Is it possible for Hibernate to use a class with no default c'tor as a component or composite-element?

Question

I need to use some legacy classes in Hibernate. One of the classes doesn't have a default constructor so I get a "org.hibernate.InstantiationException: No default constructor for entity: .." error. I do not need to persist this class directly. Here is the mapping:

<class name="test.geo.support.Observation" table="observation">
        <id access="property" column="obs_msg" name="EncodedObMsg" type="string"/>
                <property name="ReportTime" column="report_time" type="long" />
                <many-to-one name="Station" column="station_id" class="test.geo.Station"/>
    </class>
    <class name="test.geo.Station" table="station">
        <id access="property" column="station_id" name="UniqueId" type="string" />
                <component name="Point" class="test.geo.geometry.PointGeometry">
                    <property name="latitude" type="double" access="field" column="lat" />
                    <property name="longitude" type="double" access="field" column="lon" />
                </component>
    </class>

I need to persist the 'Observation' and 'Station', and want to reference the 'PointGeometry' class to persist the Station.Point. Is there any way to pull this off with 'PointGeometry' not having a default constructor?

Alex Gitelman · Answer 1 · 2011-06-09T16:00:21.883

2

You will always need a no argument constructor. If I really don't like no arg constructor to be called by my code, I make it protected.

edited Jun 09 '11 at 16:00

answered Jun 08 '11 at 20:42

Alex Gitelman

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the no arg constructor can at most be package private – hvgotcodes Jun 09 '11 at 14:35
@hvgotcodes `protected` definitelly works as it's all over my code. But I take it back about `private`. Answer edited. – Alex Gitelman Jun 09 '11 at 16:02
yes protected will work as it is less restrictive than package private. Note "package private" is one term. I did not say private. – hvgotcodes Jun 09 '11 at 16:32
I have made the no-args constructor private and Hibernate still works – hughjdavey Oct 25 '17 at 11:07

score 1 · Accepted Answer · answered Jun 08 '11 at 20:06

1

No, you need a no argument constructor. Hibernate needs a way to create objects.

You might be able to create a subclass of this class, and give the subclass the no-arg constructor.

answered Jun 08 '11 at 20:06

hvgotcodes

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score 0 · Answer 3 · edited May 23 '17 at 12:01

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No. That is a JPA requirement. In Hibernate you can implement an Interceptor that populates the object using as desired. See:

edited May 23 '17 at 12:01

Community

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answered Nov 17 '16 at 08:47

user2108278

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Is it possible for Hibernate to use a class with no default c'tor as a component or composite-element?

3 Answers3