Category Archives: Development and Testing

Java Beans and DTOs

DTO (Data Transfer Object)

Data Transfer Object is a pattern whose aim is to transport data between layers and tiers of a program. A DTO should contain NO business logic

public class UserDTO {
    String firstName;
    String lastName;
    List<String> groups;

    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public List<String> getGroups() {
        return groups;
    }
    public void setGroups(List<String> groups) {
        this.groups = groups;
    }
}

Java Beans

Java Beans are classes that follows certain conventions or event better they are Sun/Oracle standards/specifications as explained here:

https://www.oracle.com/technetwork/java/javase/documentation/spec-136004.html

Essentially, Java Beans adhere to the following:

  • all properties are private (and they are accessed through getters and setters);
  • they have zero-arg constructors (aka default constructors)
  • they implement the Serializable Interface

The main reason why we use Java Beans is to encapsulate

public classBeanClassExample() implements java.io.Serializable {

  private int id;

  //no-arg constructor
  public BeanClassExample() {
  }

  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }
}

So, yeah what is the real difference? If any?

In a nutshell, Java Beans follow strict conditions (as discussed above) and contain no behaviour (as opposed to states), except made for storage, retrieval, serialization and deserialization. It is indeed a specification, while DTO (Data Transfer Object) is a Pattern on its own. It is more than acceptable to use a Java Bean to implement a DTO pattern.

So, you want to build a bot with NodeJs?

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I have used Node.js in a number of projects and in conjunction with the module bundler called Webpack  and the automation toolkit Gulp, but still I wanted to experiment with something different that would bring up the advantages of using such a server-side platform. I remembered that the Microsoft Bot Framework employs Node.js for its Bot Builder SDK and why not building bots sounds interesting! I have actually found out that there are a few books specifically focusing on building bots with Node.js and that seemed to be like a fun task. The choice then became clear, let’s use Node.js and Twit, a Twitter API Client for Node, to build a Twitter bot that simply sends a query to the Twitter API, receives a response containing the results of the performed search, and then retweets the most recent tweet returned. Let’s see what we need to achieve this!

Set up a dedicated Twitter account for your Bot

Bots get usually banned from Twitter, so it is recommended to create Twitter account perhaps with a secondary email address specifically for the following experiment. It is highly recommended that you do not use your “official” Twitter account as it is likely that it will be short-lived.  After your new account is activated, go to the Twitter Developer Center and sign in with your new details. You might also want to have a look around and in particular have a read through the documentation on how to get started with the Twitter Developer Platform and how to create your first app.

Screen Shot 2018-03-07 at 23.05.45.png

Create a Twitter App

From your acccount, you will be able to see the newly created app from here.   After creating the application, look for ‘Keys and Access Tokens’ and click on ‘Generate Token Actions’. Make a copy of the details below as you will be using them later as part of your

config.js
  • Consumer Key
  • Consumer Secret
  • Access Token
  • Access Token Secret

The Part where you code

You will interact with your newly created Twitter App via a Nodejs library called Twit. Create a new project folder in your Dev directory (ideally the directory structure where your git installation resides):

mkdir twitter-bot
cd twitter-bot
npm init

 

This will kick off an utility that will take you through the process of creating the package.json file.

 {
  "name": "twitter-bot",
  "version": "1.0.0",
  "description": "sample twitter bot",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\"
  },
  "keywords": [
  "node",
  "twit",
  "twitter",
  "bot"
  ],
  "author": "ilacorda",
  "license": "ISC"
 }

 

Then you will need to install Twit, the Twitter API Client for Node that supports REST and Streaming API.

npm install twit

and create a file called

touch bot.js

This will be your main application file, that means the entry point of your app. You will also need a third and additional file called

config.js

where you will past the following:

  • Consumer Key
  • Consumer Secret
  • Access Token
  • Access Token Secret

It will look like this:

 

module.exports = {
  consumer_key: '',  
  consumer_secret: '',
  access_token: '',  
  access_token_secret: ''
}

 

Your directory structure should look as follows:

 

root/project-name
   |- bot.js
   |- config.js
   |- package.json

 

The part where you make the Bot do something

Next step is to make your bot to query the most recent tweets. We will need to write a function that finds the latest tweets according to the query passed as a parameter. To do so, we need to initialise a params object holding aq property that will refine our searches. In our case, we are targeting tweets with hashtag #nodejs and #Nodejs:

 

var retweet = function() {
  var params = {
    q: '#nodejs, #Nodejs',
    result_type: 'recent',
    lang: 'en'    
  }
}

 

the property

result_type: 'recent'

instructs the bot to search exclusively for the tweets that were posted since the bot was started. We can use

Twitter.get

, which accepts three arguments: API endpoint, params object (defined by us) and a callback.

Twitter.get('search/tweets', params, function(err, data) {
      // if there are no errors
        if (!err) {
          // fetch the ID of tweet
            var retweetId = data.statuses[0].id_str;
            // Instruct Tweeter to retweet
            Twitter.post('statuses/retweet/:id', {
                id: retweetId
            }, function(err, response) {
                if (response) {
                    console.log('Retweeted!!!');
                }
                // if there was an error while tweeting
                if (err) {
                    console.log('No results were returned');
                }
            });
        }


 

To post or to retweet the tweet the bot has found, we have used the Twitter.post() method to post to any of the REST API endpoints.

Usage

In order to run your bot, you should simply type the following command on terminal:

node bot.js

Alternatively, it is possible to use:

npm scripts

in a nutshell, they are scripts whose goal is to automate repetitive tasks. This requires to modify the file

package.json

by adding the following lines of code:

 

{
  "scripts": {    
    "start": "node bot.js",  
  }
}

and then you can type

npm start