According to Stellar.org : Stellar is open-source, distributed payments infrastructure. Using the Stellar network, you can build mobile wallets, banking tools, smart devices that pay for themselves, and just about anything else you can dream up involving payments! Even though Stellar is a complex distributed system, working with it doesn’t need to be complicated.
This is a tutorial for creating a simple banking application with Stellar's hybrid blockchain and Lumen (XLM) as currency. The following topics are covered in this tutorial:
- Working with Stellar Java SDK
- Creating a Stellar Bank UI using Spring Boot, Spring Security and MySql
- Open an Account and fund 10,000 XLM
- Open another account and transfer 100 XLM (or any amount)from one account to another
- View account details and blalances
Most applications interact with the Stellar network through Horizon, a RESTful HTTP API server. Horizon gives you a straightforward way to submit transactions, check accounts, and subscribe to events. The Java Stellar Sdk library provides APIs to build transactions and connect to Horizon.
For this tutorial we will be using the test network : https://horizon-testnet.stellar.org. The test network allows us to create new accounts and seed them with 10,000 Lumens(XLM) to play with.
Download the SDK from Stellar.org to your local file system.
Notice that this a jar file that needs to be imported into your local Maven repo before we can use it in our project as a dependency.
Use the following command to import the SDK jar file into your Maven repo:
mvn install:install-file -Dfile=/<path to the sdk jar> -DgroupId=<package name> -DartifactId=<packageId> -Dversion=<version> -Dpackaging=jar
For example :
mvn install:install-file -Dfile=/Users/sunil_vishnubhotla/Downloads/stellar-sdk.jar -DgroupId=com.stellar.code -DartifactId=stellar -Dversion=0.1.14 -Dpackaging=jar
Then add the dependancy in your pom.xml file like so :
<dependency>
<groupId>com.stellar.code</groupId>
<artifactId>stellar</artifactId>
<version>0.1.14</version>
</dependency>
Note: this dependancy is already added in the source pom.xml.
To run the sample install Java 1.8+, Maven, MySql for your OS and download the code. Edit the application.properties file to setup your DB connection.
And simply run this command in the source root
mvn springboot:run
And point your browser to
http://localhost:8080
login screen :
Asuming your MySql DB is up and running, you should see the login screen. As a first time user, go ahead and click the "Join us" link to create a new user with your email and a password. Use these credentials to login after you finish registering.
The following method in the is used to accomplish this in LoginController.java :
...
@RequestMapping(value = "/registration", method = RequestMethod.POST)
public ModelAndView createNewUser(@Valid User user, BindingResult bindingResult) {
ModelAndView modelAndView = new ModelAndView();
User userExists = userService.findUserByEmail(user.getEmail());
if (userExists != null) {
bindingResult.rejectValue("email", "error.user",
"There is already a user registered with the email provided");
}
if (bindingResult.hasErrors()) {
System.out.println("There was an error...");
modelAndView.setViewName("registration");
} else {
userService.saveUser(user);
modelAndView.addObject("successMessage", "User registered successfully. Please login.");
modelAndView.addObject("user", new User());
modelAndView.setViewName("login");
}
return modelAndView;
}
...
We will use the following two properties for communicating with the network :
@Value("${stellar.network.url}")
private String network;
@Value("${stellar.network.friendbot}")
private String friendbot;
After you login click the "Open a New Account" link to create a new account associated with your User credentials.
Give your account a nick name and click the Open Account button.
At this point the AccountService is called to create a new account as shown below:
...
KeyPair pair = KeyPair.random();
String seed = new String(pair.getSecretSeed());
key = pair.getAccountId();
String friendbotUrl = String.format(friendbot, key);
response = new URL(friendbotUrl).openStream();
String body = new Scanner(response, "UTF-8").useDelimiter("\\A").next();
System.out.println("New Stellar account created :)\n" + body);
Account acc = new Account(key, seed, name, email);
accountRepository.save(acc);
...
We start by calling the Stellar SDK's KeyPair object's random() method that generates and assigns our accout a unique key pair. Each account has a privete key also called the secret seed and a public key that is assigned when you create a Stellsr account. As with any blockchain implementation, you need a private key to sign all your transactions to ensure they orignate from you and that no one else can tamper with it. You do not share your privete key(hence the word private) with anyone but you do send the public key along with the transaction for the system to verify it was you who started the transaction and that you have the needed funds to carry out the transaction.
We then seed this account using the Stellar's Friendbot service to give us 10,000 XLMs.
Note down your account information as it is printed on the console output.
You can then see this account information live on https://stellarchain.io/
Make sure you switch the network to TESTNET as shown and then enter the account number.
Then enter to see 10,000 Lumens and their equivalent values in othe currencies. Know that this is just testing money and not real :-)
After we create and seed the account we can query the network to get the upto date account details:
- Stellar SDK - Stellar's Java SDK
- Spring Boot - The web framework used
- Spring Security - User authentication
- Spring Data JPA - Data access layer
- Maven - Dependency Management
- MySql - RDBMS
Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.
We use TBD for versioning. For the versions available, see the tags on this repository.
- Sunil Vishnubhotla - Initial work - sunilvb
See also the list of contributors who participated in this project.
This project is licensed under the MIT License - see the LICENSE.md file for details
- Hat tip to anyone who's code was used
- Inspiration
- etc
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