javascript - 创建自定义休息客户端

Question

我正在学习如何创建一个自定义的 Rest 客户端，以便与 Flask 中的 ReSTLess api 进行通信，以便在 Admin-on-rest 上使用。

我正在尝试解决案例 GET_LIST，但没有取得任何成功，并且我不知道下一步可以做什么？

我首先收到此错误

Fetch API cannot load localhost:5000/api/…. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'localhost:3000'; is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

现在我有下面的代码

import {
GET_LIST,
GET_ONE,
GET_MANY,
GET_MANY_REFERENCE,
CREATE,
UPDATE,
DELETE,
fetchUtils,
} from 'admin-on-rest';

const API_URL = 'http://localhost:5000/api';

/**
 * @param {String} type One of the constants appearing at the top if this file, e.g. 'UPDATE'
 * @param {String} resource Name of the resource to fetch, e.g. 'posts'
 * @param {Object} params The REST request params, depending on the type
 * @returns {Object} { url, options } The HTTP request parameters
 */
const convertRESTRequestToHTTP = (type, resource, params) => {
    let url = '';
    const { queryParameters } = fetchUtils;
    const options = {};
    switch (type) {
    case GET_LIST: {
        const { page, perPage } = params.pagination;
        const { field, order } = params.sort;
        const query = {
            sort: JSON.stringify([field, order]),
            range: JSON.stringify([(page - 1) * perPage, page * perPage - 1]),
            filter: JSON.stringify(params.filter),
        };
        url = `${API_URL}/${resource}?${queryParameters(query)}`;
        break;
    }
    case GET_ONE:
        url = `${API_URL}/${resource}/${params.id}`;
        break;
    case GET_MANY: {
        const query = {
            filter: JSON.stringify({ id: params.ids }),
        };
        url = `${API_URL}/${resource}?${queryParameters(query)}`;
        break;
    }
    case GET_MANY_REFERENCE: {
        const { page, perPage } = params.pagination;
        const { field, order } = params.sort;
        const query = {
            sort: JSON.stringify([field, order]),
            range: JSON.stringify([(page - 1) * perPage, (page * perPage) - 1]),
            filter: JSON.stringify({ ...params.filter, [params.target]: params.id }),
        };
        url = `${API_URL}/${resource}?${queryParameters(query)}`;
        break;
    }
    case UPDATE:
        url = `${API_URL}/${resource}/${params.id}`;
        options.method = 'PUT';
        options.body = JSON.stringify(params.data);
        break;
    case CREATE:
        url = `${API_URL}/${resource}`;
        options.method = 'POST';
        options.body = JSON.stringify(params.data);
        break;
    case DELETE:
        url = `${API_URL}/${resource}/${params.id}`;
        options.method = 'DELETE';
        break;
    default:
        throw new Error(`Unsupported fetch action type ${type}`);
    }
    return { url, options };
};

/**
 * @param {Object} response HTTP response from fetch()
 * @param {String} type One of the constants appearing at the top if this file, e.g. 'UPDATE'
 * @param {String} resource Name of the resource to fetch, e.g. 'posts'
 * @param {Object} params The REST request params, depending on the type
 * @returns {Object} REST response
 */
const convertHTTPResponseToREST = (response, type, resource, params) => {
    const { headers, json } = response;
    switch (type) {
    case GET_LIST:
        return {
            data: json.map(x => x),
            total: parseInt(headers.get('content-range').split('/').pop(), 10),
        };
    case CREATE:
        return { data: { ...params.data, id: json.id } };
    default:
        return { data: json };
    }
};

/**
 * @param {string} type Request type, e.g GET_LIST
 * @param {string} resource Resource name, e.g. "posts"
 * @param {Object} payload Request parameters. Depends on the request type
 * @returns {Promise} the Promise for a REST response
 */
export default (type, resource, params) => {
    const { fetchJson } = fetchUtils;
    const { url, options } = convertRESTRequestToHTTP(type, resource, params);
    return fetchJson(url, options)
        .then(response => convertHTTPResponseToREST(response, type, resource, params));
};

Answer 1

您需要通过设置正确的 CORS http header 来配置服务器以允许来自 localhost:3000 的请求