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README.rst

Example of Explicit Disclosure with Java Bindings

Copyright (c) 2023 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
SPDX-License-Identifier: Apache-2.0.0

This project demonstrates the usage of Explicit Contract Disclosure in Daml client applications built with the Java Binding library.

In this example, four parties, each hosted on their own participant (see the topology configuration in canton_ledger.conf), are involved in a simplified trade. Each party interacts with the Canton ledger via a standalone Java application. The example interaction flow is modelled as follows:

  • Party Bank (see Bank) issues IOU as units of cash to the Buyer
  • Party StockExchange (see StockExchange) issues Stock as on-ledger asset to the Seller party. Additionally, it issues price ticks for the stock as PriceQuotation. Since StockExchange is the sole stakeholder of the PriceQuotation, it discloses the contract for usage as reference data in commands requiring it as an input.
  • Then, party Seller (see Seller) owns a unit of Stock issued by the StockExchange. Seller creates an Offer contract on-ledger that can be accepted by any interested party (see Offer_Accept in the Daml model). Similarly to the StockExchange, the Seller discloses its Stock and Offer contracts off-ledger for interested parties.
  • Buyer (see Buyer) owns an amount of IOU issued by Bank. Buyer wants to exchange with the Seller and accepts its Offer on-ledger at the correct IOU market value in exchange of Seller s Stock. In the command submission that exercises Offer_Accept, the Buyer uses contracts previously disclosed by the Seller and StockExchange.

Note: For illustration, the disclosed contracts in this project are shared via files. (see Common.shareDisclosedContract).

The Daml model for the templates involved is located in daml/StockExchange.daml <daml/StockExchange.daml>`_.

For a better understanding of the explicit disclosure concept and off-ledger data sharing, refer to the Explicit Contract Disclosure documentation where this example's flow is also presented in more detail.

Running the example

  1. If you do not have it already, download and unzip Canton open-source or a later version into a location of your choice.

  2. Use the setup script for exposing the bash example utility functions in two shell terminal windows

    source setup.sh

  3. In one terminal, build the project

    build_example

  4. In the other terminal, start the Canton ledger and wait for initialization until the process prints Canton server initialization DONE

    start_canton <path_to_canton_installation>

  5. In the first terminal, run the example

    run_stock_exchange