title: DB transaction or Java DAO's method synchronization?
body: <p>I have Java-based web server, and I also have DAO singleton object with method, whose SQL operations' logic must be synchronized in some way in order to guarantee data 
  integrity (method can be accessed from several Java threads simultaneously).</p>
  
  <p><p>I was wondering to know <strong>whether DB transaction wrapping (serializable level) is better than DAO's method explicit synchronization</strong> in server side?</p>