Add SpEL support for increment/decrement operators #172
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With this commit the Spring Expression Language now supports increment (++) and decrement (--) operators. These can be used as either prefix or postfix operators. For example: 'somearray[index++]' and 'somearray[--index]' are valid. In order to support this there are serious changes to the evaluation process for expressions. The concept of a value reference for an expression component has been introduced. Value references can be passed around and at any time the actual value can be retrieved (via a get) or set (where applicable). This was needed to avoid double evaluation of expression components. For example, in evaluating the expression 'somearray[index++]--' without a value reference SpEL would need to evaluate the 'somearray[index++]' component twice, once to get the value and then again to determine where to put the new value. If that component is evaluated twice, index would be double incremented. A value reference for 'somearray[index++]' avoids this problem. Many new tests have been introduced into the EvaluationTests to ensure not only that ++ and -- work but also that the introduction of value references across the all of SpEL has not caused regressions. Issue: SPR-9751
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| Thanks, Andy! This has been merged. |
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With this commit the Spring Expression Language now supports
increment (++) and decrement (--) operators. These can be
used as either prefix or postfix operators. For example:
'somearray[index++]' and 'somearray[--index]' are valid.
In order to support this there are serious changes to the
evaluation process for expressions. The concept of a
value reference for an expression component has been introduced.
Value references can be passed around and at any time the actual
value can be retrieved (via a get) or set (where applicable). This
was needed to avoid double evaluation of expression components.
For example, in evaluating the expression 'somearray[index++]--'
without a value reference SpEL would need to evaluate the
'somearray[index++]' component twice, once to get the value and
then again to determine where to put the new value. If that
component is evaluated twice, index would be double incremented.
A value reference for 'somearray[index++]' avoids this problem.
Many new tests have been introduced into the EvaluationTests
to ensure not only that ++ and -- work but also that the
introduction of value references across the all of SpEL has
not caused regressions.
Issue: SPR-9751