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Hyperledger Composer basics, Part 3

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This content is part of the series:Hyperledger Composer basics, Part 3

Stay tuned for additional content in this series.

This tutorial builds on Part 1, where you learned how to
model and test a simple business network in a local version of the
Hyperledger Composer Playground. In Part 2, you saw how to model an
IoT GPS sensor in a shipping container by adding GPS readings to the
Shipment asset, and modify the chaincode to send an alert when the
Shipment reaches its destination port. Then you deployed the sample Perishable Goods network to the IBM Cloud in the Composer Online
Playground.

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Now, in this third and final part, you’ll install Hyperledger Fabric on
your computer, and deploy the business network archive (BNA) to an
instance of Hyperledger Fabric running on your machine (referred to as
your local Hyperledger Fabric). You’ll install more tools and
generate a Loopback-based REST interface that you can use to interact with
the sample network blockchain application.

Part 3 also includes a detailed discussion of Hyperledger Composer security
concepts. This part concludes with steps to pull it all together and
extend the iot-perishable-network to create a more “real
world” version of the Perishable Goods network.

Hyperledger Composer is now integrated into the IBM Blockchain
Platform! The new Starter Plan (free beta!) can help you kick-start your blockchain network.

Prerequisites

I’ll assume that you’ve worked through Part 2, and that you have the following software
installed on your computer:

Deploy the network to your local Hyperledger
Fabric

Hyperledger Fabric is a framework for building blockchain applications for
business purposes, and as you have already learned, Hyperledger Composer
is a companion tool that makes building blockchain applications that run
on Hyperledger Fabric easier. Up to now, you have used Composer Playground
in “browser-only” mode (in Part 1) and the Composer Online playground in
the IBM Cloud (Part 2).

Now, you’ll install and run the Hyperledger Fabric on your computer, and
use the Composer Command Line Interface (CLI) to interact with it.

First, create a directory on your computer where you want to do your local
Hyperledger Composer development. For this tutorial, I’ll refer to this
location as $COMPOSER_ROOT in code, and in prose, I’ll refer
to it as your Composer root directory. This directory can be
anywhere you want, but I recommend you create it just off your home
folder, and always set the COMPOSER_ROOT environment variable
to that directory in the current shell, since that’s how I’ll refer to
that location throughout this tutorial.

Now download the fabric-dev-servers.zip distribution file to
your Composer root directory using the curl command, and
unzip it. The sequence of commands looks like this (assuming
~/HyperledgerComposer as the root directory for this example):

                mkdir ~/HyperledgerComposer
                export COMPOSER_ROOT=~/HyperledgerComposer
                cd $COMPOSER_ROOT
                mkdir fabric-dev-servers && cd fabric-dev-servers
                curl -O https://raw.githubusercontent.com/hyperledger/composer-tools/master/packages/fabric-dev-servers/fabric-dev-servers.zip
                unzip fabric-dev-servers.zip

Note: before you continue, make sure Docker is
running.

The first time you run Hyperledger Fabric, execute this sequence of
commands:

                cd $COMPOSER_ROOT/fabric-dev-servers
                ./downloadFabric.sh
                ./startFabric.sh
                ./createPeerAdminCard.sh

It will take several minutes to run the first command, which pulls all of
the necessary Docker images. The second command starts the local
Hyperledger Fabric. The last command issues an ID card for the
fabric admin, which is PeerAdmin. Don’t worry about that for
now; I’ll cover ID cards later in the tutorial. The output of the
createPeerAdminCard.sh script looks like this:

                $ ./createPeerAdminCard.sh 
                Development only script for Hyperledger Fabric control
                Running 'createPeerAdminCard.sh'
                FABRIC_VERSION is unset, assuming hlfv1
                FABRIC_START_TIMEOUT is unset, assuming 15 (seconds)
                
                Using composer-cli at v0.15.0
                Successfully created business network card to /tmp/PeerAdmin@hlfv1.card
                
                Command succeeded
                
                Successfully imported business network card: PeerAdmin@hlfv1
                
                Command succeeded
                
                Hyperledger Composer PeerAdmin card has been imported
                The following Business Network Cards are available:
                
                
                ┌─────────────────┬───────────┬─────────┐
                │ CardName        │ UserId    │ Network │
                ├─────────────────┼───────────┼─────────┤
                │ PeerAdmin@hlfv1 │ PeerAdmin │         │
                └─────────────────┴───────────┴─────────┘
                
                Issue composer card list --name <CardName>  to get details of the card
                
                Command succeeded

Make a note of the card name, because you will need it to execute all of
the CLI commands in this tutorial.

You only need to run the createPeerAdminCard.sh script one
time. From now on, whenever you start Hyperledger Fabric, you just run the
startFabric.sh script like this:

                cd $COMPOSER_ROOT/fabric-dev-servers
                ./startFabric.sh

When the script finishes, Hyperledger Fabric is running on your computer.
To shut down the local Hyperledger Fabric, run the
stopFabric.sh script.

For the purposes of the tutorial, I suggest you leave Hyperledger Fabric up
for now.

