我正在尝试做一个 http.post 但 chrome 显示以下错误:

No Access-Control-Allow-Origin.

我的 Angular 函数是:

onSubmit(event: Event) {
  event.preventDefault();
    this.leerDatos()
    .subscribe(res => {
      //datos = res.json();
      console.log("Data send");
    }, error => {
          console.log(error.json());
      });



  }

  leerDatos(): Observable<any> {
    let headers = new Headers({ 'Content-Type': 'application/json' });
    let options = new RequestOptions({ headers: headers });

    return this.http.post(`http://localhost:8080/LegoRepositoryVincle/CoreServlet`, { name: "bob" }, options)
                    //.map(this.extractData)
                    //.catch(this.handleError);
  }

我的 servlet doPost 方法包括:

response.setContentType("application/json");
response.setCharacterEncoding("utf-8");
response.addHeader("Access-Control-Allow-Origin","http://localhost:4200");
response.addHeader("Access-Control-Allow-Credentials", "true");
response.addHeader("Access-Control-Allow-Methods","GET,POST");
response.addHeader("Access-Control-Allow-Headers","X-PINGOTHER, Origin, X-Requested-With, Content-Type, Accept, Cache-Control, Pragma");

最佳答案

如果您在开发时仍想使用 CORS，可以使用 angular/cli --proxy-config 解决此类问题。 .

本质上，如果你想向远程机器发出请求，例如 nginx Web 服务器运行时，您执行对同一个应用程序的所有调用，例如localhost:4200(angular/cli 中的默认值)。然后使用 --proxy-config 将这些响应重定向到您的服务器。

假设您的服务器的 api 具有所有 /api 前缀入口点。您需要在项目的根目录中创建一个名为 proxy.config.json 的文件并将其配置为:

{
    "/api" : {
        "target" : "http://xx.xxx.xxx.xx", // Your remote address
        "secure" : false,
        "logLevel" : "debug", // Making Debug Logs in console
        "changeOrigin": true
    }
}

然后，您所有的 http 请求都将指向 localhost:4200/api/。

最后，您应该通过运行 ng server --proxy-config proxy.config.json 来完成。

如果您注意到请求中缺少某些 header ，请从您的网络服务器添加它们或编辑您的 http.service.ts 以附加这些 header ，如本例所示:

import { Injectable } from '@angular/core';
import { Http, Headers, RequestOptions } from '@angular/http';
import { Observable } from 'rxjs/Rx';
import { isNull } from 'lodash';

@Injectable()
export class HttpClientService {

  private _host: string;
  private _authToken: string;
  private _options: RequestOptions = null;

  constructor(private _http: Http, private _config: AppConfig, private _localStorageService: LocalStorageService) {
      this._host = ''; // Your Host here, get it from a configuration file
      this._authToken = ''; // Your token here, get it from API
  }

  /**
   * @returns {RequestOptions}
   */
   createAuthorizationHeader(): RequestOptions {
      // Just checking is this._options is null using lodash
      if (isNull(this._options)) {
        const headers = new Headers();
        headers.append('Content-Type', 'application/json; charset=utf-8');
        headers.append('Authorization', this._authToken);
        this._options = new RequestOptions({headers: headers});
      }
      return this._options;
   }

   /**
    * @param url {string}
    * @param data {Object}
    * @return {Observable<any>}
    */
    get(url?: string, data?: Object): Observable<any> {
      const options = this.createAuthorizationHeader();
      return this._http.get(this._host + url, options);
    }

   /**
    * @param url {string}
    * @param data {Object}
    * @return {Observable<any>}
    */
    post(url?: string, data?: Object): Observable<any> {
      const body = JSON.stringify(data);
      const options = this.createAuthorizationHeader();
      return this._http.post(this._host + url, body, options);
    }

}

因此，您将通过此服务执行所有 api 调用，例如

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { HttpClientService } from './http.service.ts';

export class TestComponent implements OnInit {

  _observable: Observable<any> = null;

  constructor(private _http: HttpClientService) { }

  ngOnInit() {
      this._observable = this _http.get('test/')
                .map((response: Response) => console.log(response.json()));
  }

}

Angular 5 更新:

在 app.module.ts 中，现在您需要将 import { HttpModule } from '@angular/http'; 替换为 import { HttpClientModule } from ' @angular/common/http';.

该服务稍微更改为:

import { Injectable } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';
import { isNull, isUndefined } from 'lodash';

@Injectable()
export class HttpClientService {

  private _host: string;
  private _authToken: string;
  private __headers: HttpHeaders;

  constructor(private _http: HttpClient, private _config: AppConfig, private _localStorageService: LocalStorageService) {
      this._host = ''; // Your Host here, get it from a configuration file
      this._authToken = ''; // Your token here, get it from API
  }

  /**
   * @returns {HttpHeaders}
   */
   createAuthorizationHeader(): HttpHeaders {
      // Just checking is this._options is null using lodash
      if (isNull(this.__headers)) {
        const headers = new HttpHeaders()
           .set('Content-Type', 'application/json; charset=utf-8')
           .set('Authorization', this. _authToken || '');
        this.__headers= new RequestOptions({headers: headers});
      }

      return this.__headers;
   }

   /**
    * @param url {string}
    * @param data {Object}
    * @return {Observable<any>}
    */
    get(url?: string, data?: Object): Observable<any> {
      const options = this.createAuthorizationHeader();
      return this._http.get(this._host + url, {
          headers : this.createAuthorizationHeader()
      });
    }

   /**
    * @param url {string}
    * @param data {Object}
    * @return {Observable<any>}
    */
    post(url?: string, data?: Object): Observable<any> {
      const body = JSON.stringify(data);
      const options = this.createAuthorizationHeader();
      return this._http.post(this._host + url, body, {
          headers : this.createAuthorizationHeader()
      });
    }
}

关于java - 带有 java servlet 的 Angular 4 http CORS No 'Access-Control-Allow-Origin'，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44925449/