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This guide walks you through the process of creating a simple web application that fetches data from Twitter.

You'll learn how to build a Spring application that accesses profile data from a Twitter user and from people whom the user follows on Twitter.

• About 15 minutes
• An application ID and secret obtained from registering an application with Twitter.
• A favorite text editor or IDE
• JDK 6 or later
• Gradle 1.7+ or Maven 3.0+
• You can also import the code from this guide as well as view the web page directly into Spring Tool Suite (STS) and work your way through it from there.

Like all Spring's Getting Started guides, you can start from scratch and complete each step, or you can bypass basic setup steps that are already familiar to you. Either way, you end up with working code.

To start from scratch, move on to Set up the project.

To skip the basics, do the following:

• [Download][zip] and unzip the source repository for this guide, or clone it using [Git][u-git]: git clone https://github.com/spring-guides/gs-accessing-twitter.git
• cd into gs-accessing-twitter/initial.
• Jump ahead to Enable Twitter.

When you're finished, you can check your results against the code in gs-accessing-twitter/complete. [zip]: https://github.com/spring-guides/gs-accessing-twitter/archive/master.zip [u-git]: /understanding/Git

First you set up a basic build script. You can use any build system you like when building apps with Spring, but the code you need to work with Gradle and Maven is included here. If you're not familiar with either, refer to Building Java Projects with Gradle or Building Java Projects with Maven.

In a project directory of your choosing, create the following subdirectory structure; for example, with mkdir -p src/main/java/hello on *nix systems:

└── src
    └── main
        └── java
            └── hello

Below is the initial Gradle build file. But you can also use Maven. The pom.xml file is included right here. If you are using Spring Tool Suite (STS), you can import the guide directly.

build.gradle

buildscript {
    repositories {
        maven { url "http://repo.springsource.org/libs-snapshot" }
        mavenLocal()
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'idea'

jar {
    baseName = 'gs-accessing-twitter'
    version =  '0.1.0'
}

repositories {
    mavenCentral()
    maven { url "http://repo.springsource.org/libs-snapshot" }
}

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web:0.5.0.M2")
    compile("org.springframework.social:spring-social-twitter:1.1.0.BUILD-SNAPSHOT")
    compile("org.springframework.security:spring-security-crypto:3.1.4.RELEASE")
    compile("org.thymeleaf:thymeleaf-spring3:2.0.16")
    testCompile("junit:junit:4.11")
}

task wrapper(type: Wrapper) {
    gradleVersion = '1.7'
}

Note: This guide is using Spring Boot.

Before you can fetch a user's data from Twitter, you need to set up a few things in the Spring configuration. This configuration class contains everything you need to enable Twitter in your application:

src/main/java/hello/TwitterConfig.java

package hello;

import org.springframework.context.annotation.Bean;
import org.springframework.social.UserIdSource;
import org.springframework.social.config.annotation.EnableInMemoryConnectionRepository;
import org.springframework.social.connect.ConnectionFactoryLocator;
import org.springframework.social.connect.ConnectionRepository;
import org.springframework.social.connect.web.ConnectController;
import org.springframework.social.twitter.config.annotation.EnableTwitter;

@EnableTwitter(appId="someAppId", appSecret="shhhhhh!!!")
@EnableInMemoryConnectionRepository
public class TwitterConfig {

    @Bean
    public UserIdSource userIdSource() {
        return new UserIdSource() {         
            @Override
            public String getUserId() {
                return "testuser";
            }
        };
    }

    @Bean
    public ConnectController connectController(ConnectionFactoryLocator connectionFactoryLocator, ConnectionRepository connectionRepository) {
        return new ConnectController(connectionFactoryLocator, connectionRepository);
    }

}

Because the application will be accessing Twitter data, TwitterConfig is annotated with @EnableTwitter. As shown here, the appId and appSecret attributes have fake values. These correspond to your application's consumer key and secret you obtain when you register the application with Twitter. For the code to work, substitute the real values given to you by Twitter in place of the fake values.

Notice that TwitterConfig is also annotated with @EnableInMemoryConnectionRepository. After a user authorizes your application to access their Twitter data, Spring Social will create a connection. That connection will need to be saved in a connection repository for long-term use.

For the purposes of this guide's sample application, an in-memory connection repository is sufficient. Although an in-memory connection repository is fine for testing and small sample applications, you'll want to select a more persistent option for real applications. You can use @EnableJdbcConnectionRepository to persist connections to a relational database.

Within the TwitterConfig's body, two beans are declared: a ConnectController bean and a UserIdSource bean.

