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    <a href="/">Immutables</a> &larr;

    <h1>DynamoDB V1 SDK integration <iframe src="https://ghbtns.com/github-btn.html?user=immutables&repo=immutables&type=star&count=true&size=large" frameborder="0" scrolling="0" width="160px" height="30px"></iframe>
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  <h2 id="overview">Overview</h2>

<p><a href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.html"><code class="language-plaintext highlighter-rouge">DynamoDBMapper</code></a> provides an easy way to map POJOs to data in <a href="https://docs.aws.amazon.com/dynamodb/index.html"><code class="language-plaintext highlighter-rouge">DynamoDB</code></a>.
Most of the code POJOs are verbose and it makes a perfect sense to use <em>Immutables</em> to reduce boilerplate.</p>

<h2 id="how-to-use">How to use</h2>

<p><strong>NOTE</strong>: provided snippets show the idea that could be improved and / or modified to address specific needs.</p>

<p>In the project with more than one entity it makes sense to create custom <a href="/style.html"><code class="language-plaintext highlighter-rouge">Style</code></a> that would allow
to enable <em>Immutables</em> for POJO.</p>

<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nd">@Target</span><span class="o">(</span><span class="nc">ElementType</span><span class="o">.</span><span class="na">TYPE</span><span class="o">)</span>
<span class="nd">@Retention</span><span class="o">(</span><span class="nc">RetentionPolicy</span><span class="o">.</span><span class="na">CLASS</span><span class="o">)</span>
<span class="nd">@Value</span><span class="o">.</span><span class="na">Style</span><span class="o">(</span>
        <span class="n">create</span> <span class="o">=</span> <span class="s">"new"</span><span class="o">,</span>
        <span class="n">isInitialized</span> <span class="o">=</span> <span class="s">"wasInitialized"</span><span class="o">,</span>
        <span class="n">allParameters</span> <span class="o">=</span> <span class="kc">true</span><span class="o">,</span>
        <span class="n">beanFriendlyModifiables</span> <span class="o">=</span> <span class="kc">true</span><span class="o">,</span>
        <span class="n">passAnnotations</span> <span class="o">=</span> <span class="o">{</span>
                <span class="nc">DynamoDBTable</span><span class="o">.</span><span class="na">class</span><span class="o">,</span>
                <span class="nc">DynamoDBHashKey</span><span class="o">.</span><span class="na">class</span><span class="o">,</span>
                <span class="nc">DynamoDBRangeKey</span><span class="o">.</span><span class="na">class</span><span class="o">,</span>
                <span class="nc">DynamoDBAttribute</span><span class="o">.</span><span class="na">class</span><span class="o">,</span>
                <span class="nc">DynamoDBTyped</span><span class="o">.</span><span class="na">class</span><span class="o">,</span>
                <span class="nc">DynamoDBTypeConvertedEnum</span><span class="o">.</span><span class="na">class</span>
                <span class="c1">// more DynamoDB annotations to be added</span>
        <span class="o">}</span>
<span class="o">)</span>
<span class="kd">public</span> <span class="nd">@interface</span> <span class="nc">DynamoDBStyle</span> <span class="o">{}</span>
</code></pre></div></div>

<p>Application of the newly created style could look like:</p>

<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nd">@DynamoDBStyle</span>
<span class="nd">@Value</span><span class="o">.</span><span class="na">Immutable</span>
<span class="nd">@Value</span><span class="o">.</span><span class="na">Modifiable</span>
<span class="nd">@DynamoDBTable</span><span class="o">(</span><span class="n">tableName</span> <span class="o">=</span> <span class="s">"people"</span><span class="o">)</span>
<span class="kd">public</span> <span class="kd">interface</span> <span class="nc">Person</span> <span class="o">{</span>
    <span class="nd">@DynamoDBHashKey</span><span class="o">(</span><span class="n">attributeName</span> <span class="o">=</span> <span class="s">"name"</span><span class="o">)</span>
    <span class="nc">String</span> <span class="nf">getName</span><span class="o">();</span>

    <span class="nd">@DynamoDBAttribute</span><span class="o">(</span><span class="n">attributeName</span> <span class="o">=</span> <span class="s">"age"</span><span class="o">)</span>
    <span class="kt">int</span> <span class="nf">getAge</span><span class="o">();</span>
<span class="o">}</span>
</code></pre></div></div>

<p>We apply both <code class="language-plaintext highlighter-rouge">@Value.Immutable</code> and <code class="language-plaintext highlighter-rouge">@Value.Modifiable</code>. The former is bread and butter
of <em>Immutables</em> as it provides all nice features while the latter enables usage
of generated classes with <a href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.html"><code class="language-plaintext highlighter-rouge">DynamoDBMapper</code></a>. <a href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.html"><code class="language-plaintext highlighter-rouge">DynamoDBMapper</code></a>
expects the POJO to have no-arg ctor with setters and newly created <code class="language-plaintext highlighter-rouge">DynamoDBStyle</code>
annotation configures <em>Immutables</em> to generated the required structure.</p>

<p>The usage is pretty straightforward with only one caveat: <code class="language-plaintext highlighter-rouge">Modifiable...</code> implementation
should be used any time data is loaded from the <a href="https://docs.aws.amazon.com/dynamodb/index.html"><code class="language-plaintext highlighter-rouge">DynamoDB</code></a>.</p>

<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1">// assuming mapper is an instance of `DynamoDBMapper`</span>

<span class="nc">Person</span> <span class="n">john</span> <span class="o">=</span> <span class="nc">ImmutablePerson</span><span class="o">.</span><span class="na">of</span><span class="o">(</span><span class="s">"John"</span><span class="o">,</span> <span class="mi">42</span><span class="o">);</span>

<span class="n">mapper</span><span class="o">.</span><span class="na">save</span><span class="o">(</span><span class="n">john</span><span class="o">);</span>
<span class="n">john</span> <span class="o">=</span> <span class="n">mapper</span><span class="o">.</span><span class="na">load</span><span class="o">(</span><span class="nc">ModifiablePerson</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="s">"John"</span><span class="o">);</span>

<span class="nc">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">john</span><span class="o">);</span>  <span class="c1">// prints ModifiablePerson{name=John, age=42}</span>
</code></pre></div></div>


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