2021-02-04-merge-feature.html - gerrit/www.eclipse.org/ditto - Git at Google

 <!DOCTYPE html>
 <html>
 <head>
     <meta charset="utf-8">
 <meta http-equiv="X-UA-Compatible" content="IE=edge">
 <meta name="viewport" content="width=device-width, initial-scale=1">
 <meta name="description" content="">
 <meta name="keywords" content="bloghttpprotocol,  ">
 <title>  Support merge functionality for things resources </title>

 <link rel="stylesheet" href="css/syntax.css">
 <link rel="stylesheet" type="text/css" href="//cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css" crossorigin="anonymous">
 <link rel="stylesheet" href="css/modern-business.css">
 <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" crossorigin="anonymous">
 <link rel="stylesheet" href="css/customstyles.css">
 <link rel="stylesheet" href="css/boxshadowproperties.css">
 <link rel="stylesheet" href="css/theme-ditto.css">
 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:400,700|Source+Code+Pro:300,600|Titillium+Web:400,600,700">

 <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.4/jquery.min.js" crossorigin="anonymous"></script>
 <script src="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/js/bootstrap.min.js" crossorigin="anonymous"></script>
 <script src="//cdnjs.cloudflare.com/ajax/libs/anchor-js/2.0.0/anchor.min.js" crossorigin="anonymous"></script>
 <script src="js/toc.js"></script>
 <script src="js/customscripts.js"></script>

 <script type="application/ld+json">
 {
   "@context": "http://schema.org",
   "@type": "Organization",
   "url": "https://eclipse.org/ditto/",
   "logo": "https://eclipse.org/ditto/images/ditto.svg"
 }
 </script>

 <link rel="icon" type="image/png" href="images/favicon-16x16.png" sizes="16x16">
 <link rel="icon" type="image/png" href="images/favicon-32x32.png" sizes="32x32">
 <link rel="icon" type="image/png" href="images/favicon-96x96.png" sizes="96x96">

 <link rel="alternate" type="application/rss+xml" title="Eclipse Ditto Blog" href="https://www.eclipse.org/ditto/feed.xml">

 <!-- Eclipse Foundation cookie consent: -->
 <link rel="stylesheet" type="text/css" href="//www.eclipse.org/eclipse.org-common/themes/solstice/public/stylesheets/vendor/cookieconsent/cookieconsent.min.css" />
 <script src="//www.eclipse.org/eclipse.org-common/themes/solstice/public/javascript/vendor/cookieconsent/default.min.js"></script>

     <script>
         $(document).ready(function() {
             $("#tg-sb-link").click(function() {
                 $("#tg-sb-sidebar").toggle();
                 $("#tg-sb-content").toggleClass('col-md-9');
                 $("#tg-sb-content").toggleClass('col-md-12');
                 $("#tg-sb-icon").toggleClass('fa-toggle-on');
                 $("#tg-sb-icon").toggleClass('fa-toggle-off');
             });
         });
     </script>
 </head>


 <script>
     (function(w,d,s,l,i){
         w[l]=w[l]||[];
         w[l].push({'gtm.start':
             new Date().getTime(),event:'gtm.js'});
         var f=d.getElementsByTagName(s)[0],
             j=d.createElement(s),
             dl=l!='dataLayer'?'&l='+l:'';
         j.async=true;
         j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;
         f.parentNode.insertBefore(j,f);
     })(window,document,'script','dataLayer','GTM-5WLCZXC');
 </script>


 <body>
 <!-- Navigation -->
 <nav class="navbar navbar-inverse navbar-fixed-top">
     <div class="container topnavlinks">
         <div class="navbar-header">
             <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">
                 <span class="sr-only">Toggle navigation</span>
                 <span class="icon-bar"></span>
                 <span class="icon-bar"></span>
                 <span class="icon-bar"></span>
             </button>
             <a class="navbar-ditto-home" href="index.html">&nbsp;<img src="images/ditto_allwhite_symbolonly.svg" class="ditto-navbar-symbol" alt="Home"> <img src="images/ditto_allwhite_textonly.svg" class="ditto-navbar-symbol-text" alt="Eclipse Ditto™"></a>
         </div>
         <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
             <ul class="nav navbar-nav navbar-right">
                 <!-- toggle sidebar button -->
                 <!--<li><a id="tg-sb-link" href="#"><i id="tg-sb-icon" class="fa fa-toggle-on"></i> Nav</a></li>-->
                 <!-- entries without drop-downs appear here -->


