JavaServer Pages, 3rd Edition

Operand Coercing Rules

Before the operator is applied, the EL evaluator coerces the types of the operand values. An exception is thrown if no rule matches, the coercing fails, or applying the operator leads to an exception.

Property and array accessor operators

An expression of the form ${exprA.identifierB} is evaluated the same way as ${exprA['identifierB']}.

To evaluate an expression of the form ${exprA[exprB]}, the following rules are used:

• If exprA is null, return null.

• If exprB is null, return null.

• If exprA is a Map with a key matching exprB, return the value.

• If exprA is a List or array with an index matching exprB coerced to an int, return the value.

• If exprA is a bean with a property matching exprB coerced to a String, return the value.

Arithmetic operators

For addition, subtraction, and multiplication, if any operand is null, the result is 0. Otherwise both operands are coerced to numbers (to BigDecimal if one of them is BigDecimal or if one is BigInteger and the other is Float, Double, or a String with floating-point syntax, to double if one of them is Float, Double, or a String with floating-point syntax, to BigInteger if one of them is BigInteger, to long otherwise), and the result of applying the operator is returned.

For division, if any operand is null, the result is 0. Otherwise both operands are coerced to numbers (to BigDecimal if one of them is BigInteger or BigDecimal, to double otherwise), and the result of applying the operator is returned.

For modulo, if any operand ...