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POHibernate: update field in entity only if specific field is null
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  1. POHibernate: update field in entity only if specific field is null
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    copied!<p>I have the following:</p> <pre><code>public class Member { @Id @Column private String id; @Column private String location; // setters/getters } </code></pre> <p>I have to implement the following business rules:</p> <p>Set Location:</p> <ol> <li>Get member from DB based on id.</li> <li>If location is null, assign a value to location and save, otherwise do nothing.</li> </ol> <pre><code> public void setLocation(String id, String location){ Member m = memberDao.find(id); // assume m is not null if(null == m.getLocation()){ m.setLocation(location); memeberDao.saveOrUpdate(m); } else throw new MemberAlreadyHasALocationException(); } </code></pre> <p>Remove Location:</p> <ol> <li>Get member from DB based on id.</li> <li>If location has a non-null value and current value equals parameter value, set location to null and update, otherwise do nothing</li> </ol> <pre><code> public void removeLocation(String id, String location){ Member m = memberDao.find(id); if(m.getLocation() != null && m.getLocation.equalsIgnoreCase(location)){ m.setLocation(null); memeberDao.saveOrUpdate(m); } } </code></pre> <p>I am tasked with handling concurrency issues but I am not sure how to do this in hibernate. More specifically, how can I handle concurrent calls to setLocation for the same ID given that the entity with that ID does not currently have a location.</p> <p>Basically, the first update should win and the second should fail. </p> <p>Does it suffice to add a version to the Member class</p> <pre><code> @Version @Column(name="version") private Long version; </code></pre> <p>However, say that there is a gender field, I would like to be able to update the gender field without caring if the location is being updated by another transaction.</p> <p>Thanks.</p>
 

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