'int-jdbc:stored-proc-outbound-gateway' is able to MAP ur Model element(s) by itself - is this a true statement? - spring-integration

Question

Currently I am working with JDBC Spring Integration (to be very specific: <int-jdbc:stored-proc-outbound-gateway>) where the scenario is passing n-number of parameters to a stored procedure (ORACLE) and receive one return variable (with '1' or Error Message) along with n-number of CURSORS (sys_refcursor) which may have n-number of columns.
While working on this above scenario with Spring Framework I noticed the following issue(s):
My logic from front-end was, first read the 'return variable'. If that value is 1 then start reading all the CURSORS data or else through exception by redirecting user to the error page. Now, all my CURSORS were not having same number of columns as well as same length/type of data. And in middle layer I was having only one Model class to deal with all the CURSORS return elements. That was the challenge for me!
Previously I dealt with only one CURSOR. and therefore in middle layer I used Mapper class to map all CURSOR elements to my Model element's (getter and setter) to push data to the front. But then when used same concept to deal with n-number of CURSORS -that was truly a nightmare.
let me share what I did before and what I did later to resolve this situation at my end and then will draw my understanding for which will sick EXPARTS opinion at the later part of this post.
For one return variable (with '1' or Error Message) along with one CURSOR:
I had my Gateway definition as follows:
<!-- Stored Procedure Outbound-Gateway = To call a database stored procedure -->
<int-jdbc:stored-proc-outbound-gateway id="outbound-gateway-storedproc-personalinfo"
request-channel="procedureRequestChannel"
data-source="dataSource"
stored-procedure-name="pkg_personalinfo_spring.proc_personalinfo_spring"
expect-single-result="false"
ignore-column-meta-data="true">
<!-- Parameter Definitions -->
<int-jdbc:sql-parameter-definition name="firstname" direction="IN"/>
<int-jdbc:sql-parameter-definition name="lastname" direction="IN"/>
<int-jdbc:sql-parameter-definition name="p_RetVal" direction="OUT"/>
<int-jdbc:sql-parameter-definition name="get_ResultSet" type="#{T(oracle.jdbc.OracleTypes).CURSOR}" direction="OUT"/>
<!-- Parameter Mappings Before Passing & Receiving -->
<int-jdbc:parameter name="firstname" expression="payload[0]"/>
<int-jdbc:parameter name="lastname" expression="payload[1]"/>
<int-jdbc:returning-resultset name="get_ResultSet" row-mapper="com.support.PersonalinfoMapper"/>
</int-jdbc:stored-proc-outbound-gateway>
And in Mapper class I had the following simple Mapping rule:
...
PersonalInfo personalInfo = new PersonalInfo();
try{
personalInfo.setFirstname(resultSet.getString(DBConstants.FIRSTNAME));
personalInfo.setLastname(resultSet.getString(DBConstants.LASTNAME));
...
I did that because in my Model class i was having getter and setter for all CURSOR return elements.
Now, for one return variable (with '1' or Error Message) along with n-number of CURSORS:
I changed my Gateway definition as follows:
<!-- Stored Procedure Outbound-Gateway = To call a database stored procedure -->
<int-jdbc:stored-proc-outbound-gateway id="outbound-gateway-storedproc-personalinfo"
request-channel="procedureRequestChannel"
data-source="dataSource"
stored-procedure-name="pkg_personalinfo_spring.proc_personalinfo_spring"
expect-single-result="false"
ignore-column-meta-data="true">
<!-- Parameter Definitions -->
<int-jdbc:sql-parameter-definition name="firstname" direction="IN"/>
<int-jdbc:sql-parameter-definition name="lastname" direction="IN"/>
<int-jdbc:sql-parameter-definition name="p_RetVal" direction="OUT"/>
<int-jdbc:sql-parameter-definition name="get_curr_1" type="#{T(oracle.jdbc.OracleTypes).CURSOR}" direction="OUT"/>
<int-jdbc:sql-parameter-definition name="get_curr_2" type="#{T(oracle.jdbc.OracleTypes).CURSOR}" direction="OUT"/>
<!-- Parameter Mappings Before Passing & Receiving -->
<int-jdbc:parameter name="firstname" expression="payload[0]"/>
<int-jdbc:parameter name="lastname" expression="payload[1]"/>
</int-jdbc:stored-proc-outbound-gateway>
And secondly I removed the entire row mapping concept, means I didn't have any Mapper class. The only one thing I had was only one Model class with all the CURSORS element name and their getters and setters.
Also notice that in my 'Parameter Definitions', how added those two CURSORS definition but in 'Parameter Mappings Before Passing & Receiving' I have nothing now.
I ran the App without any exceptions and later through Fiddler observed the following JSON data came with RESPOND, means everything PERFECT! ;)
JSON
- {}
- get_curr_1
- -{}
- - firstname=Faisal
- - lastname=Quazi
- get_curr_2
- -{}
- - country=Bangladesh
- - capital=Dhaka
WHAT THE HACK??? Yes...I had the same feelings ;)
Now, can any one plz help to understand what is going on here. Will it be a true statement that "'int-jdbc:stored-proc-outbound-gateway' is able to MAP ur Model element(s) by itself magically???"
Is there any best practice to deal with such kind of situation(s)?
Thank u guys always :)

Answer 1

:-). I guess that by default Spring JDBC uses ColumnMapRowMapper.
So you end up after that gateway with Map<String, <Map<?, ?>>> or something similar. But it is Map anyway.
Since you further convert your payload to JSON and Jackson can get deal with maps prefectly, you finish with correct result.
I can debug it, of course, but deduction says that it can't be differently.
UPDATE
As I said. The answer is here JdbcTemplate#extractOutputParameters:
....
if (outParam.isResultSetSupported()) {
returnedResults.putAll(processResultSet((ResultSet) out, outParam));
}
else {
String rsName = outParam.getName();
SqlReturnResultSet rsParam = new SqlReturnResultSet(rsName, new ColumnMapRowMapper());
returnedResults.putAll(processResultSet((ResultSet) out, rsParam));
if (logger.isDebugEnabled()) {
logger.debug("Added default SqlReturnResultSet parameter named '" + rsName + "'");
}
}
....