Actually I intended to write: > > - JPA: I practice it on a daily base and it's very good but I feel like > there is *a mismatch *between JPA and lift / scala. Not that I have > thought a lot about it, it's just a feeling. > > Your input just confirms my feelings.
Thanks. On Sun, Nov 22, 2009 at 8:11 PM, Chris Lewis <burningodzi...@gmail.com>wrote: > I'm writing an app to deploy to googele app engine, and so I'm using > JPA. Here are the cons I've encountered: > > 1) JPA mandates conventions on model class code. In scala this usually > means any persistent fields are public vars, which is theoretically > dangerous (and generally frowned upon). I personally have mixed feelings > on mutability in domain entity classes (Mapper entities are also > mutable), and there is ongoing discussion on this topic. > > 2) Collections in JPA are java.util, not scala. This means that you > can't transform them as you can with the usual higher order functions > found scala collections (map, filter, etc), unless you use implicit > conversions (usually via jcl). Implicits make your code feel like scala > code, but I'm not a fan of having conversions rampant for this, and I > don't like to explicitly pollute my namespaces by importing jcl. > > 3) JPA is not monadic. JPA entities are from java land, and in java land > you represent optional members with null. Idiomatic scala doesn't do > nulls because they wreak havoc at runtime. Always. Consider an entity > Person with a member "middleName." In your domain it isn't required, and > so you allow null at the database level. In a JPA impl you allow this to > be null, and now everywhere you reference middleName, you absolutely > must test for null. In scala you use the Option monad, so middleName is > no longer of type String but Option[String]. NPEs are now effectively > impossible. > > chris > > Oscar Picasso wrote: > > I am starting to (re)learn lift and wondering which persistence > > mechanism I should use: Mapper, Record or JPA? > > > > It should be ready for for prime time and fit perfectly with the lift / > > scala way of doing things but still be powerful enough. > > > > * I have read that Mapper has some limitations like when dealing > > with complex object graphs, many to many relationships etc. > > * I don't know Record but I have two concern with it: is it mature > > enough? I have read that David is not satisfied with Record > > especially on the mutability front. What are the practical > > implications of not having immutability for Record? > > * JPA: I practice it on a daily base and it's very good but I feel > > like there is between JPA and lisft / scala. Not that I have > > thought a lot about it, it's just a feeling. I have also read > > there are some issues with the Hibernate Validators. > > > > Could some people on the list be kind enough to summarize the pros and > > cons of using any of these solutions at this stage? > > > > -- > > > > You received this message because you are subscribed to the Google > > Groups "Lift" group. > > To post to this group, send email to lift...@googlegroups.com. > > To unsubscribe from this group, send email to > > liftweb+unsubscr...@googlegroups.com<liftweb%2bunsubscr...@googlegroups.com> > . > > For more options, visit this group at > > http://groups.google.com/group/liftweb?hl=. > > -- > > You received this message because you are subscribed to the Google Groups > "Lift" group. > To post to this group, send email to lift...@googlegroups.com. > To unsubscribe from this group, send email to > liftweb+unsubscr...@googlegroups.com<liftweb%2bunsubscr...@googlegroups.com> > . > For more options, visit this group at > http://groups.google.com/group/liftweb?hl=. > > > -- You received this message because you are subscribed to the Google Groups "Lift" group. To post to this group, send email to lift...@googlegroups.com. To unsubscribe from this group, send email to liftweb+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/liftweb?hl=.
