.. highlight:: kotlin
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The example CorDapp
===================

.. contents::

The example CorDapp allows nodes to agree IOUs with each other, as long as they obey the following contract rules:

* The IOU's value is strictly positive
* A node is not trying to issue an IOU to itself

We will deploy and run the CorDapp on four test nodes:

* **Notary**, which hosts a validating notary service
* **PartyA**
* **PartyB**
* **PartyC**

Because data is only propagated on a need-to-know basis, any IOUs agreed between PartyA and PartyB become "shared
facts" between PartyA and PartyB only. PartyC won't be aware of these IOUs.

Downloading the example CorDapp
-------------------------------
Start by downloading the example CorDapp from GitHub:

* Set up your machine by following the :doc:`quickstart guide <getting-set-up>`

* Clone the example CorDapp from the `cordapp-example repository <https://github.com/corda/cordapp-example>`_ using
  the following command: ``git clone https://github.com/corda/cordapp-example``

* Change directories to the freshly cloned repo: ``cd cordapp-example``

Opening the example CorDapp in IntelliJ
---------------------------------------
Let's open the example CorDapp in IntelliJ IDEA:

* Open IntelliJ

* A splash screen will appear. Click ``open``, select the cloned ``cordapp-example`` folder, and click ``OK``

* Once the project is open, click ``File``, then ``Project Structure``. Under ``Project SDK:``, set the project SDK by
  clicking ``New...``, clicking ``JDK``, and navigating to ``C:\Program Files\Java\jdk1.8.0_XXX`` on Windows or ``Library/Java/JavaVirtualMachines/jdk1.8.XXX`` on MacOSX (where ``XXX`` is the
  latest minor version number). Click ``Apply`` followed by ``OK``

* Again under ``File`` then ``Project Structure``, select ``Modules``. Click ``+``, then ``Import Module``, then select
  the ``cordapp-example`` folder and click ``Open``. Choose to ``Import module from external model``, select
  ``Gradle``, click ``Next`` then ``Finish`` (leaving the defaults) and ``OK``

* Gradle will now download all the project dependencies and perform some indexing. This usually takes a minute or so

