CorDapp Build Systems

Cordapps run on the Corda platform and integrate with it and each other. To learn more about the basics of a Cordapp please read cordapp-overview. To learn about writing a Cordapp as a developer please read writing-cordapps.

This article will specifically deal with how to build cordapps, specifically with Gradle.

CorDapp JAR format

The first step to integrating a Cordapp with Corda is to ensure it is in the correct format. The correct format of a JAR is a semi-fat JAR that contains all of its own dependencies except the Corda core libraries and other Cordapps.

For example if your Cordapp depends on corda-core, your-other-cordapp and apache-commons then the Cordapp JAR will contain all classes and resources from the apache-commons JAR and its dependencies and nothing from the other two JARs.

Note

The rest of this tutorial assumes you are using gradle, the cordformation plugin and have forked from one of our cordapp templates.

The jar task included by default in the cordapp templates will automatically build your JAR in this format as long as your dependencies are correctly set.

The filename of the jar must include some sort of unique identifier to deduplicate it from other releases of the same CorDapp. This is typically done by appending the version string. It should not change once the jar has been deployed on a node. If it is then make sure no one is checking FlowContext.appName (see versioning).

Building against Corda

To build against Corda you must do the following to your build.gradle;

Add the net.corda:corda:<version> JAR as a cordaRuntime dependency.
Add each compile dependency (eg corda-core) as a cordaCompile dependency.

To make use of the Corda test facilities you must;

Add net.corda:corda-test-utils:<version> as a testCompile dependency (eg; a default Java/Kotlin compile task).

Warning

Never include corda-test-utils as a compile or cordaCompile dependency.

These configurations work by the cordformation plugin adding cordaCompile as a new configuration that compile extends from, and cordaRuntime which runtime extends from.

Choosing your Corda version

The following two lines of the build.gradle file define the Corda version used to build your CorDapp:

ext.corda_release_version = '0.13.0'
ext.corda_gradle_plugins_version = '0.13.3'

In this case, our CorDapp will use the Milestone 13 release of Corda, and version 13.3 of the Corda gradle plugins. You can find the latest published version of both here: https://bintray.com/r3/corda.

corda_gradle_plugins_versions are given in the form major.minor.patch. You should use the same major and minor versions as the Corda version you are using, and the latest patch version. A list of all the available versions can be found here: https://bintray.com/r3/corda/cordformation.

In certain cases, you may also wish to build against the unstable Master branch. See building-against-master.

Building against CorDapps

To build against a Cordapp you must add it as a cordapp dependency to your build.gradle.

Other Dependencies

If your CorDapps have any additional external dependencies, they can be specified like normal Kotlin/Java dependencies in Gradle. See the example below, specifically the apache-commons include.

For further information about managing dependencies, see the Gradle docs.

Installing CorDapps

At runtime, nodes will load any plugins present in their plugins folder. Therefore in order to install a cordapp to a node the cordapp JAR must be added to the <node_dir>/plugins/ folder, where node_dir is the folder in which the node's JAR and configuration files are stored).

The deployNodes gradle task, if correctly configured, will automatically place your cordapp JAR as well as any dependent cordapp JARs specified into the directory automatically.

Example

The following is a sample of what a gradle dependencies block for a cordapp could look like. The cordapp template is already correctly configured and this is for reference only;

dependencies {
    // Corda integration dependencies
    cordaCompile "net.corda:corda-core:$corda_release_version"
    cordaCompile "net.corda:corda-finance:$corda_release_version"
    cordaCompile "net.corda:corda-jackson:$corda_release_version"
    cordaCompile "net.corda:corda-rpc:$corda_release_version"
    cordaCompile "net.corda:corda-node-api:$corda_release_version"
    cordaCompile "net.corda:corda-webserver-impl:$corda_release_version"
    cordaRuntime "net.corda:corda:$corda_release_version"
    cordaRuntime "net.corda:corda-webserver:$corda_release_version"
    testCompile "net.corda:corda-test-utils:$corda_release_version"

    // Corda Plugins: dependent flows and services
    cordapp "net.corda:bank-of-corda-demo:1.0"

    // Some other dependencies
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre8:$kotlin_version"
    testCompile "org.jetbrains.kotlin:kotlin-test:$kotlin_version"
    testCompile "junit:junit:$junit_version"

    compile "org.apache.commons:commons-lang3:3.6"
}

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