Hello DOUG Demo Application

This is a demo application how to use a Monax blockchain, deploy a simple contract and interact with the contract via JavaScript. The NodeJS application leverages Monax's JS libraries as well as the SQLSOL in-memory SQL cache. A REST services layer is included that serves data from the SQL cache while writing data to the smart contracts. Changes in the blockchain are refleted in the SQL cache through Solidity events.

Setup

Prerequisites

The application uses an in-memory SQLite database which needs to be installed before-hand. The --no-bin-links parameter was necessary on MacOS, but might not be needed depending on your operating system! From the root of the project directory, run:

sudo npm install -g node-pre-gyp
npm install sqlite3 --save --no-bin-links
npm install

Chain Setup

For demo purposes we can use a plain single-node chain. Execute the following commands to start a new chain. Note that the resulting accounts.json contains the public key of the account which is used by the NodeJS application. If you want to use a chain with a different name, please adapt the name of the server account in config/settings.toml accordingly. Also, note that if you are running more than one blockchain, you need to use the -p parameter in the monax chains start to avoid port conflicts and consequently set the port in config/settings.toml (see Appliation Startup -> Checklist below).

monax chains make hello-chain --unsafe
monax chains start hello-chain --init-dir ~/.monax/chains/hello-chain/hello-chain_full_000/
cp ~/.monax/chains/hello-chain/accounts.json ./config/

Contract Deployment

In Bash Shell:

cd contracts
fullAccount=$(jq -r '.["hello-chain_full_000"].address' ../config/accounts.json)
monax pkgs do -c hello-chain -a $fullAccount

Note: If you do not have jq available on the commandline, you can also simply manually copy the address of the full account from accounts.json to use as parameter for the monax pkgs command.

Application Startup

From the project root directory:

Checklist

• Ensure the chain container's IP address is set correctly in config/settings.toml. To do so, run monax chains inspect hello-chain and use the IPAddress value in the settings.toml file for the host setting.
• If your chain is using a host port other than 1337 (which is mapped to port 1337 of the chain container), please adjust the chain.port setting in config/settings.toml accordingly. (Hint: Use monax chains ports hello-chain to see used ports for hello-chain)

Run Node App

• Start the application via npm start
• Use a REST client (e.g. Postman) with the following URLs:
• POST http://localhost:3080/deals Body (application/json): {"id": "234232", "buyer": "Mike", "seller": "Laura", "amount": 15000.99}
• GET http://localhost:3080/deals
• GET http://localhost:3080/deals/234232

Note: the application currently only supports storing full integer amounts in the smart contract, so a decimal amount is converted by multiplying/dividing as it enters and leaves the NodeJS application.