Class IdentificationVariable

java.lang.Object
org.eclipse.persistence.jpa.jpql.parser.AbstractExpression
org.eclipse.persistence.jpa.jpql.parser.IdentificationVariable
All Implemented Interfaces:
Expression

public final class IdentificationVariable extends AbstractExpression
An identification variable is a valid identifier declared in the FROM clause of a query.

Requirements:

  • All identification variables must be declared in the FROM clause. Identification variables cannot be declared in other clauses.
  • An identification variable must not be a reserved identifier or have the same name as any entity in the same persistence unit.
  • Identification variables are case insensitive.
  • An identification variable evaluates to a value of the type of the expression used in declaring the variable.

An identification variable can range over an entity, embeddable, or basic abstract schema type. An identification variable designates an instance of an abstract schema type or an element of a collection of abstract schema type instances.

Note that for identification variables referring to an instance of an association or collection represented as a Map, the identification variable is of the abstract schema type of the map value.

An identification variable always designates a reference to a single value. It is declared in one of three ways:

  • In a range variable declaration;
  • In a join clause;
  • In a collection member declaration.
The identification variable declarations are evaluated from left to right in the FROM clause, and an identification variable declaration can use the result of a preceding identification variable declaration of the query string.

All identification variables used in the SELECT, WHERE, ORDER BY, GROUP BY, or HAVING clause of a SELECT or DELETE statement must be declared in the FROM clause. The identification variables used in the WHERE clause of an UPDATE statement must be declared in the UPDATE clause.

An identification variable is scoped to the query (or subquery) in which it is defined and is also visible to any subqueries within that query scope that do not define an identification variable of the same name.

Since:
2.3
Version:
2.4
  • Constructor Details

    • IdentificationVariable

      public IdentificationVariable(AbstractExpression parent, String identificationVariable)
      Creates a new IdentificationVariable.
      Parameters:
      parent - The parent of this expression
      identificationVariable - The actual identification variable
    • IdentificationVariable

      public IdentificationVariable(AbstractExpression parent, String identificationVariable, boolean virtual)
      Creates a new IdentificationVariable.
      Parameters:
      parent - The parent of this expression
      identificationVariable - The actual identification variable
      virtual - Determines whether this identification variable is virtual, meaning it's not part of the query but is required for proper navigability
  • Method Details

    • accept

      public void accept(ExpressionVisitor visitor)
      Description copied from interface: Expression
      Visits this Expression by the given visitor.
      Parameters:
      visitor - The ExpressionVisitor to visit this object
    • acceptChildren

      public void acceptChildren(ExpressionVisitor visitor)
      Description copied from interface: Expression
      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.
    • addOrderedChildrenTo

      protected void addOrderedChildrenTo(List<Expression> children)
      Description copied from class: AbstractExpression
      Adds the children of this AbstractExpression to the given list.
      Overrides:
      addOrderedChildrenTo in class AbstractExpression
      Parameters:
      children - The list used to store the string representation of this AbstractExpression
    • getQueryBNF

      public JPQLQueryBNF getQueryBNF()
      Description copied from interface: Expression
      Returns the BNF of this Expression.
      Returns:
      The JPQLQueryBNF, which represents the grammar of this Expression
    • getStateFieldPathExpression

      public StateFieldPathExpression getStateFieldPathExpression()
      Returns the actual representation of the parsed information. This method should only be called if isVirtual() returns true. This is valid in an UPDATE and DELETE queries where the identification variable is not specified.
      Returns:
      The path expression that is qualified by the virtual identification variable
      Throws:
      IllegalAccessError - If this expression does not have a virtual identification variable
    • getText

      public String getText()
      Description copied from class: AbstractExpression
      Returns the encapsulated text of this AbstractExpression, which can be used in various ways, it can be a keyword, a literal, etc.
      Overrides:
      getText in class AbstractExpression
      Returns:
      Either the JPQL identifier for this AbstractExpression, the literal it encapsulates or an empty string
    • getVariableName

      public String getVariableName()
      Returns the identification variable, which has been changed to be upper case.
      Returns:
      The uppercase version of the identification variable
      Since:
      2.4
    • isVirtual

      public boolean isVirtual()
      Description copied from class: AbstractExpression
      Determines whether this AbstractExpression is virtual, meaning it's not part of the query but is required for proper navigability.
      Overrides:
      isVirtual in class AbstractExpression
      Returns:
      true if this AbstractExpression was virtually created to fully qualify path expression; false if it was parsed
    • parse

      protected void parse(WordParser wordParser, boolean tolerant)
      Description copied from class: AbstractExpression
      Parses the query by starting at the current position, which is part of the given WordParser.
      Specified by:
      parse in class AbstractExpression
      Parameters:
      wordParser - The text to parse based on the current position of the cursor
      tolerant - Determines whether the parsing system should be tolerant, meaning if it should try to parse invalid or incomplete queries
    • setVirtualIdentificationVariable

      public void setVirtualIdentificationVariable(String variableName)
      Sets a virtual identification variable because the abstract schema name was parsed without one. This is valid in an UPDATE and DELETE queries. This internally transforms the what was thought to be an identification variable to a path expression.
      Parameters:
      variableName - The identification variable that was generated to identify the "root" object
    • toParsedText

      public String toParsedText()
      Description copied from interface: Expression
      Returns a string representation of this Expression and its children. The expression should contain whitespace even if the beautified version would not have any. For instance, "SELECT e " should be returned where Expression.toActualText() would return "SELECT e".
      Specified by:
      toParsedText in interface Expression
      Overrides:
      toParsedText in class AbstractExpression
      Returns:
      The string representation of this Expression
    • toParsedText

      protected void toParsedText(StringBuilder writer, boolean actual)
      Description copied from class: AbstractExpression
      Generates a string representation of this Expression, including its children, if it has any.
      Specified by:
      toParsedText in class AbstractExpression
      Parameters:
      writer - The buffer used to append this Expression's string representation
      actual - Determines whether the string representation should represent what was parsed, i.e. include any "virtual" whitespace (such as ending whitespace) and the actual case of the JPQL identifiers