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Java JDBC ResultSet.insertRow, getting autoincrement field values

Posted on 2009-07-16
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Last Modified: 2013-11-23
Using JDBC's  java.sql.ResultSet, I write a new record and want to get the automatically-generated key for the record that was just written.  Is there a way to do that?


// my current codebase uses ResultSet to write to a table
stmt = con.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY, java.sql.ResultSet.CONCUR_UPDATABLE);
rs = stmt.executeQuery("select * from " + strTableName + " where 0=1");
rs.moveToInsertRow();
// update some fields
rs.insertRow();
// now I want to fetch the value of the autoincrement field
 
 
 
// If I switch the code to the sample below, there is a way to get the keys
 
query = "INSERT INTO collection ( name , memo ) VALUES ( " + Criteria.escape(args0.getName()) + " , " + Criteria.escape(args0.getMemo()) + " )";         
statement.execute(query,Statement.RETURN_GENERATED_KEYS);
ResultSet rs = statement.getGeneratedKeys();
if (rs.next()) {
  collectionId=rs.getInt(1);
}

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Question by:amp834
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Expert Comment

by:CEHJ
ID: 24872425
You're already doing it - with getGeneratedKeys..?
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Expert Comment

by:CEHJ
ID: 24872530
Oh i see what you mean - you want to use the first technique. Have you tried just getting the auto-inc value from the ResultSet directly with rs.getInt("autoincfieldname")?
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Author Comment

by:amp834
ID: 24872901
I tried rs.getInt("autoincfieldname"), there is no "current" rowset after the insert operation.
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LVL 86

Expert Comment

by:CEHJ
ID: 24873341
Try calling rs.last() before attempting to getInt
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Author Comment

by:amp834
ID: 24873708
I already tried that.  Supposedly it works if the database is MySql, but not necessarily for other databases.  And if other processes inserted records, then it may return their stuff.
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Expert Comment

by:CEHJ
ID: 24873981
Yes, the db/driver would have to support it.
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Author Comment

by:amp834
ID: 24874018
The db/driver "supporting it" is just a special way MySql works.  it's not a standard to "goto last record" to get the just inserted record.

So that leaves the original question again!  

Either I have to switch to the prepared-statement "insert", or find some link between the resultset and the corresponding update statement, if there is such a thing.  Perhaps JDBC definition/standard doesn't support getting the inserted keys from resultset.insertRow.

Let's see if other people have any experience with this!
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by:objects
ID: 24875222
what database are you using?
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Expert Comment

by:objects
ID: 24875484
there isn't a standard jdbc way to do it, so without knowing the database there is no way to determine what would work.
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Author Comment

by:amp834
ID: 24875714
I'm using Derby right now, but want to be able to support other databases as well, maybe MySql, SqlServer, Postgres, etc.

Perhaps a better solution would be to take the ResultSet and write it out using a prepared statement (then discard the 'insertRow' ResultSet).  I could get the assigned key reliably.  (I read a benchmark for Derby that writing using prepared statements is slower than using ResultSet).

I assume the code for ResultSet.insertRow would be dependent on each JDBC driver.  (It seems it could be built on top of JDBC's prepared statements; if so, I could look at the code to see if I could make something similar).

I read something vaguely about a RowSet, maybe a temporary buffer for storing field values.  If there is such a thing, maybe I could use that instead of inventing another wheel.



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Expert Comment

by:objects
ID: 24875740
yes writing with a resultset is typically going to be slower, whats the motivation for using insertRow() in the first place?
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by:amp834
ID: 24875800
Actually, I read that writing with ResultSet is slower.

I wanted to use ResultSet because a lot of the work was already done, with the field names, field list, setting and getting, etc.,  but I suppose I can reinvent another wheel.  Many other people should have come across this issue, I wonder if there is a simple solution.

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by:objects
ID: 24876030
> Actually, I read that writing with ResultSet is slower.

thats what I said :)

Why aren't you using something like hibernate and save yourself all the overhead of implement the jdbc yourself.
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Author Comment

by:amp834
ID: 24880360
I'm sorry, I meant writing with prepared statements was slower than with resultset (by about 20 to 30 %), but it seems you read the opposite!

I can look into using hibernate.  The reasons I stayed away:  
1. another layer to learn,
2. not sure if it can do things like scroll through a result set
3. not sure about its overhead/speed.  

For most simple gui operations, the speed doesn't matter.  But for batch processing of 500k+ records, it may.

4. I assume that hibernate would take care of getting the autoincrement value?

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Accepted Solution

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objects earned 200 total points
ID: 24883493
Well it depends on how you use it, but using a PreparedStatement as it is intended should be quicker

> 4. I assume that hibernate would take care of getting the autoincrement value?

yes
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Author Comment

by:amp834
ID: 24883701
I will wait to see if there are any other comments and will close this in a week.  (My Hibernate books should be in by then!)

By the way, objects, I have a question posted about refreshing tree nodes, if you get a chance, can you look at it?
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Author Closing Comment

by:amp834
ID: 31604369
Thanks for the help.  I will use Prepared Statements, and maybe hibernate in the future.
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