mirror of
https://github.com/corda/corda.git
synced 2024-12-20 13:33:12 +00:00
341 lines
20 KiB
HTML
341 lines
20 KiB
HTML
|
|
|
|
<!DOCTYPE html>
|
|
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
|
|
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
|
|
<head>
|
|
<meta charset="utf-8">
|
|
|
|
<meta name="viewport" content="width=device-width, initial-scale=1.0">
|
|
|
|
<title>Using attachments — R3 Corda latest documentation</title>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<link rel="stylesheet" href="_static/css/custom.css" type="text/css" />
|
|
|
|
|
|
|
|
|
|
|
|
<link rel="top" title="R3 Corda latest documentation" href="index.html"/>
|
|
<link rel="next" title="Event scheduling" href="event-scheduling.html"/>
|
|
<link rel="prev" title="Writing oracle services" href="oracles.html"/>
|
|
|
|
|
|
<script src="_static/js/modernizr.min.js"></script>
|
|
|
|
</head>
|
|
|
|
<body class="wy-body-for-nav" role="document">
|
|
|
|
<div class="wy-grid-for-nav">
|
|
|
|
|
|
<nav data-toggle="wy-nav-shift" class="wy-nav-side">
|
|
<div class="wy-side-scroll">
|
|
<div class="wy-side-nav-search">
|
|
|
|
|
|
|
|
|
|
<a href="index.html" class="icon icon-home"> R3 Corda
|
|
|
|
|
|
|
|
</a>
|
|
|
|
|
|
|
|
|
|
<div class="version">
|
|
latest
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<div role="search">
|
|
<form id="rtd-search-form" class="wy-form" action="search.html" method="get">
|
|
<input type="text" name="q" placeholder="Search docs" />
|
|
<input type="hidden" name="check_keywords" value="yes" />
|
|
<input type="hidden" name="area" value="default" />
|
|
</form>
|
|
</div>
|
|
|
|
|
|
<br>
|
|
<a href="api/index.html">API reference</a>
|
|
|
|
</div>
|
|
|
|
<div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
|
|
|
|
|
|
|
|
<p class="caption"><span class="caption-text">Overview</span></p>
|
|
<ul>
|
|
<li class="toctree-l1"><a class="reference internal" href="inthebox.html">What’s included?</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="getting-set-up.html">Getting set up</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="data-model.html">Data model</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="transaction-data-types.html">Data types</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="merkle-trees.html">Transaction Tear-offs</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="consensus.html">Consensus model</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="messaging.html">Networking and messaging</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="persistence.html">Persistence</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="creating-a-cordapp.html">Creating a Cordapp</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="creating-a-cordapp.html#gradle-plugins-for-cordapps">Gradle Plugins for Cordapps</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="running-the-demos.html">Running the demos</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="node-administration.html">Node administration</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="corda-configuration-files.html">The Corda Configuration File</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="corda-configuration-files.html#rpc-users-file">RPC Users File</a></li>
|
|
</ul>
|
|
<p class="caption"><span class="caption-text">Tutorials</span></p>
|
|
<ul class="current">
|
|
<li class="toctree-l1"><a class="reference internal" href="where-to-start.html">Where to start</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="tutorial-contract.html">Writing a contract</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="tutorial-contract-clauses.html">Writing a contract using clauses</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="tutorial-test-dsl.html">Writing a contract test</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="tutorial-clientrpc-api.html">Client RPC API</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="protocol-state-machines.html">Protocol state machines</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="oracles.html">Writing oracle services</a></li>
