Why Hibernate Eager Fetch Does Not Work? -


i trying write simple testing program simulate 2 objects in project , run trouble. have 2 simple object, parent , child 1 many relationship. following 2 objects:

import java.util.list; import javax.persistence.cascadetype; import javax.persistence.column; import javax.persistence.entity; import javax.persistence.fetchtype; import javax.persistence.id; import javax.persistence.joincolumn; import javax.persistence.onetomany; import javax.persistence.table;  import org.hibernate.session; import org.hibernate.transaction;  import com.fhp.ems.common.data.dao.hibernateinitializer;   @entity @table(name = "parent") public class parent {    private integer id;   private string data;   private list<child> child;    public parent() {}     @id   @column(name = "id", nullable = false)   public integer getid() {     return this.id;   }    public void setid(integer id) {     this.id = id;   }     @column(name = "data", length = 128)   public string getdata() {     return this.data;   }     public void setdata(string data) {     this.data = data;   }     @onetomany(cascade = { cascadetype.all }, fetch = fetchtype.eager, orphanremoval = true)   @joincolumn(name = "pid")   //@fetch(value=fetchmode.select)   public list<child> getchild() {     return child;   }     public void setchild(list<child> child) {     this.child = child;     if(child != null && child.size() > 0) {       for(child c : child) {         this.data = c.getvalue();       }     }   }      public static void main(string[] args) {     session session = null;     transaction tx = null;     try {       hibernateinitializer.initlocal();       session = hibernateinitializer.getsession(null);       int id = 101;       tx = session.begintransaction();       parent p = (parent)session.get(parent.class, 101);       //parent p = new parent();       //p.setid(id);       //child c = new child();       //c.setpid(id);       //c.setid(1);       //c.setvalue("child");       //child c1 = new child();       //c1.setpid(id);       //c1.setid(2);       //c1.setvalue("child1");       //list<child> childs = new arraylist<child>();       //childs.add(c);       //childs.add(c1);       //p.setchild(childs);       //session.saveorupdate(p);        tx.commit();     }     catch(exception exc) {       exc.printstacktrace();     }     {       hibernateinitializer.closesession(session, null);     }    }  }   import javax.persistence.column; import javax.persistence.entity; import javax.persistence.id; import javax.persistence.table;   //create table `child` ( //  `id` int(11) not null, //  `pid` int(11) not null,      //  `value` varchar(128) default null, //  primary key  (`id`) //)   @entity @table(name = "child") public class child {    private integer id;   private integer pid;   private string value;    public child() {}    @id   @column(name = "id", unique = true, nullable = false)   public integer getid() {     return this.id;   }     public void setid(integer id) {     this.id = id;   }     @column(name = "pid", nullable = false)   public integer getpid() {     return this.pid;   }     public void setpid(integer pid) {     this.pid = pid;   }     @column(name = "value", length = 128)   public string getvalue() {     return this.value;   }     public void setvalue(string value) {     this.value = value;   }   }

when run program, following error:

hibernate:      select         parent0_.id id81_1_,         parent0_.data data81_1_,         child1_.pid pid81_3_,         child1_.id id3_,         child1_.id id82_0_,         child1_.pid pid82_0_,         child1_.value value82_0_              parent parent0_      left outer join         child child1_              on parent0_.id=child1_.pid              parent0_.id=?   org.hibernate.propertyaccessexception: exception occurred inside setter    of com.fhp.ems.common.data.dao.test.parent.child   @ org.hibernate.property.basicpropertyaccessor$basicsetter.set(basicpropertyaccessor.java:89)   @ org.hibernate.tuple.entity.abstractentitytuplizer.setpropertyvalues(abstractentitytuplizer.java:583)   @ org.hibernate.tuple.entity.pojoentitytuplizer.setpropertyvalues(pojoentitytuplizer.java:229)   @ org.hibernate.persister.entity.abstractentitypersister.setpropertyvalues(abstractentitypersister.java:3822)   @ org.hibernate.engine.twophaseload.initializeentity(twophaseload.java:152)   @ org.hibernate.loader.loader.initializeentitiesandcollections(loader.java:982)   @ org.hibernate.loader.loader.doquery(loader.java:857)   @ org.hibernate.loader.loader.doqueryandinitializenonlazycollections(loader.java:274)   @ org.hibernate.loader.loader.loadentity(loader.java:2037)   @ org.hibernate.loader.entity.abstractentityloader.load(abstractentityloader.java:86)   @ org.hibernate.loader.entity.abstractentityloader.load(abstractentityloader.java:76)   @ org.hibernate.persister.entity.abstractentitypersister.load(abstractentitypersister.java:3268)   @ org.hibernate.event.def.defaultloadeventlistener.loadfromdatasource(defaultloadeventlistener.java:496)   @ org.hibernate.event.def.defaultloadeventlistener.doload(defaultloadeventlistener.java:477)   @ org.hibernate.event.def.defaultloadeventlistener.load(defaultloadeventlistener.java:227)   @ org.hibernate.event.def.defaultloadeventlistener.proxyorload(defaultloadeventlistener.java:285)   @ org.hibernate.event.def.defaultloadeventlistener.onload(defaultloadeventlistener.java:152)   @ org.hibernate.impl.sessionimpl.fireload(sessionimpl.java:1090)   @ org.hibernate.impl.sessionimpl.get(sessionimpl.java:1005)   @ org.hibernate.impl.sessionimpl.get(sessionimpl.java:998)   @ com.fhp.ems.common.data.dao.test.parent.main(parent.java:98) caused by: java.lang.reflect.invocationtargetexception   @ sun.reflect.nativemethodaccessorimpl.invoke0(native method)   @ sun.reflect.nativemethodaccessorimpl.invoke(nativemethodaccessorimpl.java:39)   @ sun.reflect.delegatingmethodaccessorimpl.invoke(delegatingmethodaccessorimpl.java:25)   @ java.lang.reflect.method.invoke(method.java:597)   @ org.hibernate.property.basicpropertyaccessor$basicsetter.set(basicpropertyaccessor.java:66)   ... 20 more caused by: org.hibernate.lazyinitializationexception: failed lazily initialize collection, no session or session closed   @ org.hibernate.collection.abstractpersistentcollection.throwlazyinitializationexception(abstractpersistentcollection.java:383)   @ org.hibernate.collection.abstractpersistentcollection.throwlazyinitializationexceptionifnotconnected(abstractpersistentcollection.java:375)   @ org.hibernate.collection.abstractpersistentcollection.readsize(abstractpersistentcollection.java:122)   @ org.hibernate.collection.persistentbag.size(persistentbag.java:248)   @ com.fhp.ems.common.data.dao.test.parent.setchild(parent.java:71)

if change earger fetch lazy fetch, works fine. if use @fetch(value=fetchmode.select), works fine. question is: why eager fetch not work?

how can have @onetomany when don't have parentid in child table?
missing key have multiple children related single parent; add parentid table child , use column in @joincolumn(name = "parentid")

edit:

  • init parent.child private list<child> child = new arraylist<child>();
  • change private integer pid; private parent pid; (and add @onetomane mappedby="parent")
  • try annotate field , not setter
  • make parent.setchild() assignment

that - - best pratice parent-child relationship


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