Examples of org.eclipse.persistence.expressions.Expression

Package org.eclipse.persistence.expressions

Examples of org.eclipse.persistence.expressions.Expression

org.eclipse.persistence.expressions.Expression
Purpose: Define an object-level representation of a database query where clause.

Description: An expression is a tree-like structure that defines the selection criteria for a query against objects in the database. The expression has the advantage over SQL by being at the object-level, i.e. the object model attributes and relationships can be used to be query on instead of the database field names. Because it is an object, not a string the expression has the advantage that is can be easily manipulated through code to easily build complex selection criterias.

Responsibilities:
- Store the selection criteria in a tree-like structure.
- Support public manipulation protocols for all comparison and function operators.
- Use opperator overloading to support all primitive types as well as objects.


    List<Class<?>> types = new ArrayList<Class<?>>(2);


    // Create the left side of the multiplication expression
    expression.getLeftExpression().accept(this);
    Expression leftExpression = queryExpression;
    types.add(type[0]);


    // Create the right side of the multiplication expression
    expression.getRightExpression().accept(this);
    Expression rightExpression = queryExpression;
    types.add(type[0]);


    // Now create the multiplication expression
    queryExpression = ExpressionMath.multiply(leftExpression, rightExpression);

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   */
  public void visit(NullIfExpression expression) {


    // Create the first expression
    expression.getFirstExpression().accept(this);
    Expression firstExpression = queryExpression;
    Class<?> actualType = type[0];


    // Create the second expression
    expression.getSecondExpression().accept(this);
    Expression secondExpression = queryExpression;


    // Now create the NULLIF expression
    queryExpression = firstExpression.nullIf(secondExpression);


    // Set the expression type

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   */
  public void visit(OrExpression expression) {


    // Create the left side of the logical expression
    expression.getLeftExpression().accept(this);
    Expression leftExpression = queryExpression;


    // Create the right side of the logical expression
    expression.getRightExpression().accept(this);
    Expression rightExpression = queryExpression;


    // Now create the OR expression
    queryExpression = leftExpression.or(rightExpression);


    // Set the expression type

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  @Override
  public void visit(RegexpExpression expression) {


    // Create the first expression
    expression.getStringExpression().accept(this);
    Expression firstExpression = queryExpression;


    // Create the expression for the pattern value
    expression.getPatternValue().accept(this);
    Expression patternValue = queryExpression;


    // Create the REGEXP expression
    queryExpression = firstExpression.regexp(patternValue);


    // Set the expression type

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   */
  public void visit(SubstringExpression expression) {


    // Create the first expression
    expression.getFirstExpression().accept(this);
    Expression firstExpression = queryExpression;


    // Create the second expression
    expression.getSecondExpression().accept(this);
    Expression secondExpression = queryExpression;


    // Create the third expression
    expression.getThirdExpression().accept(this);
    Expression thirdExpression = queryExpression;


    // Now create the SUBSTRING expression
    if (thirdExpression != null) {
      queryExpression = firstExpression.substring(secondExpression, thirdExpression);
    }

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    List<Class<?>> types = new ArrayList<Class<?>>(2);


    // Create the left side of the subtraction expression
    expression.getLeftExpression().accept(this);
    Expression leftExpression = queryExpression;
    types.add(type[0]);


    // Create the right side of the subtraction expression
    expression.getRightExpression().accept(this);
    Expression rightExpression = queryExpression;
    types.add(type[0]);


    // Now create the subtraction expression
    queryExpression = ExpressionMath.subtract(leftExpression, rightExpression);

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   */
  public void visit(TrimExpression expression) {


    // Create the TRIM character expression
    expression.getTrimCharacter().accept(this);
    Expression trimCharacter = queryExpression;


    // Create the string to trim
    expression.getExpression().accept(this);
    Expression stringExpression = queryExpression;


    switch (expression.getSpecification()) {
      case LEADING: {
        if (trimCharacter != null) {
          queryExpression = stringExpression.leftTrim(trimCharacter);
        }
        else {
          queryExpression = stringExpression.leftTrim();
        }
        break;
      }
      case TRAILING: {
        if (trimCharacter != null) {
          queryExpression = stringExpression.rightTrim(trimCharacter);
        }
        else {
          queryExpression = stringExpression.rightTrim();
        }
        break;
      }
      default: {
        if (trimCharacter != null) {
          queryExpression = stringExpression.trim(trimCharacter);
        }
        else {
          queryExpression = stringExpression.trim();
        }
        break;
      }
    }

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     * This expression is built on a different base than the one we want. Rebuild it and
     * return the root of the new tree
     */
    @Override
    public Expression rebuildOn(Expression newBase) {
        Expression newLocalBase = getBaseExpression().rebuildOn(newBase);
        Expression result = null;
        
        if (returnMapEntry){
            result = newLocalBase.mapEntry();
        } else {
            result = newLocalBase.mapKey();
        }


        result.setSelectIfOrderedBy(selectIfOrderedBy());
        return result;
    }

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    @Override
    public Expression rebuildOn(Expression oldBase, Expression newBase) {
        if (this == oldBase) {
            return newBase;
        }
        Expression newLocalBase = ((QueryKeyExpression)getBaseExpression()).rebuildOn(oldBase, newBase);
        Expression result = null;


        if (returnMapEntry){
            result = newLocalBase.mapEntry();
        } else {
            result = newLocalBase.mapKey();
        }
        result.setSelectIfOrderedBy(selectIfOrderedBy());
        return result;
    }

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                                   ReportQuery subquery) {


    queryExpression = null;


    for (String variableName : collectOuterIdentificationVariables()) {
      Expression innerExpression = queryContext.getQueryExpression(variableName);
      Expression outerExpression = queryContext.getParent().getQueryExpressionImp(variableName);
      Expression equalExpression = innerExpression.equal(outerExpression);


      if (queryExpression == null) {
        queryExpression = equalExpression;
      }
      else {
        queryExpression = queryExpression.and(equalExpression);
      }
    }


    // Aggregate the WHERE clause with the joins expression
    if (queryExpression != null) {
      Expression whereClause = subquery.getSelectionCriteria();


      if (whereClause != null) {
        whereClause = whereClause.and(queryExpression);
      }
      else {
        whereClause = queryExpression;
      }

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