Deploy to Hyperledger Fabric

In Part 2, you cloned the developerWorks project from GitHub
and modified the Perishable Goods network. I’ve provided a finished
version of that network in the
developerWorks/iot-perishable-network directory. You’ll use
that network for the rest of this tutorial.

To deploy the iot-perishable-network to your local Fabric, use
the Composer CLI and execute this sequence of commands:

                cd $COMPOSER_ROOT/developerWorks/iot-perishable-network
                composer network deploy -a dist/iot-perishable-network.bna -A admin -S adminpw -c PeerAdmin@hlfv1 -f networkadmin.card
                composer card import --file networkadmin.card

The composer network deploy command deploys the specified
network archive (dist/iot-perishable-network.bna) to the
local Hyperledger Fabric, using the PeerAdmin card you created earlier
when you ran the createPeerAdminCard.sh script to
authenticate. When the deployment is finished, an ID card is
issued for the network administrator, whose credentials
— that is, userid and password (or secret) — are stored in
the networkadmin.card file.

The output looks like this:

                $ composer network deploy -a dist/iot-perishable-network.bna -A admin -S adminpw -c PeerAdmin@hlfv1 -f networkadmin.card
                Deploying business network from archive: dist/iot-perishable-network.bna
                Business network definition:
                	Identifier: iot-perishable-network@0.1.12
                	Description: Shipping Perishable Goods Business Network
                
                ✔ Deploying business network definition. This may take a minute...
                Successfully created business network card to networkadmin.card
                
                Command succeeded

The composer card import command tells Hyperledger Composer to
import the specified card file so it can be used later to authenticate the
user whose credentials are stored in the card. In this case, the card is
for the network admin. I’ll talk more about cards later on. The output
looks like this:

                $ composer card import --file networkadmin.card 
                Successfully imported business network card: admin@iot-perishable-network
                
                Command succeeded

Interact with the network
via the Composer REST interface

You’ve deployed the iot-perishable-network to the local
Hyperledger Fabric, but how do you see what’s there? How do you interact
with it? Hyperledger Composer provides a tool called
composer-rest-server that generates a Loopback-based REST
interface to access your network.

Install the Composer REST interface
generator

First, you need to install the composer-rest-server loopback
generator. Go to a command line (Ubuntu) or open a Terminal window (MacOS)
and enter this command:

npm install -g composer-rest-server

When the installation finishes, verify that
composer-rest-server was installed correctly by running
composer-rest-server -v:

                $ composer-rest-server -v
                v0.15.0

Generate the REST interface

Make sure the Hyperledger Fabric is running and the
iot-perishable-network is deployed before generating the REST
interface (or there will be nothing to connect to). From the command line,
run the composer-rest-server command. It will prompt you for
input. You’ll see something like this:

Listing 1. Starting the REST
server

                $ composer-rest-server
                ? Enter the name of the business network card to use: admin@iot-perishable-network
                ? Specify if you want namespaces in the generated REST API: always use namespaces
                ? Specify if you want to enable authentication for the REST API using Passport: No
                ? Specify if you want to enable event publication over WebSockets: No
                ? Specify if you want to enable TLS security for the REST API: No
                
                To restart the REST server using the same options, issue the following command:
                   composer-rest-server -c admin@iot-perishable-network -n always
                
                Discovering types from business network definition ...
                Discovered types from business network definition
                Generating schemas for all types in business network definition ...
                Generated schemas for all types in business network definition
                Adding schemas for all types to Loopback ...
                Added schemas for all types to Loopback
                Web server listening at: http://localhost:3000
                Browse your REST API at http://localhost:3000/explorer

The REST server needs to know how to authenticate with Hyperledger Fabric
so it can communicate with the business network. You provide an ID card
for that (line 2) such as the admin@iot-perishable-network ID
card from earlier in the tutorial.

Namespaces help avoid name collisions. In the
iot-perishable-network, this is not a big deal since there’s
only a handful of assets, participants, and transactions. I think it’s a
good idea to always use namespaces (line 3). Testing real-world networks
with lots of participants, assets, and transactions is hard enough; using
namespaces will help you avoid headaches related to name collisions.

When using the REST interface for testing, don’t worry about authentication (line 4), events and WebSockets (line 5), or TLS security (line 6) for now. However, if you decide to deploy
the REST server as part of your production blockchain solution, make sure
to check out the links here or in the Related
topics at the end of this tutorial.

The next time you want to start the REST server with those same options,
just use the command shown (line 9) and skip the interview!

To use the REST interface, open a browser and point it to the address shown
on line 18 in Listing 1. You’ll see something like
this:

Figure 1. The REST interface

The interface is fairly intuitive. To work with an object, click it, and
when it expands, you’ll see the REST methods you can invoke (for example,
/GET, /POST, and so on). To invoke the
SetupDemo transaction (which instantiates the business
model), click the line that contains SetupDemo, which then
expands to the POST method. Click the Try it
out! button to invoke the transaction. If it succeeds, you’ll
see an HTTP 200 response code. Then you can navigate through the model and
see the various objects like the Contract, shown in Figure 2.

