Christa  Stehr

Christa Stehr

1597191161

Angular and Server Sent Events (SSE)

In this post I will show you how to connect to Server Sent Events (SSE) source in Angular app. We will create a small prototype that will connect to Server Sent Events (SSE) endpoint using Event Source API, resulting in events wrapped into Observable and run inside Angular Zone.

Server-Sent Events_ (SSE) is a server push technology enabling a client to receive automatic updates from a server via HTTP connection. The Server-Sent Events EventSource API is standardized as part of HTML5 by the W3C. —_Wikipedia

For this tutorial you will need following tools:

Creating clean Angular project

First let’s create a clean Angular project. Use the following Angular CLI command from your terminal to do so:

ng new angular-sse

This command creates a clean project and installs all dependencies. Luckily, this project doesn’t require any third party deps — Angular provides everything you need to interact with Server Sent Events (SSE)

Connecting to Server Sent Events (SSE) endpoint

Next, enter the project directory (_angular-sse _in my case), and create a new service using following terminal command:

ng generate service sse

As a result, the SseService is created and wired into the Angular project. Now, lets’ write some actual code. The snippet below is the complete code of the SseService class:

import { Injectable, NgZone } from "@angular/core";
import { Observable } from "rxjs";

@Injectable({
  providedIn: "root"
})
export class SseService {
  constructor(private _zone: NgZone) {}
  getServerSentEvent(url: string): Observable<any> {
    return Observable.create(observer => {
      const eventSource = this.getEventSource(url);
      eventSource.onmessage = event => {
        this._zone.run(() => {
          observer.next(event);
        });
      };
      eventSource.onerror = error => {
        this._zone.run(() => {
          observer.error(error);
        });
      };
    });
  }
  private getEventSource(url: string): EventSource {
    return new EventSource(url);
  }
}

Resulting service creates a concise and easy to use interface for interacting with Server Sent Events (SSE). Here, we unify the logic used to connect to any endpoint that supports SSE.

In principle, this service connects to SSE endpoint using Event Source API, allowing to box this into Observable object. This Observable is then run inside the Angular Zone. This allows Angular to detect events and execute the underlying logic correctly.

#typescript #javascript #angular #servers #front-end-development

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Angular and Server Sent Events (SSE)
Zena  Sporer

Zena Sporer

1596183180

Server-Sent Events Using Spring

Here we are going to discuss sending unidirectional asynchronous events to any web app using Spring. You can send unidirectional events using the SseEmitter class in Spring. There is already a popular solution available for sending bi-directional events using Websockets. Using WebSockets both server and clients can communicate with each other using bi-directional connections between client and server. SSE is only used for sending uni-directional events from the server to clients using the HTTP protocol.

Basic knowledge of Spring and java threading is required.

Steps involved in SSE ar:

  1. The client opens an HTTP connection
  2. The server can send any number of messages to this connection asynchronously
  3. The server can close a connection or it can be closed because of some network error or any exception at the server-side.
  4. In case the connection is closed because of any error from the server or any network error, the client will automatically try to re-connect

Events

The server can send multiple events before closing the connection. Messages sent by the server should be text-based and the message starts with a keyword followed by a colon(:) and then a string message. ‘data’ is a keyword which represents a message for a client.

#java #spring #events #sse #server sent events #event source

Christa  Stehr

Christa Stehr

1598940617

Install Angular - Angular Environment Setup Process

Angular is a TypeScript based framework that works in synchronization with HTML, CSS, and JavaScript. To work with angular, domain knowledge of these 3 is required.

  1. Installing Node.js and npm
  2. Installing Angular CLI
  3. Creating workspace
  4. Deploying your First App

In this article, you will get to know about the Angular Environment setup process. After reading this article, you will be able to install, setup, create, and launch your own application in Angular. So let’s start!!!

Angular environment setup

Install Angular in Easy Steps

For Installing Angular on your Machine, there are 2 prerequisites:

  • Node.js
  • npm Package Manager
Node.js

First you need to have Node.js installed as Angular require current, active LTS or maintenance LTS version of Node.js

Download and Install Node.js version suitable for your machine’s operating system.

Npm Package Manager

Angular, Angular CLI and Angular applications are dependent on npm packages. By installing Node.js, you have automatically installed the npm Package manager which will be the base for installing angular in your system. To check the presence of npm client and Angular version check of npm client, run this command:

  1. npm -v

Installing Angular CLI

  • Open Terminal/Command Prompt
  • To install Angular CLI, run the below command:
  1. npm install -g @angular/cli

installing angular CLI

· After executing the command, Angular CLI will get installed within some time. You can check it using the following command

  1. ng --version

Workspace Creation

Now as your Angular CLI is installed, you need to create a workspace to work upon your application. Methods for it are:

  • Using CLI
  • Using Visual Studio Code
1. Using CLI

To create a workspace:

  • Navigate to the desired directory where you want to create your workspace using cd command in the Terminal/Command prompt
  • Then in the directory write this command on your terminal and provide the name of the app which you want to create. In my case I have mentioned DataFlair:
  1. Ng new YourAppName

create angular workspace

  • After running this command, it will prompt you to select from various options about the CSS and other functionalities.

angular CSS options

  • To leave everything to default, simply press the Enter or the Return key.

angular setup

#angular tutorials #angular cli install #angular environment setup #angular version check #download angular #install angular #install angular cli

Christa  Stehr

Christa Stehr

1597191161

Angular and Server Sent Events (SSE)

In this post I will show you how to connect to Server Sent Events (SSE) source in Angular app. We will create a small prototype that will connect to Server Sent Events (SSE) endpoint using Event Source API, resulting in events wrapped into Observable and run inside Angular Zone.

