使用Access-Control-Allow-Origin访问REST失败的Angular 6

所以我试图使用来自’@ angular / common / http’的http：HttpClient将来自REST源的数据加载到我的Angular 6应用程序中.使用ng serve –open在浏览器中调用应用程序虽然不起作用.我认为CORS是这里的问题.我想我要么必须使用Access-Control-Allow-Origin等设置服务器或客户端头,但我已经尝试了多种方法,但没有成功地使这个简单的REST调用工作.以下是我编码的内容.

在浏览器中调用Angular应用程序会响应以下错误：

Failed to load http://localhost:8080/mysite-backend/rest/report/single/d83badf3: 
Response to preflight request doesn't pass access control check: 
No 'Access-Control-Allow-Origin' header is present on the requested 
resource. Origin 'http://localhost:4200' is therefore not allowed 
access.

在Chrome浏览器中调用相同的URL(http：// localhost：8080 / mysite-backend / rest / report / single / d83badf3)可以很好地工作：

{"id":"d83badf3","language":"en","categoryId":"a5","title":"Simcity","created":1527723183880,"modified":1527723183880}

在Angular 6中,我使用以下生成的服务类,使用ng生成服务导览.在其中我创建了方法getTour(id：string),它不仅仅是在URL上调用REST,而是将检索到的JSON字符串作为Tour对象返回：

import { Injectable } from '@angular/core';
import { HttpHeaders,HttpClient } from '@angular/common/http';
import { Observable,of } from 'rxjs';
import { Tour } from './tour';
import { catchError,tap } from 'rxjs/operators';

const httpOptions = {
  headers: new HttpHeaders({
    'Content-Type': 'application/json'
  })
};

@Injectable({
  providedIn: 'root'
})
export class TourService {

  // URL to the web api.
  private tourUrl = 'http://localhost:8080/mysite-backend/rest/report';

  constructor(
    private http: HttpClient
  ) { }

  /**
   * 
   * @param id: string GET tour report by id. Will 404 if id not found.
   */
  getTour(id: string): Observable<Tour> {
    httpOptions.headers.append('Access-Control-Allow-Origin','http://localhost:8080');
    httpOptions.headers.append('Access-Control-Allow-Methods','GET,POST,OPTIONS,PUT,PATCH,DELETE');
    httpOptions.headers.append('Access-Control-Allow-Headers','X-Requested-With,content-type');
    httpOptions.headers.append('Access-Control-Allow-Credentials','true');

    const url = `${this.tourUrl}/single/${id}`;
    console.log("XXX URL GET " + url)
    return this.http.get<Tour>(url,httpOptions).pipe(
      tap(_ => this.log(`fetched tour id=${id}`)),catchError(this.handleError<Tour>(`getHero id=${id}`))
    );
  }

  private handleError<T> (operation = 'operation',result?: T) {
    return (error,any): Observable<T> => {
      console.error(error);
      this.log(`${operation} failed: ${error.message}`);
      return of(result as T);
    };
  }

  private log(message: string) {
    console.log("Log message: " + message);
  }
}

这是Tour对象：

export class Tour {
    id: string;
    language: string;
    categoryId: string;
    created: Date;
    modified: Date;
    title: string;
    content: string;
}

我还将’@ angular / common / http’中的HttpClientModule添加到了app.module.ts中的进口数组和providers数组中.

RESTful WebService是用Java构建的.这里我有getReport(@PathParam(“reportId”)String reportId)方法,它获取一个Report对象并在Reponse中返回它：

import java.util.List;
import javax.inject.Inject;
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.Consumes;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

/**
 * Describes the RESTful access for reports.
 */
@Path("/report")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class ReportResource {
    @Inject
    private Logger logger;

    @GET
    @Path("/single/{reportId}")
    public Response getReport(@PathParam("reportId") String reportId) {
        //return Mock.getReport(reportId);
        return Response.ok() // 200
                       .entity(Mock.getReport(reportId))
                       .header("Access-Control-Allow-Origin","*")
                       .header("Access-Control-Allow-Methods","GET,DELETE,PUT")
                       .allow("OPTIONS").build();
    }
...
}

如何从Angular 6客户端成功调用Java RESTful WebService,我该怎么做？

.header("Access-Control-Allow-Methods",PUT")