Angular.js

AngularJS with Backend Example

Hello readers, in this basic example, developers will learn what AngularJS is and how to make AJAX calls to a Servlet using the AngularJS controller and update the view back with the JSON response from the Servlet.

1. Introduction

1.1 What is AngularJS?

AngularJS is a JavaScript MVC or Model-View-Controller framework developed by Google that lets developers build well structured, easily testable, and maintainable front-end applications. Before we start with creating an actual application using AngularJS, let us see what the actual parts of an AngularJS application are.

1.1.1 Templates

In AngularJS, a template is an HTML with additional markups. AngularJS library compiles the templates and renders the resultant HTML page.

1.1.2 Directives

Directives are the markers (i.e. attributes) on a DOM element that tell AngularJS to attach a specific behavior to that DOM element or even transform the DOM element and its children. Most of the directives in AngularJS library starts with the ng. The directives consist of the following three parts:

  • ng-app: The ng-app directive is a starting point. If the AngularJS framework finds the ng-app directive anywhere in the HTML document, it bootstraps (i.e. initializes) itself and compiles the HTML template
  • ng-model: The ng-model directive binds an HTML element to a property on the $scope object. It also binds the values of AngularJS application data to the HTML input controls.
  • ng-bind: The ng-bind directive binds the AngularJS application data to the HTML tags
  • ng-controller: The ng-controller directive is used to specify a controller in the HTML element. This controller will add behavior or maintain the data in that HTML element and its child elements

1.1.3 Expressions

An expression is like a JavaScript code which is usually wrapped inside the double curly braces such as {{ expression }}. AngularJS library evaluates the expression and produces a result.

The following table lists all the important concepts in AngularJS library.

ConceptDescription
TemplateAn HTML with additional markups.
DirectivesExtends the HTML with the custom attributes (or markers) and elements.
ModelIt is the data shown to the user in the view with which the user interacts.
ScopeA Scope is a context where the model is stored so that controllers, directives, and expressions can access it.
ExpressionsAn expression executes the JavaScript code inside the double curly braces such as {{ expression }}.
CompilerThe Compiler parses the template and instantiates the directives and expressions.
FilterA Filter formats the value of an expression for display to the user.
Data BindingThis syncs the data between the model and the view.
ControllerA controller in AngularJS maintains the application data, business logic, and behavior using the $scope object. Developers can attach properties and methods to the $scope object inside a controller function, which in turn will add or update the data and attach behaviours to the HTML elements.
ModuleThe module is the container for different parts of an application including the controllers, services, filters, and directives which configures the Injector.
ServiceA Service is reusable business logic which is independent of the views.

1.2 Why should we use AngularJS?

Using the Model-View-Controller architecture, the framework separates a web application into a simple and yet manageable structure, which comprises of “views”, “models” and “controllers”. The AngularJS library provides the in-build directives (or attributes) to extend the HTML inside a web page. When developers attach these directives to the HTML elements and attributes, it creates a dynamic web-page with very little coding.

These new APIs make a developer life easier, really! But it would be difficult for a beginner to understand this without an example. Therefore, let’s see how to integrate AngularJS in Java web applications.

2. AngularJS with Backend Example

Here is a step-by-step guide for implementing the AngularJS framework in Java.

2.1 Tools Used

We are using Eclipse Kepler SR2, JDK 8 and Maven.

2.2 Project Structure

Firstly, let’s review the final project structure, in case you are confused about where you should create the corresponding files or folder later!

Fig. 1: Application Project Structure
Fig. 1: Application Project Structure

2.3 Project Creation

This section will demonstrate on how to create a Java-based Maven project with Eclipse. In Eclipse Ide, go to File -> New -> Maven Project.

Fig. 2: Create Maven Project
Fig. 2: Create Maven Project

In the New Maven Project window, it will ask you to select project location. By default, ‘Use default workspace location’ will be selected. Just click on next button to proceed.

Fig. 3: Project Details
Fig. 3: Project Details

Select the ‘Maven Web App’ Archetype from the list of options and click next.

