juneau-doc/docs/Topics/05.juneau-config/12.ConfigStores/01.ConfigMemoryStore.html

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ConfigMemoryStore

<p>
	The {@link oaj.config.store.ConfigMemoryStore} class is simply an in-memory storage
	location for configuration files.
	There is no hard persistence and is used primarily for testing purposes.
</p>
<p>
	However, the implementation provides a good idea on how stores work (especially the write method):
</p>
<p class='bpcode w800'>
	<jk>public class</jk> ConfigMemoryStore <jk>extends</jk> ConfigStore {
	
		<jc>// Some methods ommitted.</jc>
		
		<jk>private final</jk> ConcurrentHashMap&lt;String,String&gt; <jf>cache</jf> = <jk>new</jk> ConcurrentHashMap&lt;&gt;();
		
		<ja>@Override</ja> <jc>/* ConfigStore */</jc>
		<jk>public synchronized</jk> String read(String name) {
			<jk>return</jk> <jsm>emptyIfNull</jsm>(<jf>cache</jf>.get(name));
		}
	
		<ja>@Override</ja> <jc>/* ConfigStore */</jc>
		<jk>public synchronized</jk> String write(String name, String expectedContents, String newContents) {
	
			<jc>// This is a no-op.</jc>
			<jk>if</jk> (<jsm>isEquals</jsm>(expectedContents, newContents))
				<jk>return null</jk>;
			
			String currentContents = read(name);
			
			<jk>if</jk> (expectedContents != <jk>null</jk> &amp;&amp; ! <jsm>isEquals</jsm>(currentContents, expectedContents)) 
				<jk>return</jk> currentContents;
			
			update(name, newContents);
			
			<jc>// Success!</jc>
			<jk>return null</jk>;
		}
	
		
		<ja>@Override</ja> <jc>/* ConfigStore */</jc>
		<jk>public synchronized</jk> ConfigMemoryStore update(String name, String newContents) {
			<jf>cache</jf>.put(name, newContents);
			<jk>super</jk>.update(name, newContents);  <jc>// Trigger any listeners.</jc>
			<jk>return this</jk>;
		}
	}
</p>