need help with cascade delete

[kwame Iwegbue]

I have read documentation and Gavin's hibernate book, but still have some problems with cascade delete (using cascade-all and delete-orphan)

I have two entity classes User and Patient.

 
 
@Entity
@org.hibernate.annotations.Entity(dynamicInsert = true, dynamicUpdate = true)
@org.hibernate.annotations.Proxy(lazy = false)
@Table(name="_USER")
public class User {
 
...
 
 
@OneToMany(mappedBy = "user", cascade = { CascadeType.ALL }, fetch = FetchType.EAGER)
@org.hibernate.annotations.Cascade(value=org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
private Set<Patient> patients = new HashSet<Patient>();
...
  

In the controller layer I have this delete method which uses an id from view layer to load a Patient for deletion.

  
public void delete()
 
Patient patient = patientDAO .findById(getDelete_id(), true);
 
//chase pointers and remove referrences from Users
List<User> listOfUsers = userDAO.chasePointersToPatient(patient);
logger.debug("size of set: "+ listOfUsers.size());//initalize collection
 
for(User u : listOfUsers) {
for(Patient p : u.getPatients()) {
if(p == patient) {
logger.debug("contains patient p: "+u.getPatients().contains(patient)+ "; size of set: "+ u.getPatients().size()); //contains patient p false; size of set 1
u.getPatients().remove(patient);
logger.debug("contains patient p: "+u.getPatients().contains(patient)+ "; size of set: "+ u.getPatients().size()); //contains patient p false; size of set 1
}
}
}
}
 
  

When I examine the Set in debugger, i can see the exact same patient object, with same DB id, but some how calling "contains" on the Set returns false? why?

p.s the code for userDAO.chasePointersToPatient is:

 
 
public List<User> chasePointersToPatient(Patient patient){
return (getSession()
.createQuery("from User u where patient in elements(u.patients)")
.setParameter("patient", patient)
.list());
}
   

[ June 26, 2007: Message edited by: kwame Iwegbue ]
[ June 26, 2007: Message edited by: kwame Iwegbue ]

[Jaikiran Pai]

Can you post the contents of your Patient class. Also, are you overriding the equals and hashcode method in your Patient class?

[kwame Iwegbue]

Thanks for the quick reply Jaikiran,

here is the code for my Patient class:

  
 
@Entity
@org.hibernate.annotations.Entity(dynamicInsert = true, dynamicUpdate = true)
@org.hibernate.annotations.Proxy(lazy = false)
@Table(name = "PATIENT")
public class Patient {

@Id @GeneratedValue
@Column(name="PATIENT_ID")
private Long id;

@Column(name="VISIT_COUNT")
private int visitCount = 0;

@Column(name = "PRIMARY_MD")
private String primaryMD = "un-assigned";

 
@ManyToOne(optional=false) @JoinColumn(name = "USER_ID")
private User user = new User();// Set with Spring or by caller


@OneToMany(mappedBy = "patient", cascade = { CascadeType.ALL }, fetch = FetchType.EAGER)
@org.hibernate.annotations.Cascade(value=org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
private Set<BriefNote> briefNotes = new HashSet<BriefNote>();

private Demographics demographics;// set by ActionBean (through validation feilds)

@org.hibernate.annotations.CollectionOfElements
@JoinTable(name = "PATIENT_DIAGNOSIS", joinColumns = @JoinColumn(name = "PATIENT_ID"))
@CollectionId(columns = @Column(name = "PATIENT_DIAGNOSIS_ID"),
type = @org.hibernate.annotations.Type(type ="long"), generator = "identity")
private Collection<Diagnosis> diagnoses = new ArrayList<Diagnosis>(); 


@org.hibernate.annotations.CollectionOfElements
@JoinTable(name = "PATIENT_VISIT", joinColumns = @JoinColumn(name = "PATIENT_ID"))
@CollectionId(columns = @Column(name = "PATIENT_VISIT_ID"),
type = @org.hibernate.annotations.Type(type ="long"), generator = "identity")
private Collection<Visit> visits = new ArrayList<Visit>();

public Patient() {}

public Patient(Demographics demographics) {
this.demographics = demographics;
}

public Long getId() {
return id;
}

public Demographics getDemographics() {
return demographics;
}
 
public void setDemographics(Demographics demographics) {
this.demographics = demographics;
}

