getPropertyValue throws ClassCastException when using .

pmularien · **Posted:** Mon Feb 27, 2006 10:49 am

I don't know if this is a bug or an undocumented "feature" of getPropertyValue. I had assumed that ClassMetadata.getPropertyValue would be smart enough to traverse nested properties using "." notation. It appears that it is, but only assumes that "." notation signifies the contents of a nested component instead of traversing other kinds of relationships, e.g. many-to-one (what I am trying to use it with). This is evidenced by the following code from AbstractEntityTuplizer:

Code:

      int loc = propertyPath.indexOf('.');
      String basePropertyName = loc>0 ?
         propertyPath.substring(0, loc) : propertyPath;
         
      int index = entityMetamodel.getPropertyIndex( basePropertyName );
      Object baseValue = getPropertyValue( entity, index );
      if ( loc>0 ) {
         ***ComponentType type = (ComponentType) entityMetamodel.getPropertyTypes()[index];***
         return getComponentValue( type, baseValue, propertyPath.substring(loc+1) );

The line with ***'s around it throws the expected ClassCastException when "." syntax is used to specify the property path of a ManyToOneType. Since the usage of this method with "." notation isn't specifically covered in the Javadoc, I wasn't sure whether this was intentional, or a valid bug/feature request. I can try to hack something together using BeanUtils in the meantime, but it would be easier if Hibernate was able to do this for me.

Relevant generic info:

Hibernate version:
3.1.2

Mapping documents:

Code:

... (snip) ...
         <many-to-one name="location" class="x.y.Location" column="LOCATION_ID"
               not-null="true" foreign-key="FK_JP_LOCATION"/>
... (snip) ...

mapping for x.y.Location object:

Code:

... (snip) ...
        <property name="name" column="NAME" type="string" length="100"/>
... (snip) ...

Full stack trace of any exception that occurs:
This occurs when I call getPropertyValue with the property name "location.name" on the object containing the location many-to-one relationship indicated above.

Code:

java.lang.ClassCastException at org.hibernate.tuple.AbstractEntityTuplizer.getPropertyValue(AbstractEntityTuplizer.java:282) at org.hibernate.persister.entity.AbstractEntityPersister.getPropertyValue(AbstractEntityPersister.java:3252) at
...

max · **Posted:** Mon Feb 27, 2006 11:29 am

it does not support nested properties except for component/composite stuff

pmularien · **Posted:** Mon Feb 27, 2006 11:31 am

Would it be valid to submit a bug with a patch to the Javadoc so that it's clear that is the only reason "." should be used for property names passed to this method?

max · **Posted:** Mon Feb 27, 2006 11:36 am

sure...

pmularien · **Posted:** Mon Feb 27, 2006 11:40 am

Isn't it kind of a mismatch, though, that the same "." syntax works fine within an HQL query? What is the intended purpose of the ClassMetadata.getPropertyValue API?

max · **Posted:** Mon Feb 27, 2006 11:45 am

to get the specifc value for the property on the class modelled after ClassMetaData.

and since those nested parts is not otherwise available, then it make sense to have them. (the nested stuff does not refer to ClassMetaData)

pmularien · **Posted:** Mon Feb 27, 2006 11:57 am

Thanks max, I guess what I was thinking the intention of this API was (to do PropertyUtils-style navigation of "." notation properties) is better served by just using PropertyUtils against my Hibernate object directly. It might be useful (IMHO) to add some API that would let users do this without requiring the use of PropertyUtils - especially since there must be code to do nested property navigation for use with HQL.

max · **Posted:** Mon Feb 27, 2006 2:13 pm

contribute a patch, but remember that it should only work for persistent properties....actually thinking about it we should probably just write a util that uses the existing api to do this and put it on wiki.