当您尝试上传第二个文件时，必须重置formData。

public formdata = new FormData(); 
    onSubmit() {

    this.resetform();  //Order matters here
    let headers: any = new Headers(); 
    headers.append('Content-type', 'undefined');

    formData.append("selectFile", this.formData); 
    const req5 = new HttpRequest('POST', 'url as hosted on TOMCAT', formData, 
    reportProgress: true, 
    responseType: 'text' 
    }); 
    return this.httpClient.request(req5).subscribe(e => {( 
    console.log(e);

    )} 
    }

    resetform() { 
    this.formData = new FormData(); 
    }

我希望它能解决您的问题！