# 7.1 静态文件访问原理

## 1.默认访问方法

Flask访问静态文件非常简单，只需要在项目根目录建立static文件夹。将静态资源文件放入static下即可。访问的时候访问`http://ip:port/static/fileName`即可。

需要注意的是，这里的根目录并不是项目的根目录fisher，而是app目录。这是因为，我们在实例化Flask核心对象的时候，传入了\_\_name\_\_参数，这个 \_\_name\_\_指向的就是当前文件所在目录。

![image.png](https://upload-images.jianshu.io/upload_images/7220971-8f6488aafcc6c931.png?imageMogr2/auto-orient/strip|imageView2/2/w/1240)

## 2.修改默认存储路径

修改默认存储路径，只需要在实例化Flask核心对象的时候，传入static\_folder这个关键字参数即可，但是这个时候，访问的路径应该变成`http://ip:port/static_folder的最后一级/fileName`，如果想自定义url访问路径，传入关键字参数static\_url\_path即可

```python
app = Flask(__name__, static_folder="statics", static_url_path="/static")
```

## 3.核心原理

在Flask的app.py的Flask类的构造函数的地556行，是注册静态资源视图函数的源码，可以看到实际上就是通过我们之前所讲到的add\_url\_rule注册了一个视图函数。其中的访问url路径，就是获取了static\_url\_path

```python
        if self.has_static_folder:
            assert bool(static_host) == host_matching, 'Invalid static_host/host_matching combination'
            self.add_url_rule(
                self.static_url_path + '/<path:filename>',
                endpoint='static',
                host=static_host,
                view_func=self.send_static_file
            )
```

下面是static\_url\_path的定义，可以看到他是调用了\_get\_static\_url\_path方法。 这个方法首先获取static\_url\_path关键字参数，如果有，则直接将其作为url访问路径，否则获取static\_folder关键字参数，如果有，则取他的基本路径拼拼接上"/"作为url访问路径

```python
    def _get_static_url_path(self):
        if self._static_url_path is not None:
            return self._static_url_path

        if self.static_folder is not None:
            return '/' + os.path.basename(self.static_folder)
```


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