|
|
<li class="toctree-l1 current"><a class="current reference internal" href="#">Using attachments</a><ul>
|
|
<li class="toctree-l2"><a class="reference internal" href="#attachments-demo">Attachments demo</a></li>
|
|
</ul>
|
|
</li>
|
|
<li class="toctree-l1"><a class="reference internal" href="event-scheduling.html">Event scheduling</a></li>
|
|
</ul>
|
|
<p class="caption"><span class="caption-text">Contracts</span></p>
|
|
<ul>
|
|
<li class="toctree-l1"><a class="reference internal" href="contract-catalogue.html">Contract catalogue</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="contract-irs.html">Interest Rate Swaps</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="initialmarginagreement.html">Initial Margin Agreements</a></li>
|
|
</ul>
|
|
<p class="caption"><span class="caption-text">Node API</span></p>
|
|
<ul>
|
|
<li class="toctree-l1"><a class="reference internal" href="clientrpc.html">Client RPC</a></li>
|
|
</ul>
|
|
<p class="caption"><span class="caption-text">Appendix</span></p>
|
|
<ul>
|
|
<li class="toctree-l1"><a class="reference internal" href="secure-coding-guidelines.html">Secure coding guidelines</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="release-process.html">Release process</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="release-process.html#steps-to-cut-a-release">Steps to cut a release</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="release-notes.html">Release notes</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="network-simulator.html">Network Simulator</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="node-explorer.html">Node Explorer</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="codestyle.html">Code style guide</a></li>
|
|
<li class="toctree-l1"><a class="reference internal" href="building-the-docs.html">Building the documentation</a></li>
|
|
</ul>
|
|
|
|
|
|
|
|
</div>
|
|
</div>
|
|
</nav>
|
|
|
|
<section data-toggle="wy-nav-shift" class="wy-nav-content-wrap">
|
|
|
|
|
|
<nav class="wy-nav-top" role="navigation" aria-label="top navigation">
|
|
<i data-toggle="wy-nav-top" class="fa fa-bars"></i>
|
|
<a href="index.html">R3 Corda</a>
|
|
</nav>
|
|
|
|
|
|
|
|
<div class="wy-nav-content">
|
|
<div class="rst-content">
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<div role="navigation" aria-label="breadcrumbs navigation">
|
|
<ul class="wy-breadcrumbs">
|
|
<li><a href="index.html">Docs</a> »</li>
|
|
|
|
<li>Using attachments</li>
|
|
<li class="wy-breadcrumbs-aside">
|
|
|
|
|
|
<a href="_sources/tutorial-attachments.txt" rel="nofollow"> View page source</a>
|
|
|
|
|
|
</li>
|
|
</ul>
|
|
<hr/>
|
|
</div>
|
|
<div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
|
|
<div itemprop="articleBody">
|
|
|
|
<div class="section" id="using-attachments">
|
|
<h1>Using attachments<a class="headerlink" href="#using-attachments" title="Permalink to this headline">¶</a></h1>
|
|
<p>Attachments are (typically large) Zip/Jar files referenced within a transaction, but not included in the transaction
|
|
itself. These files can be requested from the originating node as needed, although in many cases will be cached within
|
|
nodes already. Examples include:</p>
|
|
<ul class="simple">
|
|
<li>Contract executable code</li>
|
|
<li>Metadata about a transaction, such as PDF version of an invoice being settled</li>
|
|
<li>Shared information to be permanently recorded on the ledger</li>
|
|
</ul>
|
|
<p>To add attachments the file must first be added to the node’s storage service using <code class="docutils literal"><span class="pre">StorageService.importAttachment()</span></code>,
|
|
which returns a unique ID that can be added using <code class="docutils literal"><span class="pre">TransactionBuilder.addAttachment()</span></code>. Attachments can also be
|
|
uploaded and downloaded via HTTP, to enable integration with external systems. For instructions on HTTP upload/download
