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POObjectify - how do I ensure that my objects are synchronized
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  1. POObjectify - how do I ensure that my objects are synchronized
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    copied!<p>I have a simple web service, which offers two methods:</p> <p><strong>addHighscore</strong> - adds new entry to highscore if either MAX is not reached or score is higher then least entry</p> <pre><code>// check if free place in highscore int count = ofy().load().type(Highscore.class) .filter("difficulty", difficulty).count(); boolean insert = count + 1 &lt; MAX; if(insert == false) { // get last element and free if possible Highscore least = ofy().load().type(Highscore.class) .filter("difficulty", difficulty).order("-score").order("-date") .first().now(); if(highscore.getScore() &gt; least.getScore()) { ofy().delete().entity(least).now(); insert = true; } } // insert if(insert == true) ofy().save().entity(highscore).now(); </code></pre> <p><strong>getHighscore</strong> - get highscore</p> <pre><code>List&lt;Highscore&gt; list = ofy().load().type(Highscore.class) .filter("difficulty", difficulty).order("score DESC").list(); </code></pre> <p>Now my problem is the following: How do I ensure that 1) call to addHighscore sees the result of the previous call 2) a client that calls addHighscore and then getHighscore sees his results</p> <p>I read the explanation at <a href="https://developers.google.com/appengine/docs/java/datastore/structuring_for_strong_consistency" rel="nofollow">https://developers.google.com/appengine/docs/java/datastore/structuring_for_strong_consistency</a> but i have no clue how i could apply that to my own example. What could I use as ancestor key?</p> <p>Can somebody explain me how I can correct this? (If possible with pseudycode samples)</p> <p><strong>UPDATE</strong></p> <p>I remodelled my addHighscore function which now looks like this</p> <pre><code> boolean insert = ofy().transact(new Work&lt;Boolean&gt;() { @Override public Boolean run() { // run sync Key&lt;Sync&gt; ancestor = Sync.getKey(); if(ofy().load().key(ancestor).now() == null) ofy().save().entities(new Sync()).now(); // check if free place in highscore int count = ofy().load().type(Highscore.class).ancestor(ancestor).filter("difficulty", difficulty).order("-score").order("date").count(); boolean insert = count &lt; MAX; if(insert == false) { // get last element and free if possible Highscore least = ofy().load().type(Highscore.class).ancestor(ancestor).filter("difficulty", difficulty).order("-score").order("date").first().now(); // order DESC with - if(highscore.getScore() &gt; least.getScore()) { ofy().delete().entity(least).now(); insert = true; } } // insert if(insert == true) ofy().save().entity(highscore).now(); return insert; } }); </code></pre> <p>with sync</p> <pre><code>@Entity public class Sync { @Id long id = 1; public static Key&lt;Sync&gt; getKey() { return Key.create(Sync.class, 1); } } </code></pre> <p>and furthermore I added a @Parent annotation to Highscore via <code>@Parent Key&lt;Sync&gt; parent = Sync.getKey()</code></p> <p>This seems to work - I wonder if this is a proper solution. Or is there a better way to do it?</p>
 

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