Fig. 4: Archetype Selection
Fig. 4: Archetype Selection

It will ask you to ‘Enter the group and the artifact id for the project’. We will input the details as shown in the below image. The version number will be by default: 0.0.1-SNAPSHOT.

Fig. 5: Archetype Parameters
Fig. 5: Archetype Parameters

Click on Finish and the creation of a maven project is completed. If you observe, it has downloaded the maven dependencies and a pom.xml file will be created. It will have the following code:

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>AngularJsBackendEx</groupId>
	<artifactId>AngularJsBackendEx</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
</project>

Let’s start building the application!

3. Application Building

Let’s create a basic welcome application to understand the basic building blocks of AngularJS library.

3.1 Maven Dependencies

Here, we specify the dependencies for the Servlet and JSON API. The rest dependencies will be automatically resolved by the Maven framework and the updated file will have the following code:

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>AngularJsBackendEx</groupId>
	<artifactId>AngularJsBackendEx</artifactId>
	<packaging>war</packaging>
	<version>0.0.1-SNAPSHOT</version>
	<name>AngularJsBackendEx Maven Webapp</name>
	<url>http://maven.apache.org</url>
	<dependencies>
		<!-- Servlet API Dependency -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>3.0.1</version>
		</dependency>
		<dependency>
			<groupId>javax.servlet.jsp</groupId>
			<artifactId>jsp-api</artifactId>
			<version>2.1</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/org.json/json -->
		<dependency>
			<groupId>org.json</groupId>
			<artifactId>json</artifactId>
			<version>20160810</version>
		</dependency>
	</dependencies>
	<build>
		<finalName>${project.artifactId}</finalName>
	</build>
</project>

3.2 Java Class Creation

Let’s create the required Java files. Right-click on src/main/java folder, New -> Package.

Fig. 6: Java Package Creation
Fig. 6: Java Package Creation

A new pop window will open where we will enter the package name as: com.wcg.angular.backend.

Fig. 7: Java Package Name (com.wcg.angular.backend)
Fig. 7: Java Package Name (com.wcg.angular.backend)

Once the package is created in the application, we will need to create the servlet controller class. Right-click on the newly created package: New -> Class.

Fig. 8: Java Class Creation
Fig. 8: Java Class Creation

A new pop window will open and enter the file name as: FormServlet. The controller class will be created inside the package: com.wcg.angular.backend.

Fig. 9: Java Class (FormServlet.java)
Fig. 9: Java Class (FormServlet.java)

3.2.1 Implementation of Servlet Controller

This is a normal Java servlet except the part that it reads the JSON payload. As the data in angular is not a part of the parameter, hence developers cannot use the getParameter() method in the servlet. Instead, they can get the reader and read all the content before parsing it into the JSON object. Let’s see the simple code snippet that follows this implementation.

FormServlet.java

package com.wcg.angular.backend;

import java.io.BufferedReader;
import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.json.JSONObject;

@WebServlet("/formServlet")
public class FormServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	/**** This Method Is Called By The Servlet Container To Process A 'POST' Request. ****/
	public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException {
		handleRequest(req, resp);
	}

	public void handleRequest(HttpServletRequest req, HttpServletResponse resp) throws ServletException {

		String str = null;	
		StringBuffer sb = null;
		JSONObject jObj = null;
		BufferedReader br = null;

		try {
			br = req.getReader();
			sb = new StringBuffer();

			while ((str = br.readLine()) != null) {
				sb.append(str);
			}
			jObj = new JSONObject(sb.toString());
			String user_name = jObj.getString("username");

			/**** Preparing The Output Response ****/
			resp.setContentType("text/html");
			resp.setCharacterEncoding("UTF-8");
			resp.getWriter().write("Welcome " + user_name + " !!");
		} catch (IOException ex) {
			ex.printStackTrace();
		}
	}
}

3.3 Creating JSP View

This file is responsible for the AJAX call made to the servlet and for updating the response back in the JSP. Let’s see the simple code snippet to create a simple view using the angular framework.

index.jsp

<!DOCTYPE html>
<html>
	<head>
	    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
	    <title>AngularJS Application</title>
	
	    <!-- Javascript Files -->
	    <script type="text/javascript" src="resource/js/angular_v1.6.0.js"></script>	    	   
	    <script type="text/javascript" src="resource/js/form.js"></script>
	