|
|
please see “<a class="reference internal" href="node-administration.html"><span class="doc">Node administration</span></a>”.</p>
|
|
<p>Normally attachments on transactions are fetched automatically via the <code class="docutils literal"><span class="pre">ResolveTransactionsProtocol</span></code> when verifying
|
|
received transactions. Attachments are needed in order to validate a transaction (they include, for example, the
|
|
contract code), so must be fetched before the validation process can run. <code class="docutils literal"><span class="pre">ResolveTransactionsProtocol</span></code> calls
|
|
<code class="docutils literal"><span class="pre">FetchTransactionsProtocol</span></code> to perform the actual retrieval.</p>
|
|
<p>It is encouraged that where possible attachments are reusable data, so that nodes can meaningfully cache them.</p>
|
|
<div class="section" id="attachments-demo">
|
|
<h2>Attachments demo<a class="headerlink" href="#attachments-demo" title="Permalink to this headline">¶</a></h2>
|
|
<p>There is a worked example of attachments, which relays a simple document from one node to another. The “two party
|
|
trade protocol” also includes an attachment, however it is a significantly more complex demo, and less well suited
|
|
for a tutorial.</p>
|
|
<p>The demo code is in the file “src/main/kotlin/com/r3corda/demos/attachment/AttachmentDemo.kt”, with the core logic
|
|
contained within the two functions <code class="docutils literal"><span class="pre">runRecipient()</span></code> and <code class="docutils literal"><span class="pre">runSender()</span></code>. We’ll look at the recipient function first;
|
|
this subscribes to notifications of new validated transactions, and if it receives a transaction containing attachments,
|
|
loads the first attachment from storage, and checks it matches the expected attachment ID. <code class="docutils literal"><span class="pre">ResolveTransactionsProtocol</span></code>
|
|
has already fetched all attachments from the remote node, and as such the attachments are available from the node’s
|
|
storage service. Once the attachment is verified, the node shuts itself down.</p>
|
|
<div class="highlight-kotlin"><div class="highlight"><pre><span></span><span class="k">private</span> <span class="k">fun</span> <span class="nf">runRecipient</span><span class="p">(</span><span class="n">node</span><span class="p">:</span> <span class="n">Node</span><span class="p">)</span> <span class="p">{</span>
|
|
<span class="k">val</span> <span class="py">serviceHub</span> <span class="p">=</span> <span class="n">node</span><span class="p">.</span><span class="n">services</span>
|
|
|
|
<span class="c1">// Normally we would receive the transaction from a more specific protocol, but in this case we let [FinalityProtocol]</span>
|
|
<span class="c1">// handle receiving it for us.</span>
|
|
<span class="n">serviceHub</span><span class="p">.</span><span class="n">storageService</span><span class="p">.</span><span class="n">validatedTransactions</span><span class="p">.</span><span class="n">updates</span><span class="p">.</span><span class="n">subscribe</span> <span class="p">{</span> <span class="n">event</span> <span class="p">-></span>
|
|
<span class="c1">// When the transaction is received, it's passed through [ResolveTransactionsProtocol], which first fetches any</span>
|
|
<span class="c1">// attachments for us, then verifies the transaction. As such, by the time it hits the validated transaction store,</span>
|
|
<span class="c1">// we have a copy of the attachment.</span>
|
|
<span class="k">val</span> <span class="py">tx</span> <span class="p">=</span> <span class="n">event</span><span class="p">.</span><span class="n">tx</span>
|
|
<span class="k">if</span> <span class="p">(</span><span class="n">tx</span><span class="p">.</span><span class="n">attachments</span><span class="p">.</span><span class="n">isNotEmpty</span><span class="p">())</span> <span class="p">{</span>
|
|