Figure 2. The REST interface showing Contract
object

The REST interface showing the Contract object

In the video I’ll show you how to use the REST
interface in detail, so be sure to check that out.

Secure the REST interface

This is beyond the scope of this tutorial, but if you plan to run the REST
interface in production, you need a strategy to deal with it. An entire
tutorial could be done on this topic alone!

Fortunately there are resources on the Hyperledger Composer website to
help. Here are some links to the Composer docs:

For your convenience, these links are also listed in the Related topics at the end of the tutorial
as well.

Video: Using the Composer REST interface

Set up Hyperledger Composer
security

There are two levels of security with Hyperledger Composer:

Hyperledger Fabric administrator
Business network administrator

The administrator for your local Hyperledger Fabric is the Peer
Administrator (or PeerAdmin for short), which you created when you
installed the local Hyperledger Fabric. Every business network should have
an administrator as well, which is created when the network is deployed by
the Hyperledger Fabric administrator. Authentication for both is handled
using ID Cards, which you’ll learn about next.

An ID card (or card for short) is a collection of files that
contains all the information necessary to allow a participant to connect
to a business network. The card is referred to as an identity.
Before it can be used, it must be issued to the user, allowing
him or her to be authenticated and authorized to use the network. Cards
are a very handy way of securing access to a Hyperledger Fabric network.
Rather than keeping up with a password (called a secret in
Hyperledger Composer terminology), you import the card into a collection
of cards in the Hyperledger Fabric called a wallet. From that
point on, you can just reference the card to authenticate that
identity.

The general form for specifying a card is: userid@network,
where userid is the user’s unique id, and the
network is the network to which the user is
authenticated.

To handle the two levels of Hyperledger Composer security, you need a card
for at least: (1) the PeerAdmin and (2) the business network admin.

PeerAdmin

The PeerAdmin card is a special ID card used to administer the
local Hyperledger Fabric. In a development installation, such as the one
on your computer, the PeerAdmin ID card is created when you install the
local Hyperledger Fabric.

The form for a PeerAdmin card for a Hyperledger Fabric v1.0
network is PeerAdmin@hlfv1. You already used this card
earlier in the tutorial when you deployed the
iot-perishable-network to your local Hyperledger Fabric.

In general, the PeerAdmin is a special role reserved for functions such
as:

Deploying business networks
Creating, issuing, and revoking ID cards for business network
admins

As a developer, in a production Hyperledger Fabric installation, you would
not have access to the PeerAdmin card. Instead the
Hyperledger Fabric administrator would deploy your business network,
create ID cards, and so on. When developing and testing blockchain
networks using your local Hyperledger Fabric, you will use the PeerAdmin
ID card to perform these functions.

Business network admin

When the PeerAdmin deploys your network to the Hyperledger Fabric, an ID
card is issued to the business network administrator, and then this card
is used whenever the business network administrator needs to do anything
with the business network, such as using the Composer Command Line
Interface (which you’ll use shortly).

Remember the admin@iot-perishable-network card from earlier?
That was the business network admin card issued by the
PeerAdmin (that is, the local Hyperledger Fabric
administrator) when the iot-perishable-network was
deployed.

In general, the business network admin is a special role reserved for
functions such as:

Updating the running business network
Querying the various registries (participant, identity, and so
forth)
Creating, issuing, and revoking ID cards for participants in the
business network

That’s right, the admin ID card can also be used to issue other ID cards
for specific participants (I’ll show you how to do that later in the
tutorial), so that all participants have their own ID cards. Access to the
network can be controlled by these cards.

Speaking of access control, Composer implements the concept of role-based
security through permissions baked right into its architecture to handle
both authentication and authorization. A participant’s access to resources
is controlled based on the identity that has been issued to that
participant.

In this section, you’ll see how to set up access control rules to lock down
resources in your network by participant through the Access Control List
(ACL) file called permissions.acl (at the time of this
writing, the file must have this name). Here are the
highlights:

Access is applied to either grant or deny
based on resources that match the rule. By default, if a
resource matches no rule, then access to it is denied.
The file is processed top-down so that the first rule that either
grants or denies access to a particular resource is in effect and
cannot be overridden by a subsequent rule.
The format of a rule is fairly intuitive. The rule
keyword indicates the start of a rule, followed by a rule name, which
must be unique.
The rule consists of a set of name/value pairs that define the rule’s
properties.

Listing 2 shows the permissions.acl file from the
iot-perishable-network business network.

Listing 2. `permissions.acl` from the
`iot-perishable-network`

                /**
                 * Sample access control list.
                 */
                rule Default {
                    description: "Allow all participants access to all resources"
                    participant: "ANY"
                    operation: ALL
                    resource: "org.acme.shipping.perishable.*"
                    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
                }

Stay tuned!

This explanation of how rules are processed represents how access
control works at the time of this writing. Hyperledger Composer has
not reached release 1.0 yet, so this may change. The final authority
on how things work, of course, is in the code, and
ideally the documentation.