                 <li><a href="blog.html">Blog</a></li>


                 <li><a href="intro-overview.html">Documentation</a></li>


                 <li><a href="http-api-doc.html">HTTP API</a></li>


                 <li><a href="sandbox.html">Sandbox</a></li>


                   <li><a href="https://github.com/eclipse/ditto" target="_blank">
                     <img src="images/GitHub-Mark-Light-32px.png" alt="Sources at GitHub">
                   </a></li>


                   <li><a href="https://github.com/eclipse/ditto-clients" target="_blank">
                     <img src="images/GitHub-Mark-Light-32px.png" alt="SDK sources at GitHub">SDKs
                   </a></li>


                   <li><a href="https://github.com/eclipse/ditto-examples" target="_blank">
                     <img src="images/GitHub-Mark-Light-32px.png" alt="Example sources at GitHub">examples
                   </a></li>


                 <!-- entries with drop-downs appear here -->
                 <!-- conditional logic to control which topnav appears for the audience defined in the configuration file.-->


                 <li class="dropdown">
                     <a href="#" class="dropdown-toggle" data-toggle="dropdown">Links<b class="caret"></b></a>
                     <ul class="dropdown-menu">


                         <li><a href="https://projects.eclipse.org/projects/iot.ditto" target="_blank">Eclipse Ditto Project</a></li>


                         <li><a href="https://www.eclipse.org/forums/index.php/f/364/" target="_blank">Forum</a></li>


                         <li><a href="https://ci.eclipse.org/ditto/" target="_blank">Jenkins</a></li>


                         <li><a href="https://dev.eclipse.org/mhonarc/lists/ditto-dev/" target="_blank">Mailing list archives</a></li>


                         <li><a href="https://gitter.im/eclipse/ditto" target="_blank">Gitter.im chat</a></li>


                     </ul>
                 </li>


                 <!--comment out this block if you want to hide search-->
                 <li>
                     <!--start search-->
                     <div id="search-demo-container">
                         <input type="text" id="search-input" placeholder="search...">
                         <ul id="results-container"></ul>
                     </div>
                     <script src="//cdnjs.cloudflare.com/ajax/libs/simple-jekyll-search/0.0.9/jekyll-search.js" type="text/javascript"></script>
                     <script type="text/javascript">
                             SimpleJekyllSearch.init({
                                 searchInput: document.getElementById('search-input'),
                                 resultsContainer: document.getElementById('results-container'),
                                 dataSource: 'search.json',
                                 searchResultTemplate: '<li><a href="{url}" title="Support merge functionality for things resources">{title}</a></li>',
                                 noResultsText: 'No results found.',
                                 limit: 10,
                                 fuzzy: true,
                     })
                     </script>
                     <!--end search-->
                 </li>
             </ul>
         </div>
     </div>
     <!-- /.container -->
 </nav>

 <!-- Page Content -->
 <div class="container">
   <div id="main">
     <!-- Content Row -->
     <div class="row">


         <!-- Content Column -->
         <div class="col-md-12" id="tg-sb-content">
             <!-- Look the author details up from the site config. -->


 <!-- Output author details if some exist. -->
 <!-- Output author details if some exist. -->
 <!---->
 <!--<span>-->
     <!--&lt;!&ndash; Mugshot. &ndash;&gt;-->
     <!--<img src="https://www.gravatar.com/avatar/4125883975796a6f81e380b371438549?s=135" alt="A photo of Stefan Maute" />-->

 <!--&lt;!&ndash; Personal Info. &ndash;&gt;-->
     <!--Written by <a href="https://github.com/stmaute" target="_blank">Stefan Maute</a>-->
 <!--</span>-->
 <!---->

