Copying Java ResultSet

Question

I have a java.sql.ResultSet object that I need to update. However the result set is not updatable. Unfortunately this is a constraint on the particular framewor

Answer 1

Thanks for the responses. In the end I found CachedRowSet which is exactly what I needed. With this I was able to disconnect the ResultSet object and update it.

What's more, because CachedRowSet implements the ResultSet interface I was still able to pass it to my file generation method which requires an object that implements ResultSet.

Answer 2

The normal practice would be to map the ResultSet to a List<Entity> where Entity is your own class which contains information about the data represented by a single database row. E.g. User, Person, Address, Product, Order, etcetera, depending on what the table actually contains.

List<Entity> entities = new ArrayList<Entity>();
// ...
while (resultSet.next()) {
    Entity entity = new Entity();
    entity.setId(resultSet.getLong("id"));
    entity.setName(resultSet.getString("name"));
    entity.setValue(resultSet.getInt("value"));
    // ...
    entities.add(entity);
}
// ...
return entities;

Then, you can access, traverse and modify it the usual Java way. Finally, when persisting it back in the DB, use a PreparedStatement to update them in batches in a single go.

String sql = "UPDATE entity SET name = ?, value = ? WHERE id = ?";
// ...
statement = connection.prepareStatement(sql);
for (Entity entity : entities) {
    statement.setString(1, entity.getName());
    statement.setInt(2, entity.getValue());
    statement.setLong(3, entity.getId());
    // ...
    statement.addBatch();
}
statement.executeBatch();
// ...

Note that some DB's have a limit on the batch size. Oracle's JDBC driver has a limit on around 1000 items. You may want to call executeBatch() every 1000 items then. It should be simple using a counter inside the loop.

See also:

• Collections tutorial
• PreparedStatement tutorial