pessimistic-locking

I'd like to achieve pessimistic lock with GORM's where query. Something like def query = Person.where { firstName == "Bart" } //instead of where.findAll() List personsLocked = where.lockAll() I know, I can achieve that by criteria API: List personsLocked = Person.createCriteria().list { eq('firstName', 'Bart') lock true } Is there a way to achieve this via the "where" query ? lock is not available in the grails.gorm.DetachedCriteria (result of where ) and is only available from the org.codehaus.groovy.grails.orm.hibernate.query.AbstractHibernateCriteriaBuilder provided by createCriteira or by

I am writing a web application where two different users can update a list of things, to do list, for example. I have come to realize that, optimistic locking mechanism works best since I don't expect high contention. I was looking at transaction isolation levels and now I am a little confused. Looks like different transaction isolation levels also solve similar problems. How are these two different concepts related to each other? If possible, with a simple example. Both of these things are related to data consistency and concurrent access, but they are two different mechanisms. Locking

I know what optimistic and pessimistic locking is, but when you write a java code how do you do it? Suppose I am using Oracle with Java, do I have any methods in JDBC that will help me do that? How will I configure this thing? Any pointers will be appreciated. You can implement optimistic locks in your DB table in this way (this is how optimistic locking is done in Hibernate): Add integer "version" column to your table. Increase the value of this column with each update of corresponding row. To obtain lock, just read "version" value of the row. Add "version = obtained_version" condition to