 <article class="post" itemscope itemtype="http://schema.org/BlogPosting">

     <header class="post-header">
         <h1 class="post-title" itemprop="name headline">Support merge functionality for things resources</h1>
         <p class="post-meta">Published by <img src="https://www.gravatar.com/avatar/4125883975796a6f81e380b371438549?s=135" alt="A photo of Stefan Maute" style="width:50px;border-radius:50%;display:inline-block;margin-right:5px;" /><span itemprop="author" itemscope itemtype="http://schema.org/Person"><span itemprop="name"><a href="https://github.com/stmaute" target="_blank">Stefan Maute</a> </span></span> on <time datetime="2021-02-04T00:00:00+00:00" itemprop="datePublished">Feb 4, 2021</time> - Tags:


             <a href="tag_blog.html">blog</a>,


             <a href="tag_http.html">http</a>,


             <a href="tag_protocol.html">protocol</a>


         </p>


     </header>

     <div class="post-content" itemprop="articleBody">


 <!-- this handles the automatic toc. use ## for subheads to auto-generate the on-page minitoc. if you use html tags, you must supply an ID for the heading element in order for it to appear in the minitoc. -->
 <script>
 $( document ).ready(function() {
   // Handler for .ready() called.

 $('#toc').toc({ minimumHeaders: 0, listType: 'ul', showSpeed: 0, headers: 'h2,h3,h4' });

 /* this offset helps account for the space taken up by the floating toolbar. */
 $('#toc').on('click', 'a', function() {
   var target = $(this.getAttribute('href'))
     , scroll_target = target.offset().top

   $(window).scrollTop(scroll_target - 10);
   return false
 })

 });
 </script>

 <div id="toc"></div>


         <p>With the upcoming release of Eclipse Ditto <strong>version 2.0.0</strong> it will be possible to merge existing things and their subresources.</p>

 <h2 id="merge-functionality-for-things-resources">Merge functionality for things resources</h2>
 <p>Ditto now supports merging of existing things and all of its subresources with the provided payload in the request.
 This can be done by using the HTTP API with the PATCH method, via the Ditto protocol, and also by using the Ditto Java Client.
 For all three ways there is an example provided in this blog post.</p>

 <p>In contrast to the already existing PUT resource, this new functionality <strong>allows partial updates</strong> on a thing and all its subresources.
 To get more into detail, from now on it is possible to add or update attributes, and a feature property at the same time,
 without overwriting the complete thing. Another use case might be to update several feature properties within a single request
 and let all other parts of the thing untouched.</p>

 <p>Ditto uses the <a href="https://tools.ietf.org/html/rfc7396">JSON Merge Patch</a> semantics to merge the request body
 with the existing thing. In short, a JSON merge patch resembles the original JSON structure of a thing, and
 the fields provided in the patch are added, updated, or deleted in the existing thing.</p>

 <p>Please be aware that <code class="highlighter-rouge">null</code> values have a special meaning when applying a merge patch. A <code class="highlighter-rouge">null</code> value indicates
 the removal of existing fields in the updated thing.
 For more details and examples, please refer to <a href="https://tools.ietf.org/html/rfc7396">RFC-7396</a>.</p>

 <h3 id="permissions-to-merge-things-and-things-subresources">Permissions to merge things and things subresources</h3>
 <p>In order to execute such a merge operation, the authorized subject needs to have WRITE permission at all resources
 that should change by the merge. Consequently, if the permission is missing for some part of the merge,
 the merge is rejected and <strong>not</strong> applied at all.</p>

 <h2 id="examples">Examples</h2>

 <p>To demonstrate the new merge feature, we assume that the following thing already exists:</p>

