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     <h1 id="consuming-delta-responses">Consuming Delta Responses<a class="headerlink" href="#consuming-delta-responses" title="Permalink">&para;</a></h1>
 <p>Delta responses is a feature on top of OData 2.0 for requesting changes. The feature is defined in OData 4.0 and this is a preliminary and lightweight implementation close to the OData 4.0 specification <a href="http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398316">(see here)</a>.</p>
 <p>How delta responses can be produced by an OData service is documented here: <a href="/doc/odata2/tutorials/delta.html">server side delta responses</a>.</p>
 <h3 id="use-case">Use Case<a class="headerlink" href="#use-case" title="Permalink">&para;</a></h3>
 <p>A client reads a feed and later wants to get only the update of changed and deleted entries.</p>
 <h3 id="principle">Principle<a class="headerlink" href="#principle" title="Permalink">&para;</a></h3>
 <p>A client has to read a complete (paged) feed. With the last feed page the service has to provide a delta link instead of a next link. A delta link us usually the same feed url containing a delta token as proprietary query parameter. With the delta link the client can query the service again and gets back a delta feed containing entries which were changed or deleted since the complete feed was received.</p>
 <p><img alt="Class Diagram Delta Feeds" src="/img/DeltaFeedClassDiagram.png"/></p>
 <h3 id="examples">Examples<a class="headerlink" href="#examples" title="Permalink">&para;</a></h3>
 <p>Example for a delta link: <code>http://&lt;host&gt;:&lt;port&gt;/odata/Rooms?!deltatoken=123</code></p>
 <h5 id="delta-feed-handling">Delta Feed Handling<a class="headerlink" href="#delta-feed-handling" title="Permalink">&para;</a></h5>
 <p>Depends on the general client sample <a href="...">here</a></p>
 <pre><code>// retrieve a feed
 ODataFeed feed = client.readFeed("Container1", "Rooms", contentType);
 String deltaLink = feed.getFeedMetadata().getDeltaLink();

 // store feed data
 List&lt;ODataEntry&gt; entries = feed.getEntries();

 // get delta link from feed
 String deltaLink = feed.getFeedMetadata().getDeltaLink();

 // query delta feed using delta link
 ODataDeltaFeed deltaFeed = client.readDeltaFeed("Container1", "Rooms", contentType, deltaLink);

 List&lt;ODataEntry&gt; changedEntries = deltaFeed.getEntries();
 List&lt;DeletedEntryMetada) deletedEntries = deltaFeed.getDeletedEntries();

 // proceed with data handling of entries, changedEntries and deletedEntries
 </code></pre>
 <h5 id="response-deserialization">Response Deserialization<a class="headerlink" href="#response-deserialization" title="Permalink">&para;</a></h5>
 <p>Precondition: Query the delta link using any HTTP client.</p>
 <pre><code>InputStream content = ...; // retrieve content

 EdmEntityContainer entityContainer = edm.getEntityContainer("Container1");

 ODataFeed deltaFeed = EntityProvider.readDeltaFeed(contentType, entityContainer.getEntitySet("Rooms"),
   content, EntityProviderReadProperties.init().build());
 </code></pre>
 <h3 id="links">Links<a class="headerlink" href="#links" title="Permalink">&para;</a></h3>
 <ul>
 <li>Delta Links (for Atom and Json)</li>
 <li>Tombstones <a href="http://tools.ietf.org/html/rfc6721">RFC6721</a> for deleted entries in Atom format</li>
 <li>Deleted Entries in Json as a lightweight implementation of <a href="http://docs.oasis-open.org/odata/odata-json-format/v4.0/cos01/odata-json-format-v4.0-cos01.html#_Toc372793080">Delta Responses</a></li>
 </ul>

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	<h1 id="consuming-delta-responses">Consuming Delta Responses<a class="headerlink" href="#consuming-delta-responses" title="Permalink">¶</a></h1>
	<p>Delta responses is a feature on top of OData 2.0 for requesting changes. The feature is defined in OData 4.0 and this is a preliminary and lightweight implementation close to the OData 4.0 specification <a href="http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398316">(see here)</a>.</p>
	<p>How delta responses can be produced by an OData service is documented here: <a href="/doc/odata2/tutorials/delta.html">server side delta responses</a>.</p>
	<h3 id="use-case">Use Case<a class="headerlink" href="#use-case" title="Permalink">¶</a></h3>
	<p>A client reads a feed and later wants to get only the update of changed and deleted entries.</p>
	<h3 id="principle">Principle<a class="headerlink" href="#principle" title="Permalink">¶</a></h3>
	<p>A client has to read a complete (paged) feed. With the last feed page the service has to provide a delta link instead of a next link. A delta link us usually the same feed url containing a delta token as proprietary query parameter. With the delta link the client can query the service again and gets back a delta feed containing entries which were changed or deleted since the complete feed was received.</p>
	<p><img alt="Class Diagram Delta Feeds" src="/img/DeltaFeedClassDiagram.png"/></p>
	<h3 id="examples">Examples<a class="headerlink" href="#examples" title="Permalink">¶</a></h3>
	<p>Example for a delta link: <code>http://<host>:<port>/odata/Rooms?!deltatoken=123</code></p>
	<h5 id="delta-feed-handling">Delta Feed Handling<a class="headerlink" href="#delta-feed-handling" title="Permalink">¶</a></h5>
	<p>Depends on the general client sample <a href="...">here</a></p>
	<pre><code>// retrieve a feed
	ODataFeed feed = client.readFeed("Container1", "Rooms", contentType);
	String deltaLink = feed.getFeedMetadata().getDeltaLink();

	// store feed data
	List<ODataEntry> entries = feed.getEntries();

	// get delta link from feed
	String deltaLink = feed.getFeedMetadata().getDeltaLink();

	// query delta feed using delta link
	ODataDeltaFeed deltaFeed = client.readDeltaFeed("Container1", "Rooms", contentType, deltaLink);

	List<ODataEntry> changedEntries = deltaFeed.getEntries();
	List<DeletedEntryMetada) deletedEntries = deltaFeed.getDeletedEntries();

	// proceed with data handling of entries, changedEntries and deletedEntries
	</code></pre>
	<h5 id="response-deserialization">Response Deserialization<a class="headerlink" href="#response-deserialization" title="Permalink">¶</a></h5>
	<p>Precondition: Query the delta link using any HTTP client.</p>
	<pre><code>InputStream content = ...; // retrieve content

	EdmEntityContainer entityContainer = edm.getEntityContainer("Container1");

	ODataFeed deltaFeed = EntityProvider.readDeltaFeed(contentType, entityContainer.getEntitySet("Rooms"),
	content, EntityProviderReadProperties.init().build());
	</code></pre>
	<h3 id="links">Links<a class="headerlink" href="#links" title="Permalink">¶</a></h3>
	<ul>
	<li>Delta Links (for Atom and Json)</li>
	<li>Tombstones <a href="http://tools.ietf.org/html/rfc6721">RFC6721</a> for deleted entries in Atom format</li>
	<li>Deleted Entries in Json as a lightweight implementation of <a href="http://docs.oasis-open.org/odata/odata-json-format/v4.0/cos01/odata-json-format-v4.0-cos01.html#_Toc372793080">Delta Responses</a></li>
	</ul>

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