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<!DOCTYPE html>

<head>

<title>

Feign

</title>

{

"@context": "http://schema.org",

"@type": "Organization",

"url": "http://seedstack.org",

"logo": "http://seedstack.org/img/logos/seedstack.png"

}

</script>

in your code." />

window.seedstack = {

baseUrl: "http:\/\/seedstack.org\/",

state: {}

};

</script>

</head>

<body>

height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>

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=

'//www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);

})(window,document,'script','dataLayer','GTM-5R5FP9');</script>

<a class="logo" href="http://seedstack.org/">SeedStack</a>

<span class="sr-only">Toggle navigation</span>

</button>

</div>

<a href="http://seedstack.org/docs">Documentation</a>

</li>

<a href="http://seedstack.org/guides">Guides</a>

</li>

</li>

</li>

<a href="http://seedstack.org/community">Community</a>

</li>

</a>

<li><a href="http://seedstack.org/glossary">Glossary</a></li>

<li><a href="http://seedstack.org/project">Project info</a></li>

<li><a target="_blank" href="http://seedstack.org/javadoc"><i style="margin-top: 3px" class="pull-right fa fa-external-link"></i> Javadoc</a></li>

<li><a target="_blank" href="https://github.com/seedstack/distribution/releases"><i style="margin-top: 3px" class="pull-right fa fa-external-link"></i> Releases</a></li>

<li><a target="_blank" href="https://github.com/seedstack"><i style="margin-top: 3px" class="pull-right fa fa-external-link"></i> GitHub</a></li>

</ul>

</li>

<li>

</span>

</div>

</form>

</div>

</li>

</ul>

</div>

<p class="hidden-xs">Additional features and extensions for SeedStack applications.</p>

</div>

</div>

<ul>

</ul>

</div>

<h1 class="nocount">Feign</h1>

<p>This component allows you to define an HTTP client with a simple Java interface that you can then inject and use transparently

in your code.</p>

<li class="active"><a href="#tab-org-seedstack-addons-feign-feign-maven" data-toggle="tab" aria-expanded="true"><img class="pull-left" style="margin: 0 5px 0 0; height: 20px;" src="http://seedstack.org//img/logos/maven.png">Maven</a></li>

<li class=""><a href="#tab-org-seedstack-addons-feign-feign-gradle" data-toggle="tab" aria-expanded="true"><img class="pull-left" style="margin: 0 5px 0 0; height: 20px;" src="http://seedstack.org//img/logos/gradle.png">Gradle</a></li>

</ul>

<groupId>org.seedstack.addons.feign</groupId>

<artifactId>feign</artifactId><span id="org-seedstack-addons-feign-feign-version" style="display: none;">

</dependency></code></pre>

<span id="org-seedstack-addons-feign-feign-warn" style="display: none;"><i class="fa fa-warning" style="color: orange;"></i> Specifying versions manually is error-prone, use <a href="http://seedstack.org/docs/basics#dependency-management">dependency management</a> instead.</span>

<a style="cursor: pointer; display: block;" id="org-seedstack-addons-feign-feign-show" onclick="$('#org-seedstack-addons-feign-feign-version, #org-seedstack-addons-feign-feign-warn').show(); $('#org-seedstack-addons-feign-feign-show').hide();">Show version</a>

</small>

</div>

<pre style="margin-top: 0; border: solid 1px #eee; border-top: none;"><code class="language-gradle no-linenums" style="background-color: #fff;">dependencies {

compile("org.seedstack.addons.feign:feign:1.5.0")

}</code></pre>

</div>

<p>First, you need to create an interface annotated by <code>@FeignApi</code>, with each method being an HTTP call. Annotate each method with <code>@RequestLine</code>:</p>

<pre><code class="language-java">@FeignApi

public interface Api {

@RequestLine("GET /message")

List<Message> getMessages();

@RequestLine("GET /message/{id}")

Message getMessage(@Param("id") int id);

}

</code></pre>

<p>Then, you can use this API by injecting it:</p>

<pre><code class="language-java">public class MyClass {

@Inject

private Api api;

@Logging

private Logger logger;

public void someMethod() {

List<Message> messages = api.getMessages();

for (Message message : messages) {

logger.info("Received message from {}", message.author);

}

</code></pre>

</div>

<p>For more information about OpenFeign, look into its documentation: <a href="https://github.com/OpenFeign/feign">https://github.com/OpenFeign/feign</a>.</p>

