https://github.com/linktosriram/clojure-spring-guide

Guidelines for using Clojure with Spring Framework
https://github.com/linktosriram/clojure-spring-guide

annotations clojure clojure-spring-guide java spring spring-boot spring-framework

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Guidelines for using Clojure with Spring Framework

• Host: GitHub
• URL: https://github.com/linktosriram/clojure-spring-guide
• Owner: linktosriram
• Created: 2017-11-18T08:35:13.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2017-11-18T10:18:25.000Z (almost 7 years ago)
• Last Synced: 2024-09-29T00:05:28.677Z (about 2 months ago)
• Topics: annotations, clojure, clojure-spring-guide, java, spring, spring-boot, spring-framework
• Homepage: https://linktosriram.github.io/clojure-spring-guide/
• Size: 2.93 KB
• Stars: 10
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# clojure-spring-guide

Guidelines for using Clojure with Spring Framework

[Clojure Style Guide](https://goo.gl/WWfjB)

# Controllers

* Use [@RestController](https://goo.gl/DpiwnS)

* Use [@GetMapping](https://goo.gl/Y1tX55), [@PostMapping](https://goo.gl/BsajaA) family of annotations over traditional [@RequestMapping](https://goo.gl/naenPG) ones

* Consume and Produce [MediaType.APPLICATION_JSON_UTF8_VALUE](https://goo.gl/US1rUY)

* When returning clojure data structures out of controllers, use [cheshire](https://goo.gl/TCNat)

```clojure

(ns ...

  (:require [cheshire.core :as json]))

```

and then return using

```clojure

(json/generate-string {:a 1 :b 2})

```

* When using annotations like [@PathVariable](https://goo.gl/b5XdMB), [@RequestParam](https://goo.gl/nm7ZiD) etc., specify the `value` attribute as the debugging information is not available. The value attribute can be dash-case.

Otherwise the following error will occur: `Name for argument type [java.lang.String] not available, and parameter name information not found in class file either.`

* We cannot require another namespace or import a class in `(ns :gen-class )`. The code emitted by ns macro calls `:gen-class` before calling any of the `:require` or `:import`.

Thus the required namespace/class or not compiled when `:gen-class` is called. We can use fully qualified names to solve this, but that would be ugly.

A Better solution is to call `(gen-class ...)` after `(ns ...)`

* Method arguments types and return types still need to be fully qualified (except java.lang.*)

* Method names should be camelCase instead of dash-case due to Java restrictions

* If you prefer, you can return [CompletableFuture](https://goo.gl/QQ6uv2) from the controller method to be asynchronous with the following macro

```clojure

(ns ...

  (:import (java.util.concurrent CompletableFuture)

           (java.util.function Supplier)))

           

(defmacro async

  "Wraps the given `body` inside a CompletableFuture."

  [& body]

  `(CompletableFuture/supplyAsync

     (reify

       Supplier

       ~(list 'get '[this] (cons 'do body)))))

```

and then use it like

```clojure

(async

  (println "Async Controller method")

  (+ 3 5))

```

## Complete Example

```clojure

(ns com.clojurespring.controller

  (:require [cheshire.core :as json])

  (:import (org.springframework.web.bind.annotation RestController GetMapping PathVariable)))

(gen-class

  :name ^{RestController {}} com.clojurespring.SampleController

  :methods [[^{GetMapping {:value    ["/hello"]

                           :produces ["application/json;charset=UTF-8"}}

                           hello [^{PathVariable {:value "name"}} String] java.util.concurrent.Future]])

(defn -hello

  [this name]

  (async

    (println "Inside async controller...")

    (json/generate-string {:a       1

                           :message (str "Hello " name " from Clojure controller"))))

```

### Request

```bash

curl -X GET -H "Accept: application/json;charset=UTF-8" "http://server.name/hello/rich"

```

### Response

```json

{

  "a": 1,

  "message": "Hello rich from Clojure controller"

}

```

# Contributing

Nothing written in this guide is set in stone. It's my desire to work together with everyone interested in Clojure coding style, so that we could ultimately create a resource that will be beneficial to the entire Clojure community.

Feel free to open tickets or send pull requests with improvements. Thanks in advance for your help!