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corda/docs/source/creating-a-cordapp.rst
Clinton Alexander f2a93ea67b Fixed review comments.
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Creating a Cordapp

A Cordapp is an application that runs on the Corda platform using the platform APIs and plugin system. They are self contained in separate JARs from the node server JAR that are created and distributed.

App Plugins

Note

Currently apps are only supported for JVM languages.

To create an app plugin you must you must extend from CordaPluginRegistry. The JavaDoc contains specific details of the implementation, but you can extend the server in the following ways:

  1. Required protocols: Specify which protocols will be whitelisted for use in your web APIs.
  2. Service plugins: Register your services.
  3. Web APIs: You may register your own endpoints under /api/ of the built-in web server.
  4. Static web endpoints: You may register your own static serving directories for serving web content.

Services

Services are classes which are constructed after the node has started. It is provided a ServiceHubInternal which allows a richer API than the ServiceHub exposed to contracts. It enables adding protocols, registering message handlers and more. The service does not run in a separate thread, so the only entry point to the service is during construction, where message handlers should be registered and threads started.

Starting Nodes

To use an app you must also have a node server. To create a node server run the gradle installTemplateNodes task.

This will output the node JAR to build/libs/corda.jar and several sample/standard node setups to build/nodes. For now you can use the build/nodes/nodea configuration as a template.

Each node server must have a node.conf file in the same directory as the node JAR file. After first execution of the node server there will be many other configuration and persistence files created in this directory.

Note

Outside of development environments do not store your node directories in the build folder.

Installing Apps

Once you have created your app JAR you can install it to a node by adding it to <node_dir>/plugins/. In this case the node_dir is the location where your node server's JAR and configuration file is.

Note

If the directory does not exist you can create it manually.

Starting your Node

Now you have a node server with your app installed, you can run it by navigating to <node_dir> and running

java -jar corda.jar

The plugin should automatically be registered and the configuration file used.

Warning

If your working directory is not <node_dir> your plugins and configuration will not be used.