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Saturday, August 13, 2011

ADF: Expression Language Conversion

Expression Language (EL) is widely used in ADF Binding to reference items in the Binding Context. In some scenario, direct use of EL reference isn't enough and manipulation of several EL references needed to accomplish the task. While you can always manipulate the logics in a manged bean, if you want to go with "declarative", here is why I am saying about.

Varchar2 type in SQL format (database) is converted to String automatically, but Number type in SQL is converted to oracle.jbo.domain.Number format. EL inherit generic Java API and can only recognize java.lang.Number type.

Therefore, if you have two EL binding references to two database Number attributes: #{bindings.NumberAtt1.inputValue} and {bindings.NumberAtt2.inputValue}. If you want to evaluate if the first number greater than the second number, you cannot use compareTo() method which is belongs to oracle.jbo.domain.Number and you cannot use #{A > B} because A or B is not java.lang.Number

A simple conversion is to attach ".value" in the end of EL binding reference and it will convert it to a java.lang.Double format type.