 <div class="language-json highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span><span class="w">
   </span><span class="s2">"thingId"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme:coffeebrewer"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"policyId"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme:coffeebrewer-policy"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"definition"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme:coffeebrewer:0.1.0"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"attributes"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"manufacturer"</span><span class="p">:</span><span class="w"> </span><span class="s2">"ACME demo corp."</span><span class="p">,</span><span class="w">
     </span><span class="s2">"location"</span><span class="p">:</span><span class="w"> </span><span class="s2">"Berlin, main floor"</span><span class="p">,</span><span class="w">
     </span><span class="s2">"serialno"</span><span class="p">:</span><span class="w"> </span><span class="s2">"42"</span><span class="p">,</span><span class="w">
     </span><span class="s2">"model"</span><span class="p">:</span><span class="w"> </span><span class="s2">"Speaking coffee machine"</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"features"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"coffee-brewer"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"definition"</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="s2">"com.acme:coffeebrewer:0.1.0"</span><span class="p">],</span><span class="w">
       </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"brewed-coffees"</span><span class="p">:</span><span class="w"> </span><span class="mi">0</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">},</span><span class="w">
     </span><span class="s2">"water-tank"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"configuration"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
           </span><span class="s2">"smartMode"</span><span class="p">:</span><span class="w"> </span><span class="kc">true</span><span class="p">,</span><span class="w">
           </span><span class="s2">"brewingTemp"</span><span class="p">:</span><span class="w"> </span><span class="mi">87</span><span class="p">,</span><span class="w">
           </span><span class="s2">"tempToHold"</span><span class="p">:</span><span class="w"> </span><span class="mi">44</span><span class="p">,</span><span class="w">
           </span><span class="s2">"timeoutSeconds"</span><span class="p">:</span><span class="w"> </span><span class="mi">6000</span><span class="w">
         </span><span class="p">},</span><span class="w">
         </span><span class="s2">"status"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
           </span><span class="s2">"waterAmount"</span><span class="p">:</span><span class="w"> </span><span class="mi">731</span><span class="p">,</span><span class="w">
           </span><span class="s2">"temperature"</span><span class="p">:</span><span class="w"> </span><span class="mi">44</span><span class="w">
         </span><span class="p">}</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">}</span><span class="w">
   </span><span class="p">}</span><span class="w">
 </span><span class="p">}</span><span class="w">
 </span></code></pre></div></div>

 <h3 id="permissions-to-execute-the-example">Permissions to execute the example</h3>
 <p>For this example, the authorized subject needs to have unrestricted WRITE permissions on all affected paths
 of the JSON merge patch: <em>attributes/manufacturingYear</em>, <em>features/water-tank/properties/configuration/smartMode</em>, and
 <em>features/water-tank/properties/configuration/tempToHold</em>.
 The WRITE permission must not be revoked on any level further down the hierarchy.
 Consequently, it is also sufficient for the authorized subject to have unrestricted WRITE permission at root level or
 unrestricted WRITE permission at /attributes and /features etc.</p>

 <p>The following subparts will show how to use the merge feature via the HTTP API, the Ditto protocol
 and the Ditto Java Client.</p>

 <h3 id="merge-via-http-api">Merge via HTTP API</h3>
 <p>An existing thing can be merged via the HTTP API using the <em>PATCH</em> method with the following request body.
 Notice that this request will add the “manufacturingYear” to the attributes, update the “tempToHold” to 50 and
 delete the “smartMode” key from  the feature property “water-tank”.</p>

 <p>The <code class="highlighter-rouge">Content-Type</code> header for this request must be <em>application/merge-patch+json</em>.</p>

 <p>PATCH /things/com.acme:coffeebrewer</p>

 <div class="language-json highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span><span class="w">
   </span><span class="s2">"attributes"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"manufacturingYear"</span><span class="p">:</span><span class="w"> </span><span class="s2">"2020"</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"features"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"water-tank"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"configuration"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
           </span><span class="s2">"smartMode"</span><span class="p">:</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w">
           </span><span class="s2">"tempToHold"</span><span class="p">:</span><span class="w"> </span><span class="mi">50</span><span class="w">
         </span><span class="p">}</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">}</span><span class="w">
   </span><span class="p">}</span><span class="w">
 </span><span class="p">}</span><span class="w">
 </span></code></pre></div></div>

 <p>After the request was successfully performed the thing will look like this:</p>