The general format for each property is
property: "MATCH_EXPRESSION". The properties are:

description— a human-readable name for the rule in
double quotes. Example:
description: "This is a description"

participant— fully qualified name of the
Participant to which access is granted or denied, surrounded by double
quotes. Multiple participants may be specified in the
MATCH_EXPRESSION through the use of the single asterisk
(*) wildcard to indicate “all”, double asterisk
(**) to indicate recursion within a namespace, or
ANY, which matches all participants in all namespaces.

Examples:

participant: "org.acme.shipping.perishable.Grower"—
Apply the rule to org.acme.shipping.perishable.Grower
only.
participant: "org.acme.shipping.perishable.*"—
Apply the rule to all participants in the
org.acme.shipping.perishable namespace.
participant: "org.acme.shipping.**"— Apply the
rule to all participants in the org.acme.shipping
namespace, and recursively any namespaces beneath it.
participant: "ANY"— Apply the rule to all
participants in all namespaces.

operation— the MATCH_EXPRESSION may be
one or more of CREATE, READ,
UPDATE, DELETE, or ALL. Multiple
values may be separated by commas (for example, CREATE,READ
will grant both CREATE and READ access to the
resource). Use ALL by itself to indicate the rule applies to
all operations.

Examples:

operation: ALL— Apply the rule to all CRUD
operations.
operation: CREATE— Apply the rule only to the
CREATE operation
operation: READ,UPDATE— Apply the rule to
READ and UPDATE operations.

resource— defines the “thing” to which the rule
applies. A resource can be any class (that is, an asset, participant, or
transaction) from the business model. Through the use of wildcards,
multiple classes can also be specified, in the same way as for participant
above.

Examples:

resource: "org.acme.shipping.perishable.TemperatureReading"—
The rule applies only to the
org.acme.shipping.perishable.TemperatureReading
transaction.
resource: "org.acme.shipping.perishable.*"— The
rule applies to all classes in the
org.acme.shipping.perishable namespace.
resource: "org.acme.shipping.**"— Apply the rule
to all resources in the org.acme.shipping namespace, and
recursively to any namespaces beneath it.

action— the action that applies when the rule
fires. One of: ALLOW to grant access, or DENY to
deny the specified participant(s) access to the resource(s).

Examples:

action: ALLOW— Allow access to the specified
resource(s).
action: DENY— Deny access to the specified
resource(s).

Note: If your network has no permissions.acl, then access is
granted to all participants (that is, access is wide open — there
is no resource-level security).

You will see how to use rules later in the tutorial. Also, the Composer ACL documentation has lots of examples, so be sure to
check that out.

Issue a new ID – Playground

ID cards can be kind of abstract, and difficult to visualize. So let’s look
at one in Playground (in fact, you already have, you just might not have
realized it).

Start the Hyperledger Composer Playground and import the
iot-perishable-network (don’t forget to create the BNA by
running npm install if you haven’t already). You imported a
network in Part 2, so check that out if you need a refresher.

Make sure to invoke the SetupDemo transaction to create the
participants and store them in the participant registry. Why? Because you
cannot issue an ID card for a participant that is not in the participant
registry. In order to work with the classes from the business model, you
must instantiate the model, and that’s what
SetupDemo does for you. Please review the “Test the business
network” section from Part 1 of this tutorial series if you want more information on
working with business models.

Once the model is instantiated, in the upper right corner where you see
admin, click to expand the drop-down and select
ID Registry. On the next screen, choose Issue
new ID and then enter grower1 as the ID
Name, and select farmer@email.com from the drop-down. See
Figure 3.

Figure 3. Issue a new ID card in Playground

Click the Create New button to issue the ID. Once the
grower1 ID card has been issued, it will show up in
the ID registry. See Figure 4.

Figure 4. New grower1 ID card in Playground

I’ll show you how to issue ID cards using the Composer CLI later in the
tutorial.

Interact with the network via the Composer
CLI

I showed you how to install the Composer Command Line Interface (CLI) in
Part 2, and you used it earlier in this tutorial to deploy the
iot-perishable-network and import the
admin@iot-perishable-network card. Now you will use the CLI
to interact with the iot-perishable-network business network.
The CLI is really handy because it lends itself to use in scripts, and
it’s easy to use, as you’ll see. To use the CLI, you’ll need to go to the
command line (Ubuntu) or open a terminal window (MacOS).

Ping the network

Once you’ve deployed the iot-perishable-network network, you
can send it a ping, which doesn’t have any side effects. It’s a
safe way to just see if your network is up and running. Enter this
command:

composer network ping --card admin@iot-perishable-network

If the ping subcommand succeeds, you will see output like
this:

                $ composer network ping --card admin@iot-perishable-network
                The connection to the network was successfully tested: iot-perishable-network
                	version: 0.15.0
                	participant: org.hyperledger.composer.system.NetworkAdmin#admin
                
                Command succeeded

Invoke the SetupDemo transaction

The SetupDemo transaction is used to instantiate the model.
Enter this command:

                composer transaction submit --card admin@iot-perishable-network -d '{"$class": "org.acme.shipping.perishable.SetupDemo"}'

The output looks like this:

                $ composer transaction submit --card admin@iot-perishable-network -d '{"$class": "org.acme.shipping.perishable.SetupDemo"}'
                Transaction Submitted.
                
