Creating Custom SpringBoot Starter for Twitter4j

SpringBoot provides lot of starter modules to get up and running quickly. SpringBoot’s auto-configure mechanism takes care of configuring SpringBeans on our behalf based on various criteria.

In addition to the springboot starters that comes out-of-the-box provided by Core Spring Team, we can also create our own starter modules.

In this post we will look into how to create a custom SpringBoot starter. To demonstrate it we are going to create twitter4j-spring-boot-starter which will auto-configure Twitter4J beans.

To accomplish this, we are going to create:

  1.  twitter4j-spring-boot-autoconfigure module which contains Twitter4J AutoConfiguration bean definitions 
  2. twitter4j-spring-boot-starter module which pulls in twitter4j-spring-boot-autoconfigure and twitter4j-core dependencies 
  3. Sample application which uses twitter4j-spring-boot-starter 

Create Parent Module spring-boot-starter-twitter4j

First we are going to create a parent pom type module to define dependency versions and sub-modules.

<?xml version="1.0" encoding="UTF-8"?>
<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>com.sivalabs</groupId>
    <artifactId>spring-boot-starter-twitter4j</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>spring-boot-starter-twitter4j</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <twitter4j.version>4.0.3</twitter4j.version>
        <spring-boot.version>1.3.2.RELEASE</spring-boot.version>
    </properties>

    <modules>
        <module>twitter4j-spring-boot-autoconfigure</module>
        <module>twitter4j-spring-boot-starter</module>
        <module>twitter4j-spring-boot-sample</module>
    </modules>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <dependency>
                <groupId>org.twitter4j</groupId>
                <artifactId>twitter4j-core</artifactId>
                <version>${twitter4j.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>

</project>

In this pom.xml we are defining the SpringBoot and Twitter4j versions in section so that we don’t need to specify versions all over the places. 


Create twitter4j-spring-boot-autoconfigure module 

Create a child module with name twitter4j-spring-boot-autoconfigure in our parent maven module spring-boot-starter-twitter4j

Add the maven dependencies such as spring-boot, spring-boot-autoconfigure, twitter4j-core and junit as follows:

<?xml version="1.0" encoding="UTF-8"?>
<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>com.sivalabs</groupId>
    <artifactId>twitter4j-spring-boot-autoconfigure</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>com.sivalabs</groupId>
        <artifactId>spring-boot-starter-twitter4j</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.twitter4j</groupId>
            <artifactId>twitter4j-core</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>
</project>

Note that we have specified twitter4j-core as optional dependency because twitter4j-core should be added to the project only when twitter4j-spring-boot-starter is added to the project.

Create Twitter4jProperties to hold the Twitter4J config parameters 

Create Twitter4jProperties.java to hold the Twitter4J OAuth config parameters.
package com.sivalabs.spring.boot.autoconfigure;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.NestedConfigurationProperty;

@ConfigurationProperties(prefix= Twitter4jProperties.TWITTER4J_PREFIX)
public class Twitter4jProperties {

    public static final String TWITTER4J_PREFIX = "twitter4j";

    private Boolean debug = false;

    @NestedConfigurationProperty
    private OAuth oauth = new OAuth();

    public Boolean getDebug() {
        return debug;
    }

    public void setDebug(Boolean debug) {
        this.debug = debug;
    }

    public OAuth getOauth() {
        return oauth;
    }

    public void setOauth(OAuth oauth) {
        this.oauth = oauth;
    }

    public static class OAuth {

        private String consumerKey;
        private String consumerSecret;
        private String accessToken;
        private String accessTokenSecret;

        public String getConsumerKey() {
            return consumerKey;
        }
        public void setConsumerKey(String consumerKey) {
            this.consumerKey = consumerKey;
        }
        public String getConsumerSecret() {
            return consumerSecret;
        }
        public void setConsumerSecret(String consumerSecret) {
            this.consumerSecret = consumerSecret;
        }
        public String getAccessToken() {
            return accessToken;
        }
        public void setAccessToken(String accessToken) {
            this.accessToken = accessToken;
        }
        public String getAccessTokenSecret() {
            return accessTokenSecret;
        }
        public void setAccessTokenSecret(String accessTokenSecret) {
            this.accessTokenSecret = accessTokenSecret;
        }
    }
}

With this configuration object we can configure the twitter4j properties in application.properties as follows:

 

twitter4j.debug=true
twitter4j.oauth.consumer-key=your-consumer-key-here
twitter4j.oauth.consumer-secret=your-consumer-secret-here
twitter4j.oauth.access-token=your-access-token-here
twitter4j.oauth.access-token-secret=your-access-token-secret-here

Create Twitter4jAutoConfiguration to auto-configure Twitter4J 

Here comes the key part of our starter. Twitter4jAutoConfiguration configuration class contains the bean definitions that will be automatically configured based on some criteria. 
What is that criteria? 
  • If twitter4j.TwitterFactory.class is on classpath 
  • If TwitterFactory bean is not already defined explicitly 
So, the Twitter4jAutoConfiguration goes like this.
package com.sivalabs.spring.boot.autoconfigure;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import twitter4j.Twitter;
import twitter4j.TwitterFactory;
import twitter4j.conf.ConfigurationBuilder;

