谈谈JSONAPI在PHP中的应用

来源:转载

现在服务端程序员的主要工作已经不再是套模版,而是编写基于 JSON 的 API 接口。可惜大家编写接口的风格往往迥异,这就给系统集成带来了很多不必要的沟通成本,如果你有类似的困扰,那么不妨关注一下 JSONAPI ,它是一个基于 JSON 构建 API 的规范标准,一个简单的 API 接口大致如下所示:



JSONAPI


简单说明一下:根节点中的 data 用来放置主对象的内容,其中 type 和 id 是必须要有的字段,用来表示主对象的类型和标识,其它简单的属性统统放置到 attributes 里,如果主对象存在一对一、一对多等关联对象,那么放置到 relationships 里,不过只是通过 type 和 id 字段放置一个链接,关联对象的实际内容统统放置在根接点中的 included 里。


有了 JSONAPI,数据解析的过程变得规范起来,节省了不必要的沟通成本。不过如果要手动构建 JSONAPI 数据还是很麻烦的,好在通过使用 Fractal 可以让实现过程相对自动化一些,上面的例子如果用 Fractal 实现大概是这个样子:


<?php
use League/Fractal/Manager;
use League/Fractal/Resource/Collection;
$articles = [
[
'id' => 1,
'title' => 'JSON API paints my bikeshed!',
'body' => 'The shortest article. Ever.',
'author' => [
'id' => 42,
'name' => 'John',
],
],
];
$manager = new Manager();
$resource = new Collection($articles, new ArticleTransformer());
$manager->parseIncludes('author');
$manager->createData($resource)->toArray();
?>

如果让我选最喜爱的 PHP 工具包,Fractal 一定榜上有名,它隐藏了实现细节,让使用者完全不必了解 JSONAPI 协议即可上手。不过如果你想在自己的项目里使用的话,与直接使用 Fractal 相比,可以试试 Fractalistic ,它对 Fractal 进行了封装,使其更好用:


<?php
Fractal::create()
->collection($articles)
->transformWith(new ArticleTransformer())
->includeAuthor()
->toArray();
?>

如果你是裸写 PHP 的话,那么 Fractalistic 基本就是最佳选择了,不过如果你使用了一些全栈框架的话,那么 Fractalistic 可能还不够优雅,因为它无法和框架本身已有的功能更完美的融合,以 Lavaral 为例,它本身内置了一个 API Resources 功能,在此基础上我实现了一个 JsonApiSerializer,可以和框架完美融合,代码如下:


<?php
namespace App/Http/Serializers;
use Illuminate/Http/Resources/MissingValue;
use Illuminate/Http/Resources/Json/Resource;
use Illuminate/Http/Resources/Json/ResourceCollection;
use Illuminate/Pagination/AbstractPaginator;
class JsonApiSerializer implements /JsonSerializable
{
protected $resource;
protected $resourceValue;
protected $data = [];
protected static $included = [];
public function __construct($resource, $resourceValue)
{
$this->resource = $resource;
$this->resourceValue = $resourceValue;
}
public function jsonSerialize()
{
foreach ($this->resourceValue as $key => $value) {
if ($value instanceof Resource) {
$this->serializeResource($key, $value);
} else {
$this->serializeNonResource($key, $value);
}
}
if (!$this->isRootResource()) {
return $this->data;
}
$result = [
'data' => $this->data,
];
if (static::$included) {
$result['included'] = static::$included;
}
if (!$this->resource->resource instanceof AbstractPaginator) {
return $result;
}
$paginated = $this->resource->resource->toArray();
$result['links'] = $this->links($paginated);
$result['meta'] = $this->meta($paginated);
return $result;
}
protected function serializeResource($key, $value, $type = null)
{
if ($type === null) {
$type = $key;
}
if ($value->resource instanceof MissingValue) {
return;
}
if ($value instanceof ResourceCollection) {
foreach ($value as $k => $v) {
$this->serializeResource($k, $v, $type);
}
} elseif (is_string($type)) {
$included = $value->resolve();
$data = [
'type' => $included['type'],
'id' => $included['id'],
];
if (is_int($key)) {
$this->data['relationships'][$type]['data'][] = $data;
} else {
$this->data['relationships'][$type]['data'] = $data;
}
static::$included[] = $included;
} else {
$this->data[] = $value->resolve();
}
}
protected function serializeNonResource($key, $value)
{
switch ($key) {
case 'id':
$value = (string)$value;
case 'type':
case 'links':
$this->data[$key] = $value;
break;
default:
$this->data['attributes'][$key] = $value;
}
}
protected function links($paginated)
{
return [
'first' => $paginated['first_page_url'] ?? null,
'last' => $paginated['last_page_url'] ?? null,
'prev' => $paginated['prev_page_url'] ?? null,
'next' => $paginated['next_page_url'] ?? null,
];
}
protected function meta($paginated)
{
return [
'current_page' => $paginated['current_page'] ?? null,
'from' => $paginated['from'] ?? null,
'last_page' => $paginated['last_page'] ?? null,
'per_page' => $paginated['per_page'] ?? null,
'to' => $paginated['to'] ?? null,
'total' => $paginated['total'] ?? null,
];
}
protected function isRootResource()
{
return isset($this->resource->isRoot) && $this->resource->isRoot;
}
}
?>

对应的 Resource 基本还和以前一样,只是返回值改了一下:


<?php
namespace App/Http/Resources;
use App/Article;
use Illuminate/Http/Resources/Json/Resource;
use App/Http/Serializers/JsonApiSerializer;
class ArticleResource extends Resource
{
public function toArray($request)
{
$value = [
'type' => 'articles',
'id' => $this->id,
'name' => $this->name,
'author' => $this->whenLoaded('author'),
];
return new JsonApiSerializer($this, $value);
}
}
?>

对应的 Controller 也和原来差不多,只是加入了一个 isRoot 属性,用来识别根:


<?php
namespace App/Http/Controllers;
use App/Article;
use App/Http/Resources/ArticleResource;
class ArticleController extends Controller
{
protected $article;
public function __construct(Article $article)
{
$this->article = $article;
}
public function show($id)
{
$article = $this->article->with('author')->findOrFail($id);
$resource = new ArticleResource($article);
$resource->isRoot = true;
return $resource;
}
}
?>

整个过程没有对 Laravel 的架构进行太大的侵入,可以说是目前 Laravel 实现 JSONAPI 的最优解决方案了,有兴趣的可以研究一下JsonApiSerializer 的实现,虽然只有一百多行代码,但是我却费了好大的力气才实现,可以说是行行皆辛苦啊。


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