Obtaining user authorization from Twitter involves a "dance" of redirects between the application and Twitter. This "dance" is formally known as OAuth's Resource Owner Authorization. Don't worry if you don't know much about OAuth. Spring Social's ConnectController takes care of the OAuth dance for you.

Notice that ConnectController is created by injecting a ConnectionFactoryLocator and a ConnectionRepository via the constructor. You won't need to explicitly declare these beans, however. The @EnableTwitter annotation ensures that a ConnectionFactoryLocator bean is created, and the @EnableInMemoryConnectionRepository annotation creates an in-memory implementation of ConnectionRepository.

Connections represent a three-way agreement between a user, an application, and an API provider such as Twitter. Although Twitter and the application itself are readily identifiable, you'll need a way to identify the current user. That's what the UserIdSource bean is for.

Here, the userIdSource bean is defined by an inner-class that always returns "testuser" as the user ID. The sample application has only one user. In a real application, you probably want to create an implementation of UserIdSource that determines the user ID from the currently authenticated user (perhaps by consulting with an Authentication obtained from Spring Security's SecurityContext).

Although much of what ConnectController does involves redirecting to Twitter and handling a redirect from Twitter, it also shows connection status when a GET request to /connect is made. ConnectController defers to a view named connect/{provider ID}Connect when no existing connection is available and to connect/{providerId}Connected when a connection exists for the provider. In this case, {provider ID} is "twitter".

ConnectController does not define its own connection views, so you need to create them. First, here's a Thymeleaf view to be shown when no connection to Twitter exists:

src/main/resources/templates/connect/twitterConnect.html

<html>
	<head>
		<title>Hello Twitter</title>
	</head>
	<body>
		<h3>Connect to Twitter</h3>
		
		<form action="/connect/twitter" method="POST">
			<div class="formInfo">
				<p>You aren't connected to Twitter yet. Click the button to connect Spring Social Showcase with your Twitter account.</p>
			</div>
			<p><button type="submit">Connect to Twitter</button></p>
		</form>
	</body>
</html>

The form on this view will POST to /connect/twitter, which is handled by ConnectController and will kick off the OAuth authorization code flow.

Here's the view to be displayed when a connection exists:

src/main/resources/templates/connect/twitterConnected.html

<html>
	<head>
		<title>Hello Twitter</title>
	</head>
	<body>
		<h3>Connected to Twitter</h3>
		
		<p>
			You are now connected to your Twitter account.
			Click <a href="/">here</a> to see your Twitter friends.
		</p>		
	</body>
</html>

With Twitter configured in your application, you now can write a Spring MVC controller that fetches data for the user who authorized the application and presents it in the browser. HelloController is just such a controller:

src/main/java/hello/HelloController.java

package hello;

import javax.inject.Inject;

import org.springframework.social.twitter.api.CursoredList;
import org.springframework.social.twitter.api.Twitter;
import org.springframework.social.twitter.api.TwitterProfile;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
@RequestMapping("/")
public class HelloController {

    private Twitter twitter;

    @Inject
    public HelloController(Twitter twitter) {
        this.twitter = twitter;     
    }

    @RequestMapping(method=RequestMethod.GET)
    public String helloTwitter(Model model) {
        if (!twitter.isAuthorized()) {
            return "redirect:/connect/twitter";
        }

        model.addAttribute(twitter.userOperations().getUserProfile());
        CursoredList<TwitterProfile> friends = twitter.friendOperations().getFriends();
        model.addAttribute("friends", friends);
        return "hello";
    }

}

HelloController is created by injecting a Twitter object into its constructor. The Twitter object is a reference to Spring Social's Twitter API binding.

The helloTwitter() method is annotated with @RequestMapping to indicate that it should handle GET requests for the root path (/). The first thing it does is check to see if the user has authorized the application to access the user's Twitter data. If not, then the user is redirected to ConnectController with the option to begin the authorization process.

If the user authorizes the application to access the data, the application can fetch almost any data pertaining to the authorizing user. For the purposes of this guide, the application only fetches the user's profile as well as a list of profiles belonging to Twitter users whom the user follows (but not those who follow the user). Both are placed into the model to be displayed by the view identified as "hello".

Speaking of the "hello" view, here it is as a Thymeleaf template:

src/main/resources/templates/hello.html

<html>
	<head>
		<title>Hello Twitter</title>
	</head>
	<body>
		<h3>Hello, <span th:text="${twitterProfile.name}">Some User</span>!</h3>
		
		<h4>These are your friends:</h4>
		
		<ul>
			<li th:each="friend:${friends}" th:text="${friend.name}">Friend</li>
		</ul>
	</body>
</html>

This template simply displays a greeting to the user and a list of the user's friends. Note that even though the full user profiles were fetched, only the names from those profiles are used in this template.

