ozenero | Mobile & Web Programming Tutorials

In this tutorial, we’re gonna build a full Reactive Application in which, Spring WebFlux, Spring Data Reactive MongoDB are used for backend, and Angular, RxJS, EventSource are on client side.

I. Technologies

– Java 1.8
– Maven 3.3.9
– Spring Tool Suite 3.9.0.RELEASE
– Spring Boot 2.0.0.RELEASE
– Angular 13
– RxJS 5.1.0
– MongoDB 3.4.10

II. Overview

1. Full Stack Architecture

angular-4-spring-webflux-reactive-mongodb-architecture

2. Reactive Spring Boot Server

2.1 Dependency

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-mongodb-reactive</artifactId>
</dependency>

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

2.2 Reactive Repository

We just need to create an interface that extends ReactiveCrudRepository to do CRUD operations for a specific type. This repository follows reactive paradigms and uses Project Reactor types (Flux, Mono) which are built on top of Reactive Streams.

import org.springframework.data.repository.reactive.ReactiveCrudRepository;
import reactor.core.publisher.Flux;

public interface ReactiveCustomerRepository extends ReactiveCrudRepository<Customer, String> {

	Mono<Customer> findByLastname(String lastname);
	Flux<Customer> findByAge(int age);

	@Query("{ 'firstname': ?0, 'lastname': ?1}")
	Mono<Person> findByFirstnameAndLastname(String firstname, String lastname);
}

2.3 Activate reactive Spring Data MongoDB

Support for reactive Spring Data is activated through an @EnableReactiveMongoRepositories annotation:

import org.springframework.data.mongodb.config.AbstractReactiveMongoConfiguration;
import org.springframework.data.mongodb.repository.config.EnableReactiveMongoRepositories;

import com.mongodb.reactivestreams.client.MongoClient;
import com.mongodb.reactivestreams.client.MongoClients;

@EnableReactiveMongoRepositories
public class MongoDbReactiveConfig extends AbstractReactiveMongoConfiguration {

	@Override
	public MongoClient reactiveMongoClient() {
		return MongoClients.create();
	}

	@Override
	protected String getDatabaseName() {
		return "jsa_mongodb";
	}
}

2.4 Call Reactive Repository

We can forward the reactive parameters provided by Spring Web Reactive, pipe them into the repository, get back a Flux/Mono and then work with result in reactive way.

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@CrossOrigin(origins = "http://localhost:4200")
@RestController
public class CustomerController {

	@Autowired
	ReactiveCustomerRepository customerRepository;

	@GetMapping("/customers")
	public Flux<Customer> getAllCustomers() {
		return customerRepository.findAll();
	}

	@PostMapping("/customers/create")
	public Mono<Customer> createCustomer(@Valid @RequestBody Customer customer) {
		return customerRepository.save(customer);
	}

	@PutMapping("/customers/{id}")
	public Mono<ResponseEntity<Customer>> updateCustomer(@PathVariable("id") String id, @RequestBody Customer customer) {
		return customerRepository.findById(id).flatMap(customerData -> {
			customerData.setName(customer.getName());
			customerData.setAge(customer.getAge());
			customerData.setActive(customer.isActive());
			return customerRepository.save(customerData);
		}).map(updatedcustomer -> new ResponseEntity<>(updatedcustomer, HttpStatus.OK))
				.defaultIfEmpty(new ResponseEntity<>(HttpStatus.NOT_FOUND));
	}

	@DeleteMapping("/customers/{id}")
	public ResponseEntity<String> deleteCustomer(@PathVariable("id") String id) {
		try {
			customerRepository.deleteById(id).subscribe();
		} catch (Exception e) {
			return new ResponseEntity<>("Fail to delete!", HttpStatus.EXPECTATION_FAILED);
		}
		return new ResponseEntity<>("Customer has been deleted!", HttpStatus.OK);
	}

	@DeleteMapping("/customers/delete")
	public ResponseEntity<String> deleteAllCustomers() {
		try {
			customerRepository.deleteAll().subscribe();
		} catch (Exception e) {
			return new ResponseEntity<>("Fail to delete!", HttpStatus.EXPECTATION_FAILED);
		}
		return new ResponseEntity<>("All customers have been deleted!", HttpStatus.OK);
	}