                Command succeeded

Invoke the TemperatureReading transaction

The TemperatureReading transaction is invoked by the IoT
sensor in the shipping container each time a temperature reading is taken
and needs to be recorded in the blockchain. Enter this command:

                composer transaction submit --card admin@iot-perishable-network -d '{ "$class": "org.acme.shipping.perishable.TemperatureReading", "centigrade": 0, "shipment": "resource:org.acme.shipping.perishable.Shipment#SHIP_001"}'

The output looks like this:

                $ composer transaction submit --card admin@iot-perishable-network -d '{ "$class": "org.acme.shipping.perishable.TemperatureReading", "centigrade": 0, "shipment": "resource:org.acme.shipping.perishable.Shipment#SHIP_001"}'
                Transaction Submitted.
                
                Command succeeded

Invoke the ShipmentReceived transaction

The ShipmentReceived transaction is invoked by the Importer
when the shipment is received. Enter this command:

                composer transaction submit --card admin@iot-perishable-network -d '{ "$class": "org.acme.shipping.perishable.ShipmentReceived", "shipment": "resource:org.acme.shipping.perishable.Shipment#SHIP_001"}'

The output looks like this:

                $ composer transaction submit --card admin@iot-perishable-network -d '{ "$class": "org.acme.shipping.perishable.ShipmentReceived", "shipment": "resource:org.acme.shipping.perishable.Shipment#SHIP_001"}'
                Transaction Submitted.
                
                Command succeeded

Update the network

This is handy whenever you make a change during development and you need to
update the deployed network. After you run npm install to
rebuild the BNA, enter this command:

                composer network update -a dist/iot-perishable-network.bna --card admin@iot-perishable-network

The output looks like this:

                $ composer network update -a dist/iot-perishable-network.bna --card admin@iot-perishable-network
                Deploying business network from archive: dist/iot-perishable-network.bna
                Business network definition:
                	Identifier: iot-perishable-network@0.1.12
                	Description: Shipping Perishable Goods Business Network
                
                ✔ Updating business network definition. This may take a few seconds...
                Successfully created business network card to undefined
                
                Command succeeded

Be sure to check out the CLI documentation for a complete reference of commands, examples,
and lots more.

Everything you’ve learned so far has been building to this point: You can
now modify the iot-perishable-network into a more realistic
blockchain application. Here’s what you will do in this section:

Make changes to the network model:
- Add new participants to represent the IoT sensors in the
  shipping container
- Add new transactions that more realistically model a shipping
  workflow
- Add new events that are broadcast when certain points in the
  workflow are reached
Add chaincode for the new transactions
Modify the network’s permissions
Add Cucumber feature tests to unit test your changes
Build the network and run the unit tests
Deploy the network to your local Hyperledger Fabric
Issue IDs for the Grower, Temperature and GPS sensors, Shipper, and
Importer
Run transactions through the CLI

When you’re finished modifying the iot-perishable-network, you
will have learned the basic skills needed to use Hyperledger Composer, you
will be ready to tackle a real-world blockchain application project, you
will be the envy of all your friends, and tales of your Hyperledger
Composer and Fabric prowess will spread far and wide (okay, I may be
embellishing a bit with those last two).

If you get stuck at any point and need a little help, be sure to check out
the solution code, which is in a project called
iot-perishable-network-advanced that you have already cloned
to your computer when you cloned the developerWorks project from GitHub.

Note: You are welcome to use whatever editor you’re comfortable with, but I
will use VSCode (which you installed in Part 2) for all the changes in
this section, and the instructions below will reflect that. If you’re not
using VSCode, please adapt accordingly.

To make the changes listed above, you’ll start with the model. Open the
models/perishable.cto model file in VSCode and make the
changes below. Note: I have omitted comments from the model snippets below
only to save space in this tutorial. If you look at
iot-perishable-network-advanced, you’ll see that I have added
comments for each model element I added, and I recommend you do the
same.

First, modify the ShipmentReceived transaction to add an
optional property called receivedDateTime, and then add three
new transactions that extend ShipmentTransaction to update
the blockchain (ledger) when a shipment (1) has been packed, (2) has been
picked up for loading, and (3) has been loaded onto the container
ship:

                transaction ShipmentReceived extends ShipmentTransaction {
                  o DateTime receivedDateTime optional
                }
                
                transaction ShipmentPacked extends ShipmentTransaction {
                }
                
                transaction ShipmentPickup extends ShipmentTransaction {
                }
                
                transaction ShipmentLoaded extends ShipmentTransaction {
                }

Next, modify the Shipment asset to add four new properties for
the shipment-related transactions so that when these transactions run,
they are stored in the blockchain with the Shipment. The
highlighted lines below are the ones you need to add (lines 9-12).

                asset Shipment identified by shipmentId {
                  o String shipmentId
                  o ProductType type
                  o ShipmentStatus status
                  o Long unitCount
                  --> Contract contract
                  o TemperatureReading[] temperatureReadings optional
                  o GpsReading[] gpsReadings optional
                  o ShipmentPacked shipmentPacked optional
                  o ShipmentPickup shipmentPickup optional
                  o ShipmentLoaded shipmentLoaded optional
                  o ShipmentReceived shipmentReceived optional
                }