</div>

</div></p>

<h2 id="configuration">Configuration</h2>

<p>Configuration is done by</p>

<p>Feign is configurable by endpoint, and in its basic form is:</p>

<li class="active"><a href="#tab-feign-config" data-toggle="tab" aria-expanded="true">Configuration</a></li>

</ul>

<div class="tab-pane in active" id="tab-feign-config"><pre><code class="language-yaml">feign:

endpoints:

com.mycompany.myapp.Api: http://base.url.to.api:port

</code></pre>

<p><code>com.mycompany.myapp.Api</code> is the fully qualified name of your api interface, and you can add as many as you want.

<p>With all the options, the configuration file looks like this:</p>

<pre><code class="language-yaml">feign:

endpoints:

com.mycompany.myapp.Api:

baseUrl: http://base.url.to.api:port

encoder: feign.jackson.JacksonEncoder

decoder: feign.jackson.JacksonDecoder

errorDecoder: com.mycompany.myapp.MyApiErrorDecoder

logger: feign.slf4j.SLF4JLogger

logLevel: NONE

hystrixWrapper: AUTO

fallback: com.mycompany.myapp.Fallback

retryer: com.mycompany.myapp.MyRetryer

</code></pre>

<p>The values in this example are the default values, except for <code>baseUrl</code> and <code>fallback</code> that don’t have default values.</p>

<ul>

<li><code>baseUrl</code> is this only mandatory option.</li>

<li><code>encoder</code> and <code>decoder</code> let you configure how your data is transformed when sent and received, respectively.</li>

<li><code>errorDecoder</code> let you define a custom injectable errorDecoder related to this API for request error handling. (See <a href="https://github.com/OpenFeign/feign#error-handling">https://github.com/OpenFeign/feign#error-handling</a> )</li>

<li><code>logger</code> let you choose which logger to use to log the requests.</li>

<li><code>logLevel</code> is an enum (<code>NONE</code>, <code>BASIC</code>, <code>HEADERS</code>, <code>FULL</code>).</li>

<li><code>hystrixWrapper</code> is an enum (<code>AUTO</code>, <code>ENABLED</code>, <code>DISABLED</code>). Feign comes with Hystrix circuit-breaker support. <code>DISABLED</code> disables this functionality. <code>ENABLED</code> tells Feign to wrap all requests in Hystrix mechanism, but the lib Hystrix must be in the classpath of your project. <code>AUTO</code> mode will scan the classpath and if Hystrix is present, will wrap requests with it.</li>

<li><code>fallback</code> takes a fully qualified class name and is only relevant when Hystrix is used. The fallback class must implement your API interface and will be used to return default values in case the requests are in error.</li>

<li><code>retryer</code> let you define a custom injectable Retryer related to this endpoint for retry policy handling. ( See <a href="https://github.com/OpenFeign/feign#retry">https://github.com/OpenFeign/feign#retry</a> ). See below for more retry configuration options.</li>

</ul>

<h2 id="authentication">Authentication</h2>

<p>To call an API protected with authentication you can specify a header in your Feign interface with the <code>@Headers</code> annotation (example for basic authentication):</p>

<pre><code class="language-java">@FeignApi

@Headers({"Authorization: Basic {credentials}"})

public interface neosdServer {

@RequestLine("GET /file/getfilesprop")

List<NeosdFile> getfilesprop(@Param("credentials") String credentials);

@RequestLine("GET /file/getfiles")

List<String> getfiles(@Param("credentials") String credentials);

}

</code></pre>

</div>

<p>Note that <code>@Headers</code> can also be used on individual methods.</p>

</div>

<p>Then, pass the credentials as method parameter. An example implementation, with credentials coming from your application configuration, coudl be:</p>

<pre><code class="language-java">public class MyClass {

@Configuration("myApp.credentials.user")

private String username;

@Configuration("myApp.credentials.password")

private String password;

@Inject

private NeoSdClient client;

public void myMethod() {

List<String> files = client.getFiles(encodeCredentials());

}

private String encodeCredentials() {

return BaseEncoding

.base64()

.encode((username + ":" + password)

.getBytes(Charsets.UTF_8));

}

</code></pre>

<h2 id="fallback">Fallback</h2>

<p>A fallback class is done by implementing the Feign interface and return default values from it:</p>

