java - JPA @OneToOne with same type -


how annotate code have person 2 addresses :

@entity public person {      // ... other attributes person      @onetoone     public address homeaddress;      @onetoone     public address workaddress; }  @entity public address {      // ... other attributes address      @onetoone     public person person; }

can use onetoone ? should have use options on annotations ?

unfortunately not possible achieve @onetoone. reason:

the persistence provider have 1 person id 2 entries address table. not sufficient decide relation given address belongs to.

the simplest solution add type field (an enum) address entity , map addresses @onetomany/@manytoone.

in order home address, need iterate on addresses , check type.

alternatively, create types homeaddress , workaddress derive address. keep @onetoone relations, end 2 additional types.

imo cleaner entity relation mapping not sufficient reason doing this, inviting issues. example homeaddress can never workaddress.

edit: if both address ids stored in person table, should able use the@onetoone relation. ensure deletion of attached address entities , deletion of orphaned address entities, can use cascading , orphan removal:

@onetoone(cascade=cascadetype.all, orphanremoval=true)

although might makes sure there no orphaned address records in db, not entirely true. orphan removal works when remove referenced entity inside transaction while entities attached. furthermore not work bulk updates. delete person ... query happily delete persons , not touch connected addresses.


Comments

Post a Comment

Popular posts from this blog

php - Why I am getting the Error "Commands out of sync; you can't run this command now" -

the documentation of error mentioned in title says if commands out of sync; can't run command now in client code, calling client functions in wrong order. this can happen, example, if using mysql_use_result() , try execute new query before have called mysql_free_result(). can happen if try execute 2 queries return data without calling mysql_use_result() or mysql_store_result() in between. from here: http://dev.mysql.com/doc/refman/5.0/en/commands-out-of-sync.html but in first query not fetching data mysql database, inserting. , in second query getting data database. here code $connection = mysqli_connect("localhost","username","password","tbl_msgs"); if(mysqli_connect_errno($connection)) { die("failed connect mysql: " . mysqli_connect_error()); } $query = "insert users (total_comments, total_views) values ({$total_comments}, {$total_views});"; $query .= "insert msgs (no...
Read more

linux - Does gcc have any options to add version info in ELF binary file? -

i mean whether gcc can insert source code version infor elf binary section or similar. not want change source file, add info gcc option in makefile. you can emit version info text file, turn text file object file statically link executable. the first step simple have write code: script or write version info in format plain text file. write makefile rule produce version.o version.txt, using objcopy . you'll have object file 2 useful symbols defined in it: beginning , end of textual version info. add generated object executable, , you'll able access version 2 ways: running strings on binary, or writing code in application print version string (you'll need declare start , end symbols variables in header file).
Read more

java - Are there any classes that implement javax.persistence.Parameter<T>? -

i'm using named queries fetch entities database using jpa , hibernate , came across puzzling me: how come there no default implementations of javax.persistence.parameter interface? i rather impressed how @staticmetamodel used criteriabuilder in jpa2 meaning type safety , don't have mess around setting string names. wanted apply similar of jpa1 ejb's i'm working on: dealergroup_.class: public dealergroup_ { public parameter<integer> id = new parameterimpl<integer>("id"); /// etc... } dealergroupfacade.class: // ... public dealergroup fetch(integer id) { typedquery<dealergroup> query = em.createnamedquery("dealergroup.fetchbyid", dealergroup.class); query.setparameter(dealergroup_.id, query); return query.getsingleresult(); } // ... i surprised find there no implementations of parameter interface - of course, implement myself absence makes me suspicious may mistake using in way? should implementing parameter...
Read more