Mule ESB MEL Expression returns NULL

Question

Good morning to everybody.

I have an issue with using MEL Expression in a JDBC ORACLE database query.

In particular the Mule flow accepts a Excel file that is transformed in a Map through a Datamapper and its fields are used to make a query in a database in this form:

<jdbc-ee:query key="Fill Table" value="INSERT INTO BUFF_SBIL_ZONALE (DATA_ORA,MACRO_ZONA,SEGNO_SBIL,PRZ_MSD_VEN,PRZ_MSD_ACQ,ID_BIS,FILE_NAME,DATA_LOAD)                                                 
VALUES (TO_DATE(#[map-payload:DATA_ORA], 'DD/MM/YYYY  hh:mi:ss'),#[map-payload:MACROZONA],#[map-payload:SEGNO],#[map-payload:P_medioMSD_VEN],#[map-payload:P_medioMSD_ACQ],#[message.inboundProperties['correlationId']],#[message.InvocationProperty['originalFilename']],SYSDATE)"/>

The query seems correct but when I execute the application, I receive an exception that advice me that #[map-payload:P_medioMSD_VEN] is NULL (correctly, because in the Excel file it does not exist) and the MEL Expression cannot read a NULL value. The problem, so, is not a SQL issue but a MEL issue that does not accept a NULL database field value.

Does anybody know how to bypass the MEL Exception in order to accepts the mullable value?

Thanks in advance to everybody

The exception thrown is: * org.mule.api.expression.RequiredValueException: Expression Evaluator "bean" with expression "xy" returned null but a value was required. *

Answer 1

I found the solution. I'll write here just for someboby that will have the same problem.

If you want to make a MEL expression value optional (ie a NULL value is a right value), you should write a '?' at the end of a MEL expression.

#[map-payload:P_medioMSD_ACQ?]

Putting a '?' the value is optional and a NULL value is accepted

Answer 2

Before passing them to MEL , check if fields are NOT NULL . If you know certain fields will always be NULL , don't specify it in insert query at all, it will get default value of NULL in db