	@GetMapping("/customers/findbyname")
	public Flux<Customer> findByName(@RequestParam String name) {
		return customerRepository.findByName(name);
	}
}

In the rest controller methods which are annotated by @RequestMapping, we have used some methods of autowired repository which are implemented interface ReactiveCrudRepository:

public interface ReactiveCrudRepository<T, ID> extends Repository<T, ID> {

	<S extends T> Mono<S> save(S entity);
	Mono<T> findById(ID id);
	Flux<T> findAll();
	Mono<Void> deleteById(ID id);
	Mono<Void> deleteAll();
	// ...
}

And findByName method that we create in our interface ReactiveCustomerRepository:

public interface ReactiveCustomerRepository extends ReactiveCrudRepository<Customer, String> {
	Flux<Customer> findByName(String name);
}

Remember that we want to connect to backend from a client application deployed in a different port, so we must enable CORS using @CrossOrigin annotation.

3. Reactive Angular Client

3.1 Reactive Service

This service interacts with the backend using Server-Sent Events.

import { Injectable } from '@angular/core';
import { HttpClient, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import * as EventSource from 'eventsource';

@Injectable()
export class CustomerService {

  private baseUrl = 'http://localhost:8080/api/customers';
  private customersList: Customer[] = new Array();
  private customersListSearch: Customer[] = new Array();

  constructor(private http: HttpClient) {
  }

  createCustomer(customer: Object): Observable<Object> {
    return this.http.post(`${this.baseUrl}` + `/create`, customer);
  }

  updateCustomer(id: string, value: any): Observable<Object> {
    return this.http.put(`${this.baseUrl}/${id}`, value);
  }

  deleteCustomer(id: string): Observable<any> {
    return this.http.delete(`${this.baseUrl}/${id}`, { responseType: 'text' });
  }

  getCustomersList(): Observable<any> {
    this.customersList = new Array();

    return Observable.create((observer) => {
      const eventSource = new EventSource(`${this.baseUrl}`);
      eventSource.onmessage = (event) => {
        console.log('eventSource.onmessage: ', event);
        const json = JSON.parse(event.data);
        this.customersList.push(new Customer(json['id'], json['name'], json['age'], json['active']));
        observer.next(this.customersList);
      };
      eventSource.onerror = (error) => observer.error('eventSource.onerror: ' + error);
      return () => eventSource.close();
    });
  }

  deleteAll(): Observable<any> {
    return this.http.delete(`${this.baseUrl}` + `/delete`, { responseType: 'text' });
  }

  findCustomers(name): Observable<any> {
    this.customersListSearch = new Array();

    return Observable.create((observer) => {
      const eventSource = new EventSource(`${this.baseUrl}` + `/findbyname?name=` + name);
      eventSource.onmessage = (event) => {
        console.log('eventSource.onmessage: ', event);
        const json = JSON.parse(event.data);
        this.customersListSearch.push(new Customer(json['id'], json['name'], json['age'], json['active']));
        observer.next(this.customersListSearch);
      };
      eventSource.onerror = (error) => observer.error('eventSource.onerror: ' + error);
      return () => eventSource.close();
    });
  }
}

Whenever we receive an event through the EventSource object, onmessage() is invoked. That’s where we parse data and update item list.

Using RxJS Observable object, any Observer that subscribed to the Observable we created can receive events when the item list gets updated (when calling observer.next(...)).

For more details about RxJS, please visit:
Introduction to RxJS – Extensions for JavaScript Reactive Streams

3.2 Reactive Component

This Component calls Service above and keep result inside an Observable object:

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs/Observable';

import { CustomerService } from '../customer.service';
import { Customer } from '../customer';

@Component({
  selector: 'customers-list',
  templateUrl: './customers-list.component.html',
  styleUrls: ['./customers-list.component.css']
})
export class CustomersListComponent implements OnInit {

  customers: Observable<Customer[]>;

  constructor(private customerService: CustomerService) {  }

  ngOnInit() {
    this.reloadData();
  }

  deleteCustomers() {
    this.customerService.deleteAll()
      .subscribe(
        data => console.log(data),
        error => console.log('ERROR: ' + error)
      );
  }

  reloadData() {
    this.customers = this.customerService.getCustomersList();
  }
}

