来自本地服务器上项目的servlet的Angular Http.get请求（json数据正确返回但未显示，但可与模拟api一起使用）

Question

控制台错误：

Error with getting users from service. Response with status: 404 Not Found for URL: http://localhost:8080/ChatApp/GetAllUsersServlet

当我将外部项目部署到某处时，也会发生相同的问题，因此使用url： http : //java.cyclone2.khleuven.be : 38034/ ChatApp/ GetAllUsersServlet您可以自己看到其中是带有json的有效url，但stil 404错误。

期望在本地服务器上运行的servlet的角度代码：

export class UserService {
  // private usersUrl = 'api/users'; // mock api
  private usersUrl = 'http://localhost:8080/ChatApp/GetAllUsersServlet'; // external users from local server
  private headers = new Headers({'Content-Type': 'application/json'});

  constructor(private http: Http) { }
  getUsers(): Promise<User[]> {
    return this.http.get(this.usersUrl)
               .toPromise() // Http.get returns RxJS Observeable, converted to Promise here
               .then(response => response.json().data as User[]) // .data for mock inMemoryDataService
               .catch(this.handleError);
  }

Servlet返回什么：

[{"fname":"TestFname","password":"test","gender":"Female","name":"TestName","id":1,"email":"test@test.com","age":21,"username":"Test","status":"offline"},{"fname":"Test4Fname","password":"test","gender":"Female","name":"Test4Name","id":4,"email":"test4@test.com","age":21,"username":"Test4","status":"offline"},{"fname":"Test3Fname","password":"test","gender":"Female","name":"Test3Name","id":3,"email":"test3@test.com","age":28,"username":"Test3","status":"offline"},{"fname":"Test2Fname","password":"test","gender":"Male","name":"Test2Name","id":2,"email":"test2@test.com","age":22,"username":"Test2","status":"offline"}]

模拟api中的确切内容确实给出了正确的结果：

import { InMemoryDbService } from 'angular-in-memory-web-api';
export class InMemoryDataService implements InMemoryDbService {
  createDb() {
    let users = [{"fname":"TestFname","password":"test","gender":"Female",
      "name":"TestName","id":1,"email":"test@test.com","age":21,"username":"Test","status":"offline"},
      {"fname":"Test4Fname","password":"test","gender":"Female",
      "name":"Test4Name","id":4,"email":"test4@test.com","age":21,"username":"Test4","status":"offline"},{"fname":"Test3Fname","password":"test","gender":"Female","name":"Test3Name","id":3,"email":"test3@test.com","age":28,"username":"Test3","status":"offline"},
      {"fname":"Test2Fname","password":"test","gender":"Male",
      "name":"Test2Name","id":2,"email":"test2@test.com","age":22,"username":"Test2","status":"offline"}]
    return {users};
  }
}

任何帮助将不胜感激，因为我真的不知道为什么它不起作用。 尝试了类似的东西，但JSON数据更少，并且有效。 是的，该servlet的服务器在本地运行。

getUsers（）被此方法使用和显示，但是由于它可以与模拟数据一起使用，因此应该可以吗？：

export class UsersComponent  {
    users: User[];
    selectedUser: User;

    constructor(
      private userService: UserService,
      private router: Router) { }

    gotoInfo(): void {
      this.router.navigate(['/info', this.selectedUser.username]);
    }
    onSelect(user: User): void {
      this.selectedUser = user;
    }
    getUsers(): void {
      this.userService.getUsers().then(users => this.users = users);
    }
    ngOnInit(): void {
      this.getUsers();
    }
 }

Servlet（启用cors）：

受保护的无效processRequest（HttpServletRequest请求，HttpServletResponse响应）引发ServletException，IOException {UserDB db = new UserDB（）;

JSONArray array = new JSONArray();
for (User users: db.getAll()) {
    try {
        array.put(users.getJSONObject());
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

// setting the response type to json
response.setContentType("application/json");
// setting the CORS request
response.setHeader("Access-Control-Allow-Origin", "*");

response.getWriter().write(array.toString());

Answer 1

除非您从NgModule中删除类似以下InMemoryWebApiModule.forRoot(InMemoryDataService)类的内容，否则以前使用in-memory-web-api会干扰您的http请求。

编辑：基于您知道以下内容的代码注释实现：

完成此操作后，我还可以指出，您的get请求中存在问题，因为这样一来您就不会在组件中获取任何数据。 您的响应仅包含一个数组，而不包含 data ，因此应为：

 
 
 
  
  .then(response => response.json() as User[])