 <div class="language-json highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span><span class="w">
   </span><span class="s2">"thingId"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme:coffeebrewer"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"policyId"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme:coffeebrewer-policy"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"definition"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme:coffeebrewer:0.1.0"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"attributes"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"manufacturer"</span><span class="p">:</span><span class="w"> </span><span class="s2">"ACME demo corp."</span><span class="p">,</span><span class="w">
     </span><span class="s2">"manufacturingYear"</span><span class="p">:</span><span class="w"> </span><span class="s2">"2020"</span><span class="p">,</span><span class="w">
     </span><span class="s2">"location"</span><span class="p">:</span><span class="w"> </span><span class="s2">"Berlin, main floor"</span><span class="p">,</span><span class="w">
     </span><span class="s2">"serialno"</span><span class="p">:</span><span class="w"> </span><span class="s2">"42"</span><span class="p">,</span><span class="w">
     </span><span class="s2">"model"</span><span class="p">:</span><span class="w"> </span><span class="s2">"Speaking coffee machine"</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"features"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"coffee-brewer"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"definition"</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="s2">"com.acme:coffeebrewer:0.1.0"</span><span class="p">],</span><span class="w">
       </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"brewed-coffees"</span><span class="p">:</span><span class="w"> </span><span class="mi">0</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">},</span><span class="w">
     </span><span class="s2">"water-tank"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"configuration"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
           </span><span class="s2">"brewingTemp"</span><span class="p">:</span><span class="w"> </span><span class="mi">87</span><span class="p">,</span><span class="w">
           </span><span class="s2">"tempToHold"</span><span class="p">:</span><span class="w"> </span><span class="mi">50</span><span class="p">,</span><span class="w">
           </span><span class="s2">"timeoutSeconds"</span><span class="p">:</span><span class="w"> </span><span class="mi">6000</span><span class="w">
         </span><span class="p">},</span><span class="w">
         </span><span class="s2">"status"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
           </span><span class="s2">"waterAmount"</span><span class="p">:</span><span class="w"> </span><span class="mi">731</span><span class="p">,</span><span class="w">
           </span><span class="s2">"temperature"</span><span class="p">:</span><span class="w"> </span><span class="mi">44</span><span class="w">
         </span><span class="p">}</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">}</span><span class="w">
   </span><span class="p">}</span><span class="w">
 </span><span class="p">}</span><span class="w">
 </span></code></pre></div></div>

 <p>It is also possible to apply the <em>PATCH</em> method to all subresources of a thing, e.g. merging only the attributes of a thing.  <br />
 Check out the newly added <em>PATCH</em> resources in our <a href="http-api-doc.html">HTTP API</a>.</p>

 <h3 id="merge-via-ditto-protocol">Merge via Ditto protocol</h3>
 <p>It is also possible to merge the existing thing via the Ditto protocol.
 Applying the following Ditto merge command to the existing thing will lead to the same result as in the above HTTP example.</p>

 <div class="language-json highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span><span class="w">
   </span><span class="s2">"topic"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme/coffeebrewer/things/twin/commands/merge"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"headers"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"content-type"</span><span class="p">:</span><span class="w"> </span><span class="s2">"application/merge-patch+json"</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"path"</span><span class="p">:</span><span class="w"> </span><span class="s2">"/"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"value"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"thingId"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme:coffeebrewer"</span><span class="p">,</span><span class="w">
     </span><span class="s2">"attributes"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"manufacturingYear"</span><span class="p">:</span><span class="w"> </span><span class="s2">"2020"</span><span class="w">
     </span><span class="p">},</span><span class="w">
     </span><span class="s2">"features"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"water-tank"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
           </span><span class="s2">"configuration"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
             </span><span class="s2">"smartMode"</span><span class="p">:</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w">
             </span><span class="s2">"tempToHold"</span><span class="p">:</span><span class="w"> </span><span class="mi">50</span><span class="w">
           </span><span class="p">}</span><span class="w">
         </span><span class="p">}</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">}</span><span class="w">
   </span><span class="p">}</span><span class="w">
 </span><span class="p">}</span><span class="w">
 </span></code></pre></div></div>

 <p>Another Ditto protocol example to merge a feature property:</p>

 <div class="language-json highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span><span class="w">
   </span><span class="s2">"topic"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme/coffeebrewer/things/twin/commands/merge"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"headers"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"content-type"</span><span class="p">:</span><span class="w"> </span><span class="s2">"application/merge-patch+json"</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"path"</span><span class="p">:</span><span class="w"> </span><span class="s2">"/features/coffee-brewer/properties/brewed-coffees"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"value"</span><span class="p">:</span><span class="w"> </span><span class="mi">42</span><span class="w">
 </span><span class="p">}</span><span class="w">
 </span></code></pre></div></div>

