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[英]XMLHttpRequest cannot load . . . No 'Access-Control-Allow-Origin' header is present on the requested resource.
[英]Error with XMLHttpRequest - “No 'Access-Control-Allow-Origin' header is present on the requested resource.”
我正在使用Angular 2创建应用程序的前端,并且正在尝试使用XMLHttpRequest从第三方站点加载图像。
我的代码如下:
loadFile(fileUrl) {
const promise = new Promise((resolve, reject) => {
const request = new XMLHttpRequest();
request.open('GET', fileUrl, true);
request.setRequestHeader('Accept', 'image/jpeg');
request.onload = () => {
if (request.status === 200) {
resolve(request);
}
else {
reject(Error(request.statusText));
}
};
request.onerror = () => {
reject(Error('Network error.'));
};
request.send();
});
return promise;
}
这是我用来测试的代码:
import FileHelper from './file-helper';
describe('File Helper', () => {
it('should retrieve the contents of an image on the web', (done) => {
let fileLoadPromise, fileContent;
fileLoadPromise = FileHelper.loadFile('http://adsoftheworld.com/files/steve-jobs.jpg');
fileLoadPromise.then((request: XMLHttpRequest) => {
fileContent = request.responseText;
expect(request.responseType).toEqual('image/jpeg');
done();
}).catch(error => {
console.log(error);
done.fail();
});
expect(fileContent).toBeTruthy();
});
});
我环顾了互联网,有几页说我应该在标题中添加image/jpeg
,因此我使用了以下方法: request.setRequestHeader('Accept', 'image/jpeg');
,但是无论何时运行此代码,我仍然会收到以下错误:
XMLHttpRequest cannot load http://adsoftheworld.com/files/steve-jobs.jpg. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:9876' is therefore not allowed access.
谁能帮我?
您面临的问题称为CORS, https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS通过提供标头Access-Control-Allow-Origin:*,您将可以访问通过ajax生成图像,但问题是为什么要使用ajax? 只是使用img标签对不对?
<img src="http://adsoftheworld.com/files/steve-jobs.jpg"/>
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