import {Injectable} from "@angular/core";
import {Http, Jsonp} from "@angular/http";
import "rxjs/add/operator/map";
@Injectable()
export class HttpServer {
  constructor(public jsonp: Jsonp, public http: Http) {

  }
 /*
  *   url: 服务器api接口地址
  *   params: 传递参数对象
  */
  // get方法
  httpGet(url, params) {
    return this.http.get(url, {search: params}).map(res=>res.json);
  }
  // post方法
  httpPost(url, params) {
    return this.http.post(url, {search: params}).map(res=>res.json);
  }
  // 跨域请求
  jsonpGet(url, params) {
    return this.jsonp.get(url, {search: params}).map(res=>res.json());
  }
}

import {HttpServer} from "./http.server.ts";
...
providers: [HttpServer]
...

...
import {URLSearchParams} from "@angular/http";
...
// 使用服务
// 设置参数
var params = new URLSearchParams();
params.set("callback", "JSONP_CALLBACK");
// 调用jsonpGet方法，跨域请求数据
httpServer.jsonpGet("http://localhost:3000/users", params).subscribe(res=> {
  console.log(res);
});