Now add an abstract participant to represent an IoT device that is
identified by a String property called deviceId, and add two
subclasses of it: one to represent a temperature sensor, and another to
represent a GPS sensor. These participants will update the blockchain with
their respective readings. Devices are network participants? That’s right;
a participant in a blockchain network does not have to be a human
being.

                abstract participant IoTDevice identified by deviceId {
                  o String deviceId
                }
                
                participant TemperatureSensor extends IoTDevice {
                }
                
                participant GpsSensor extends IoTDevice {
                }

Finally, in a real blockchain application, events would be emitted at each
important point in the workflow: when a shipment has been packed, when it
has been picked up, and so forth. Add four new events to represent these
points in the shipment workflow.

                event ShipmentPackedEvent {
                  o String message
                  --> Shipment shipment
                }
                
                event ShipmentPickupEvent {
                  o String message
                  --> Shipment shipment
                }
                
                event ShipmentLoadedEvent {
                  o String message
                  --> Shipment shipment
                }
                
                event ShipmentReceivedEvent {
                  o String message
                  --> Shipment shipment
                }

That’s it for the model changes. Next, you need to make a few modifications
to the existing JavaScript transactions, and add chaincode for the new
transactions.

Add transaction chaincode

Until now, all of the chaincode for the networks you’ve worked with has
been contained in lib/logic.js. Obviously, a real-world
blockchain application could have lots of transactions, causing
logic.js to become cluttered, and eventually difficult to
maintain.

So long as all of your transaction code is in the lib
directory of your model, Hyperledger Composer has no problem resolving the
function calls. To illustrate this, you will make a few changes to
logic.js and add a few more JavaScript source files.

In VSCode, right-click the lib directory and choose
New File, and then enter
instantiateModelForTesting.js as the file name. Now paste in
the following header, or the “license check” step of the build will fail,
giving you an error message when you build the code later:

Listing 3. The Apache 2.0 license header. Make sure to paste
this into every new JavaScript file you create in your
project.

                /*
                 * Licensed under the Apache License, Version 2.0 (the "License");
                 * you may not use this file except in compliance with the License.
                 * You may obtain a copy of the License at
                 *
                 * http://www.apache.org/licenses/LICENSE-2.0
                 *
                 * Unless required by applicable law or agreed to in writing, software
                 * distributed under the License is distributed on an "AS IS" BASIS,
                 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
                 * See the License for the specific language governing permissions and
                 * limitations under the License.
                 */

Now add the following lines of code to instantiate a TemperatureSensor and
GpsSensor as part of the testing setup. Add just the highlighted lines.
I’ve included surrounding lines of existing code for context, so you can
locate them in the code:

                .
                .
                // create the shipper
                var shipper = factory.newResource(NS, 'Shipper', 'shipper@email.com');
                var shipperAddress = factory.newConcept(NS, 'Address');
                shipperAddress.country = 'Panama';
                shipper.address = shipperAddress;
                shipper.accountBalance = 0;
            
                // create the Temperature sensor
                var temperatureSensor = factory.newResource(NS, 'TemperatureSensor', 'SENSOR_TEMP001');
                // create the GPS sensor
                var gpsSensor = factory.newResource(NS, 'GpsSensor', 'SENSOR_GPS001');
                
                // create the contract
                var contract = factory.newResource(NS, 'Contract', 'CON_001');
                contract.grower = factory.newRelationship(NS, 'Grower', 'farmer@email.com');
                contract.importer = factory.newRelationship(NS, 'Importer', 'supermarket@email.com');
                .
                .
                .then(function() {
                    return getParticipantRegistry(NS + '.Shipper');
                })
                .then(function(shipperRegistry) {
                    // add the shippers
                    return shipperRegistry.addAll([shipper]);
                })
                .then(function() {
                    return getParticipantRegistry(NS + '.TemperatureSensor');
                })
                .then(function(temperatureSensorRegistry) {
                    // add the temperature sensors
                    return temperatureSensorRegistry.addAll([temperatureSensor]);
                })
                .then(function() {
                    return getParticipantRegistry(NS + '.GpsSensor');
                })
                .then(function(gpsSensorRegistry) {
                    // add the GPS sensors
                    return gpsSensorRegistry.addAll([gpsSensor]);
                })
                .then(function() {
                    return getAssetRegistry(NS + '.Contract');
                })
                .then(function(contractRegistry) {
                    // add the contracts
                    return contractRegistry.addAll([contract]);
                })
                .
                .

Why the function renaming?

It’s my firm belief that code names should mirror their model artifacts
as closely as possible. The purpose of the setupDemo
function is to instantiate the model for testing purposes, so let’s
just call it that. Then there’s the payOut function,
which does handle the participant payout when a shipment is received,
but (IMO) it doesn’t cleanly map to the model, so let’s call it
receiveShipment since it will be invoked once the
shipment is received.

