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Subject: Re: [jira] [Commented] (CAY-1622) Generated classes shouldn't produce
 serialVersionUID compiler warning
From: Andrus Adamchik <andrus@objectstyle.org>
In-Reply-To: <4E8ABF70.1040201@gmail.com>
Date: Tue, 4 Oct 2011 11:19:42 +0300
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To: dev@cayenne.apache.org

Very cool.=20

Can we also create some unit tests for this to ensure it works as =
advertised. E.g. a possible caveat is consistent alphabetic ordering of =
relationships and attributes (IIRC they are ordered by default, but it =
is worth creating some tests to see how entity creation affects the =
result). Also I think in relationships loop we may add a check for the =
target entity type.

Andrus


On Oct 4, 2011, at 11:10 AM, Dzmitry Kazimirchyk wrote:

> Just committed fix to the trunk (r1178712). UID generation algorithm =
uses same approach as java.io.ObjectStreamClass.getSerialVersionUID(). =
Generated id depends on ObjEntity's superclass, ObjAttributes and =
ObjRelationships names and types.
>=20
> Here is the diff:
>=20
> Modified: =
cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/=
apache/cayenne/map/ObjEntity.java
> =
URL:http://svn.apache.org/viewvc/cayenne/main/trunk/framework/cayenne-jdk1=
.5-unpublished/src/main/java/org/apache/cayenne/map/ObjEntity.java?rev=3D1=
178712&r1=3D1178711&r2=3D1178712&view=3Ddiff
> =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
> --- =
cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/=
apache/cayenne/map/ObjEntity.java (original)
> +++ =
cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/=
apache/cayenne/map/ObjEntity.java Tue Oct  4 07:57:40 2011
> @@ -19,6 +19,9 @@
>=20
> package org.apache.cayenne.map;
>=20
> +import java.io.ByteArrayOutputStream;
> +import java.io.DataOutputStream;
> +import java.security.MessageDigest;
> import java.util.ArrayList;
> import java.util.Arrays;
> import java.util.Collection;
> @@ -1250,5 +1253,42 @@ public class ObjEntity extends Entity im
>     public void setExcludingSuperclassListeners(boolean =
excludingSuperclassListeners) {
>         this.excludingSuperclassListeners =3D =
excludingSuperclassListeners;
>     }
> +
> +    /**
> +     * Returns unique id for this ObjEntity.
> +     *
> +     * @since 3.1
> +     */
> +    public long getSerialVersionUID() throws Exception {
> +        ByteArrayOutputStream bout =3D new ByteArrayOutputStream();
> +        DataOutputStream dout =3D new DataOutputStream(bout);
> +
> +        dout.writeUTF(getClassName());
> +
> +        if (getSuperClassName() !=3D null) {
> +            dout.writeUTF(getSuperClassName());
> +        }
> +
> +        for (ObjAttribute attr : getAttributes()) {
> +            dout.writeUTF(attr.getName());
> +            dout.writeUTF(attr.getType());
> +        }
> +
> +        for (ObjRelationship rel : getRelationships()) {
> +            dout.writeUTF(rel.getName());
> +            dout.writeUTF(rel.getCollectionType() !=3D null
> +                    ? rel.getCollectionType() : "to-one");
> +        }
> +
> +        dout.flush();
> +
> +        MessageDigest md =3D MessageDigest.getInstance("SHA");
> +        byte[] hashBytes =3D md.digest(bout.toByteArray());
> +        long hash =3D 0;
> +        for (int i =3D Math.min(hashBytes.length, 8) - 1; i>=3D 0; =
i--) {
> +            hash =3D (hash<<  8) | (hashBytes[i]&  0xFF);
> +        }
> +        return hash;
> +    }
>=20
> }
>=20
>=20
> Dzmitry
>=20
> On 10/04/2011 08:22 AM, Andrus Adamchik wrote:
>> +1. We had a brief discussion with Dzmitry to that extent last night. =
Here is an extract from that chat:
>>=20
>>> Generated classes (the ones with _XXX) are made from ObjEntities, so =
if we can use an alg. based on ObjEntity state, I think that should be =
enough just need to account for all its parts (superclass, objattribute =
names and types; objrelationship names and types)
>> So yeah, IMO it does have to be like hashcode of sorts based on =
ObjEntity state...
>>=20
>> Andrus
>>=20
>> On Oct 4, 2011, at 2:53 AM, Mike Kienenberger wrote:
>>=20
>>> No, it should be more clever than that.  Otherwise, every time you
>>> regenerate the template, the generated code will change even if
>>> nothing else had changed.   That will also break serialization.
>>>=20
>>> Ideally, it should return the same number whenever the same fields =
and
>>> types are used for the generated class.
>>>=20
>>> Maybe build the number by iterating over the attributes and
>>> relationships and feeding it into
>>> org.apache.commons.lang.builder.HashCodeBuilder, basing it on the
>>> order and type
>>>=20
>>>=20
>>> On Mon, Oct 3, 2011 at 7:41 PM, Ari Maniatis (Commented) (JIRA)
>>> <jira@apache.org>  wrote:
>>>>   [ =
https://issues.apache.org/jira/browse/CAY-1622?page=3Dcom.atlassian.jira.p=
lugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D13119757#c=
omment-13119757 ]
>>>>=20
>>>> Ari Maniatis commented on CAY-1622:
>>>> -----------------------------------
>>>>=20
>>>> Do we just want to add this to the velocity templates:
>>>>=20
>>>> private static final long serialVersionUID =3D =
${random(1,9223372036854775807)};
>>>>=20
>>>>> Generated classes shouldn't produce serialVersionUID compiler =
warning
>>>>> =
---------------------------------------------------------------------
>>>>>=20
>>>>>                Key: CAY-1622
>>>>>                URL: https://issues.apache.org/jira/browse/CAY-1622
>>>>>            Project: Cayenne
>>>>>         Issue Type: Bug
>>>>>         Components: Core Library
>>>>>   Affects Versions: 3.0
>>>>>           Reporter: Bob Harner
>>>>>           Priority: Minor
>>>>>=20
>>>>> It is probably a good idea for Cayenne not to produce any compiler =
warnings, but auto-generated entity classes always have the "The =
serializable class _Foo does not declare a static final serialVersionUID =
field of type long" compiler warning.
>>>>> The @SuppressWarnings("serial") annotation will get rid of the =
warnings, but of course it is not recommended to manually update the =
generated  classes.
>>>>> Users could configure the IDE to ignore these warnings (yuk), but =
then other team members will still see them.
>>>>> Another option is to for users to set up a custom velocity =
template to include this annotation.
>>>>> But the best solution would be for Cayenne to either automatically =
generate either the serialVersionUID itself or the =
@SuppressWarnings("serial") annotation that suppresses the compiler =
warning.
>>>> --
>>>> This message is automatically generated by JIRA.
>>>> If you think it was sent incorrectly, please contact your JIRA =
administrators: =
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
>>>> For more information on JIRA, see: =
http://www.atlassian.com/software/jira
>>>>=20
>>>>=20
>>>>=20
>=20
>=20