Java Hibernate delete Object -

today did experiments hibernate. first of there no deeper sense behind program. wanted try framework. planed following db tables:

• car (auto)
• driver (fahrer)
• wohnung (flat)
• guest (fahrgast)

with following bidirectional mappings:

• driver – flat onetoone
• driver – car onetomany
• car – guest manytomany

after preparing single classes wrote worker insert demodata. point works expected. remove 1 of drivers. hibernate tells me, re-saved guest. unfortunately don’t understand why. expected fine after removing driver driver collection of corresponding cars.

class car

package mycode;  import java.time.localdate; import java.util.arraylist; import java.util.list;  import javax.persistence.cascadetype; import javax.persistence.column; import javax.persistence.entity; import javax.persistence.generatedvalue; import javax.persistence.id; import javax.persistence.manytomany; import javax.persistence.onetomany; import javax.persistence.table;  @entity @table(name="auto") public class auto {  @id @generatedvalue private int id; @column(name="nummernschild", nullable = false) private string nummernschild; @onetomany(cascade=cascadetype.all, mappedby="auto") private list<fahrer>fahrers = new arraylist<fahrer>(); @manytomany(cascade=cascadetype.all) private list<fahrgast>fahrgasts = new arraylist<fahrgast>();  public list<fahrgast> getfahrgasts() {     return fahrgasts; } public void setfahrgasts(list<fahrgast> fahrgasts) {     this.fahrgasts = fahrgasts; } public list<fahrer> getfahrers() {     return fahrers; } public void setfahrers(list<fahrer> fahrers) {     this.fahrers = fahrers; } private localdate kaufdatum; public localdate getkaufdatum() {     return kaufdatum; } public void setkaufdatum(localdate kaufdatum) {     this.kaufdatum = kaufdatum; } public int getid() {     return id; } public void setid(int id) {     this.id = id; } public string getnummernschild() {     return nummernschild; } public void setnummernschild(string nummernschild) {     this.nummernschild = nummernschild; }  } 

class driver

package mycode;  import javax.persistence.cascadetype; import javax.persistence.entity; import javax.persistence.generatedvalue; import javax.persistence.id; import javax.persistence.joincolumn; import javax.persistence.manytoone; import javax.persistence.onetoone; import javax.persistence.table;  @entity @table(name="fahrer") public class fahrer { @id @generatedvalue() private int id; private string vorname, nachname; private int alter;  @onetoone (cascade=cascadetype.all) @joincolumn(name="id") private wohnung wohnung; @manytoone(cascade=cascadetype.all) private auto auto;   public auto getauto() {     return auto; } public void setauto(auto auto) {     this.auto = auto; } public wohnung getwohnung() {     return wohnung; } public void setwohnung(wohnung wohnung) {     this.wohnung = wohnung; }  public int getid() {     return id; } public void setid(int id) {     this.id = id; } public string getvorname() {     return vorname; } public void setvorname(string vorname) {     this.vorname = vorname; } public string getnachname() {     return nachname; } public void setnachname(string nachname) {     this.nachname = nachname; } public int getalter() {     return alter; } public void setalter(int alter) {     this.alter = alter; }  } 

class flat

package mycode;  import javax.persistence.cascadetype; import javax.persistence.column; import javax.persistence.entity; import javax.persistence.generatedvalue; import javax.persistence.id; import javax.persistence.joincolumn; import javax.persistence.onetoone; import javax.persistence.table;  import org.hibernate.annotations.genericgenerator; import org.hibernate.annotations.parameter;  @entity @table(name="wohnung") public class wohnung {     @id @generatedvalue(generator = "newgenerator")     @genericgenerator(name="newgenerator", strategy="foreign" , parameters= {@parameter(value="fahrer", name="property")}) private int id;  @column(nullable=false) private string ort, straße; @onetoone(cascade=cascadetype.all) @joincolumn(name="id") private fahrer fahrer; public int getid() {     return id; } public void setid(int id) {     this.id = id; } public string getort() {     return ort; } public void setort(string ort) {     this.ort = ort; } public string getstraße() {     return straße; } public void setstraße(string straße) {     this.straße = straße; } public fahrer getfahrer() {     return fahrer; } public void setfahrer(fahrer fahrer) {     this.fahrer = fahrer; }   } 

