commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Henri Yandell (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LANG-403) HashcodeBuilder is broken for Annotations
Date Tue, 05 Jan 2010 06:32:54 GMT

    [ https://issues.apache.org/jira/browse/LANG-403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796555#action_12796555
] 

Henri Yandell commented on LANG-403:
------------------------------------

Looking into this - what I'm not getting here is why you would use HashCodeBuidler to build
an annotation's hashcode; or rather, why you would make a class that implements an annotation
like this. I'm thinking this is a theoretical issue only. 

> HashcodeBuilder is broken for Annotations
> -----------------------------------------
>
>                 Key: LANG-403
>                 URL: https://issues.apache.org/jira/browse/LANG-403
>             Project: Commons Lang
>          Issue Type: Bug
>          Components: lang.builder.*
>    Affects Versions: 2.3
>            Reporter: Jay Liang
>             Fix For: 3.0
>
>
> HashCodeBuilder does not produce a correct hashCode that conforms to java language specs.
Running the following code snippets, i get 
> @Simple$CustomAnnotation(name=blah, type=class java.lang.String) hashCode= 895255138
> Simple$CustomAnnotationImpl@665753[_name=blah,_type=class java.lang.String] hashCode=
122852694
> hashCode should be 895255138
> The hashCode should computed according to http://java.sun.com/j2se/1.5.0/docs/api/java/lang/annotation/Annotation.html#hashCode()
for annotations.
> {code:java}
> public class Simple{
>   @Retention(RetentionPolicy.RUNTIME)
>   @Target({FIELD, METHOD, PARAMETER})
>   private @interface CustomAnnotation{
>     public String name();
>     public Class<?> type();
>   }
>   private static class CustomAnnotationImpl implements CustomAnnotation{
>     final String _name;
>     final Class<?> _type;
>     public CustomAnnotationImpl(String name, Class<?> type) {
>       _name = name;
>       _type = type;
>     }
>     public String name() {
>       return _name;
>     }
>     public Class<?> type() {
>       return _type;
>     }
>     public Class<? extends Annotation> annotationType() {
>       return CustomAnnotation.class;
>     }
>     @Override
>     public int hashCode() {
>       return HashCodeBuilder.reflectionHashCode(this);
>     }
>     /**
>      * This conform to specs defined at http://java.sun.com/j2se/1.5.0/docs/api/java/lang/annotation/Annotation.html#hashCode
>      * @return good annotation hashCode
>      */
>     public int goodHashCode() {
>       return (127 * "name".hashCode() ^ _name.hashCode()) + (127 *"type".hashCode() ^
_type.hashCode());
>     }
>     
>     @Override
>     public String toString() {
>       return ToStringBuilder.reflectionToString(this);
>     }
>   }
>   private static class Test{
>     @CustomAnnotation(name="blah", type=String.class)
>     String _blah;
>     @Override
>     public String toString() {
>       return ToStringBuilder.reflectionToString(this);
>     }
>   }
>   
>   public static void main(String[] args) throws Exception{
>     for(Field f : Test.class.getDeclaredFields()){
>       for(Annotation a : f.getAnnotations()){
>         System.out.println(a + " hashCode= " + a.hashCode());
>         CustomAnnotationImpl c =  new Simple.CustomAnnotationImpl("blah", String.class);
>         System.out.println(c + " hashCode= " + c.hashCode());
>         System.out.println("hashCode should be "+ c.goodHashCode());
>       }
>     }
>   }
> } 
> {code}

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message