Awesome

auction cordapp <img src="../../webIDE.png" height=25 />

This CorDapp serves as a demo of building an auction application on Corda. It leverages different features of Corda like SchedulableState, StatePointer and OwnableState. It also demonstrate how to perform a DvP (Delivery vs Payment) transaction on Corda.

It has a full-functional client included and an angular UI to interact with the nodes.

Concepts

States

• Asset: It is an OwnableState that represents an asset that could be put on auction. The owner of the asset should be able to put this asset on an auction.

• AuctionState: It represents the auction. It is designed as a SchedulableState, such that auction could be scheduled to be made inactive, once the auction deadline is reached.

Contracts:

• AssetContract: It is used to govern the evolution of the asset. In this case mostly change of ownership. Left black for simplicity. Has two commands, CreateAsset and TransferAsset.

• AuctionContract: It governs the evolution of the auction. The has the following commands:

  • CreateAuction: Validation rules governing the creation of the auction.

  • Bid: Validation rules governing the bidding process of the auction.

  • EndAuction: Validation rules governing end of the auction i.e making the auction inactive once the auction bidding deadline has been reached.

  • Settlement: Validation rules for settlement of the auction i.e. transfer of asset to the highest bidder and the highest bid amount transfer to the auctioneer.

  • Exit: Rules governing the exit (consumption/deletion) of the auction state.

Flows:

• CreateAssetFlow: This flow is used create an asset. Implemented in CreateAssetFlow.java

• CreateAuctionFlow: This flow is used to create an auction (CreateAuctionFlow.java can be found here). Once an asset has been created using theCreateAssetFlow, this flow can be used to put the asset on auction. The AuctionState references to the Asset using a StatePointer.

Refer here to learn more about StatePointer: https://medium.com/corda/linking-corda-states-using-statepointer-16e24e5e602

• BidFlow: It is used to place a bid on an auction. Bids can be placed only till a predetermined deadline defined in the AuctionState. Implemented in BidFlow.java.

• EndAuctionFlow: This is a scheduled flow, which run automatically on auction deadline to mark the corresponding auction as inactive, so that it stop receiving bids.The auction flow can be found here

• AuctionSettlementFlow: It is used to settle an auction once the bidding deadline has passed. It internally triggers two flows:

  • AuctionDvPFlow: This flow takes care of the dvp operation for settlement of the auction. It transfers the asset on auction to the highest bidder and the highest bid amount is transferred to the auctioneer. It happens as an atomic transaction.

  • AuctionExitFlow: Once the auction us settled, this flow is used to exit the auction state. This flow can also be triggered to exit an auction which did not receive any bid till its deadline.

Usage

Pre-requisites:

See https://docs.corda.net/getting-set-up.html.

Running the nodes:

Open a terminal and go to the project root directory and type: (to deploy the nodes using bootstrapper)

./gradlew clean deployNodes

Then type: (to run the nodes)

./build/nodes/runnodes

Running the client:

The client can be run by executing the below command from the project root:

./gradlew runAuctionClient

Please make sure that the nodes are already running before starting the client. The client can be accessed at http://localhost:8085/

Running our Demo

1. Click on the "Setup Demo Data" button to create somde demo data to play with or you may use the skip button if you wish to setup the deata yourself.

2. The demo data setup would have created some assets from each of the parties. The assets can be found under MyAssets Section. These assets could be put on auction. New assets can be create using the create asset button. The drop down at the top right corner can be used to toggle between parties. The balance next to it indicates the current active parties cash balance. Cash can be issued using the Issue Cash Button.

3. Click on an asset to put it on auction. Input the Base Price and the Auction Deadline and click in the Create Auction button to Create the Auction.

4. Once an auction is created it would be available in the Active Auction section. Its now ready to accept bids. Switch to PartyB and place a bid, by clicking on the auction available in the Active Auction section.

5. Place one more bid by switching to PartyC.

6. What for the auction to end.

7. Once the auction is ended its ready to be settled. Settlement can be initiated by the highest bidder. Considering PartyC is the highest bidder, switch to PartyC.

8. Issue cash equivalent or greater than the highest bid amount for PartyC to pay for the auction settlement.

9. Now click on the auction and initiate the settlement using the Pay and Settle Button.

Notice the below things that would happed on auction settlement:

• Auctioned Assets ownership would be transferred to the highest bidder. The asset would now appear in the auction winners asset list (My Assets section).
• The auctioneers cash balance would be credited with amount equivalent to the highest bid.
• The highest bidders (PartyC in this case) cash balance would also be debited with amount equivalent to the highest bid.
• The AuctionState would be consumed and the auction would no longer be visible.