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Re: Persistence API - magic?

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On 9/6/2011 3:52 PM, nroberts wrote:

> One tutorial on persistence that I found (
> http://www.javaworld.com/javaworld/jw-01-2008/jw-01-jpa1.html?page=3 )
> explains how to make them by hand but it uses an orm.xml or
> annotations to tell Java what table and what columns to connect an
> entity object with.  The eclipse stuff doesn't seem to do that at
> all.  The orm.xml file exists, but it's practically empty containing
> nothing but the root element and xml tag.


I'm actually working on learning some JPA/JSF stuff right now too.  The 
orm.xml stuff confuses me because I haven't seen it before.  I'm used to 
a persistence.xml file being used.  I'm concerned about versions here 
and portability, because you seem to be configuring the tool directly, 
and not using the JPA config file.

Does anyone know what this config file is about?  What version of the 
library uses it?  It either seems specific to his library, and therefore 
non-portable, or it's really old.


> I was thinking that perhaps it was order based, but the order of the
> columns in the zip table to do not match.


It's based on name, afaik.  The entity manager will strip off the "get" 
or "set" of your accessors/mutators, or it will use the field name, and 
look up a column of the same name.   Sometimes case doesn't matter (may 
depend on your database, i.e., it could be non-portable to rely on case 
insensitivity).  There's also ways of mapping from one column to an 
object property if the names are different.


> COUNTRY_ID comes between ID
> and CODE.  The names are close but the case is different and the
> "country" column is actually COUNTRY_ID.

@Entity
public class MyClass {
   @Id
   int id;
   @Column( name="COUNTRY_ID" )
   String country;
  ...
}

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Persistence API - magic? nroberts <roberts.noah@gmail.com> - 2011-09-06 15:52 -0700
  Re: Persistence API - magic? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-09-06 21:40 -0300
    Re: Persistence API - magic? nroberts <roberts.noah@gmail.com> - 2011-09-07 07:56 -0700
      Re: Persistence API - magic? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-09-07 17:34 -0300
  Re: Persistence API - magic? markspace <-@.> - 2011-09-06 17:47 -0700
    Re: Persistence API - magic? Lew <lewbloch@gmail.com> - 2011-09-06 18:26 -0700
      Re: Persistence API - magic? markspace <-@.> - 2011-09-06 19:01 -0700
    Re: Persistence API - magic? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-09-07 06:14 -0300
    Re: Persistence API - magic? nroberts <roberts.noah@gmail.com> - 2011-09-07 08:10 -0700
      Re: Persistence API - magic? markspace <-@.> - 2011-09-07 09:15 -0700
        Re: Persistence API - magic? Lew <lewbloch@gmail.com> - 2011-09-07 10:36 -0700
          Re: Persistence API - magic? markspace <-@.> - 2011-09-07 10:57 -0700
            Re: Persistence API - magic? Lew <lewbloch@gmail.com> - 2011-09-07 11:06 -0700
  Re: Persistence API - magic? Lew <lewbloch@gmail.com> - 2011-09-06 18:09 -0700
  Re: Persistence API - magic? Roedy Green <see_website@mindprod.com.invalid> - 2011-09-08 12:32 -0700
    Re: Persistence API - magic? "John B. Matthews" <nospam@nospam.invalid> - 2011-09-08 19:23 -0400

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