 <h3 id="using-the-ditto-client-to-merge-things">Using the ditto-client to merge things</h3>
 <p>The merge functionality is also supported via the <a href="client-sdk-java.html">Ditto Java Client</a>
 with the upcoming (<strong>Ditto Java Client version 2.0.0</strong>).</p>

 <p>Example for merging a thing with the Ditto Java Client:</p>

 <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">final</span> <span class="n">String</span> <span class="n">THING_ID</span> <span class="o">=</span> <span class="s">"com.acme:coffeebrewer"</span><span class="o">;</span>
 <span class="kd">final</span> <span class="n">String</span> <span class="n">FEATURE_ID</span> <span class="o">=</span> <span class="s">"water-tank"</span><span class="o">;</span>
 <span class="kd">final</span> <span class="n">JsonPointer</span> <span class="n">ATTRIBUTE_KEY</span> <span class="o">=</span> <span class="n">JsonFactory</span><span class="o">.</span><span class="na">newPointer</span><span class="o">(</span><span class="s">"manufacturingYear"</span><span class="o">);</span>
 <span class="kd">final</span> <span class="n">String</span> <span class="n">ATTRIBUTE_VALUE</span> <span class="o">=</span> <span class="s">"2020"</span><span class="o">;</span>
 <span class="kd">final</span> <span class="n">Feature</span> <span class="n">FEATURE</span> <span class="o">=</span> <span class="n">ThingsModelFactory</span><span class="o">.</span><span class="na">newFeatureBuilder</span><span class="o">()</span>
         <span class="o">.</span><span class="na">withId</span><span class="o">(</span><span class="n">FEATURE_ID</span><span class="o">)</span>
         <span class="o">.</span><span class="na">properties</span><span class="o">(</span><span class="n">ThingsModelFactory</span><span class="o">.</span><span class="na">newFeaturePropertiesBuilder</span><span class="o">()</span>
                         <span class="o">.</span><span class="na">set</span><span class="o">(</span><span class="s">"smartMode"</span><span class="o">,</span> <span class="kc">false</span><span class="o">)</span>
                         <span class="o">.</span><span class="na">set</span><span class="o">(</span><span class="s">"tempToHold"</span><span class="o">,</span> <span class="mi">50</span><span class="o">)</span>
                         <span class="o">.</span><span class="na">build</span><span class="o">())</span>
         <span class="o">.</span><span class="na">build</span><span class="o">();</span>

 <span class="kd">final</span> <span class="n">Thing</span> <span class="n">THING</span> <span class="o">=</span> <span class="n">ThingsModelFactory</span><span class="o">.</span><span class="na">newThingBuilder</span><span class="o">()</span>
         <span class="o">.</span><span class="na">setId</span><span class="o">(</span><span class="n">THING_ID</span><span class="o">)</span>
         <span class="o">.</span><span class="na">setAttribute</span><span class="o">(</span><span class="n">ATTRIBUTE_KEY_NEW</span><span class="o">,</span> <span class="n">JsonFactory</span><span class="o">.</span><span class="na">newValue</span><span class="o">(</span><span class="n">ATTRIBUTE_VALUE</span><span class="o">))</span>
         <span class="o">.</span><span class="na">setFeature</span><span class="o">(</span><span class="n">FEATURE</span><span class="o">)</span>
         <span class="o">.</span><span class="na">build</span><span class="o">();</span>

 <span class="c1">// initialize the ditto-client</span>
 <span class="kd">final</span> <span class="n">DittoClient</span> <span class="n">dittoClient</span> <span class="o">=</span> <span class="o">...</span> <span class="o">;</span>