	    <!-- CSS Styling -->
	    <style type="text/css">
	        .cssStyling {
	            color: green;
	            font-size: larger;	            
	        }
	    </style>
	</head>
	<body>
	    <h1>AngularJS Backend Application</h1>
	    <div ng-app="myApp">
	        <form ng-controller="UserController" ng-submit="sendData()">
	            <p>
	                <label>Enter your name: </label>
	                <input id="user_name" type="text" ng-model="name" placeholder="User Name" onblur="this.placeholder = 'User Name'" onfocus="this.placeholder = ''" />
	            </p>
	            <p>
	                <button id="formBtn" type="submit">Submit</button>
	            </p>
	            <!-- Display's Output On The Screen -->
	            <p>
	            	<span id="welcomeText" class="cssStyling">{{msgFromServlet}}</span>
	        	</p>
	        </form>	        
	    </div>
	</body>
</html>

3.3.1 Creating AngularJS Controller

The Javascript file i.e. form.js includes the function (i.e. UserController) as the “controller” in the Model-View-Controller. It submits the form data to the server and reads back the response message to the $scope.msgFromServlet.

form.js

/* 
 * Description - AngularJS Script for Form Submission
 * Created By - Yatin Batra  
 * */

var helloAjaxApp = angular.module("myApp", []);

helloAjaxApp.controller("UserController", [ '$scope', '$http', function($scope, $http) {

	$http.defaults.headers.post["Content-Type"] = "application/x-www-form-urlencoded; charset=utf-8";
	$scope.sendData = function() {
		$http({
			url : 'formServlet',
			method : "POST",
			data : {
				'username' : $scope.name
			}
		}).then(function(response) {
			/**** Success Case ****/
			console.log("Success -> " + response.data);
			$scope.msgFromServlet = response.data;
		}, function(response) {
			/**** Failure Case ****/
			console.log("Failure -> " + response.data);
			$scope.msgFromServlet = response.data;
		});
	};
} ]);

4. Run the Application

As we are ready for all the changes, let us compile the project and deploy the application on the Tomcat7 server. To deploy the application on Tomat7, right-click on the project and navigate to Run as -> Run on Server.

Fig. 10: How to Deploy Application on Tomcat
Fig. 10: How to Deploy Application on Tomcat

Tomcat will deploy the application in its web-apps folder and shall start its execution to deploy the project so that we can go ahead and test it in the browser.

5. Project Demo

Open your favorite browser and hit the following URL. The output page (i.e. the welcome form) will be displayed.

http://localhost:8082/AngularJsBackendEx/

Server name (localhost) and port (8082) may vary as per your Tomcat configuration. Developers can debug the example and see what happens after every step. Enjoy!

Fig. 11: Welcome Page
Fig. 11: Welcome Page

The user enters the name of a person and clicks the Submit button. The data will pass as a HTTP request using the AngularJS and the servlet will return the response as below.

Fig. 12: Greetings Message
Fig. 12: Greetings Message

That’s all for this post. Happy Learning!!

6. Conclusion

In this section, developers learned how to create a simple AngularJS enabled Java web application. Developers can download the sample application as an Eclipse project in the Downloads section. I hope this article served you with whatever developers were looking for.

7. Download the Eclipse Project

This was an example of AngularJS with Backend implementation.

Download
You can download the full source code of this example here: AngularJsBackendEx

Yatin

The author is graduated in Electronics & Telecommunication. During his studies, he has been involved with a significant number of projects ranging from programming and software engineering to telecommunications analysis. He works as a technical lead in the information technology sector where he is primarily involved with projects based on Java/J2EE technologies platform and novel UI technologies.
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3 Comments
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dbbbb
dbbbb
5 years ago

after creation of a Maven project no src/main/java folder is created (there is only src/main/resources)

SaraHu
SaraHu
5 years ago
Reply to  dbbbb

I had the same issue, you can create java folder manually under src/main/ folder, or as Yatin specified in creating package snapshot write full path for source folder

mirketa
4 years ago

Thanks for sharing this valuable information

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