Django（51）drf渲染模块源码分析

前言

渲染模块的原理和解析模块是一样，drf默认的渲染有2种方式，一种是json格式，另一种是模板方式。

渲染模块源码入口

入口：APIView类中dispatch方法中的：self.response = self.finalize_response(request, response, *args, **kwargs)

渲染模块源码分析

我们首先点击finalize_response进入查看源码

def finalize_response(self, request, response, *args, **kwargs):
    """
    Returns the final response object.
    """
    # Make the error obvious if a proper response is not returned
    # 断言是否是HttpResponseBase对象
    assert isinstance(response, HttpResponseBase), (
        'Expected a `Response`, `HttpResponse` or `HttpStreamingResponse` '
        'to be returned from the view, but received a `%s`'
        % type(response)
    )

    # 判断是否是Response对象
    if isinstance(response, Response):
        if not getattr(request, 'accepted_renderer', None):
            # 渲染模块的正式入口
            neg = self.perform_content_negotiation(request, force=True)
            request.accepted_renderer, request.accepted_media_type = neg

        response.accepted_renderer = request.accepted_renderer
        response.accepted_media_type = request.accepted_media_type
        response.renderer_context = self.get_renderer_context()

    # Add new vary headers to the response instead of overwriting.
    vary_headers = self.headers.pop('Vary', None)
    if vary_headers is not None:
        patch_vary_headers(response, cc_delim_re.split(vary_headers))

    for key, value in self.headers.items():
        response[key] = value

    return response

上述代码是响应模块的源码，该源码中包含了渲染模块的源码，就是这句neg = self.perform_content_negotiation(request, force=True)，我们可以点击查看

def perform_content_negotiation(self, request, force=False):
    """
    Determine which renderer and media type to use render the response.
    """
    # 确定使用哪种渲染器和媒体类型来渲染响应。
    # 渲染器列表
    renderers = self.get_renderers()
    conneg = self.get_content_negotiator()

    try:
        return conneg.select_renderer(request, renderers, self.format_kwarg)
    except Exception:
        if force:
            return (renderers[0], renderers[0].media_type)
        raise

代码中有个get_renderers就是渲染器列表，点击查看

def get_renderers(self):
    """
    Instantiates and returns the list of renderers that this view can use.
    """
    return [renderer() for renderer in self.renderer_classes]

这就是渲染器列表的源码，跟解析器列表的源码大同小异，接着再点击renderer_classer查看

renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES

到这里我们就知道了，drf默认的渲染器在settings下的DEFAUIT_RENDERER_CLASSES中，配置如下

'DEFAULT_RENDERER_CLASSES': [
        'rest_framework.renderers.JSONRenderer',
        'rest_framework.renderers.BrowsableAPIRenderer',
    ],

如果我们想局部配置渲染器，只需在自己定义的视图类中添加render_classes 即可，一般也不用做修改，以上分析只是让大家知道drf是怎么配置渲染器的，这样以后我们自定义渲染器也就十分简单了