CorDapp Template

Welcome to the CorDapp template. The CorDapp template is a stubbed-out CorDapp which you can use to bootstrap your own CorDapp projects.

This is the JAVA version of the CorDapp template. For the KOTLIN version click here.

Pre-Requisites

You will need the following installed on your machine before you can start:

• JDK 8 installed and available on your path (Minimum version: 1.8_131).
• Eclipse (Minimum version MARS.2)
• Eclipse Buildship: Eclipse Plug-ins for Gradle
• git
• Optional: h2 web console (download the "platform-independent zip")

For more detailed information, see the getting set up page on the Corda docsite.

Getting Set Up

To get started, clone this repository with:

 git clone https://github.com/balajimore/cordapp-template-java-eclipse

And change directories to the newly cloned repo:

 cd cordapp-template-java-eclipse

Building the CorDapp template:

Unix:

 ./gradlew deployNodes

Windows:

 gradlew.bat deployNodes

Note: You'll need to re-run this build step after making any changes to the template for these to take effect on the node.

Running the Nodes

Once the build finishes, change directories to the folder where the newly built nodes are located:

 cd build/nodes

The Gradle build script will have created a folder for each node. You'll see three folders, one for each node and a runnodes script. You can run the nodes with:

Unix:

 ./runnodes --log-to-console --logging-level=DEBUG

Windows:

runnodes.bat --log-to-console --logging-level=DEBUG

You should now have three Corda nodes running on your machine serving the template.

When the nodes have booted up, you should see a message like the following in the console:

 Node started up and registered in 5.007 sec

Interacting with the CorDapp via HTTP

The CorDapp defines a couple of HTTP API end-points and also serves some static web content. Initially, these return generic template responses.

The nodes can be found using the following port numbers, defined in the build.gradle, as well as the node.conf file for each node found under build/nodes/NodeX or build/nodes/NodeX:

 NodeA: localhost:10007
 NodeB: localhost:10010

As the nodes start up, they should tell you which host and port their embedded web server is running on. The API endpoints served are:

 /api/template/templateGetEndpoint

And the static web content is served from:

 /web/template

Using the Example RPC Client

The TemplateClient.java file is a simple utility which uses the client RPC library to connect to a node and log its transaction activity. It will log any existing states and listen for any future states. To build the client use the following Gradle task:

 ./gradlew runTemplateClient

To run the client:

Via IntelliJ:

Select the 'Run Template RPC Client' run configuration which, by default, connect to NodeA (RPC port 10006). Click the Green Arrow to run the client.

Via the command line:

Run the following Gradle task:

 ./gradlew runTemplateClient

Note that the template rPC client won't output anything to the console as no state objects are contained in either NodeA's or NodeB's vault.

Running the Nodes Across Multiple Machines

The nodes can also be set up to communicate between separate machines on the same subnet.

After deploying the nodes, navigate to the build folder (build/ nodes) and move some of the individual node folders to separate machines on the same subnet (e.g. using a USB key). It is important that no nodes - including the controller node - 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: controller, nodea, runnodes, runnodes.bat
• Machine 2: nodeb, nodec, runnodes, runnodes.bat

You must now edit the configuration file for each node, including the controller. Open each node's config file ([nodeName]/node.conf), and make the following changes:

• Change the artemis address to the machine's ip address (e.g. artemisAddress="10.18.0.166:10005")
• Change the network map address to the ip address of the machine where the controller node is running (e.g. networkMapAddress="10.18.0.166:10002") (please note that the controller will not have a network map address)

Each machine should now run its nodes using runnodes or runnodes.bat files. Once they are up and running, the nodes should be able to communicate among themselves in the same way as when they were running on the same machine.

Further reading

Tutorials and developer docs for CorDapps and Corda are here.