class guest

package mycode;  import java.util.arraylist; import java.util.list;  import javax.persistence.column; import javax.persistence.entity; import javax.persistence.generatedvalue; import javax.persistence.id; import javax.persistence.manytomany; import javax.persistence.table;  @entity @table(name="fahrgast") public class fahrgast { @id @generatedvalue private int id; @column(nullable=false) private int kundennummmer; private string vornname, nachname; @manytomany(mappedby="fahrgasts") private list<auto>autos = new arraylist<auto>();  public list<auto> getautos() {     return autos; } public void setautos(list<auto> autos) {     this.autos = autos; } public int getid() {     return id; } public void setid(int id) {     this.id = id; } public int getkundennummmer() {     return kundennummmer; } public void setkundennummmer(int kundennummmer) {     this.kundennummmer = kundennummmer; } public string getvornname() {     return vornname; } public void setvornname(string vornname) {     this.vornname = vornname; } public string getnachname() {     return nachname; } public void setnachname(string nachname) {     this.nachname = nachname; }   } 

class worker

package mycode;  import java.time.localdate; import java.util.arraylist; import java.util.list;  import org.hibernate.session; import org.hibernate.sessionfactory; import org.hibernate.boot.registry.standardserviceregistrybuilder; import org.hibernate.cfg.configuration;  public class worker {      private session session;     private sessionfactory sf;     public static void main(string[] args) {          worker worker = new worker();         worker.work();     }      private void init()     {         configuration configuration = new configuration().configure();          sf = configuration.buildsessionfactory();         session = sf.opensession();      }      private void work()     {         init();         auto auto = new auto();          auto.setnummernschild("hh:mk:"+1);         localdate ld = localdate.now();         auto.setkaufdatum(ld);          session.begintransaction();         (int i=0; i<10; i++)         {               auto = new auto();             auto.setnummernschild("hh:mk:"+i);             ld = localdate.now();             auto.setkaufdatum(ld);              auto auto2 = new auto();              auto2.setnummernschild("hh:mk:"+i);             ld = localdate.now();             auto2.setkaufdatum(ld);              //auto.setid(i);              fahrer fahrer = new fahrer();              fahrer.setvorname("hans");             fahrer.setnachname("huber");             fahrer fahrer2 = new fahrer();              fahrer2.setvorname("anna");             fahrer2.setnachname("schmidt");             double temp = math.random();             int alter = (int)(temp*50);             fahrer.setalter(alter);              fahrer2.setalter(alter);              fahrer.setauto(auto);             fahrer2.setauto(auto2);             wohnung wohnung = createwohnung(i);             wohnung.setfahrer(fahrer);             fahrer.setwohnung(wohnung);             wohnung wohnung2 = createwohnung(i*10);             fahrer2.setwohnung(wohnung2);             wohnung2.setfahrer(fahrer2);             auto.getfahrers().add(fahrer);             auto2.getfahrers().add(fahrer2);              double zufall = math.random()*100;             int zu = (int)zufall;             (int z=0; z<zu; z++)             {                 fahrgast fahrgast = new fahrgast();                  fahrgast.setvornname("hans"+z);                 fahrgast.setnachname("dampf"+z);                 double kundennummer = math.random()*10000;                 fahrgast.setkundennummmer((int)kundennummer);                 fahrgast.getautos().add(auto);                 fahrgast.getautos().add(auto2);                 auto.getfahrgasts().add(fahrgast);                 auto2.getfahrgasts().add(fahrgast);              } //          session.save(fahrer); //          session.save(fahrer2);             session.save(auto);             session.save(auto2);          }          fahrer abfrage = session.get(fahrer.class, 2);         list<fahrer>fahrers = session.createcriteria(fahrer.class).list();         list<fahrer>tobedeletet = new arraylist<fahrer>();         (fahrer aktuell : fahrers)         {             auto car = aktuell.getauto();             list<fahrer>cardriver = car.getfahrers();             fahrer temp = null;             (fahrer driver: cardriver)             {                 if (driver.getid()==abfrage.getid())                 {                     tobedeletet.add(aktuell);                     temp = driver;                  }             }             cardriver.remove(temp);             session.update(car);         }           (fahrer aktuell : tobedeletet)         {             session.remove(aktuell);         }           system.out.println(abfrage.getvorname()+ " "+abfrage.getnachname());           session.gettransaction().commit();         session.close();         sf.close();      }      private wohnung createwohnung(int i)     {         wohnung wohnung = new wohnung();          wohnung.setort("bla"+i);         wohnung.setstraße("blub"+i);         return wohnung;     }  } 

