问在以角度表示服务的组件之间传递参数：

EN

app.component.ts(as first component)  ->  db-srv-conn.service.ts(as service) -> main.component.ts(as destination component)

    import { HttpClient } from '@angular/common/http';
    import { BehaviorSubject, Observable } from 'rxjs';
    
    export class DbSrvConnService {
       private bsubject=new BehaviorSubject<any>("t");
       constructor(private http:HttpClient) { }
     
  sendMassage(massage: string) {
               this.bsubject.next(massage);
       }


   getMassage(): Observable<any> {
        return this.subject.asObservable();
       }
    }

import { DbSrvConnService } from 'src/app/sevices/db-srv-conn.service';

export class AppComponent{
  constructor(private DbSrvConnService:DbSrvConnService) { }
...
login(){
    const massage=this.formGroupLogin.value.massage;  
    if (status==1){
            this.DbSrvConnService.send_user(massage);
          }
}

    import { DbSrvConnService } from 'src/app/sevices/db-srv-conn.service';
    ...
    
   massages: any;
  subscription: Subscription;

      constructor(private DbSrvConnService:DbSrvConnService) { 
        this.subscription = this.DbSrvConnService.getMessage().subscribe(massage => {
          console.log(massage);
          
        });