Hyperledger - First DAPP

BNA for Basic CU option

It will demonstrates the core functionality of Hyperledger Composer by changing the value of an asset.

Participant - SampleParticipant

               Asset - SampleAsset

               Transaction -  SampleTransaction

               Event  - SampleEvent

SampleAssets are owned by a SampleParticipant, and the value property on a SampleAsset can be modified by submitting a SampleTransaction. The SampleTransaction emits a SampleEvent that notifies applications of the old and new values for each modified SampleAsset.

Create a SampleParticipant participant:

{

  "$class": "org.example.basic.SampleParticipant",

  "participantId": "EMP1",

  "firstName": "Manish",

  "lastName": "Jain"

}

Create a SampleAsset asset:

{

  "$class": "org.example.basic.SampleAsset",

  "assetId": "assetId:1",

  "owner": "resource:org.example.basic.SampleParticipant#EMP1",

  "value": "HP Laptop"

}

Submit a SampleTransaction transaction:

{

  "$class": "org.example.basic.SampleTransaction",

  "asset": "resource:org.example.basic.SampleAsset#assetId:1",

  "newValue": "Dell Laptop"

}

After submitting this transaction, you should now see the transaction in the Transaction Registry and that a SampleEvent has been emitted. As a result, the value of the assetId:1 should now be new value in the Asset Registry.

'o' indicates has-a relationship

'-->' indicates pass by reference

Models/Sample.cto

namespace org.example.basic

asset SampleAsset identified by assetId {

  o String assetId

  --> SampleParticipant owner

  o String value

}

participant SampleParticipant identified by participantId {

  o String participantId

  o String firstName

  o String lastName

}

transaction SampleTransaction {

  --> SampleAsset asset

  o String newValue

}

event SampleEvent {

  --> SampleAsset asset

  o String oldValue

  o String newValue

}

Lib/sample.js

async function sampleTransaction(tx) { 

    // Save the old value of the asset.

    const oldValue = tx.asset.value;

    // Update the asset with the new value.

    tx.asset.value = tx.newValue;

    // Get the asset registry for the asset.

    const assetRegistry = await getAssetRegistry('org.example.basic.SampleAsset');

    // Update the asset in the asset registry.

    await assetRegistry.update(tx.asset);

    // Emit an event for the modified asset.

    let event = getFactory().newEvent('org.example.basic', 'SampleEvent');

    event.asset = tx.asset;

    event.oldValue = oldValue;

    event.newValue = tx.newValue;

    emit(event);

}

Permission.acl

rule EverybodyCanReadEverything {

    description: "Allow all participants read access to all resources"

    participant: "org.example.basic.SampleParticipant"

    operation: READ

    resource: "org.example.basic.*"

    action: ALLOW

}

rule EverybodyCanSubmitTransactions {

    description: "Allow all participants to submit transactions"

    participant: "org.example.basic.SampleParticipant"

    operation: CREATE

    resource: "org.example.basic.SampleTransaction"

    action: ALLOW

}

rule OwnerHasFullAccessToTheirAssets {

    description: "Allow all participants full access to their assets"

    participant(p): "org.example.basic.SampleParticipant"

    operation: ALL

    resource(r): "org.example.basic.SampleAsset"

    condition: (r.owner.getIdentifier() === p.getIdentifier())

    action: ALLOW

}

rule SystemACL {

    description: "System ACL to permit all access"

    participant: "org.hyperledger.composer.system.Participant"

    operation: ALL

    resource: "org.hyperledger.composer.system.**"

    action: ALLOW

}

rule NetworkAdminUser {

    description: "Grant business network administrators full access to user resources"

    participant: "org.hyperledger.composer.system.NetworkAdmin"

    operation: ALL

    resource: "**"

    action: ALLOW

}

rule NetworkAdminSystem {

    description: "Grant business network administrators full access to system resources"

    participant: "org.hyperledger.composer.system.NetworkAdmin"

    operation: ALL

    resource: "org.hyperledger.composer.system.**"

    action: ALLOW

}