hibernate - @ManyToMany inconsistent data on both side problem -

i have blog-like scenario , 2 java classes : post , tag , @manytomany relationship , post_tag association table , here simplified definitions:

public class post {   @manytomany(fetch=fetchtype.lazy)    @fetch(fetchmode.select)   @jointable(name = "post_tag"     , joincolumns        = @joincolumn(name="post_id")     , inversejoincolumns = @joincolumn(name="tag_id")    )   private set<posttag> tags = new hashset<posttag>(); }  public class tag  {   @manytomany(mappedby="tags" , fetch=fetchtype.lazy)   private set<post> comments = new hashset<post>(); } 

it seems ok , fails in following testing scenario :

1. create tag , tag1
2. create 1st post , post1
3. create 2nd post , post2
4. add tag1 post1.gettags() , post2.gettags()
5. update post1 , post2
6. list list = dao.getpostbytag(tag1)
7. assert list.size() == 2 , failed

here test code :

public void testgetcommentsbytag() {   tag tag1 = tagdao.save(new tag("tag1"));   asserttrue(tag1.getid() > 0);     post post1 = dao.save("...");   post post2 = dao.save("...");    post1.gettags().add(tag1);   post2.gettags().add(tag1);   dao.update(post1);   dao.update(post2);    list<post> list = dao.getpostsbytag(tag1 , 0 , 100);    assertsame(2 , list.size()); // failed !   asserttrue(list.contains(post1));   asserttrue(list.contains(post2)); } 

and here dao.getpostsbytag()'s implementation :

public list<post> getpostsbytag(tag tag , int start, int count) {   session session = (session) em.getdelegate();   criteria c = session.createcriteria(post.class);    c.createcriteria("tags")    .add(restrictions.eq("id", tag.getid()));    c.setfirstresult(start);   c.setmaxresults(count);   c.setcacheable(true);    return c.list(); } 

the returned list size == 0 ! noticed generated sql command , found hibernate first getpostsbytag() , insert association table , makes getpostsbytag() return 0-length list. :

hibernate:      insert              tag     values         (?, ?, ?, ?) hibernate:      insert              post         (...)      values         (???) hibernate:      insert              post         (...)      values         (???) hibernate:      select         ooxx             post this_      inner join         post_tag tags3_              on this_.id=tags3_.post_id      inner join         tag tag1_              on tags3_.tag_id=tag1_.id              , tag1_.id=?      order         this_.created desc limit ?  hibernate:      insert              post_tag         (post_id, tag_id)      values         (?, ?) hibernate:      insert              post_tag         (post_id, tag_id)      values         (?, ?) 

how make sure getpostsbytag() executed after inserting association table ?

i know there 'endtransaction() , , startnewtransaction()' methods in spring-junit3 , seems not available in spring-with-junit4.

but wonder how can pass test in one transaction ? thanks.

environments : spring4 (springjunit4classrunner) , hibernate-3.5.6 , jpa 2.0

you can create 2 methods in test class executed each time test method called. these methods open transaction , rollback after it:

@before public void setup() throws exception {      em.gettransaction().begin(); }  @after public void teardown() throws exception {           em.gettransaction().rollback(); } 

you should check if have flushmode different deffault because flushs made before query...