code: public void setVariable(String var, String expression) {
          ValueExpression exp = factory.createValueExpression(
                                    elManager.getELContext(),
                                    bracket(expression), Object.class);
          elManager.setVariable(var, exp);
      }
docs: Assign an EL expression to an EL variable.  The expression is parsed,
  but not evaluated, and the parsed expression is mapped to the EL
  variable in the local variable map.
  Any previously assigned expression to the same variable will be replaced.
  If the expression is <code>null</code>, the variable will be removed.
  @param var The name of the variable.
  @param expression The EL expression to be assigned to the variable.