 <span class="n">dittoClient</span><span class="o">.</span><span class="na">twin</span><span class="o">().</span><span class="na">merge</span><span class="o">(</span><span class="n">THING_ID</span><span class="o">,</span> <span class="n">THING</span><span class="o">)</span>
         <span class="o">.</span><span class="na">whenComplete</span><span class="o">(((</span><span class="n">adaptable</span><span class="o">,</span> <span class="n">throwable</span><span class="o">)</span> <span class="o">-&gt;</span> <span class="o">{</span>
             <span class="k">if</span> <span class="o">(</span><span class="n">throwable</span> <span class="o">!=</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span>
                 <span class="n">LOGGER</span><span class="o">.</span><span class="na">error</span><span class="o">(</span><span class="s">"Received error while sending MergeThing: '{}' "</span><span class="o">,</span> <span class="n">throwable</span><span class="o">.</span><span class="na">toString</span><span class="o">());</span>
             <span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
                 <span class="n">LOGGER</span><span class="o">.</span><span class="na">info</span><span class="o">(</span><span class="s">"Received response for MergeThing: '{}'"</span><span class="o">,</span> <span class="n">adaptable</span><span class="o">);</span>
             <span class="o">}</span>
         <span class="o">}));</span>
 </code></pre></div></div>

 <p>After running this code snippet, the existing thing should look like the above result for the HTTP example.</p>

 <p>More examples for merging an attribute, all attributes and a feature property via Ditto Java Client.</p>
 <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1">// initialize the ditto-client</span>
 <span class="kd">final</span> <span class="n">DittoClient</span> <span class="n">dittoClient</span> <span class="o">=</span> <span class="o">...</span> <span class="o">;</span>

     <span class="c1">// merge attribute</span>
     <span class="n">dittoClient</span><span class="o">.</span><span class="na">twin</span><span class="o">()</span>
         <span class="o">.</span><span class="na">forId</span><span class="o">(</span><span class="s">"com.acme:coffeebrewer"</span><span class="o">)</span>
         <span class="o">.</span><span class="na">mergeAttribute</span><span class="o">(</span><span class="s">"manufacturingYear"</span><span class="o">,</span> <span class="s">"2021"</span><span class="o">)</span>
         <span class="o">.</span><span class="na">whenComplete</span><span class="o">(...);</span>

     <span class="c1">// merge attributes</span>
     <span class="n">dittoClient</span><span class="o">.</span><span class="na">twin</span><span class="o">()</span>
         <span class="o">.</span><span class="na">forId</span><span class="o">(</span><span class="s">"com.acme:coffeebrewer"</span><span class="o">)</span>
         <span class="o">.</span><span class="na">mergeAttributes</span><span class="o">(</span><span class="n">JsonObject</span><span class="o">.</span><span class="na">newBuilder</span><span class="o">().</span><span class="na">set</span><span class="o">(</span><span class="s">"manufacturingYear"</span><span class="o">,</span> <span class="s">"2021"</span><span class="o">).</span><span class="na">build</span><span class="o">())</span>
         <span class="o">.</span><span class="na">whenComplete</span><span class="o">(...);</span>

     <span class="c1">// merge feature property</span>
     <span class="n">dittoClient</span><span class="o">.</span><span class="na">twin</span><span class="o">()</span>
         <span class="o">.</span><span class="na">forFeature</span><span class="o">(</span><span class="s">"com.acme:coffeebrewer"</span><span class="o">,</span> <span class="s">"water-tank"</span><span class="o">)</span>
         <span class="o">.</span><span class="na">mergeProperty</span><span class="o">(</span><span class="s">"configuration/smartMode"</span><span class="o">,</span> <span class="kc">false</span><span class="o">)</span>
         <span class="o">.</span><span class="na">whenComplete</span><span class="o">(...);</span>
 </code></pre></div></div>

 <h2 id="merge-events">Merge events</h2>
 <p>In this section we want to cover the new <code class="highlighter-rouge">ThingMerged</code> event which will be emitted after successfully applying an <code class="highlighter-rouge">MergeThing</code> command.
 For every HTTP request or Ditto protocol message which performs a merge operation on a thing there will be sent out
 exactly one <code class="highlighter-rouge">ThingMerged</code> event. This event contains the <strong>path</strong> and the <strong>value</strong> of the merge operation.
 The <strong>path</strong> describes on which level of the thing the <strong>value</strong> was merged.</p>

 <h3 id="merge-event-example">Merge event example</h3>
 <p>Let’s assume we want to patch/merge multiple feature properties at once.
 PATCH /things/com.acme:coffeebrewer/features</p>

