400错误的请求错误，Angular4 +

Question

我正在尝试从数据库中获取数据。 我可以登录，但无法从数据库中检索数据。 但是，通过Postman进行测试会返回状态200。

这是我的API调用索引：

export let CONTEXTROOT="http://localhost:8080/core/api/";

这是我的getDashboardData（）函数：

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable,pipe } from 'rxjs';
import { catchError } from 'rxjs/operators';
import { map } from 'rxjs/operators';
import { CONTEXTROOT } from '../contextRoot';
// import 'rxjs/add/operator/do';  // for debugging

/**
 * This class provides the Data service with methods to get and post data.
 */
@Injectable()
export class DataService {

  /**
   * Creates a new DataService with the injected Http.
   * @param {Http} http - The injected Http.
   * @constructor
   */
  constructor(private http: HttpClient) {}

  /**
   * Returns an Observable for the HTTP GET request for the JSON resource.
   * @return {string[]} The Observable for the HTTP request.
   */
  getDashBoardData(): Observable<any> {
    return this.http.get(CONTEXTROOT+'dashboard')
    //              .do(data => console.log('server data:', data))  // debug
                    .pipe(catchError(this.handleError));
  }

这是我的错误处理功能：

    private handleError (error: any) {
    // In a real world app, we might use a remote logging infrastructure
    // We'd also dig deeper into the error to get a better message
    let errMsg = (error.message) ? error.message :
      error.status ? `${error.status} - ${error.statusText}` : 'Server error';
    console.error(errMsg); // log to console instead
    return Observable.throw(errMsg);
  }
}

为什么我不能启用“获取数据”？我也有启用Chrome的CORS插件。