`getQueryBNF()`	Returns the BNF of this `Expression`.
`boolean`	`isNull()`

Methods inherited from class org.eclipse.persistence.jpa.jpql.parser.AbstractExpression
children, getGrammar, getIdentifierVersion, getLength, getOffset, getParent, getQueryBNF, getRoot, isAncestor, orderedChildren, populatePosition, toActualText, toParsedText, toString

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - NullExpression
```
public NullExpression(AbstractExpression parent)
```
    Creates a new NullExpression.
    
    Parameters:
    
    parent - The parent of this NullExpression
- Method Detail
  - accept
```
public void accept(ExpressionVisitor visitor)
```
    Visits this Expression by the given visitor.
    
    Parameters:
    
    visitor - The ExpressionVisitor to visit this object
  - acceptChildren
```
public void acceptChildren(ExpressionVisitor visitor)
```
    Visits the children of this Expression. This method can be used to optimize traversing the children since a new list is not created every time Expression.children() is called.
    This does not traverse the Expression sub-hierarchy, use a subclass of AbstractTraverseChildrenVisitor in order to traverse the entire sub-hierarchy.
    
    Parameters:
    
    visitor - The visitor to visit the children of this object.
  - findQueryBNF
```
public JPQLQueryBNF findQueryBNF(Expression expression)
```
    Retrieves the JPQLQueryBNF that represents the fragment of this Expression that was used when parsing the given Expression.
    
    Specified by:
    
    findQueryBNF in interface Expression
    
    Overrides:
    
    findQueryBNF in class AbstractExpression
    
    Parameters:
    
    expression - The Expression that is a descendant of this one
    
    Returns:
    
    The JPQLQueryBNF that was used to parse the given expression
  - getQueryBNF
```
public JPQLQueryBNF getQueryBNF()
```
    Returns the BNF of this Expression.
    
    Returns:
    
    The JPQLQueryBNF, which represents the grammar of this Expression
  - isNull
```
public boolean isNull()
```

Class NullExpression

Field Summary

Fields inherited from class org.eclipse.persistence.jpa.jpql.parser.AbstractExpression

Fields inherited from interface org.eclipse.persistence.jpa.jpql.parser.Expression

Constructor Summary

Method Summary

Methods inherited from class org.eclipse.persistence.jpa.jpql.parser.AbstractExpression

Methods inherited from class java.lang.Object

Constructor Detail

NullExpression

Method Detail

accept

acceptChildren

findQueryBNF

getQueryBNF

isNull