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From Dzmitry Kazimirchyk <dkazimirc...@gmail.com>
Subject Re: [jira] [Commented] (CAY-1622) Generated classes shouldn't produce serialVersionUID compiler warning
Date Tue, 04 Oct 2011 08:10:24 GMT
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.

Here is the diff:

Modified: cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/map/ObjEntity.java
URL:http://svn.apache.org/viewvc/cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/map/ObjEntity.java?rev=1178712&r1=1178711&r2=1178712&view=diff
==============================================================================
--- cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/map/ObjEntity.java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+++ cayenne/main/trunk/framework/cayenne-jdk1.5-unpublished/src/main/java/org/apache/cayenne/map/ObjEntity.java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 @@

  package org.apache.cayenne.map;

+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 = excludingSuperclassListeners;
      }
+
+    /**
+     * Returns unique id for this ObjEntity.
+     *
+     * @since 3.1
+     */
+    public long getSerialVersionUID() throws Exception {
+        ByteArrayOutputStream bout = new ByteArrayOutputStream();
+        DataOutputStream dout = new DataOutputStream(bout);
+
+        dout.writeUTF(getClassName());
+
+        if (getSuperClassName() != 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() != null
+                    ? rel.getCollectionType() : "to-one");
+        }
+
+        dout.flush();
+
+        MessageDigest md = MessageDigest.getInstance("SHA");
+        byte[] hashBytes = md.digest(bout.toByteArray());
+        long hash = 0;
+        for (int i = Math.min(hashBytes.length, 8) - 1; i>= 0; i--) {
+            hash = (hash<<  8) | (hashBytes[i]&  0xFF);
+        }
+        return hash;
+    }

  }


Dzmitry

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:
>
>> 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...
>
> Andrus
>
> On Oct 4, 2011, at 2:53 AM, Mike Kienenberger wrote:
>
>> 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.
>>
>> Ideally, it should return the same number whenever the same fields and
>> types are used for the generated class.
>>
>> 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
>>
>>
>> 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=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13119757#comment-13119757
]
>>>
>>> Ari Maniatis commented on CAY-1622:
>>> -----------------------------------
>>>
>>> Do we just want to add this to the velocity templates:
>>>
>>> private static final long serialVersionUID = ${random(1,9223372036854775807)};
>>>
>>>> Generated classes shouldn't produce serialVersionUID compiler warning
>>>> ---------------------------------------------------------------------
>>>>
>>>>                 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
>>>>
>>>> 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
>>>
>>>
>>>


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