Angular 7中的Post方法不适用于Spring Boot Rest Controller

Question

我在Angular 7中无法识别post方法的问题。我遇到了错误：Http failure response for http://localhost:4200/sendMail: 404 Not Found。 这是我在Angular中的post方法：

sendEmail(email: EmailModel): Observable<EmailModel> {

        const url = `sendMail`;
        return this.http.post<EmailModel>(url, email, httpOptions).pipe(
            tap(_ => this.log('Category is stored!!!')),

            catchError(this.handleError<EmailModel>('addHero'))

        )
    }

这是我在Spring Boot中的post方法：

@PostMapping("/sendMail")
    @ResponseStatus(HttpStatus.OK)
    @ResponseBody
    public String sendMail(@RequestBody EmailModel emailModel) {
        MimeMessage message = sender.createMimeMessage();
        MimeMessageHelper helper = new MimeMessageHelper(message);

        System.out.println(emailModel);

        try {
            helper.setTo("saomi@gmail.com");
            helper.setText("Greetings :)");
            helper.setSubject("Mail From Spring Boot");
        } catch (MessagingException e) {
            e.printStackTrace();
            return "Error while sending mail ..";
        }
        sender.send(message);
        return "Mail Sent Success!";
    }
}

当我通过邮递员在此路径上发送邮件时，在Spring Boot上可以很好地工作：

http://localhost:8080/sendMail

这是我的proxy.conf.json：

{
    "/api": {
        "target": "http://localhost:8080",
      "secure": false,
      "changeOrigin": true
    }
}

其余API正常工作。