Project structure
~~~~~~~~~~~~~~~~~
The example CorDapp has the following structure:

.. sourcecode:: none

    .
    ├── config
    │   ├── dev
    │   │   └── log4j2.xml
    │   └── test
    │       └── log4j2.xml
    ├── doc
    │   └── example_flow.plantuml
    ├── gradle
    │   └── wrapper
    │       ├── gradle-wrapper.jar
    │       └── gradle-wrapper.properties
    ├── lib
    │   ├── README.txt
    │   └── quasar.jar
    ├── java-source
    │   └── ...
    ├── kotlin-source
    │   ├── build.gradle
    │   └── src
    │       ├── main
    │       │   ├── kotlin
    │       │   │   └── com
    │       │   │       └── example
    │       │   │           ├── api
    │       │   │           │   └── ExampleApi.kt
    │       │   │           ├── client
    │       │   │           │   └── ExampleClientRPC.kt
    │       │   │           ├── contract
    │       │   │           │   └── IOUContract.kt
    │       │   │           ├── flow
    │       │   │           │   └── ExampleFlow.kt
    │       │   │           ├── model
    │       │   │           │   └── IOU.kt
    │       │   │           ├── plugin
    │       │   │           │   └── ExamplePlugin.kt
    │       │   │           ├── schema
    │       │   │           │   └── IOUSchema.kt
    │       │   │           └── state
    │       │   │               └── IOUState.kt
    │       │   └── resources
    │       │       ├── META-INF
    │       │       │   └── services
    │       │       │       └── net.corda.webserver.services.WebServerPluginRegistry
    │       │       ├── certificates
    │       │       │   ├── readme.txt
    │       │       │   ├── sslkeystore.jks
    │       │       │   └── truststore.jks
    │       │       └── exampleWeb
    │       │           ├── index.html
    │       │           └── js
    │       │               └── angular-module.js
    │       └── test
    │           └── kotlin
    │               └── com
    │                   └── example
    │                       ├── Main.kt
    │                       ├── contract
    │                       │   └── IOUContractTests.kt
    │                       └── flow
    │                           └── IOUFlowTests.kt
    ├── .gitignore
    ├── LICENCE
    ├── README.md
    ├── TRADEMARK
    ├── build.gradle
    ├── gradle.properties
    ├── gradlew
    ├── gradlew.bat
    └── settings.gradle

The key files and directories are as follows:

* The **root directory** contains some gradle files, a README and a LICENSE
* **config** contains log4j configs
* **gradle** contains the gradle wrapper, which allows the use of Gradle without installing it yourself and worrying
  about which version is required
* **lib** contains the Quasar jar which rewrites our CorDapp's flows to be checkpointable
* **kotlin-source** contains the source code for the example CorDapp written in Kotlin

  * **kotlin-source/src/main/kotlin** contains the source code for the example CorDapp
  * **kotlin-source/src/main/resources** contains the certificate store, some static web content to be served by the
    nodes and the WebServerPluginRegistry file
  * **kotlin-source/src/test/kotlin** contains unit tests for the contracts and flows, and the driver to run the nodes
    via IntelliJ

* **java-source** contains the same source code, but written in Java. CorDapps can be developed in any language
  targeting the JVM

Running the example CorDapp
---------------------------
There are two ways to run the example CorDapp:

* Via the terminal
* Via IntelliJ

Both approaches will create a set of test nodes, install the CorDapp on these nodes, and then run the nodes. You can
read more about how we generate nodes :doc:`here <generating-a-node>`.

Running the example CorDapp from the terminal
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Building the example CorDapp
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
* Open a terminal window in the ``cordapp-example`` directory

* Run the ``deployNodes`` Gradle task to build four nodes with our CorDapp already installed on them:

  * Unix/Mac OSX: ``./gradlew deployNodes``

  * Windows: ``gradlew.bat deployNodes``

.. note:: CorDapps can be written in any language targeting the JVM. In our case, we've provided the example source in
   both Kotlin (``/kotlin-source/src``) and Java (``/java-source/src``). Since both sets of source files are
   functionally identical, we will refer to the Kotlin version throughout the documentation.

* After the build finishes, you will see the following output in the ``kotlin-source/build/nodes`` folder:

  * A folder for each generated node
  * A ``runnodes`` shell script for running all the nodes simultaneously on osX
  * A ``runnodes.bat`` batch file for running all the nodes simultaneously on Windows

* Each node in the ``nodes`` folder will have the following structure:

  .. sourcecode:: none
      
      . nodeName
      ├── additional-node-infos  // 
      ├── certificates
      ├── corda.jar              // The Corda node runtime
      ├── corda-webserver.jar    // The development node webserver runtime
      ├── cordapps               // The node's CorDapps
      │   ├── corda-finance-3.2-corda.jar
      │   └── cordapp-example-0.1.jar
      ├── drivers
      ├── logs
      ├── network-parameters
      ├── node.conf              // The node's configuration file
      ├── nodeInfo-<HASH>        // The hash will be different each time you generate a node
      └── persistence.mv.db      // The node's database

.. note:: ``deployNodes`` is a utility task to create an entirely new set of nodes for testing your CorDapp. In production, 
   you would instead create a single node as described in :doc:`generating-a-node` and build your CorDapp JARs as described 
   in :doc:`cordapp-build-systems`.
      
Running the example CorDapp
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Start the nodes by running the following command from the root of the ``cordapp-example`` folder:

* Unix/Mac OSX: ``kotlin-source/build/nodes/runnodes``
* Windows: ``call kotlin-source\build\nodes\runnodes.bat``

.. warning:: On Unix/Mac OSX, do not click/change focus until all seven additional terminal windows have opened, or some
   nodes may fail to start.

For each node, the ``runnodes`` script creates a node tab/window:

.. sourcecode:: none

      ______               __
     / ____/     _________/ /___ _
    / /     __  / ___/ __  / __ `/         Top tip: never say "oops", instead
   / /___  /_/ / /  / /_/ / /_/ /          always say "Ah, Interesting!"
   \____/     /_/   \__,_/\__,_/

   --- Corda Open Source corda-3.0 (4157c25) -----------------------------------------------


   Logs can be found in                    : /Users/joeldudley/Desktop/cordapp-example/kotlin-source/build/nodes/PartyA/logs
   Database connection url is              : jdbc:h2:tcp://localhost:59472/node
   Incoming connection address             : localhost:10007
   Listening on port                       : 10007
   Loaded CorDapps                         : corda-finance-corda-3.0, cordapp-example-0.1, corda-core-corda-3.0
   Node for "PartyA" started up and registered in 38.59 sec


   Welcome to the Corda interactive shell.
   Useful commands include 'help' to see what is available, and 'bye' to shut down the node.

   Fri Mar 02 17:34:02 GMT 2018>>> 

For every node except the notary, the script also creates a webserver terminal tab/window:

.. sourcecode:: none

    Logs can be found in /Users/username/Desktop/cordapp-example/kotlin-source/build/nodes/PartyA/logs/web
    Starting as webserver: localhost:10009
    Webserver started up in 42.02 sec

It usually takes around 60 seconds for the nodes to finish starting up. To ensure that all the nodes are running, you
can query the 'status' end-point located at ``http://localhost:[port]/api/status`` (e.g.
``http://localhost:10009/api/status`` for ``PartyA``).

Running the example CorDapp from IntelliJ
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Select the ``Run Example CorDapp - Kotlin`` run configuration from the drop-down menu at the top right-hand side of
  the IDE

* Click the green arrow to start the nodes:

  .. image:: resources/run-config-drop-down.png
    :width: 400

* To stop the nodes, press the red square button at the top right-hand side of the IDE, next to the run configurations

Interacting with the example CorDapp
------------------------------------

Via HTTP
~~~~~~~~
The nodes' webservers run locally on the following ports:

* PartyA: ``localhost:10009``
* PartyB: ``localhost:10012``
* PartyC: ``localhost:10015``

These ports are defined in each node's node.conf file under ``kotlin-source/build/nodes/NodeX/node.conf``.

Each node webserver exposes the following endpoints:

* ``/api/example/me``
* ``/api/example/peers``
* ``/api/example/ious``
* ``/api/example/create-iou`` with parameters ``iouValue`` and ``partyName`` which is CN name of a node

There is also a web front-end served from ``/web/example``.

.. warning:: The content in ``/web/example`` is only available for demonstration purposes and does not implement
   anti-XSS, anti-XSRF or other security techniques. Do not use this code in production.

Creating an IOU via the endpoint
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
An IOU can be created by sending a PUT request to the ``/api/example/create-iou`` endpoint directly, or by using the
the web form served from ``/web/example``.

To create an IOU between PartyA and PartyB, run the following command from the command line:

.. sourcecode:: bash

   curl -X PUT 'http://localhost:10009/api/example/create-iou?iouValue=1&partyName=O=PartyB,L=New%20York,C=US'

Note that both PartyA's port number (``10009``) and PartyB are referenced in the PUT request path. This command
instructs PartyA to agree an IOU with PartyB. Once the process is complete, both nodes will have a signed, notarised
copy of the IOU. PartyC will not.

Submitting an IOU via the web front-end
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
To create an IOU between PartyA and PartyB, navigate to ``/web/example``, click the "create IOU" button at the top-left
of the page, and enter the IOU details into the web-form. The IOU must have a positive value. For example:

.. sourcecode:: none

  Counterparty: Select from list
  Value (Int):   5

And click submit. Upon clicking submit, the modal dialogue will close, and the nodes will agree the IOU.

Checking the output
^^^^^^^^^^^^^^^^^^^
Assuming all went well, you can view the newly-created IOU by accessing the vault of PartyA or PartyB:

*Via the HTTP API:*

* PartyA's vault: Navigate to http://localhost:10009/api/example/ious
* PartyB's vault: Navigate to http://localhost:10012/api/example/ious

*Via web/example:*

* PartyA: Navigate to http://localhost:10009/web/example and hit the "refresh" button
* PartyB: Navigate to http://localhost:10012/web/example and hit the "refresh" button

The vault and web front-end of PartyC (at ``localhost:10015``) will not display any IOUs. This is because PartyC was
not involved in this transaction.

Via the interactive shell (terminal only)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Nodes started via the terminal will display an interactive shell:

.. sourcecode:: none

    Welcome to the Corda interactive shell.
    Useful commands include 'help' to see what is available, and 'bye' to shut down the node.

    Fri Jul 07 16:36:29 BST 2017>>>

Type ``flow list`` in the shell to see a list of the flows that your node can run. In our case, this will return the
following list:

.. sourcecode:: none

   com.example.flow.ExampleFlow$Initiator
   net.corda.core.flows.ContractUpgradeFlow$Initiator
   net.corda.core.flows.ContractUpgradeFlow$Initiator
   net.corda.finance.flows.CashExitFlow
   net.corda.finance.flows.CashIssueAndPaymentFlow
   net.corda.finance.flows.CashIssueFlow
   net.corda.finance.flows.CashPaymentFlow

Creating an IOU via the interactive shell
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
We can create a new IOU using the ``ExampleFlow$Initiator`` flow. For example, from the interactive shell of PartyA,
you can agree an IOU of 50 with PartyB by running
``flow start ExampleFlow$Initiator iouValue: 50, otherParty: "O=PartyB,L=New York,C=US"``.