<span class="k">val</span> <span class="py">attachment</span> <span class="p">=</span> <span class="n">serviceHub</span><span class="p">.</span><span class="n">storageService</span><span class="p">.</span><span class="n">attachments</span><span class="p">.</span><span class="n">openAttachment</span><span class="p">(</span><span class="n">tx</span><span class="p">.</span><span class="n">attachments</span><span class="p">.</span><span class="n">first</span><span class="p">())</span>
|
|
<span class="n">assertEquals</span><span class="p">(</span><span class="n">PROSPECTUS_HASH</span><span class="p">,</span> <span class="n">attachment</span><span class="o">?.</span><span class="n">id</span><span class="p">)</span>
|
|
|
|
<span class="n">println</span><span class="p">(</span><span class="s">"File received - we're happy!\n\nFinal transaction is:\n\n${Emoji.renderIfSupported(event.tx)}"</span><span class="p">)</span>
|
|
<span class="n">thread</span> <span class="p">{</span>
|
|
<span class="n">node</span><span class="p">.</span><span class="n">stop</span><span class="p">()</span>
|
|
<span class="p">}</span>
|
|
<span class="p">}</span>
|
|
<span class="p">}</span>
|
|
<span class="p">}</span>
|
|
</pre></div>
|
|
</div>
|
|
<p>The sender correspondingly builds a transaction with the attachment, then calls <code class="docutils literal"><span class="pre">FinalityProtocol</span></code> to complete the
|
|
transaction and send it to the recipient node:</p>
|
|
<div class="highlight-kotlin"><div class="highlight"><pre><span></span><span class="k">private</span> <span class="k">fun</span> <span class="nf">runSender</span><span class="p">(</span><span class="n">node</span><span class="p">:</span> <span class="n">Node</span><span class="p">,</span> <span class="n">otherSide</span><span class="p">:</span> <span class="n">Party</span><span class="p">)</span> <span class="p">{</span>
|
|
<span class="k">val</span> <span class="py">serviceHub</span> <span class="p">=</span> <span class="n">node</span><span class="p">.</span><span class="n">services</span>
|
|
<span class="c1">// Make sure we have the file in storage</span>
|
|
<span class="k">if</span> <span class="p">(</span><span class="n">serviceHub</span><span class="p">.</span><span class="n">storageService</span><span class="p">.</span><span class="n">attachments</span><span class="p">.</span><span class="n">openAttachment</span><span class="p">(</span><span class="n">PROSPECTUS_HASH</span><span class="p">)</span> <span class="p">==</span> <span class="k">null</span><span class="p">)</span> <span class="p">{</span>
|
|
<span class="n">com</span><span class="p">.</span><span class="n">r3corda</span><span class="p">.</span><span class="n">demos</span><span class="p">.</span><span class="n">Role</span><span class="o">::</span><span class="k">class</span><span class="p">.</span><span class="n">java</span><span class="p">.</span><span class="n">getResourceAsStream</span><span class="p">(</span><span class="s">"bank-of-london-cp.jar"</span><span class="p">).</span><span class="n">use</span> <span class="p">{</span>
|
|
<span class="k">val</span> <span class="py">id</span> <span class="p">=</span> <span class="n">node</span><span class="p">.</span><span class="n">storage</span><span class="p">.</span><span class="n">attachments</span><span class="p">.</span><span class="n">importAttachment</span><span class="p">(</span><span class="n">it</span><span class="p">)</span>
|
|
<span class="n">assertEquals</span><span class="p">(</span><span class="n">PROSPECTUS_HASH</span><span class="p">,</span> <span class="n">id</span><span class="p">)</span>
|
|
<span class="p">}</span>
|
|
<span class="p">}</span>
|
|
|
|
<span class="c1">// Create a trivial transaction that just passes across the attachment - in normal cases there would be</span>
|
|
<span class="c1">// inputs, outputs and commands that refer to this attachment.</span>
|
|
