Hibernate saveOrUpdate() tries to save when it should update

Question

I have a Hibernate entity called IssueParticipant. It basically describes the relationship between a user and an issue (which is like a JIRA or Bugzilla issue). It represents a sort of many-to-many linking table in the database, linking a user ID to an issue ID, but also includes other information related to notification settings, and so it is treated as its own entity.

I was having huge problems with using the userId and issueId as a composite key, so I created a synthethic key which is a String (and a varchar in the postgres database), which is formed as: _.

Now, I have a screen where a user can edit all of the users associated with an issue, while also editing the notification settings. In a controller class I create a List of IssueParticipants like this:

IssueParticipant participant = new IssueParticipant();
participant.setUser(accountUser);
participant.setIssue(issue);

So these are of course not managed by Hibernate at this point.

Then in my DAO I iterate through them and call saveOrUpdate(), expecting that if an IssueParticipant with the same synthetic key exists in the database, it will updated; otherwise it will be inserted:

    for (IssueParticipant participant : participants) {
        getCurrentSession().saveOrUpdate(participant);
        savedIds.add(participant.getIssueUserKey());
    }

(savedIds is a List I am maintaining so that I later will know what IssueParticipants I should delete from the database).

Instead of what I expect, though, I get an Exception:

org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "issue_participant_pkey"

Here is my entity class, abbreviated:

public class IssueParticipant extends Entity {

    private String issueUserKey;
    private Long issueId;
    private Long userId;

     // Edit: adding 'dateAdded' definition
    private Date dateAdded;
// ...

    // below may be null
    private SPUser user;
    private Issue issue;

    public static IssueParticipant nulledIssueParticipant() {
        IssueParticipant ip = new IssueParticipant();
        return ip;
    }
    public String getIssueUserKey() {
        return issueUserKey;
    }

    public void setIssueUserKey(String issueUserKey) {
        this.issueUserKey = issueUserKey;
    }

    public Long getId() {
        // currently meaningless
        return 0L;
    }

    public Long getIssueId() {
        return this.issueId;
    }

    public void setIssueId(Long issueId) {
        this.issueId = issueId;
        updateKey();
    }

    public Long getUserId() {
        return this.userId;
    }

    public void setUserId(Long userId) {
        this.userId = userId;
        updateKey();
    }

    private void updateKey() {
        issueUserKey = getIssueId() + KEY_SEP + getUserId();
    }

    public SPUser getUser() {
        return user;
    }

    public void setUser(SPUser user) {
        this.user = user;
        setUserId(user.getId());
    }

    public Issue getIssue() {
        return issue;
    }

    public void setIssue(Issue issue) {
        this.issue = issue;
        setIssueId(issue.getId());
    }

// edit: adding 'dateAdded' methods
public Date getDateAdded() {
    return dateAdded;
}

public void setDateAdded(Date dateAdded) {
    this.dateAdded = dateAdded;
}

...

}

Here is its hbm file:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping default-lazy="false">
    <class name="com.xxx.yyy.IssueParticipant" table="issue_participant">
        <id name="issueUserKey" column="issue_user_key" type="string">
            <generator class="assigned"/>
        </id> 
        <version name="dateAdded" column="date_added" type="timestamp" unsaved-value="null" />
        <property name="issueId" column="issue_id" />
        <many-to-one name="user" column="user_id" class="com.xxx.yyy.SPUser" not-null="true" cascade="none" />
        <property name="alertRss" column="alert_rss" type="boolean" />
        <property name="alertEmail" column="alert_email" type="boolean" />
        <property name="alertWeb" column="alert_web" type="boolean" />
        <property name="alertClient" column="alert_client" type="boolean" />

    </class>
</hibernate-mapping>

And indeed user_issue_key is the primary key in the corresponding database table.

I feel like the right solution might just be to use SpringJDBC in this case, but I'd really love to figure out what's going on here. Anyone have any thoughts? Thanks in advance.

Answer 1

saveOrUpdate() doesn't query the database to decide whether it should save or update the given entity. It makes that decision based on the state of the entity, as follows:

• if the object is already persistent in this session, do nothing
• if another object associated with the session has the same identifier, throw an exception
• if the object has no identifier property, save() it
• if the object's identifier has the value assigned to a newly instantiated object, save() it
• if the object is versioned by a <version> or <timestamp>, and the version property value is the same value assigned to a newly instantiated object, save() it
• otherwise update() the object

So, as far as I understand in your case decision is based on the value of dateAdded field, therefore you need to keep it to distinguish between new and detached instances.

See also:

• 11.7. Automatic state detection

Answer 2

You can get it to query the database to make this determination if you really want to. Change your identifier mapping to:

<id name="issueUserKey" column="issue_user_key" type="string" unsaved-value="undefined">
    <generator class="assigned"/>
</id> 

Usually that is not the best way though. You do in fact have a <version/> mapping which is usually a better fallback from the identifier for deciding between save/update without the overhead of querying the database. You tried setting it to unsaved-value="null". But you did not show the property mapping for your IssueParticipant.dateAdded property (which is what you try to map as <version/>; you do realize version is incremented every update right?; also, you do know about <timestamp/> instead of <version/> right?). Anyway, that is where your problem is. Could you show the definition of your IssueParticipant.dateAdded property?