The following issue has been updated:
Updater: Andrew Stevens (mailto:[EMAIL PROTECTED])
Date: Mon, 14 Feb 2005 4:04 PM
Changes:
Version changed to 1.2.2
Version changed to 1.2.1
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For a full history of the issue, see:
http://opensource.atlassian.com/projects/xdoclet/browse/XDT-941?page=history
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View the issue:
http://opensource.atlassian.com/projects/xdoclet/browse/XDT-941
Here is an overview of the issue:
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Key: XDT-941
Summary: hashcode bug in ValueObject when Relation is included
Type: Bug
Status: Open
Priority: Major
Original Estimate: Unknown
Time Spent: Unknown
Remaining: Unknown
Project: XDoclet
Components:
EJB Module
Versions:
1.2
1.2.1
1.2.2
Assignee: xdoclet-devel (Use for new issues)
Reporter: Sebastian Hennebrueder
Created: Thu, 24 Jun 2004 5:19 AM
Updated: Mon, 14 Feb 2005 4:04 PM
Environment: Windows 2000, eclipse 3.0 RC1, Myeclipse 3.08
Description:
When ValueObject of a entity EJB includes a 1:n relation to a second entity EJB
the hashCode of the generated Value Object changes each time it is calculated.
###### Reason is:
Bad calculation of hashcode
The following happens:
1)
internally the relation ValueObject is hold as a Collection. The getter returns
a new Array
public de.laliluna.test.AttributeValue[] getAttributeValues()
{
return (test.AttributeValue[])this.AttributeValues.toArray(new
test.AttributeValue[AttributeValues.size()]);
}
2)
hashcode is calculated like this
result = 37*result + ((this.getAttributeValues() != null) ?
this.getAttributeValues().hashCode() : 0);
3)
hashCode of a new Array is allways different. Take the following code to test
it:
private void testArrayHashCode(){
Collection c = new ArrayList();
for (int i = 0; i< 10 ; i++){
Object o[] = c.toArray();
System.out.println(o.hashCode());
}
}
###### Solution is:
when there is a 1:n relation the hashcode for the ValuObject should be
calculated like
AttributeValue attributeValue[]= this.getAttributeValues();
for (int i = 0; i < attributeValue.length; i++) {
result = 37*result + ((attributeValue[i]!= null) ?
attributeValue[i].hashCode() : 0);
}
###### References
Effektiv Java Programmieren, Joshua Bloch
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&frame=right&th=da63e9665f3f9e16&seekm=40b9fb89%240%2431679%24afc38c87%40news.optusnet.com.au#link1
Hope I could help
Sebastian
http://www.laliluna.de
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