<span class="k">val</span> <span class="py">ptx</span> <span class="p">=</span> <span class="n">TransactionType</span><span class="p">.</span><span class="n">General</span><span class="p">.</span><span class="n">Builder</span><span class="p">(</span><span class="n">notary</span> <span class="p">=</span> <span class="k">null</span><span class="p">)</span>
|
|
<span class="n">ptx</span><span class="p">.</span><span class="n">addAttachment</span><span class="p">(</span><span class="n">serviceHub</span><span class="p">.</span><span class="n">storageService</span><span class="p">.</span><span class="n">attachments</span><span class="p">.</span><span class="n">openAttachment</span><span class="p">(</span><span class="n">PROSPECTUS_HASH</span><span class="p">)</span><span class="o">!!</span><span class="p">.</span><span class="n">id</span><span class="p">)</span>
|
|
|
|
<span class="c1">// Despite not having any states, we have to have at least one signature on the transaction</span>
|
|
<span class="n">ptx</span><span class="p">.</span><span class="n">signWith</span><span class="p">(</span><span class="n">ALICE_KEY</span><span class="p">)</span>
|
|
|
|
<span class="c1">// Send the transaction to the other recipient</span>
|
|
<span class="k">val</span> <span class="py">tx</span> <span class="p">=</span> <span class="n">ptx</span><span class="p">.</span><span class="n">toSignedTransaction</span><span class="p">()</span>
|
|
<span class="n">serviceHub</span><span class="p">.</span><span class="n">startProtocol</span><span class="p">(</span><span class="n">LOG_SENDER</span><span class="p">,</span> <span class="n">FinalityProtocol</span><span class="p">(</span><span class="n">tx</span><span class="p">,</span> <span class="n">emptySet</span><span class="p">(),</span> <span class="n">setOf</span><span class="p">(</span><span class="n">otherSide</span><span class="p">))).</span><span class="n">success</span> <span class="p">{</span>
|
|
<span class="n">thread</span> <span class="p">{</span>
|
|
<span class="n">Thread</span><span class="p">.</span><span class="n">sleep</span><span class="p">(</span><span class="m">1000L</span><span class="p">)</span> <span class="c1">// Give the other side time to request the attachment</span>
|
|
<span class="n">node</span><span class="p">.</span><span class="n">stop</span><span class="p">()</span>
|
|
<span class="p">}</span>
|
|
<span class="p">}.</span><span class="n">failure</span> <span class="p">{</span>
|
|
<span class="n">println</span><span class="p">(</span><span class="s">"Failed to relay message "</span><span class="p">)</span>
|
|
<span class="p">}</span>
|
|
<span class="p">}</span>
|
|
</pre></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
|
|
|
|
</div>
|
|
</div>
|
|
<footer>
|
|
|
|
<div class="rst-footer-buttons" role="navigation" aria-label="footer navigation">
|
|
|
|
<a href="event-scheduling.html" class="btn btn-neutral float-right" title="Event scheduling" accesskey="n">Next <span class="fa fa-arrow-circle-right"></span></a>
|
|
|
|
|
|
<a href="oracles.html" class="btn btn-neutral" title="Writing oracle services" accesskey="p"><span class="fa fa-arrow-circle-left"></span> Previous</a>
|
|
|
|
</div>
|
|
|
|
|
|
<hr/>
|
|
|
|
<div role="contentinfo">
|
|
<p>
|
|
© Copyright 2016, Distributed Ledger Group, LLC.
|
|
|
|
</p>
|
|
</div>
|
|
Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
|
|
|
|
</footer>
|
|
|
|
</div>
|
|
</div>
|
|
|
|
</section>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
|
|
<script type="text/javascript">
|
|
var DOCUMENTATION_OPTIONS = {
|
|
URL_ROOT:'./',
|
|
VERSION:'latest',
|
|
COLLAPSE_INDEX:false,
|
|
FILE_SUFFIX:'.html',
|
|
HAS_SOURCE: true
|
|
};
|
|
</script>
|
|
<script type="text/javascript" src="_static/jquery.js"></script>
|
|
<script type="text/javascript" src="_static/underscore.js"></script>
|
|
<script type="text/javascript" src="_static/doctools.js"></script>
|
|
|
|
|
|
|
|
|
|
|
|
<script type="text/javascript" src="_static/js/theme.js"></script>
|
|
|
|
|
|
|
|
|
|
<script type="text/javascript">
|
|
jQuery(function () {
|
|
SphinxRtdTheme.StickyNav.enable();
|
|
});
|
|
</script>
|
|
|
|
|
|
</body>
|
|
</html> |