@Configuration
@ConditionalOnClass({ TwitterFactory.class, Twitter.class })
@EnableConfigurationProperties(Twitter4jProperties.class)
public class Twitter4jAutoConfiguration {

    private static Log log = LogFactory.getLog(Twitter4jAutoConfiguration.class);

    @Autowired
    private Twitter4jProperties properties;

    @Bean
    @ConditionalOnMissingBean
    public TwitterFactory twitterFactory(){

        if (this.properties.getOauth().getConsumerKey() == null
            || this.properties.getOauth().getConsumerSecret() == null
            || this.properties.getOauth().getAccessToken() == null
            || this.properties.getOauth().getAccessTokenSecret() == null)
        {
            String msg = "Twitter4j properties not configured properly." + 
                         " Please check twitter4j.* properties settings in configuration file.";
            log.error(msg);
            throw new RuntimeException(msg);
        }

        ConfigurationBuilder cb = new ConfigurationBuilder();
        cb.setDebugEnabled(properties.getDebug())
          .setOAuthConsumerKey(properties.getOauth().getConsumerKey())
          .setOAuthConsumerSecret(properties.getOauth().getConsumerSecret())
          .setOAuthAccessToken(properties.getOauth().getAccessToken())
          .setOAuthAccessTokenSecret(properties.getOauth().getAccessTokenSecret());
        TwitterFactory tf = new TwitterFactory(cb.build());
        return tf;
    }

    @Bean
    @ConditionalOnMissingBean
    public Twitter twitter(TwitterFactory twitterFactory){
        return twitterFactory.getInstance();
    }

}

We have used @ConditionalOnClass({ TwitterFactory.class, Twitter.class }) to specify that this auto configuration should take place only when TwitterFactory.class, Twitter.class classes are present. 

We have also used @ConditionalOnMissingBean on bean definition methods to specify consider this bean definition only if TwitterFactory/Twitter beans are not already defined explicitly. 
Also note that we have annotated with @EnableConfigurationProperties(Twitter4jProperties.class) to enable support for ConfigurationProperties and injected Twitter4jProperties bean. 
Now we need to configure our custom Twitter4jAutoConfiguration in src/main/resources/META-INF/spring.factories file as follows:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.sivalabs.spring.boot.autoconfigure.Twitter4jAutoConfiguration 

Create twitter4j-spring-boot-starter module 

Create a child module with name twitter4j-spring-boot-starter in our parent maven module spring-boot-starter-twitter4j.
<?xml version="1.0" encoding="UTF-8"?>
<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>com.sivalabs</groupId>
    <artifactId>twitter4j-spring-boot-starter</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>com.sivalabs</groupId>
        <artifactId>spring-boot-starter-twitter4j</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>


    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>com.sivalabs</groupId>
            <artifactId>twitter4j-spring-boot-autoconfigure</artifactId>
            <version>${project.version}</version>
        </dependency>

        <dependency>
            <groupId>org.twitter4j</groupId>
            <artifactId>twitter4j-core</artifactId>
        </dependency>

    </dependencies>

</project>

Note that in this maven module we are actually pulling in twitter4j-core dependency. 

We don’t need to add any code in this module, but optionally we can specify what are the dependencies we are going to provide through this starter in src/main/resources/META-INF/spring.provides file as follows: 
provides: twitter4j-core 
That’s all for our starter. 
Let us create a sample using our brand new starter twitter4j-spring-boot-starter

Create twitter4j-spring-boot-sample sample application 

Let us create a simple SpringBoot application and add our twitter4j-spring-boot-starter dependency.
<?xml version="1.0" encoding="UTF-8"?>
<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>com.sivalabs</groupId>
    <artifactId>twitter4j-spring-boot-sample</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.2.RELEASE</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <dependencies>

        <dependency>
            <groupId>com.sivalabs</groupId>
            <artifactId>twitter4j-spring-boot-starter</artifactId>
            <version>1.0-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

</project>

Create the entry-point class SpringbootTwitter4jDemoApplication as follows:

 

package com.sivalabs.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringbootTwitter4jDemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootTwitter4jDemoApplication.class, args);
    }
}

Create TweetService as follows:

 

package com.sivalabs.demo;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import twitter4j.ResponseList;
import twitter4j.Status;
import twitter4j.Twitter;
import twitter4j.TwitterException;

@Service
public class TweetService {

    @Autowired
    private Twitter twitter;

    public List<String> getLatestTweets(){
        List<String> tweets = new ArrayList<>();
        try {
            ResponseList<Status> homeTimeline = twitter.getHomeTimeline();
            for (Status status : homeTimeline) {
                tweets.add(status.getText());
            }
        } catch (TwitterException e) {
            throw new RuntimeException(e);
        }
        return tweets;
    }
}

Now create a Test to verify our Twitter4j AutoConfigutation. 

Before that make sure you have set your twitter4j oauth configuration parameter to your actual values. You can get them from https://apps.twitter.com/

 

package com.sivalabs.demo;

import java.util.List;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import twitter4j.TwitterException;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(SpringbootTwitter4jDemoApplication.class)
public class SpringbootTwitter4jDemoApplicationTest  {


    @Autowired
    private TweetService tweetService;

    @Test
    public void testGetTweets() throws TwitterException {
        List<String> tweets = tweetService.getLatestTweets();
        for (String tweet : tweets) {
            System.err.println(tweet);
        }
    }

}

Now you should be able to see the latest tweets on your console output. 

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