finally configuration file

<?xml version='1.0' encoding='utf-8'?> <hibernate-configuration> <session-factory>     <!-- database connection settings -->     <property       name="connection.driver_class">org.postgresql.driver</property>     <property name="connection.url">jdbc:postgresql://192.168.2.252:5432/test</property>     <property name="connection.username">postgres</property>     <property name="connection.password">postgres</property>      <!-- jdbc connection pool (use built-in) -->     <property name="connection.pool_size">1</property>      <!-- sql dialect -->     <property name="hibernate.dialect">org.hibernate.dialect.postgresqldialect</property>      <!-- enable hibernate's automatic session context management -->     <property name="current_session_context_class">thread</property>      <!-- disable second-level cache  -->     <property name="cache.provider_class">org.hibernate.cache.internal.nocacheprovider</property>      <!-- echo executed sql stdout -->     <property name="show_sql">true</property>      <!-- drop , re-create database schema on startup -->     <property name="hbm2ddl.auto">create</property>     <mapping class="mycode.auto"/>     <mapping class="mycode.fahrer"/>     <mapping class="mycode.wohnung"/>     <mapping class="mycode.fahrgast"/> </session-factory> 

can tell me, how delete 1 of drivers?

the error message: error: hhh000346: error during managed flush [deleted object re-saved cascade (remove deleted object associations): [mycode.fahrgast#3]] exception in thread "main" javax.persistence.entitynotfoundexception: deleted object re-saved cascade (remove deleted object associations): [mycode.fahrgast#3] @ org.hibernate.internal.exceptionconverterimpl.convert(exceptionconverterimpl.java:126) @ org.hibernate.internal.exceptionconverterimpl.convert(exceptionconverterimpl.java:155) @ org.hibernate.internal.exceptionconverterimpl.convert(exceptionconverterimpl.java:162) @ org.hibernate.internal.sessionimpl.doflush(sessionimpl.java:1441) @ org.hibernate.internal.sessionimpl.managedflush(sessionimpl.java:491) @ org.hibernate.internal.sessionimpl.flushbeforetransactioncompletion(sessionimpl.java:3201) @ org.hibernate.internal.sessionimpl.beforetransactioncompletion(sessionimpl.java:2411) @ org.hibernate.engine.jdbc.internal.jdbccoordinatorimpl.beforetransactioncompletion(jdbccoordinatorimpl.java:467) @ org.hibernate.resource.transaction.backend.jdbc.internal.jdbcresourcelocaltransactioncoordinatorimpl.beforecompletioncallback(jdbcresourcelocaltransactioncoordinatorimpl.java:146) @ org.hibernate.resource.transaction.backend.jdbc.internal.jdbcresourcelocaltransactioncoordinatorimpl.access$100(jdbcresourcelocaltransactioncoordinatorimpl.java:38) @ org.hibernate.resource.transaction.backend.jdbc.internal.jdbcresourcelocaltransactioncoordinatorimpl$transactiondrivercontrolimpl.commit(jdbcresourcelocaltransactioncoordinatorimpl.java:220) @ org.hibernate.engine.transaction.internal.transactionimpl.commit(transactionimpl.java:68) @ mycode.worker.work(worker.java:133) @ mycode.worker.main(worker.java:19)

first things first, hope know alter reserved word, alter table <table_name>;, have change column name in fahrer class:

@column(name = "_alter") // choose name want private int alter; 

after that, why need many bidirectional relationships? , look, have:

class fahrer {     // ...     @manytoone(cascade = cascadetype.all)     private auto auto; 

that means, when delete fahrer, auto deleted to. realy want?

now @ code:

// @ first check if id equal abfrage , add list if (driver.getid() == abfrage.getid()) {     tobedeletet.add(aktuell);     temp = driver; }  // @ end formed list tobedeleted witch contains elements same id.  (fahrer aktuell : tobedeletet) {     session.remove(aktuell); } 

to honest, i'm java beginner, may miss something. deleting entity same id value few times propably not necessary.