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5.2 KiB
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19 lines
5.2 KiB
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<title>2. Building a Gateway Using Spring MVC</title><link rel="stylesheet" type="text/css" href="css/manual-multipage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="multi_spring-cloud-gateway.html" title="Spring Cloud Gateway"><link rel="up" href="multi_spring-cloud-gateway.html" title="Spring Cloud Gateway"><link rel="prev" href="multi_gateway-starter.html" title="1. How to Include Spring Cloud Gateway"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2. Building a Gateway Using Spring MVC</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi_gateway-starter.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> </td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="_building_a_gateway_using_spring_mvc" href="#_building_a_gateway_using_spring_mvc"></a>2. Building a Gateway Using Spring MVC</h1></div></div></div><p>Spring Cloud Gateway provides a utility object called <code class="literal">ProxyExchange</code> which you can use inside a regular Spring MVC handler as a method parameter. It supports basic downstream HTTP exchanges via methods that mirror the HTTP verbs, or forwarding to a local handler via the <code class="literal">forward()</code> method.</p><p>Example (proxying a request to "/test" downstream to a remote server):</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@RestController</span></em>
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<em><span class="hl-annotation" style="color: gray">@SpringBootApplication</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> GatewaySampleApplication {
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<em><span class="hl-annotation" style="color: gray">@Value("${remote.home}")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> URI home;
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<em><span class="hl-annotation" style="color: gray">@GetMapping("/test")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> ResponseEntity<?> proxy(ProxyExchange<Object> proxy) <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">throws</span> Exception {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> proxy.uri(home.toString() + <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"/image/png"</span>).get();
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}
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}</pre><p>There are convenience methods on the <code class="literal">ProxyExchange</code> to enable the handler method to discover and enhance the URI path of the incoming request. For example you might want to extract the trailing elements of a path to pass them downstream:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@GetMapping("/proxy/path/**")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> ResponseEntity<?> proxyPath(ProxyExchange<?> proxy) <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">throws</span> Exception {
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String path = proxy.path(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"/proxy/path/"</span>);
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> proxy.uri(home.toString() + <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"/foos/"</span> + path).get();
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}</pre><p>All the features of Spring MVC are available to Gateway handler methods. So you can inject request headers and query parameters, for instance, and you can constrain the incoming requests with declarations in the mapping annotation. See the documentation for <code class="literal">@RequestMapping</code> in Spring MVC for more details of those features.</p><p>Headers can be added to the downstream response using the <code class="literal">header()</code> methods on <code class="literal">ProxyExchange</code>.</p><p>You can also manipulate response headers (and anything else you like in the response) by adding a mapper to the <code class="literal">get()</code> etc. method. The mapper is a <code class="literal">Function</code> that takes the incoming <code class="literal">ResponseEntity</code> and converts it to an outgoing one.</p><p>First class support is provided for "sensitive" headers ("cookie" and "authorization" by default) which are not passed downstream, and for "proxy" headers (<code class="literal">x-forwarded-*</code>).</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi_gateway-starter.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> </td></tr><tr><td width="40%" align="left" valign="top">1. How to Include Spring Cloud Gateway </td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud-gateway.html">Home</a></td><td width="40%" align="right" valign="top"> </td></tr></table></div></body></html> |