code: protected synchronized Object getCompiledExpression() {
          if (compiledExpression == null) {
              try {
                  compiledExpression = Ognl.parseExpression(getExpression());
              }
              catch (OgnlException e) {
                  throw new IllegalArgumentException("[" + getExpression() + "] is not a valid OGNL expression", e);
              }
          }
          return compiledExpression;
      }
docs: Return a compiled OGNL expression.
  
  @return compiled OGNL expression