Server-Sent Events_ (SSE) is a server push technology enabling a client to receive automatic updates from a server via HTTP connection. The Server-Sent Events EventSource API is standardized as part of HTML5 by the W3C. —_Wikipedia

For this tutorial you will need following tools:

Creating clean Angular project

First let’s create a clean Angular project. Use the following Angular CLI command from your terminal to do so:

ng new angular-sse

This command creates a clean project and installs all dependencies. Luckily, this project doesn’t require any third party deps — Angular provides everything you need to interact with Server Sent Events (SSE)

Connecting to Server Sent Events (SSE) endpoint

Next, enter the project directory (_angular-sse _in my case), and create a new service using following terminal command:

ng generate service sse

As a result, the SseService is created and wired into the Angular project. Now, lets’ write some actual code. The snippet below is the complete code of the SseService class:

import { Injectable, NgZone } from "@angular/core";
import { Observable } from "rxjs";

@Injectable({
  providedIn: "root"
})
export class SseService {
  constructor(private _zone: NgZone) {}
  getServerSentEvent(url: string): Observable<any> {
    return Observable.create(observer => {
      const eventSource = this.getEventSource(url);
      eventSource.onmessage = event => {
        this._zone.run(() => {
          observer.next(event);
        });
      };
      eventSource.onerror = error => {
        this._zone.run(() => {
          observer.error(error);
        });
      };
    });
  }
  private getEventSource(url: string): EventSource {
    return new EventSource(url);
  }
}

Resulting service creates a concise and easy to use interface for interacting with Server Sent Events (SSE). Here, we unify the logic used to connect to any endpoint that supports SSE.

In principle, this service connects to SSE endpoint using Event Source API, allowing to box this into Observable object. This Observable is then run inside the Angular Zone. This allows Angular to detect events and execute the underlying logic correctly.

#typescript #javascript #angular #servers #front-end-development

Roberta  Ward

Roberta Ward

1593184320

Basics of Angular: Part-1

What is Angular? What it does? How we implement it in a project? So, here are some basics of angular to let you learn more about angular.

Angular is a Typescript-based open-source front-end web application platform. The Angular Team at Google and a community of individuals and corporations lead it. Angular lets you extend HTML’s syntax to express your apps’ components clearly. The angular resolves challenges while developing a single page and cross-platform applications. So, here the meaning of the single-page applications in angular is that the index.html file serves the app. And, the index.html file links other files to it.

We build angular applications with basic concepts which are NgModules. It provides a compilation context for components. At the beginning of an angular project, the command-line interface provides a built-in component which is the root component. But, NgModule can add a number of additional components. These can be created through a template or loaded from a router. This is what a compilation context about.

What is a Component in Angular?

Components are key features in Angular. It controls a patch of the screen called a view. A couple of components that we create on our own helps to build a whole application. In the end, the root component or the app component holds our entire application. The component has its business logic that it does to support the view inside the class. The class interacts with the view through an API of properties and methods. All the components added by us in the application are not linked to the index.html. But, they link to the app.component.html through the selectors. A component can be a component and not only a typescript class by adding a decorator @Component. Then, for further access, a class can import it. The decorator contains some metadata like selector, template, and style. Here’s an example of how a component decorator looks like:

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

Role of App Module

Modules are the package of functionalities of our app. It gives Angular the information about which features does my app has and what feature it uses. It is an empty Typescript class, but we transform it by adding a decorator @NgModule. So, we have four properties that we set up on the object pass to @NgModule. The four properties are declarations, imports, providers, and bootstrap. All the built-in new components add up to the declarations array in @NgModule.

@NgModule({
declarations: [
  AppComponent,
],
imports: [
  BrowserModule,
  HttpClientModule,
  AppRoutingModule,
  FormsModule
],
bootstrap: [AppComponent]
})

What is Data Binding?

Data Binding is the communication between the Typescript code of the component and the template. So, we have different kinds of data binding given below:

  • When there is a requirement to output data from our Typescript code in the HTML template. String interpolation handles this purpose like {{data}} in HTML file. Property Binding is also used for this purpose like [property] = “data”.
  • When we want to trigger any event like clicking a button. Event Binding works while we react to user events like (event) = “expression”.
  • When we can react to user events and output something at the same time. Two-way Binding is used like [(ngModel)] = “data”.

image for understanding data binding

#angular #javascript #tech blogs #user interface (ui) #angular #angular fundamentals #angular tutorial #basics of angular

studio52 dubai

studio52 dubai

1621850716

7 Tips for a Successful Live Event Coverage - Studio 52

Live events have been a growing trend in the events industry this past year, offering many businesses a much-needed lifeline. Read on for our simple tips to planning your virtual event

#event coverage services #event photography #event video production #event videography #event coverage services #event photography