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PODesign patterns for converting objects with nested lists
 

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  1. PODesign patterns for converting objects with nested lists
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    <p>I have a service where the flow is basically the following:</p> <ol> <li>Receive an input object. This is just a POJO object and I don't have much say in the design of it.</li> <li>Convert to a normalized object for my service.</li> <li>Perform some business logic on the normalized object, and gather some extra data about it.</li> <li>Convert to an output object for another service that the data gets passed to. (Another POJO.)</li> <li>Pass the converted data to another service.</li> </ol> <p>What this means, though, is that a good portion of my service is converting from type <code>InputFoo</code> to type <code>NormalizedFoo</code> to type <code>OutputFoo</code>.</p> <p>This would be a pretty easy task. I'm using the Google Collections library and can have a class like this:</p> <pre><code>public class InputFooToNormalizedFooConverter implements Function&lt;InputFoo, NormalizedFoo&gt; { public NormalizedFoo apply(InputFoo input) { NormalizedFoo output = new NormalizedFoo(); output.setProperty(input.getProperty()); } } </code></pre> <p>and another class like this:</p> <pre><code>public class NormalizedFooFooToOutputFooConverter implements Function&lt;NormalizedFoo, OutputFoo&gt; { public NormalizedFoo apply(InputFoo input) { NormalizedFoo output = new NormalizedFoo(); output.setProperty(input.getProperty()); } } </code></pre> <p>But each type of Foo essentially has a hierarchy like so:</p> <pre><code>public class Foo { List&lt;Bar&gt; barItems; // .. other properties } public class Bar { List&lt;Baz&gt; bazItems; List&lt;Quux&gt; quuxItems; // .. other properties } public class Baz { // .. other properties } public class Quux { // .. other properties } </code></pre> <p>This means that I have <code>NormalizedFooToOutputFooConverter</code> that has a <code>NormalizedBarToOutputBarConverter implements Function&lt;NormalizedBar, OutputBar&gt;</code> type and so on and so forth.</p> <p>Even worse, the input doesn't <em>quite</em> match up exactly to the normalized model. It's more like</p> <pre><code>public class InputFoo { public List&lt;InputBar&gt; bars; public List&lt;InputBaz&gt; bazs; public List&lt;InputQuux&gt; quuxs; // .. other properties } public class InputBar { private String barId; // .. other properties } public class InputBaz { private String barId; private String bazId; // .. other properties } public class InputQuux { private String barId; private String quuxId; // .. other properties } </code></pre> <p>In these models, I can figure out which <code>Baz</code> and <code>Quux</code> belongs to which <code>Bar</code> based on the <code>barId</code> that each one has.</p> <p>At this point, I have about 20 different converters for going from <code>Input</code> to <code>Normalized</code> and <code>Normalized</code> to <code>Output</code>. And worse still, some of them have name like <code>ReallyLongInputTypeToReallyLongNormalizedTypeConverter</code> creating extremely long class names. I feel like I'm doing something wrong here, with all the converters. Is there a better way to organize my converters?</p>
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    1. PTQuestion
    1. USashays
    1. USashays
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    1. COInterfaces don't have member variables.
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      1. PODesign patterns for converting objects with nested lists
      1. USAlexander Pogrebnyak
    2. COFair enough, but I don't think it matters much to the example whether the Foo class is an interface or a class, since I don't have access to change it. I juat know the shape.
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      1. PODesign patterns for converting objects with nested lists
      1. USashays
    3. COMaybe some bean mapping framework like Orika can reduce some pain? http://code.google.com/p/orika/
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      1. PODesign patterns for converting objects with nested lists
      1. USdenis.solonenko
 

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