public User getUser() {
return user;
}
 
public void setUser(User user) {
this.user = user;
}
 
public String getPrimaryMD() {
return primaryMD;
}
 
public void setPrimaryMD(String primaryMD) {
this.primaryMD = primaryMD;
}
 
public Collection<Diagnosis> getDiagnoses() {
return diagnoses;
}
 
public void setDiagnoses(Collection<Diagnosis> diagnoses) {
this.diagnoses = diagnoses;
}
 
public Collection<Visit> getVisits() {
return visits;
}
 
public void setVisits(Collection<Visit> visits) {
this.visits = visits;
}

public int getVisitCount() {
return visitCount;
}
 
public void setVisitCount(int visitCount) {
this.visitCount = visitCount;
}
 
public Set<BriefNote> getBriefNotes() {
return briefNotes;
}
 
public void setBriefNotes(Set<BriefNote> briefNotes) {
this.briefNotes = briefNotes;
}
/**
 * Convenience method for bidirectional association management.
 * 
 * @param briefNote the child to associate with.
 */
public void addBriefNote(BriefNote briefNote) {
if(briefNote == null) {
throw new IllegalArgumentException("Null BriefNote!");
}
if(briefNote.getPatient() != null) {
briefNote.getPatient().getBriefNotes().remove(briefNote);
briefNote.setPatient(this);
briefNotes.add(briefNote);
}
}

public void removeBriefNote(BriefNote briefNote) {
if(briefNote == null) throw new IllegalArgumentException("Null BriefNote!");
briefNote.setPatient(null);
briefNotes.remove(briefNote);
}


 
public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Patient)) return false;
        final Patient patient = (Patient) o;
        return getDemographics()
        .getLastname()
        .equals(patient.getDemographics().getLastname());
    }
 
    public int hashCode() {
       int result;
           result = (getDemographics() != null ? getDemographics().hashCode() : 0);
           result = 29 * result + (user != null ? user.hashCode() : 0);
           return result;
    }
 
    public String toString() {
       return  "Patient id: ('" + getId() + "'), " +
       "Name: '" + getDemographics().getFirstname() +" "+ 
        getDemographics().getLastname() + "'";
    }
 

}
 

[Jaikiran Pai]

I havent yet looked at the entire code, but i believe the reason why the contains method is returning false, has to do with the logic present in the equals and the hashcode method:

Originally posted by kwame Iwegbue:

public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof Patient)) return false;
final Patient patient = (Patient) o;
return getDemographics()
.getLastname()
.equals(patient.getDemographics().getLastname());
}

public int hashCode() {
int result;
result = (getDemographics() != null ? getDemographics().hashCode() : 0);
result = 29 * result + (user != null ? user.hashCode() : 0);
return result;
}

Can you try printing out the hashcode values for each of the patient objects in

u.getPatients()

and also the hashcode of the patient that you are checking for:

Patient patient = patientDAO .findById(getDelete_id(), true);

This will help you to figure out whether the logic involved in the equals or the hashcode method is not right

[kwame Iwegbue]

seems you're right about the hashcode problem:

log shows:

  
for(User u : listOfUsers) {
for(Patient p : u.getPatients()) {
if(p == patient) {
logger.debug("hash for p: " +p.hashCode());
logger.debug("hash for patient: " +patient.hashCode());
logger.debug("contains patient p: "+u.getPatients().contains(patient)+ "; size of set: "+ u.getPatients().size() +"contains patient with hash: "+ u.getPatients().getClass().hashCode());
u.getPatients().remove(patient);
logger.debug("contains patient p: "+u.getPatients().contains(patient)+ "; size of set: "+ u.getPatients().size());
}
}
}
 

...
 
hash for p: 932558523
 
hash for patient: 932558523
 
u.getPatient.getClass() with hash: 2825452
 
  

I don;t understand how this can be? The set only contains 1 object "p", which it compares in the foreach and returns the same hashcode as "patient".

[kwame Iwegbue]

I removed my implementation of equals and hashcode, now the code works fine. I wonder why I had those in the first place?

[Jaikiran Pai]

Originally posted by kwame Iwegbue:
I removed my implementation of equals and hashcode, now the code works fine.

Glad to know, it works

Originally posted by kwame Iwegbue:
I wonder why I had those in the first place?

Overriding the eqauls and hashcode is perfectly fine, as long as they are implemented correct. If you are more curious about the best strategies for implementing equals and hashcode in your persistent classes, have a look at Equals and HashCode - Hibernate