Annotation Interface Formula

@Target({METHOD,FIELD}) @Retention(RUNTIME) public @interface Formula
Specifies an expression written in native SQL that is used to read the value of an attribute instead of storing the value in a Column.

A Formula mapping defines a "derived" attribute, whose state is determined from other columns and functions when an entity is read from the database.

A formula may involve multiple columns and SQL operators: 

// perform calculations using SQL operators
@Formula("sub_total * (1.0 + tax)")
BigDecimal totalWithTax;

It may even call SQL functions: 

// call native SQL functions
@Formula("upper(substring(middle_name from 0 for 1))")
Character middleInitial;

By default, the fields of an entity are not updated with the results of evaluating the formula after an insert or update. The @Generated annotation may be used to specify that this should happen: 

@Generated  // evaluate the formula after an insert
@Formula("sub_total * (1.0 + tax)")
BigDecimal totalWithTax;

For an entity with secondary tables, a formula may involve columns of the primary table, or columns of any one of the secondary tables. But it may not involve columns of more than one table.

The @ColumnTransformer annotation is an alternative in certain cases, allowing the use of native SQL to read and write values to a column. 

// it might be better to use @ColumnTransformer in this case
@Formula("decrypt(credit_card_num)")
String getCreditCardNumber() { ... }
See Also:

  • Required Element Summary

    Required Elements
    Modifier and Type
    Required Element
    Description
    String
    value
    The formula, written in native SQL.

  • Element Details

    • value

      String value
      The formula, written in native SQL.