<pre><code class="language-java">public class Fallback implements Api {

@Override

List<Message> getMessages() {

// return your default value here

}

@Override

Message getMessage(@Param("id") int id) {

// return your default value here

}

</code></pre>

</div>

<p>For more information on Hystrix: <a href="https://github.com/Netflix/Hystrix/wiki">https://github.com/Netflix/Hystrix/wiki</a></p>

</div>

<h2 id="retry-configuration">Retry configuration</h2>

<p>Feign plugin retry configuration has two levels : global configuration and endpoint configuration.</p>

<p>The endpoint configuration has priority upon global configration, letting you having global settings and, if necessary specific settings for particular endpoints.</p>

<p>To resume, if an endpoint has a retry configuration set, it will be applyed, if not, the global configuration will be applyed, if there is no retry configuration set (global or specific ), the default feign retry configuration will be applyed.</p>

<p>There are two type of retry configuration : standard parameters or retryer class configuration. Both types can’t be defined for the same configuration level (global /endpoint ).</p>

<h3 id="standard-parameters-configuration">Standard parameters configuration</h3>

<p>The following retry parameters can be set :

* <code>period</code> : The initial time period, in milliseconds, between two requests attemps. Feign will increase this period by half ( multiply by 1.5 ) until it reaches the maximum allowed period.

* <code>maxPeriod</code> : Maximum allowed period, in milliseconds, between two attempts. Feign won’t increase a retry period more than this parameter.

* <code>maxAttempts</code> : Maximum retry attempts for a single request. If the request still fails after the last attempt, the feign API will throw an exception.</p>

<h4 id="global-configuration">Global configuration</h4>

<p>Here is a sample for global retry configuration, applyed to each endpoint with no retry/retryer configuration</p>

<pre><code class="language-yaml">feign:

retry:

period: 100

maxPeriod: 1000

maxAttempts: 3

endpoints:

com.mycompany.myapp.Api: http://base.url.to.api:port

</code></pre>

<h4 id="endpoint-configuration">Endpoint configuration</h4>

<p>Here is a sample for specific endpoint retry configuration, applyed only to this specific endpoint :</p>

<pre><code class="language-yaml">feign:

endpoints:

com.mycompany.myapp.Api: http://base.url.to.api:port

retry:

period: 100

maxPeriod: 1000

maxAttempts: 3

</code></pre>

<h3 id="retryer-class-configuration">Retryer class configuration</h3>

<p>With feign, you can define a retryer having the role to determine if a request should be retryed or not, letting you decide of the retry policy you want to apply to your endpoint ( See <a href="https://github.com/OpenFeign/feign#retry">https://github.com/OpenFeign/feign#retry</a> ). This feature is supported in the seedstack feign plugin. Your custom retryer class has to implement the feign «Retryer» interface and added to your plugin configuration. Note that this class is injectable.</p>

<h4 id="global-configuration-1">Global configuration</h4>

<p>Here is a sample for global retryer configuration, applyed to each endpoint with no retry/retryer configuration</p>

<pre><code class="language-yaml">feign:

retryer: com.mycompany.myapp.MyRetryer

endpoints:

com.mycompany.myapp.Api: http://base.url.to.api:port

</code></pre>

<h4 id="endpoint-configuration-1">Endpoint configuration</h4>

<p>Here is a sample for a specific endpoint retryer configuration, applyed only to this specific endpoint :</p>

<pre><code class="language-yaml">feign:

endpoints:

com.mycompany.myapp.Api: http://base.url.to.api:port

retryer: com.mycompany.myapp.MyRetryer

</code></pre>

</div>

<p style="margin-top: 20px;">To dump the <code>feign</code> configuration options:</p>

<pre><code class="language-bash">mvn -q -Dargs="feign" seedstack:config</code></pre>

</div>

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<div class="headline"><h2>About</h2></div>

SeedStack is an opinionated, easy-to-use Java development stack for building applications and micro-services.

</p>

<p>

<i class="fa fa-info-circle"></i> <a target="_blank" href="http://seedstack.org/javadoc">Javadoc</a>

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<p>

Code licensed under the <a href="https://www.mozilla.org/MPL/2.0" target="_blank">Mozilla Public License 2.0</a>.

<br/>

Documentation licensed under <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA 4.0</a>.

