Angular 2 navigation re initialize all services and components

I have searched a lot in stackoverflow but I don't find a real explanation to my problem.... I'm trying to make a simple angular2 application, with a RouterModule, a simple Service and a simple Component. So :
My Router Module :

import { NgModule } from '@angular/core'; import { RouterModule, Routes } from '@angular/router'; import { StudentListComponent } from '../students-list.component'; import { StudentComponent } from '../student.component'; const routes: Routes = [ { path: 'students', component : StudentListComponent }, { path: 'student/:id', component: StudentComponent }, { path: '**', redirectTo : '/students', pathMatch: 'full' }, { path: '', redirectTo : '/students', pathMatch: 'full' } ]; @NgModule({ imports: [ RouterModule.forRoot(routes) ], exports: [ RouterModule ] }) export class AppRouterModule { } 

My Component :

import { Component, OnInit } from '@angular/core'; import { StudentService } from './services/student.service'; import { Student } from './class/Student'; @Component({ selector: 'student-list', templateUrl: 'app/views/students-list.component.html', styleUrls: ['app/views/styles/students-list.component.css'], providers : [ StudentService ] }) export class StudentListComponent implements OnInit { private studentService: StudentService; students: Student[]; constructor(studentService: StudentService) { console.log('reinit component'); this.studentService = studentService; } ngOnInit(): void { if(!this.students) this.studentService.getStudents().then( (students) => this.students = students ); } } 

My Service :

import { Injectable } from '@angular/core'; import { Http } from '@angular/http'; import 'rxjs/add/operator/toPromise'; import { Student } from '../class/Student'; import { Note } from '../class/Note'; import { CourseService } from './course.service'; @Injectable() export class StudentService { static service: StudentService; private httpUrl = "http://localhost/NotesApp/webServ/"; private students: Student[]; private courseService: CourseService; private http:Http; constructor(courseService: CourseService, http:Http){ console.log('reinit service'); this.courseService = courseService; this.http = http; } getStudents(): Promise<Student[]> { return this .http .get(this.httpUrl+'getStudents') .toPromise() .then( response => this.hydratedStudentArray( response.json() ) ) .catch( this.handleError ); } getStudentById(id: number): Promise<Student> { return this .http .get(this.httpUrl+'getStudent/'+id) .toPromise() .then(response => this.hydratedStudent( response.json()[0]) ) .catch( this.handleError ); } private hydratedStudentArray(jsonArray: { id: number, firstname: string, lastname: string }[]): Student[]{ let hydratedArray: Student[] = []; for (let jsonElement of jsonArray){ hydratedArray.push(new Student(jsonElement.id, jsonElement.lastname, jsonElement.firstname)); } return hydratedArray; } private hydratedStudent(jsonElement: { id: number, firstname: string, lastname: string }): Student{ return new Student(jsonElement.id, jsonElement.lastname, jsonElement.firstname); } private handleError(error: any): Promise<any> { console.error('An error occurred', error); // for demo purposes only return Promise.reject(error.message || error); } } 

So my problem is : When I navigate using a link like <a routerLink="/students">Students</a> or <a [routerLink]="['/student', student.id]" >{{ student.lastname }} {{ student.firstname }}</a>, this trigger the console.log I have written in the component and service constructor..., I see 'reinit component' and 'reinit service' in my console each time I navigate ... How can I avoid this ? Thanks