This will print out the following progress steps:

.. sourcecode:: none

    ✅   Generating transaction based on new IOU.
    ✅   Verifying contract constraints.
    ✅   Signing transaction with our private key.
    ✅   Gathering the counterparty's signature.
        ✅   Collecting signatures from counterparties.
        ✅   Verifying collected signatures.
    ✅   Obtaining notary signature and recording transaction.
        ✅   Requesting signature by notary service
                Requesting signature by Notary service
                Validating response from Notary service
        ✅   Broadcasting transaction to participants
    ✅   Done

Checking the output
^^^^^^^^^^^^^^^^^^^
We can also issue RPC operations to the node via the interactive shell. Type ``run`` to see the full list of available
operations.

You can see the newly-created IOU by running ``run vaultQuery contractStateType: com.example.state.IOUState``.

As before, the interactive shell of PartyC will not display any IOUs.

Via the h2 web console
~~~~~~~~~~~~~~~~~~~~~~
You can connect directly to your node's database to see its stored states, transactions and attachments. To do so,
please follow the instructions in :doc:`node-database`.

Using the example RPC client
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
``/src/main/kotlin-source/com/example/client/ExampleClientRPC.kt`` defines a simple RPC client that connects to a node,
logs any existing IOUs and listens for any future IOUs. If you haven't created
any IOUs when you first connect to one of the nodes, the client will simply log any future IOUs that are agreed.

Running the client via IntelliJ
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Run the 'Run Example RPC Client' run configuration. By default, this run configuration is configured to connect to
PartyA. You can edit the run configuration to connect on a different port.

Running the client via the command line
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Run the following gradle task:

``./gradlew runExampleClientRPCKotlin``

This will connect the RPC client to PartyA and log their past and future IOU activity.

You can close the application using ``ctrl+C``.

For more information on the client RPC interface and how to build an RPC client application, see:

* :doc:`Client RPC documentation <clientrpc>`
* :doc:`Client RPC tutorial <tutorial-clientrpc-api>`

Running nodes across machines
-----------------------------
The nodes can be configured to communicate as a network even when distributed across several machines:

* Deploy the nodes as usual:

  * Unix/Mac OSX: ``./gradlew deployNodes``
  * Windows: ``gradlew.bat deployNodes``

* Navigate to the build folder (``kotlin-source/build/nodes``)
* For each node, open its ``node.conf`` file and change ``localhost`` in its ``p2pAddress`` to the IP address of the machine
  where the node will be run (e.g. ``p2pAddress="10.18.0.166:10007"``)
* These changes require new node-info files to be distributed amongst the nodes. Use the network bootstrapper tool
  (see :doc:`network-bootstrapper`) to update the files and have them distributed locally:

  ``java -jar network-bootstrapper.jar kotlin-source/build/nodes``

* Move the node folders to their individual machines (e.g. using a USB key). It is important that none of the
  nodes - including the notary - end up on more than one machine. Each computer should also have a copy of ``runnodes``
  and ``runnodes.bat``.

  For example, you may end up with the following layout:

  * Machine 1: ``Notary``, ``PartyA``, ``runnodes``, ``runnodes.bat``
  * Machine 2: ``PartyB``, ``PartyC``, ``runnodes``, ``runnodes.bat``

* After starting each node, the nodes will be able to see one another and agree IOUs among themselves

.. warning:: The bootstrapper must be run **after** the ``node.conf`` files have been modified, but **before** the nodes 
   are distributed across machines. Otherwise, the nodes will not be able to communicate.

.. note:: If you are using H2 and wish to use the same ``h2port`` value for two or more nodes, you must only assign them that
   value after the nodes have been moved to their individual machines. The initial bootstrapping process requires access to 
   the nodes' databases and if two nodes share the same H2 port, the process will fail.

Testing your CorDapp
--------------------

Corda provides several frameworks for writing unit and integration tests for CorDapps.

Contract tests
~~~~~~~~~~~~~~
You can run the CorDapp's contract tests by running the ``Run Contract Tests - Kotlin`` run configuration.

Flow tests
~~~~~~~~~~
You can run the CorDapp's flow tests by running the ``Run Flow Tests - Kotlin`` run configuration.

Integration tests
~~~~~~~~~~~~~~~~~
You can run the CorDapp's integration tests by running the ``Run Integration Tests - Kotlin`` run configuration.

Debugging your CorDapp
----------------------

See :doc:`debugging-a-cordapp`.