Now open logic.js, select the entire function body of
setupDemo, and then cut it from logic.js and
paste it into the new file. Finally, rename the function to
instantiateModelForTesting.

Next, in logic.js, rename the payOut function to
receiveShipment so that it more closely matches the
transaction in the model. Then add the following code to emit the
ShipmentReceivedEvent just after the block of code that
computes the payout. The highlighted lines are the ones you should modify
and/or add (modify line 6, add lines 17-27). I’ve included surrounding
lines of existing code for context.

                /**
                 * A shipment has been received by an importer
                 * @param {org.acme.shipping.perishable.ShipmentReceived} shipmentReceived - the ShipmentReceived transaction
                 * @transaction
                 */
                function receiveShipment(shipmentReceived) {
                    .
                    .
                    //console.log('Payout: ' + payOut);
                    contract.grower.accountBalance += payOut;
                    contract.importer.accountBalance -= payOut;
                
                    //console.log('Grower: ' + contract.grower.$identifier + ' new balance: ' + contract.grower.accountBalance);
                    //console.log('Importer: ' + contract.importer.$identifier + ' new balance: ' + contract.importer.accountBalance);
                
                    var NS = 'org.acme.shipping.perishable';
                    // Store the ShipmentReceived transaction with the Shipment asset it belongs to
                    shipment.shipmentReceived = shipmentReceived;
                
                    var factory = getFactory();
                    var shipmentReceivedEvent = factory.newEvent(NS, 'ShipmentReceivedEvent');
                    var message = 'Shipment ' + shipment.$identifier + ' received';
                    //console.log(message);
                    shipmentReceivedEvent.message = message;
                    shipmentReceivedEvent.shipment = shipment;
                    emit(shipmentReceivedEvent);
                
                    return getParticipantRegistry('org.acme.shipping.perishable.Grower')
                        .then(function (growerRegistry) {
                            // update the grower's balance
                            return growerRegistry.update(contract.grower);
                        })
                    .
                    .

Now you’ll need to add JavaScript chaincode for the three new transactions
you added to the model, and you’ll create a new JavaScript source file for
that. In VSCode, right-click the lib directory and choose
New File, and then enter shipment.js as
the file name. Add the functions below to this file. Make sure to
paste in the Apache 2.0 comment header at the top of the file. See
Listing 3.

Transaction: `ShipmentPacked`
chaincode

First, add a function to handle the ShipmentPacked
transaction. When the Grower participant (or one of its authorized agents)
packs the shipment for pickup and transport, it invokes the
ShipmentPacked blockchain transaction to record this fact in
the ledger.

When this transaction is invoked, a ShipmentPackedEvent is
emitted ,notifying any interested parties of this, and then the chaincode
updates the ledger.

Name the new function packShipment using the “verb/object”
function naming idiom. In JavaScript code, the comments shown below are
mandatory for Hyperledger Composer to recognize the function as a
transaction.

Copy all of the code below and paste it into
shipment.js.

                /**
                 * ShipmentPacked transaction - invoked when the Shipment is packed and ready for pickup.
                 * 
                 * @param {org.acme.shipping.perishable.ShipmentPacked} shipmentPacked - the ShipmentPacked transaction
                 * @transaction
                 */
                function packShipment(shipmentPacked) {
                    var shipment = shipmentPacked.shipment;
                    var NS = 'org.acme.shipping.perishable';
                    var contract = shipment.contract;
                    var factory = getFactory();
                
                    // Add the ShipmentPacked transaction to the ledger (via the Shipment asset)
                    shipment.shipmentPacked = shipmentPacked;
                
                    // Create the message
                    var message = 'Shipment packed for shipment ' + shipment.$identifier;
                
                    // Log it to the JavaScript console
                    //console.log(message);
                
                    // Emit a notification telling subscribed listeners that the shipment has been packed
                    var shipmentPackedEvent = factory.newEvent(NS, 'ShipmentPackedEvent');
                    shipmentPackedEvent.shipment = shipment;
                    shipmentPackedEvent.message = message;
                    emit(shipmentPackedEvent);
                
                    // Update the Asset Registry
                    return getAssetRegistry(NS + '.Shipment')
                        .then(function (shipmentRegistry) {
                            // add the temp reading to the shipment
                            return shipmentRegistry.update(shipment);
                        });
                }

Transaction: `ShipmentPickup`
chaincode

Next, when the Shipper participant (or one of its authorized agents) picks
up the packed shipment for transport, it invokes the
ShipmentPickup blockchain transaction to record this fact in
the ledger. Add a function to handle the ShipmentPickup
transaction called pickupShipment.

When this transaction is invoked, a ShipmentPickupEvent is
emitted, notifying any interested parties of this, and then the chaincode
updates the ledger.

Copy all of the code below and paste it into shipment.js.