Although it is possible to package this service as a traditional WAR file for deployment to an external application server, the simpler approach demonstrated below creates a standalone application. You package everything in a single, executable JAR file, driven by a good old Java main() method. And along the way, you use Spring's support for embedding the Tomcat servlet container as the HTTP runtime, instead of deploying to an external instance.

src/main/java/hello/Application.java

package hello;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.SpringApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;

@Configuration
@EnableAutoConfiguration
@Import(TwitterConfig.class)
@ComponentScan
public class Application {

    /*
     * SPRING BOOTSTRAP MAIN
     */
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

} 

The main() method defers to the SpringApplication helper class, providing Application.class as an argument to its run() method. This tells Spring to read the annotation metadata from Application and to manage it as a component in the Spring application context.

The @ComponentScan annotation tells Spring to search recursively through the hello package and its children for classes marked directly or indirectly with Spring's @Component annotation. This directive ensures that Spring finds and registers the GreetingController, because it is marked with @Controller, which in turn is a kind of @Component annotation.

The @Import annotation tells Spring to import additional Java configuration. Here it is asking Spring to import the TwitterConfig class where you enabled Twitter in your application.

The @EnableAutoConfiguration annotation switches on reasonable default behaviors based on the content of your classpath. For example, because the application depends on the embeddable version of Tomcat (tomcat-embed-core.jar), a Tomcat server is set up and configured with reasonable defaults on your behalf. And because the application also depends on Spring MVC (spring-webmvc.jar), a Spring MVC DispatcherServlet is configured and registered for you — no web.xml necessary! Auto-configuration is a powerful, flexible mechanism. See the API documentation for further details.

Now that your Application class is ready, you simply instruct the build system to create a single, executable jar containing everything. This makes it easy to ship, version, and deploy the service as an application throughout the development lifecycle, across different environments, and so forth.

Below are the Gradle steps, but if you are using Maven, you can find the updated pom.xml right here and build it by typing mvn clean package.

Update your Gradle build.gradle file's buildscript section, so that it looks like this:

buildscript {
    repositories {
        maven { url "http://repo.springsource.org/libs-snapshot" }
        mavenLocal()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:0.5.0.M2")
    }
}

Further down inside build.gradle, add the following to the list of applied plugins:

apply plugin: 'spring-boot'

You can see the final version of build.gradle [right here]((https://github.com/spring-guides/gs-accessing-twitter/blob/master/complete/build.gradle).

The Spring Boot gradle plugin collects all the jars on the classpath and builds a single "über-jar", which makes it more convenient to execute and transport your service. It also searches for the public static void main() method to flag as a runnable class.

Now run the following command to produce a single executable JAR file containing all necessary dependency classes and resources:

$ ./gradlew build

If you are using Gradle, you can run the JAR by typing:

$ java -jar build/libs/gs-accessing-twitter-0.1.0.jar

If you are using Maven, you can run the JAR by typing:

$ java -jar target/gs-accessing-twitter-0.1.0.jar

Note: The procedure above will create a runnable JAR. You can also opt to build a classic WAR file instead.

If you are using Gradle, you can run your service at the command line this way:

$ ./gradlew clean build && java -jar build/libs/gs-accessing-twitter-0.1.0.jar

Note: If you are using Maven, you can run your service by typing mvn clean package && java -jar target/gs-accessing-twitter-0.1.0.jar.

... app starts up ...

Once the application starts up, you can point your web browser to http://localhost:8080. Because no connection is established yet, you see this screen prompting you to connect with Twitter:

When you click Connect to Twitter, the browser is redircted to Twitter for authorization:

At this point, Twitter asks if you'd like to allow the sample application to read tweets from your profile and see who you follow. Here the screen is misleading, because the application in this case will only read your profile details and the profile details of the people you follow. Click Authorize app to grant permission.

Once permission is granted, Twitter redirects the browser to the application. A connection is created and stored in the connection repository. You should see this page indicating that a connection was successful:

If you click on the link on the connection status page, you are taken to the home page. This time, now that a connection exists, you see your name on Twitter and a list of your friends:

Congratulations! You've developed a simple web application that uses Spring Social to obtain user authorization to fetch data from the user's Twitter profile and from the profiles of people whom the user follows.