 <div class="language-json highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span><span class="w">
   </span><span class="s2">"coffee-brewer"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"brewed-coffees"</span><span class="p">:</span><span class="w"> </span><span class="mi">10</span><span class="w">
     </span><span class="p">}</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"water-tank"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"configuration"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"smartMode"</span><span class="p">:</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w">
         </span><span class="s2">"tempToHold"</span><span class="p">:</span><span class="w"> </span><span class="mi">30</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">}</span><span class="w">
   </span><span class="p">}</span><span class="w">
 </span><span class="p">}</span><span class="w">
 </span></code></pre></div></div>

 <p>The following <code class="highlighter-rouge">ThingMerged</code> event is emitted:</p>

 <div class="language-json highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span><span class="w">
   </span><span class="s2">"topic"</span><span class="p">:</span><span class="w"> </span><span class="s2">"com.acme/coffeebrewer/things/twin/events/merged"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"headers"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"content-type"</span><span class="p">:</span><span class="w"> </span><span class="s2">"application/merge-patch+json"</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"path"</span><span class="p">:</span><span class="w"> </span><span class="s2">"/features"</span><span class="p">,</span><span class="w">
   </span><span class="s2">"value"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
     </span><span class="s2">"coffee-brewer"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"brewed-coffees"</span><span class="p">:</span><span class="w"> </span><span class="mi">10</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">},</span><span class="w">
     </span><span class="s2">"water-tank"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
       </span><span class="s2">"properties"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
         </span><span class="s2">"configuration"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span><span class="w">
           </span><span class="s2">"smartMode"</span><span class="p">:</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w">
           </span><span class="s2">"tempToHold"</span><span class="p">:</span><span class="w"> </span><span class="mi">30</span><span class="w">
         </span><span class="p">}</span><span class="w">
       </span><span class="p">}</span><span class="w">
     </span><span class="p">}</span><span class="w">
   </span><span class="p">},</span><span class="w">
   </span><span class="s2">"revision"</span><span class="p">:</span><span class="w"> </span><span class="mi">42</span><span class="p">,</span><span class="w">
   </span><span class="s2">"timestamp"</span><span class="p">:</span><span class="w"> </span><span class="s2">"2021-02-04T09:42:39Z"</span><span class="w">
 </span><span class="p">}</span><span class="w">
 </span></code></pre></div></div>

 <h2 id="feedback">Feedback?</h2>

 <p>Please <a href="feedback.html">get in touch</a> if you have feedback or questions towards this new functionality.</p>

 <p><br />
 <br /></p>
 <figure><img class="docimage" src="images/ditto.svg" alt="Ditto" style="max-width: 500px" /></figure>

 <p>–<br />
 The Eclipse Ditto team</p>


     </div>


 </article>

 <hr class="shaded"/>

 <footer>
             <div class="row">
                 <div class="col-lg-12 footer">
                     <div class="logo">
                         <a href="https://eclipse.org"><img src="images/eclipse_foundation_logo.svg" alt="Eclipse logo"/></a>
                     </div>
                     <p class="notice">
                         &copy;2021 Eclipse Ditto™.
                          Site last generated: Apr 8, 2021 <br />
                     </p>
                     <div class="quickLinks">
                         <a href="https://www.eclipse.org/legal/privacy.php" target="_blank">
                             &gt; Privacy Policy
                         </a>
                         <a href="https://www.eclipse.org/legal/termsofuse.php" target="_blank">
                             &gt; Terms of Use
                         </a>
                         <a href="https://www.eclipse.org/legal/copyright.php" target="_blank">
                             &gt; Copyright Agent
                         </a>
                         <a href="https://www.eclipse.org/legal" target="_blank">
                             &gt; Legal
                         </a>
                         <a href="https://www.eclipse.org/legal/epl-2.0/" target="_blank">
                             &gt; License
                         </a>
                         <a href="https://eclipse.org/security" target="_blank">
                             &gt; Report a Vulnerability
                         </a>
                     </div>
                 </div>
             </div>
 </footer>


         </div>
     <!-- /.row -->
 </div>
 <!-- /.container -->
 </div>
 <!-- /#main -->
     </div>

 </body>
 </html>