In HTML template, we add async pipe that subscribes to the Observable and update component whenever a new event comes:

<div *ngFor="let customer of customers | async">
	<customer-details [customer]='customer'></customer-details>
</div>

<div>
	<button type="button" class="button btn-danger" (click)='deleteCustomers()'>Delete All</button>
</div>

III. Practice

1. Reactive Spring Boot Server

1.1 Project Structure

angular-4-spring-webflux-reactive-mongodb-spring-boot-server-structure

– Class Customer corresponds to document in customer collection.
– ReactiveCustomerRepository is an interface extends ReactiveCrudRepository, will be autowired in CustomerController for implementing repository methods.
– CustomerController is a REST Controller which has request mapping methods for RESTful requests such as: getAll, create, update, delete Customers.
– Configuration for Spring Data MongoDB properties in application.properties
– Dependencies for Spring Boot WebFlux and Spring Data MongoDB in pom.xml

1.2 Dependency

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-mongodb-reactive</artifactId>
</dependency>

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

1.3 Data Model

package com.javasampleapproach.reactive.mongodb.model;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document(collection = "customer")
public class Customer {
	@Id
	private String id;

	private String name;
	private int age;
	private boolean active;

	public Customer() {
	}

	public Customer(String name, int age) {
		this.name = name;
		this.age = age;
	}

	public String getId() {
		return id;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getName() {
		return this.name;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public int getAge() {
		return this.age;
	}

	public boolean isActive() {
		return active;
	}

	public void setActive(boolean active) {
		this.active = active;
	}

	@Override
	public String toString() {
		return "Customer [id=" + id + ", name=" + name + ", age=" + age + ", active=" + active + "]";
	}
}

1.4 Reactive Repository

package com.javasampleapproach.reactive.mongodb.repo;

import org.springframework.data.repository.reactive.ReactiveCrudRepository;

import com.javasampleapproach.reactive.mongodb.model.Customer;

import reactor.core.publisher.Flux;

public interface ReactiveCustomerRepository extends ReactiveCrudRepository<Customer, String> {

	Flux<Customer> findByName(String name);
}

1.5 Enable reactive Spring Data MongoDB

package com.javasampleapproach.reactive.mongodb.config;

import org.springframework.data.mongodb.config.AbstractReactiveMongoConfiguration;
import org.springframework.data.mongodb.repository.config.EnableReactiveMongoRepositories;

import com.mongodb.reactivestreams.client.MongoClient;
import com.mongodb.reactivestreams.client.MongoClients;

@EnableReactiveMongoRepositories
public class MongoDbReactiveConfig extends AbstractReactiveMongoConfiguration {

	@Override
	public MongoClient reactiveMongoClient() {
		return MongoClients.create();
	}

	@Override
	protected String getDatabaseName() {
		return "jsa_mongodb";
	}

}

1.6 REST Controller

package com.javasampleapproach.reactive.mongodb.controller;

import java.time.Duration;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.javasampleapproach.reactive.mongodb.model.Customer;
import com.javasampleapproach.reactive.mongodb.repo.ReactiveCustomerRepository;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@CrossOrigin(origins = "http://localhost:4200")
@RestController
@RequestMapping(value = "/api")
public class CustomerController {

	@Autowired
	ReactiveCustomerRepository customerRepository;

	@GetMapping("/customers")
	public Flux getAllCustomers() {
		System.out.println("Get all Customers...");

		return customerRepository.findAll().delayElements(Duration.ofMillis(1000));
	}

	@PostMapping("/customers/create")
	public Mono createCustomer(@Valid @RequestBody Customer customer) {
		System.out.println("Create Customer: " + customer.getName() + "...");

		customer.setActive(false);
		return customerRepository.save(customer);
	}

	@PutMapping("/customers/{id}")
	public Mono> updateCustomer(@PathVariable("id") String id,
			@RequestBody Customer customer) {
		System.out.println("Update Customer with ID = " + id + "...");

		return customerRepository.findById(id).flatMap(customerData -> {
			customerData.setName(customer.getName());
			customerData.setAge(customer.getAge());
			customerData.setActive(customer.isActive());
			return customerRepository.save(customerData);
		}).map(updatedcustomer -> new ResponseEntity<>(updatedcustomer, HttpStatus.OK))
				.defaultIfEmpty(new ResponseEntity<>(HttpStatus.NOT_FOUND));
	}

