axios学习

下面是对于request config的官方说明，更多信息请移步axios官网

{
  // `url` is the server URL that will be used for the request
  url: '/user',

  // `method` is the request method to be used when making the request
  method: 'get', // default

  // `baseURL` will be prepended to `url` unless `url` is absolute.
  // It can be convenient to set `baseURL` for an instance of axios to pass relative URLs
  // to methods of that instance.
  baseURL: 'https://some-domain.com/api/',

  // `transformRequest` allows changes to the request data before it is sent to the server
  // This is only applicable for request methods 'PUT', 'POST', and 'PATCH'
  // The last function in the array must return a string or an instance of Buffer, ArrayBuffer,
  // FormData or Stream
  // You may modify the headers object.
  transformRequest: [function (data, headers) {
    // Do whatever you want to transform the data

    return data;
  }],

  // `transformResponse` allows changes to the response data to be made before
  // it is passed to then/catch
  transformResponse: [function (data) {
    // Do whatever you want to transform the data

    return data;
  }],

  // `headers` are custom headers to be sent
  headers: {'X-Requested-With': 'XMLHttpRequest'},

  // `params` are the URL parameters to be sent with the request
  // Must be a plain object or a URLSearchParams object
  params: {
    ID: 12345
  },

  // `paramsSerializer` is an optional function in charge of serializing `params`
  // (e.g. https://www.npmjs.com/package/qs, http://api.jquery.com/jquery.param/)
  paramsSerializer: function(params) {
    return Qs.stringify(params, {arrayFormat: 'brackets'})
  },

  // `data` is the data to be sent as the request body
  // Only applicable for request methods 'PUT', 'POST', and 'PATCH'
  // When no `transformRequest` is set, must be of one of the following types:
  // - string, plain object, ArrayBuffer, ArrayBufferView, URLSearchParams
  // - Browser only: FormData, File, Blob
  // - Node only: Stream, Buffer
  data: {
    firstName: 'Fred'
  },

  // `timeout` specifies the number of milliseconds before the request times out.
  // If the request takes longer than `timeout`, the request will be aborted.
  timeout: 1000,

  // `withCredentials` indicates whether or not cross-site Access-Control requests
  // should be made using credentials
  withCredentials: false, // default

  // `adapter` allows custom handling of requests which makes testing easier.
  // Return a promise and supply a valid response (see lib/adapters/README.md).
  adapter: function (config) {
    /* ... */
  },

  // `auth` indicates that HTTP Basic auth should be used, and supplies credentials.
  // This will set an `Authorization` header, overwriting any existing
  // `Authorization` custom headers you have set using `headers`.
  auth: {
    username: 'janedoe',
    password: 's00pers3cret'
  },

  // `responseType` indicates the type of data that the server will respond with
  // options are 'arraybuffer', 'blob', 'document', 'json', 'text', 'stream'
  responseType: 'json', // default

  // `xsrfCookieName` is the name of the cookie to use as a value for xsrf token
  xsrfCookieName: 'XSRF-TOKEN', // default

  // `xsrfHeaderName` is the name of the http header that carries the xsrf token value
  xsrfHeaderName: 'X-XSRF-TOKEN', // default

  // `onUploadProgress` allows handling of progress events for uploads
  onUploadProgress: function (progressEvent) {
    // Do whatever you want with the native progress event
  },

  // `onDownloadProgress` allows handling of progress events for downloads
  onDownloadProgress: function (progressEvent) {
    // Do whatever you want with the native progress event
  },

  // `maxContentLength` defines the max size of the http response content allowed
  maxContentLength: 2000,

  // `validateStatus` defines whether to resolve or reject the promise for a given
  // HTTP response status code. If `validateStatus` returns `true` (or is set to `null`
  // or `undefined`), the promise will be resolved; otherwise, the promise will be
  // rejected.
  validateStatus: function (status) {
    return status >= 200 && status < 300; // default
  },

  // `maxRedirects` defines the maximum number of redirects to follow in node.js.
  // If set to 0, no redirects will be followed.
  maxRedirects: 5, // default

