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POSaving complex aggregates using Repository Pattern
 

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  1. POSaving complex aggregates using Repository Pattern
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    <p>We have a complex aggregate (sensitive names obfuscated for confidentiality reasons).</p> <p>The root, R, is composed of collections of Ms, As, Cs, Ss. Ms have collections of other low-level details. etc etc</p> <p>R really is an aggregate (no fair suggesting we split it!)</p> <p>We use lazy loading to retrieve the details. No problem there.</p> <p>But we are struggling a little with how to save such a complex aggregate. </p> <p>From the caller's point of view:</p> <pre><code>r = repository.find(id); r.Ps.add(factory.createP()); r.Cs[5].updateX(123); r.Ms.removeAt(5); repository.save(r); </code></pre> <p>Our competing solutions are:</p> <ol> <li><p>Dirty flags Each entity in the aggregate in the aggregate has a dirty flag. The save() method in the repository walks the tree looking for dirty objects and saves them. Deletes and adds are a little trickier - especially with lazy-loading - but doable.</p></li> <li><p>Event listener accumulates changes. Repository subscribes a listener to changes and accumulates events. When save is called, the repository grabs all the change events and writes them to the DB.</p></li> <li><p>Give up on repository pattern. Implement overloaded save methods to save the parts of the aggregate separately. The original example would become:</p> <p>r = repository.find(id); r.Ps.add(factory.createP()); r.Cs[5].updateX(123); r.Ms.removeAt(5); repository.save(r.Ps); repository.save(r.Cs); repository.save(r.Ms);</p></li> </ol> <p>(or worse)</p> <p>Advice please! What should we do?</p>
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    1. USKevin Lawrence
    1. USKevin Lawrence
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      1. POSaving complex aggregates using Repository Pattern
      1. USJeff Sternal
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    1. COI take it you aren't using an off-the-shelf ORM, which would generally take care of this for you?
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      1. POSaving complex aggregates using Repository Pattern
      1. USJasonTrue
    2. COThat's correct.
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      1. POSaving complex aggregates using Repository Pattern
      1. USKevin Lawrence
 

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