	@DeleteMapping("/customers/{id}")
	public ResponseEntity deleteCustomer(@PathVariable("id") String id) {
		System.out.println("Delete Customer with ID = " + id + "...");

		try {
			customerRepository.deleteById(id).subscribe();
		} catch (Exception e) {
			return new ResponseEntity<>("Fail to delete!", HttpStatus.EXPECTATION_FAILED);
		}

		return new ResponseEntity<>("Customer has been deleted!", HttpStatus.OK);
	}

	@DeleteMapping("/customers/delete")
	public ResponseEntity deleteAllCustomers() {
		System.out.println("Delete All Customers...");

		try {
			customerRepository.deleteAll().subscribe();
		} catch (Exception e) {
			return new ResponseEntity<>("Fail to delete!", HttpStatus.EXPECTATION_FAILED);
		}

		return new ResponseEntity<>("All customers have been deleted!", HttpStatus.OK);
	}

	@GetMapping("/customers/findbyname")
	public Flux findByName(@RequestParam String name) {

		return customerRepository.findByName(name).delayElements(Duration.ofMillis(1000));
	}
}

To make the result live, we use delayElements(). It causes a delayed time between 2 events.

1.7 Configuration for Spring Data MongoDB

application.properties

spring.data.mongodb.database=jsa_mongodb
spring.data.mongodb.port=27017

2. Reactive Angular Client

2.1 User Interface

angular-4-spring-webflux-reactive-mongodb-angular-client-ui

2.2 Project Structure

angular-4-spring-webflux-reactive-mongodb-angular-client-structure

In this example, we have:
– 4 components: customers-list, customer-details, create-customer, search-customers.
– 3 modules: FormsModule, HttpClientModule, AppRoutingModule.
– customer.ts: class Customer (id, name, age, active).
– customer.service.ts: Service for HttpClient methods.

2.3 AppModule

app.module.ts

import { AppRoutingModule } from './app-routing.module';
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { HttpClientModule } from '@angular/common/http';

import { AppComponent } from './app.component';

import { CustomersListComponent } from './customers/customers-list/customers-list.component';
import { CustomerDetailsComponent } from './customers/customer-details/customer-details.component';
import { CreateCustomerComponent } from './customers/create-customer/create-customer.component';
import { SearchCustomersComponent } from './customers/search-customers/search-customers.component';

import { CustomerService } from './customers/customer.service';

@NgModule({
  declarations: [
    AppComponent,
    CustomersListComponent,
    CustomerDetailsComponent,
    CreateCustomerComponent,
    SearchCustomersComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    AppRoutingModule,
    HttpClientModule
  ],
  providers: [CustomerService],
  bootstrap: [AppComponent]
})

export class AppModule { }

2.4 Model

customer.ts

export class Customer {
  id: string;
  name: string;
  age: number;
  active: boolean;

  constructor(id?: string, name?: string, age?: number, active?: boolean) {
    this.id = id;
    this.name = name;
    this.age = age;
    this.active = active;
  }
}

2.5 Service

customer.service.ts

import { Injectable } from '@angular/core';
import { HttpClient, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import * as EventSource from 'eventsource';

import { Customer } from './customer';

@Injectable()
export class CustomerService {

  private baseUrl = 'http://localhost:8080/api/customers';
  private customersList: Customer[] = new Array();
  private customersListSearch: Customer[] = new Array();

  constructor(private http: HttpClient) {
  }

  createCustomer(customer: Object): Observable<Object> {
    return this.http.post(`${this.baseUrl}` + `/create`, customer);
  }

  updateCustomer(id: string, value: any): Observable<Object> {
    return this.http.put(`${this.baseUrl}/${id}`, value);
  }

  deleteCustomer(id: string): Observable<any> {
    return this.http.delete(`${this.baseUrl}/${id}`, { responseType: 'text' });
  }

  getCustomersList(): Observable<any> {
    this.customersList = new Array();