                /**
                 * ShipmentPickup - invoked when the Shipment has been picked up from the packer.
                 * 
                 * @param {org.acme.shipping.perishable.ShipmentPickup} shipmentPickup - the ShipmentPickup transaction
                 * @transaction
                 */
                function pickupShipment(shipmentPickup) {
                    var shipment = shipmentPickup.shipment;
                    var NS = 'org.acme.shipping.perishable';
                    var contract = shipment.contract;
                    var factory = getFactory();
                
                    // Add the ShipmentPacked transaction to the ledger (via the Shipment asset)
                    shipment.shipmentPickup = shipmentPickup;
                
                    // Create the message
                    var message = 'Shipment picked up for shipment ' + shipment.$identifier;
                
                    // Log it to the JavaScript console
                    //console.log(message);
                
                    // Emit a notification telling subscribed listeners that the shipment has been packed
                    var shipmentPickupEvent = factory.newEvent(NS, 'ShipmentPickupEvent');
                    shipmentPickupEvent.shipment = shipment;
                    shipmentPickupEvent.message = message;
                    emit(shipmentPickupEvent);
                
                    // Update the Asset Registry
                    return getAssetRegistry(NS + '.Shipment')
                        .then(function (shipmentRegistry) {
                            // add the temp reading to the shipment
                            return shipmentRegistry.update(shipment);
                        });
                }

Transaction: `ShipmentLoaded`
chaincode

Finally, when the Shipper participant (or one of its authorized agents)
loads the shipment onto the container ship, it invokes the
ShipmentLoaded blockchain transaction to record this fact in
the ledger. Add a function to handle the ShipmentLoaded event
called loadShipment.

When this transaction is invoked, a ShipmentLoadedEvent is
emitted, notifying any interested parties of this, and then the chaincode
updates the ledger.

Copy all of the code below and paste it into shipment.js.

                /**
                 * ShipmentLoaded - invoked when the Shipment has been loaded onto the container ship.
                 * 
                 * @param {org.acme.shipping.perishable.ShipmentLoaded} shipmentLoaded - the ShipmentLoaded transaction
                 * @transaction
                 */
                function loadShipment(shipmentLoaded) {
                    var shipment = shipmentLoaded.shipment;
                    var NS = 'org.acme.shipping.perishable';
                    var contract = shipment.contract;
                    var factory = getFactory();
                
                    // Add the ShipmentPacked transaction to the ledger (via the Shipment asset)
                    shipment.shipmentLoaded = shipmentLoaded;
                
                    // Create the message
                    var message = 'Shipment loaded for shipment ' + shipment.$identifier;
                
                    // Log it to the JavaScript console
                    //console.log(message);
                
                    // Emit a notification telling subscribed listeners that the shipment has been packed
                    var shipmentLoadedEvent = factory.newEvent(NS, 'ShipmentLoadedEvent');
                    shipmentLoadedEvent.shipment = shipment;
                    shipmentLoadedEvent.message = message;
                    emit(shipmentLoadedEvent);
                
                    // Update the Asset Registry
                    return getAssetRegistry(NS + '.Shipment')
                        .then(function (shipmentRegistry) {
                            // add the temp reading to the shipment
                            return shipmentRegistry.update(shipment);
                        });
                }

Change access control permissions

In a real blockchain application, it is not ideal to grant any participant
permission to do anything they want to. For example, a Grower shouldn’t be
able to invoke transactions that make sense only for a Shipper, and a GPS
sensor shouldn’t be allowed to record temperature readings in the
blockchain.

So how do you prevent that from happening? In other words, how do you build
your network such that you control access to its resources? Through the
Access Control List (ACL) file.

You’ve already seen it in Parts 1 and 2 of this series, but I just sort of
glossed over it, and promised to cover it in more detail at a later point.
Well, that time has come.

It’s time to talk about access control, which begins with
permissions.acl. You saw this file earlier, but it’s time to
put that knowledge to use. You’ll modify the
iot-perishable-network to ensure that resources can be
accessed only by certain participants that make sense to access that
resource. As an illustration, I’ve summarized the access control settings
that make sense for the iot-perishable-network in Table
1.

You may notice the rule names and think they look a bit odd. I like to
encode as much information in a name as possible without making it
ridiculously long, or completely nonsensical. Here’s my thinking: the rule
is named Participant_Operation_Resource. So
Grower_R_Grower means, “Grant the Grower participant READ
access to Grower instances”.

Table 1. Participant access control — The type of
access is in parentheses: R = READ, U = UPDATE, C = CREATE

Participant	Participants accessed	Assets accessed	Transactions accessed
Grower	Grower (R)	Shipment (RU), Contract (RU)	ShipmentPacked (C)
Shipper	Shipper (R)	Shipment (RU), Contract (RU)	ShipmentPickup, ShipmentLoaded (C)
Importer	Importer (R), Grower (RU)	Shipment (RU), Contract	ShipmentReceived (C)
TemperatureSensor	NONE	Shipment (RU), Contract (RU)	TemperatureReading (C)
GpsSensor	NONE	Shipment (RU), Contract (RU)	GpsReading (C)

The rules are codified below. Open permissions.acl (in the
root of the network project), delete its current contents, and replace
then with the listings that follow. The entire listing is very long, so
I’ll talk through it one section at a time.

The first two rules grant permission to the Hyperledger Composer system
Participant and NetworkAdmin participants to
access everything in the org.hyperledger.composer.system
namespace, and every class in the network, respectively.