  // `socketPath` defines a UNIX Socket to be used in node.js.
  // e.g. '/var/run/docker.sock' to send requests to the docker daemon.
  // Only either `socketPath` or `proxy` can be specified.
  // If both are specified, `socketPath` is used.
  socketPath: null, // default

  // `httpAgent` and `httpsAgent` define a custom agent to be used when performing http
  // and https requests, respectively, in node.js. This allows options to be added like
  // `keepAlive` that are not enabled by default.
  httpAgent: new http.Agent({ keepAlive: true }),
  httpsAgent: new https.Agent({ keepAlive: true }),

  // 'proxy' defines the hostname and port of the proxy server
  // Use `false` to disable proxies, ignoring environment variables.
  // `auth` indicates that HTTP Basic auth should be used to connect to the proxy, and
  // supplies credentials.
  // This will set an `Proxy-Authorization` header, overwriting any existing
  // `Proxy-Authorization` custom headers you have set using `headers`.
  proxy: {
    host: '127.0.0.1',
    port: 9000,
    auth: {
      username: 'mikeymike',
      password: 'rapunz3l'
    }
  },

  // `cancelToken` specifies a cancel token that can be used to cancel the request
  // (see Cancellation section below for details)
  cancelToken: new CancelToken(function (cancel) {
  })
}

特别注意：

1.在使用axios时，有一个params作为传递参数，一个是data，这两个参数是有区别的。
    params：是一定会拼接在url上的参数，不管你是不是post方式
    data: 是对post方式，放在body里的数据

如下图：

2.在使用post方式请求api时，关于后台接口无法获取axios传递的参数问题：

这是因为axios的默认请求头中Content-Type是text/plain，application/json格式，可查看：

我们需要通过设置Content-Type就可以解决这个问题：

axios.defaults.headers.post['Content-Type'] = 'application/x-www-form-urlencoded';

这个第三个图片就可以看到，原来在没有设置content-type时，Request payload,这是一个流，而设置完以后，这个数据就变为了Form Data,更多详细说明请看官方文档。

其实在formData是错误的解释，这里他依然采用的是key-value的形式给后台传值，因为我在传递data时：直接就是如下：

const data = {
    header: ['dict_key','dict_value','order'],
    data: [
        {
            'dict_key': '字典key',
            'dict_value: 'dictkey',
            'order': 12
        },
        ........
    ]
}

// 这种方式传递到axios中的data时，他依然会以key-value给后台传值，实际上你在后台可以通过getParameterMap()获取到data的字符串key,但你没法通过getParameter("header"),浏览器返回的那个结果就能看出来，已经把data转为字符串，作为formdata的一个key,而对应的值就是一个“”。

上面的方式可以通过getParamterMap()去遍历获取到key，但没法使用Spring Boot的那些映射方法，所以上面额方法不够好，也不算是formdata数据，那么如何做呢？如下：

// 构造formData数据,关键在这里
const data = new FormData()
data.append('header', this.tableHeader)
data.append('dicts', JSON.stringify(this.tableData))
// 调用导入接口，传入对象，表头和表数据
      imoprtDict(data).then(response => {
        if (response.data.success) {
          this.$message({
            message: '批量导入成功！',
            type: 'success'
          })
        } else {
          this.$message.error('批量导入失败!')
                }
// api
export function imoprtDict(data) {
  return request({
    url: '/dict/import',
    method: 'post',
    data
  })
}

这个时候请求后台，如图：

总结：

1.params参数一定会在url后面显示拼接
2.data参数说明：
// `data` is the data to be sent as the request body
// Only applicable for request methods 'PUT', 'POST', and 'PATCH'
// When no `transformRequest` is set, must be of one of the following types:
// - string, plain object, ArrayBuffer, ArrayBufferView, URLSearchParams
// - Browser only: FormData, File, Blob
// - Node only: Stream, Buffer
3.通常我们不要自作聪明去设置headers
4.如果data是一个formData对象，那么Content-Type自动就是multipart/form-data; boundary=----WebKitFo