如何在角度请求中设置多个标头值？

Question

我尝试将标头值为large = pd.Series([random.choice(string.ascii_uppercase) + random.choice(string.ascii_uppercase) for _ in range(100000)]) In [275]: %timeit [x.lower() if pd.notnull(x) else x for x in large] 73.3 ms ± 4.24 ms per loop (mean ± std. dev. of 7 runs, 10 loops each) In [276]: %timeit large.str.lower() 28.2 ms ± 684 µs per loop (mean ± std. dev. of 7 runs, 10 loops each) In [277]: %timeit [x.lower() for x in large] 14.1 ms ± 784 µs per loop (mean ± std. dev. of 7 runs, 100 loops each) 的请求发送到我的REST API。我尝试通过以下代码实现这一点

Conent-type

它工作正常，并且在Chrome开发者工具的“请求标头”部分下，我的请求带有 getTokenizedLoginStatus(user: User): Observable<any> { httpOptions = { headers: new HttpHeaders({'Content-type': 'text/plain'}) }; return this.http.post<any>(apiUrl + '/archive/users/tokenizedLogin', user, httpOptions); } 标头。但是，现在我想在请求中发送多个标头，如下图所示

Content-type: text/plain

当我发出请求时，Content-Type标头值不再存在，并且出现错误提示。

getTokenizedLoginStatus(user: User): Observable<any> {
                httpOptions = {
                  headers: new HttpHeaders({'Content-type': 'text/plain', 'User': 'someone', 'Token': '123456'})
                };
                return this.http.post<any>(apiUrl + '/archive/users/tokenizedLogin', user, httpOptions);
     }

但是在我的Java代码中，我定义了Access-Control-Allow-Origin如下：

 Failed to load
 http://localhost:8080/DemoProject/archive/users/tokenizedLogin:
 Response to preflight request doesn't pass access control check: No
 'Access-Control-Allow-Origin' header is present on the requested
 resource. Origin 'http://localhost:4200' is therefore not allowed
 access.

我不明白为什么Content-Type不再作为请求的一部分发送，或者为什么我的API抛出该错误。以及如何修改我的代码以同时发送所有这些标头？