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<!--replace-end-7--><!--replace-end-4--><!--replace-end-1--></head><body><div class="ui fluid container universe"><!--replace-start-2--><!--replace-start-3--><!--replace-start-6--><div class="ui text container" id="zettel-container" style="position: relative"><div class="zettel-view"><article class="ui raised attached segment zettel-content"><div class="pandoc"><h1 id="title-h1">Creating a RESTful API: Validation</h1><p>We can provide server-side validation for our projects by using a <strong>schema validator</strong>. This is a program that declaratively parses the JSON values received as requests from the client. This makes it easy to systematically validate the data that we receive from any HTTP requests where the client sends a body to the endpoint.</p><p>One of the most popular schema validators for NodeJS is <span class="zettel-link-container errors"><span class="zettel-link" title="Wiki-link does not refer to any existing zettel"><a>joi</a></span></span>.</p><h2 id="demonstration">Demonstration</h2><p>Let’s say we have a POST request that expects a single field as the body that must be a string and greater than two characters long. First we define our schema:</p><pre><code class="js language-js">const schema = Joi.object({
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name: Joi.string().min(3).required(),
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});
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const { error } = schema.validate(req.body);</code></pre><p>The <code>schema</code> variable is an object whose keys should match those of the intended request body. Instead of actual values we provide Joi’s in-built validators, concatenated as necessary. We then store the results of the validation in a variable.</p><p>Next we add handling in the case of errors:</p><pre><code class="js language-js">if (error) {
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error.details.map((joiErr) => res.status(400).send(joiErr.message));
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return;
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}</code></pre><p>We loop through the error array and return 400s as the response if they are found. If there are no errors, the Joi object will return <code>undefined</code>.</p></div></article><nav class="ui attached segment deemphasized backlinksPane" id="neuron-backlinks-pane"><h3 class="ui header">Backlinks</h3><ul class="backlinks"><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="Validating_Mongoose_schemas.html">Validating Mongoose schemas</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>What is the relationship between this Mongoose validation and the <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: Creating a RESTful API: Validation"><a href="Validation_in_NodeJS.html">Joi</a></span></span> validation that we use when validating API requests in Node/Express? They complement each other. We use Joi to validate the client request to the API. If this is valid, the process would then move onto the next stage which would be transforming the data from a REST request to a database request implemented through Mongoose, where a second layer of validation would appy. We would also have validation on the client-side.</p></div></li></ul></li><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="2_POST.html">Creating a RESTful API: POST requests</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>We should accept alterations to the database that are not first validated. We can use the <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: Creating a RESTful API: Validation"><a href="Validation_in_NodeJS.html">Joi validator</a></span></span> to vet the request:</p></div></li></ul></li></ul></nav><nav class="ui attached segment deemphasized bottomPane" id="neuron-tags-pane"><div><span class="ui basic label zettel-tag" title="Tag">APIs</span><span class="ui basic label zettel-tag" title="Tag">REST</span><span class="ui basic label zettel-tag" title="Tag">node-js</span></div></nav><nav class="ui bottom attached icon compact inverted menu blue" id="neuron-nav-bar"><!--replace-start-9--><!--replace-end-9--><a class="right item" href="impulse.html" title="Open Impulse"><i class="wave square icon"></i></a></nav></div></div><!--replace-end-6--><!--replace-end-3--><!--replace-end-2--><div class="ui center aligned container footer-version"><div class="ui tiny image"><a href="https://neuron.zettel.page"><img alt="logo" src="https://raw.githubusercontent.com/srid/neuron/master/assets/neuron.svg" title="Generated by Neuron 1.9.35.3" /></a></div></div></div></body></html>
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