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Date: Sat, 1 Aug 2009 09:05:17 -0700 (PDT)
From: "Pinaki Poddar (JIRA)" <jira@apache.org>
To: dev@openjpa.apache.org
Subject: [jira] Resolved: (OPENJPA-1198) Query by Example
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     [ https://issues.apache.org/jira/browse/OPENJPA-1198?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Pinaki Poddar resolved OPENJPA-1198.
------------------------------------

    Resolution: Fixed

> Query by Example
> ----------------
>
>                 Key: OPENJPA-1198
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-1198
>             Project: OpenJPA
>          Issue Type: New Feature
>          Components: query
>    Affects Versions: 2.0.0
>            Reporter: Pinaki Poddar
>            Assignee: Pinaki Poddar
>             Fix For: 2.0.0
>
>
> I am planning to add a new query by example feature to Criteria Query API.
> The proposed new method will appear in CriteriaBuilder to create a predicate.
> Comments welcome (see below for further details). 
>     /**
>      * Create a predicate based upon the attribute values of a given
>      * "example" entity instance. The predicate is the conjunction 
>      * or disjunction of predicates for subset of attribute of the entity.
>      * <br>
>      * By default, all the singular entity attributes (the basic, embedded
>      * and uni-cardinality relations) that have a non-null or non-default
>      * value for the example instance and are not an identity or version
>      * attribute are included. The comparable attributes can be further
>      * pruned by specifying variable list of attributes as the final argument.
>      * 
>      * @param example an instance of an entity class
>      * @param style specifies various aspects of comparison such as whether
>      * non-null attribute values be included, how string-valued attribute be 
>      * compared, whether the individual attribute based predicates are ANDed
>      * or ORed etc.
>      *  
>      * @return a predicate 
>      */
>     public <T> Predicate example(From<?, T> expression, T example, ComparisonStyle style,
>         <Attribute<? super T,?>>... excludes) ;
> ========================================================================
> The limitation is that the style is 'global' i.e. applies to all attributes. If we want to tune comparison style
> per attribute, the  API gets somewhat more cumbersome to use. Ideas are welcome.

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