HTTP协议消息头中，Content-Type表示媒体类型。
设置参数值为application/json。请求中的数据将以JSON形式传输。参考代码如下：
import { http } from '@kit.NetworkKit';
class Header {
public contentType: string;
constructor(contentType: string) {
this.contentType = contentType;
}
}
let httpRequest = http.createHttp();
let promise = httpRequest.request("EXAMPLE_URL", {
method: http.RequestMethod.GET,
connectTimeout: 60000,
readTimeout: 60000,
header: new Header('application/json')
}); 参考链接