    return Observable.create((observer) => {
      const eventSource = new EventSource(`${this.baseUrl}`);
      eventSource.onmessage = (event) => {
        console.log('eventSource.onmessage: ', event);
        const json = JSON.parse(event.data);
        this.customersList.push(new Customer(json['id'], json['name'], json['age'], json['active']));
        observer.next(this.customersList);
      };

      eventSource.onerror = (error) => observer.error('eventSource.onerror: ' + error);

      return () => eventSource.close();
    });
  }

  deleteAll(): Observable<any> {
    return this.http.delete(`${this.baseUrl}` + `/delete`, { responseType: 'text' });
  }

  findCustomers(name): Observable<any> {
    this.customersListSearch = new Array();

    return Observable.create((observer) => {
      const eventSource = new EventSource(`${this.baseUrl}` + `/findbyname?name=` + name);
      eventSource.onmessage = (event) => {
        console.log('eventSource.onmessage: ', event);
        const json = JSON.parse(event.data);
        this.customersListSearch.push(new Customer(json['id'], json['name'], json['age'], json['active']));
        observer.next(this.customersListSearch);
      };

      eventSource.onerror = (error) => observer.error('eventSource.onerror: ' + error);

      return () => eventSource.close();
    });
  }
}

2.6 Components

2.6.1 CustomerDetailsComponent

customer-details.component.ts

import { Component, OnInit, Input } from '@angular/core';

import { CustomerService } from '../customer.service';
import { Customer } from '../customer';

import { CustomersListComponent } from '../customers-list/customers-list.component';

@Component({
  selector: 'customer-details',
  templateUrl: './customer-details.component.html',
  styleUrls: ['./customer-details.component.css']
})
export class CustomerDetailsComponent implements OnInit {

  @Input() customer: Customer;

  constructor(private customerService: CustomerService, private listComponent: CustomersListComponent) { }

  ngOnInit() {
  }

  updateActive(isActive: boolean) {
    this.customerService.updateCustomer(this.customer.id,
      { name: this.customer.name, age: this.customer.age, active: isActive })
      .subscribe(
        data => {
          console.log(data);
          this.customer = data as Customer;
        },
        error => console.log(error)
      );
  }

  deleteCustomer() {
    this.customerService.deleteCustomer(this.customer.id)
      .subscribe(
        data => {
          console.log(data);
          this.listComponent.reloadData();
        },
        error => console.log(error)
      );
  }

}

customer-details.component.html

<div *ngIf="customer">
	<div>
		<label>Name: </label> {{customer.name}}
	</div>
	<div>
		<label>Age: </label> {{customer.age}}
	</div>
	<div>
		<label>Active: </label> {{customer.active}}
	</div>

	<span class="button is-small btn-primary" *ngIf='customer.active' (click)='updateActive(false)'>Inactive</span>

	<span class="button is-small btn-primary" *ngIf='!customer.active' (click)='updateActive(true)'>Active</span>

	<span class="button is-small btn-danger" (click)='deleteCustomer()'>Delete</span>

	<hr/>
</div>

2.6.2 CustomersListComponent

customers-list.component.ts

import { Component, OnInit } from '@angular/core';
import { Router } from '@angular/router';
import { Observable } from 'rxjs/Observable';

import { CustomerService } from '../customer.service';
import { Customer } from '../customer';

@Component({
  selector: 'customers-list',
  templateUrl: './customers-list.component.html',
  styleUrls: ['./customers-list.component.css']
})
export class CustomersListComponent implements OnInit {

  customers: Observable<Customer[]>;

  constructor(private customerService: CustomerService, private router: Router) { }

  ngOnInit() {
    this.reloadData();
  }

  deleteCustomers() {
    this.customerService.deleteAll()
      .subscribe(
        data => {
          console.log(data);
          this.navigateToAdd();
        },
        error => console.log('ERROR: ' + error)
      );
  }

  reloadData() {
    this.customers = this.customerService.getCustomersList();
  }

  navigateToAdd() {
    this.router.navigate(['add']);
  }
}

customers-list.component.html

<br/>
<div *ngFor="let customer of customers | async" style="width: 300px;">
	<customer-details [customer]='customer'></customer-details>
</div>

<div>
	<button type="button" class="button btn-danger" (click)='deleteCustomers()'>Delete All</button>
</div>

