wasNull () ?

Java SQL resultset that we use to get values has a wasNull() method to check whether the last retrieved value is actually null or not...

for instance we use simply,
rs.getXXX("column_name") to get DB column values for our Results,.

but for getByte, getShort, getInt, getLong, getFloat, and getDouble these will return by default a 0 value if the actual resulted column value is a JDBC NULL. and for boolean, false for getBoolean().

this is a point where the developer has to concern about the real outcome of the results, given by a JDBC resultset..

in my case i had a kind of web service to execute a scheduled JOB . where this Webservice call will initiate some sort of Data persistence in the oracle DB. at the end of the service call we have to create a validation XML file, to log all the data string we sent to the DB and the resulted DB values. this file is used to compare the input data set and resulted out put data set from the DB.

so each time when the original web service call contains null values for some of NULL allowed columns , we save those NULL values correctly to our local DB and DB values are 100% OK with the original data set we used. but at the time of data verification it turns into a failure.....

it took some times to identify that composing the result XML string, we are using rs.getXXX 's to retrieve values for those columns and due to that all the NULL integer fields are returning as 0 for the result.

SQL result set has a method called rs.wasNull() to handle this kind of scenarios. so that the said method will return true or false according to the last retrieved value is actual a NULL or not.

Note: we have to call this wasNull before any other getXXX() is called for the resultset.


int lotSize = rs.getInt("lot_size");
if(rs.wasNull()){
// it is Null
}else{
// is not NUll
}


i really wonder how EJB3 queries handle this, worth to have a look on this ..
is it the EJB3 - entity bean's

@Column(name = "column_name",nullable= true)

annotation doing the magic..?