Hibernate version:
3.0.05

Hi! I'm a complete newbie to hibernate, and just starting to get things working. I'm trying to get hibernate to behave the way my previous home-rolled DAOs did. One such behavior is this: If you try to insert a record into a table that has the same natural key as one that already exists, don't do the insert.

For example: I have a class that has 2 properties: name and description. If I create an object with the name and description both set to "test", hibernate will persist the object and get an ID assigned. If I create a second object of the same type with the same name and description ("test"), I'd like hibernate to NOT insert a second row.

Now, I could do a hit on the database myself to look up that object, and then I'd know the primary key for that object, and I'd be done. But that's extra code to do each time I do an insert (and it's an extra database hit) that I'd rather automate if possible. I ran across natural ID's, and thought this might be a good solution. However, even with the natural ID defined in the mapping file, and equals defined in the class, I still get an insert of a new row. I'd like to avoid that.

Mapping documents:

<?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>
<!--
Auto-generated mapping file from
the hibernate.org cfg2hbm engine
-->
<class name="pinnacle.dao.datavo.hibernatetest.CoordinateFeatureType" table="COORDINATE_FEATURE_TYPE" schema="PINNACLE">
<id name="id" type="long">
<column name="ID" />

<generator class="seqhilo">
<param name="sequence">SQ_COORDINATE_FEATURE_TYPE</param>

<param name="max_lo">100</param>
</generator>
</id>

<natural-id mutable="true">
<property name="name" type="string">
<column name="NAME" length="100" />
</property>

<property name="description" type="string">
<column name="DESCRIPTION" length="500" />
</property>
</natural-id>

<set name="coordinateFeatures" inverse="true">
<key>
<column name="FEATURE_TYPE_ID" precision="22" scale="0" />
</key>

<one-to-many class="pinnacle.dao.datavo.hibernatetest.CoordinateFeature" />
</set>
</class>
</hibernate-mapping>

POJO:

public class CoordinateFeatureType implements java.io.Serializable {

// Fields

private long id;
private String name;
private String description;
private Set coordinateFeatures;

// Constructors

/** default constructor */
public CoordinateFeatureType() {
}

/** constructor with id */
public CoordinateFeatureType(long id) {
this.id = id;
}

// Property accessors

public long getId() {
return this.id;
}

public void setId(long id) {
this.id = id;
}

public String getName() {
return this.name;
}

public void setName(String name) {
this.name = name;
}

public String getDescription() {
return this.description;
}

public void setDescription(String description) {
this.description = description;
}

public Set getCoordinateFeatures() {
return this.coordinateFeatures;
}

public void setCoordinateFeatures(Set coordinateFeatures) {
this.coordinateFeatures = coordinateFeatures;
}

public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if ( (obj == null) || (obj.getClass() != this.getClass())) {
return false;
}
CoordinateFeatureType o = (CoordinateFeatureType) obj;
// object must be corrent type at this point
return
EqualsUtil.areEqual(this.getName(), o.getName()) &&
EqualsUtil.areEqual(this.getDescription(), o.getDescription());
}

public int hashCode() {
int result = HashCodeUtil.SEED;
result += HashCodeUtil.hash(result, this.getName());
result += HashCodeUtil.hash(result, this.getDescription());
return result;
}
}

My code to test looks like this (I know it's simplistic to the extreme, but I just want to see what I can get working before I start implementing patterns) Running this code a second time should not result in a table insert (or, that's my hope.) What should I change to make this work?

Running Code
Configuration cfg = new Configuration();
SessionFactory f = cfg.buildSessionFactory();
Session s = f.openSession();
Transaction tx = s.beginTransaction();
CoordinateFeatureType t = new CoordinateFeatureType();
t.setName("test");
t.setDescription("test");
s.saveOrUpdate(t);
tx.commit();

Thanks for any help!

-Jim

I have found the same thing as you wrt natural-id not being enforced.
Apparently, it is not implemented to do so...
http://forum.hibernate.org/viewtopic.ph ... =naturalid
... which suggests that natural-id is only good for the Restrictions.naturalId() type lookup and creation of unique constraints for the database (if you are generating db guff from your mappings).
If you've discovered anything to the contrary in the last 5 months, please share :)