<br/>

Some illustrations by <a href="https://www.Vecteezy.com/">www.Vecteezy.com</a>

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<i class="fa fa-stack-overflow"></i> <a target="_blank" href="http://stackoverflow.com/questions/ask?tags=seedstack">StackOverflow</a>

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Mousetrap.bind('right', function () {

if (seedstack.state.nextPage) {

window.location = seedstack.state.nextPage;

}

return false;

});

Mousetrap.bind('?', function () {

seedstack.ui.openHelp();

return false;

});

Mousetrap.bind('esc', function () {

seedstack.ui.closeHelp();

seedstack.ui.closeSearch();

seedstack.ui.closeVersions();

return false;

});

var originalCallback = Mousetrap.stopCallback;

Mousetrap.stopCallback = function (e, element, combo) {

if (combo === 'esc') {

return false;

}

return originalCallback(e, element, combo);

};

function bindShortcuts(value) {

$.each(value, function (sequence, item) {

if (typeof item === 'string') {

Mousetrap.bind("g " + sequence, function () {

window.location = item;

return false;

});

} else if (typeof item === 'object') {

Mousetrap.bind("g " + sequence, function () {

window.location = item.path;

return false;

});

if (item.shortcuts && location.pathname.indexOf(item.path) === 0) {

bindShortcuts(item.shortcuts);

}

});

}

bindShortcuts(seedstack.ui.shortcuts);

$('.quick-paste span').each(function (index, element) {

$(element).attr({"id": "quick-paste-line"});

$(element).append("<span data-toggle=\"tooltip\" data-placement=\"top\" data-title=\"Copy\" data-clipboard-target=\"#quick-paste-line\" class=\"copy-button\"><i class=\"fa fa-clipboard\"></i></span>");

});

var preId = 0;

$('.doc-content pre').each(function (index, element) {

preId++;

$(element).attr({"id": "snippet-" + preId});

$(element).prepend("<span data-toggle=\"tooltip\" data-placement=\"left\" data-title=\"Copy\" data-clipboard-target=\"#snippet-" + preId + "\" class=\"copy-button\"><i class=\"fa fa-clipboard\"></i></span>");

});

var clipboard = new Clipboard('.copy-button', {

target: function (trigger) {

var elt = $($(trigger).data('clipboard-target'));

elt.find('code > table > tbody > tr').show();

return elt.get(0);

}

});

clipboard.on('success', function (e) {

var elt = $($(e.trigger).data('clipboard-target'));

hideJavaImports($(elt).children("code"));

var tooltip = $("body #" + $(e.trigger).attr("aria-describedby"));

tooltip.css('left', '-=14px');

tooltip.children(".tooltip-inner").html("Copied!");

e.clearSelection();

});

clipboard.on('error', function (e) {

var tooltip = $("body #" + $(e.trigger).attr("aria-describedby"));

tooltip.css('left', '-=83px');

tooltip.children(".tooltip-inner").html("Error! Copy manually");

});

$('[data-toggle="tooltip"]').tooltip({

container: 'body'

});

$('#hotkeys-modal, #versions-modal').bind('hidden.bs.modal', function () {

$("html").css("margin-right", "0px");

}).bind('show.bs.modal', function () {

$("html").css("margin-right", "-15px");

});

var query = seedstack.strings.parseQueryString(location);

if (query.h && query.h.length > 0) {

$('.doc-content').highlight(query.h);

if (query.scroll) {

var firstOccurence = $('span[class=highlight]:first');

if (firstOccurence.length > 0) {

$('html, body').animate({

scrollTop: firstOccurence.offset().top - 20

}, 250);

}

$(window).scroll(function () {

if ($(this).scrollTop() > 200) {

$('.scrollup').fadeIn();

} else {

$('.scrollup').fadeOut();

}

});

$('.scrollup').click(function () {

$("html, body").animate({scrollTop: 0}, 250);

return false;

});

</script>

var js, fjs = d.getElementsByTagName(s)[0], t = window.twttr || {};

if (d.getElementById(id)) return t;

js = d.createElement(s);

js.id = id;

js.src = "https://platform.twitter.com/widgets.js";

fjs.parentNode.insertBefore(js, fjs);

t._e = [];

t.ready = function (f) {

t._e.push(f);

};

return t;

}(document, "script", "twitter-wjs"));</script>

</body>

</html>

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