2.6.3 CreateCustomerComponent

create-customer.component.ts

import { Component, OnInit } from '@angular/core';
import { FormsModule } from '@angular/forms';

import { Customer } from '../customer';
import { CustomerService } from '../customer.service';

@Component({
  selector: 'create-customer',
  templateUrl: './create-customer.component.html',
  styleUrls: ['./create-customer.component.css']
})
export class CreateCustomerComponent implements OnInit {

  customer: Customer = new Customer();
  submitted = false;

  constructor(private customerService: CustomerService) { }

  ngOnInit() {
  }

  newCustomer(): void {
    this.submitted = false;
    this.customer = new Customer();
  }

  save() {
    this.customerService.createCustomer(this.customer)
      .subscribe(data => console.log(data), error => console.log(error));
    this.customer = new Customer();
  }

  onSubmit() {
    this.submitted = true;
    this.save();
  }
}

create-customer.component.html

<h3>Create Customer</h3>
<div [hidden]="submitted" style="width: 300px;">
	<form (ngSubmit)="onSubmit()">
		<div class="form-group">
			<label for="name">Name</label> <input type="text"
				class="form-control" id="name" required [(ngModel)]="customer.name"
				name="name">
		</div>

		<div class="form-group">
			<label for="age">Age</label> <input type="text"
				class="form-control" id="age" required [(ngModel)]="customer.age"
				name="age">
		</div>

		<button type="submit" class="btn btn-success">Submit</button>
	</form>
</div>

<div [hidden]="!submitted">
	<h4>You submitted successfully!</h4>
	<button class="btn btn-success" (click)="newCustomer()">Add</button>
</div>

2.6.4 SearchCustomersComponent

search-customers.component.ts

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs/Observable';

import { CustomerService } from '../customer.service';
import { Customer } from '../customer';

@Component({
  selector: 'search-customers',
  templateUrl: './search-customers.component.html',
  styleUrls: ['./search-customers.component.css']
})
export class SearchCustomersComponent implements OnInit {

  customers: Observable<Customer[]>;
  name: string;

  constructor(private customerService: CustomerService) { }

  ngOnInit() {
    this.name = '';
  }

  search() {
    this.customers = this.customerService.findCustomers(this.name);
  }
}

search-customers.component.html

<h3>Find Customers By Name</h3>
<input type="text" [(ngModel)]="name" placeholder="enter name" class="input">
 
<button class="btn btn-success" (click)="search()">Search</button>
<hr />
<ul>
	<li *ngFor="let customer of customers | async">
		<h5>{{customer.name}} - Age: {{customer.age}} - Active:	{{customer.active}}</h5>
	</li>
</ul>

2.7 AppRoutingModule

app-routing.module.ts

import { CreateCustomerComponent } from './customers/create-customer/create-customer.component';
import { CustomersListComponent } from './customers/customers-list/customers-list.component';
import { SearchCustomersComponent } from './customers/search-customers/search-customers.component';

import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

const routes: Routes = [
  { path: '', redirectTo: 'customers', pathMatch: 'full' },
  { path: 'customers', component: CustomersListComponent },
  { path: 'add', component: CreateCustomerComponent },
  { path: 'search', component: SearchCustomersComponent },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})

export class AppRoutingModule { }

2.8 App Component

app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
})

export class AppComponent {
  title = 'JavaSampleApproach';
  description = 'Angular4-MongoDB';

  constructor() { }

}

app.component.html

<div class="container-fluid">
	<div style="color: blue;">
		<h1>{{title}}</h1>
		<h3>{{description}}</h3>
	</div>

	<nav>
		<a routerLink="customers" class="btn btn-primary active" role="button" routerLinkActive="active">Customers</a>
		<a routerLink="add" class="btn btn-primary active" role="button" routerLinkActive="active">Add</a>
		<a routerLink="search" class="btn btn-primary active" role="button" routerLinkActive="active">Search</a>
	</nav>
	<router-outlet></router-outlet>
</div>

3. Run & Check Result

– Build and Run Spring Boot project with commandlines: mvn clean install and mvn spring-boot:run.
– Run the Angular App with command: npm start.

– Open browser with url http://localhost:4200/, add some Customers.
– Click on Customers tab, each Customer displays one after another with 1s delayed time.

angular-4-spring-webflux-reactive-mongodb-result