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EL expressions will coerce the type automatically. Here is the summary of the coercion rules.


Note: The coercion is also applied to function arguments. For example, {c:doSomething(null)} will cause doSomething("") being called if it expects a String object.

Boolean Character Number String
Boolean obj[1] ERROR ERROR obj.toString()
Character ERROR obj (short)obj obj.toString()
Number obj ERROR (char)obj obj.toString()
String (not empty) Boolean.valueOf(obj) obj.charAt(0) Number[2].valueOf(x) obj
String (empty) false (char)0 0 "" (obj)
null false (char)0 0 ""
Other ERROR ERROR ERROR obj.toString()

  1. obj represents the object being corerced
  2. The real class is determined at run time, such as Integer and Float.
  • The handling of an empty string and null is the same

Version History

Last Update : 2011/5/27


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