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Getting started

The contræct-maven-plugin is a maven plugin that simplifies interacting with smart contracts on the aeternity blockchain. It generates Java classes out of the sophia contract sourcecode which provide a convenient to deploy a contract on the chain or call a function.

It also wraps the input and output objects of those function calls - no parsing is necessary.

Detail description

The plugin takes a contract written in sophia language as input and generates a Java class representing the contract and its methods. The following statements apply due to the code generation:

  • creates a method to deploy the contract on the chain
  • create method for every entrypoint to call entrypoints of a deployed contract
  • methods will be executed using dryRun - which means it will not be committed and thus included in a block
  • if a method is stateful - transaction additionally will be committed and thus included in a block. The method waits until the transaction is confirmed
  • if a method is payable - an additional parameter is available to set the amount to deposit
  • all input parameters are parsed to a typed Java classes (if possible), also the result is parsed to a Java type (if possible)
  • in case of errors during dryRun call or committing the transaction, exceptions are raised with details from the node
  • initialization of an instance can be done using an existing contractId, thus the methods of an already deployed contract can be called

Gas estimation

Whenever stateful entrypoints are called using the generated classes, at first a dryRun is done. Therefore a fixed gas limit (default: 50000) is passed as parameter, which should be sufficient for almost all contract calls. After performing the dryRun the exact gas used is returned and the corresponding contractCallModel is updated. The following sample shows the relevant part of the Java class generated by the plugin: 

contractCallModel = contractCallModel.toBuilder()
                        .gasLimit(dryRunResult.getContractCallObject()
                        .getGasUsed()).build();

System requirements

Include dependencies

contraect-maven-plugin

To add the contræct-maven-plugin to you build, simply add the following snippet to your pom.xml

<build>
    <plugins>
        <plugin>
            <groupId>com.kryptokrauts</groupId>
            <artifactId>contraect-maven-plugin</artifactId>
            <version>2.0.0</version>
            <configuration>
                ...
            </configuration>
        </plugin>
    </plugins>
</build>
The content of the <configuration> section is covered in the Plugin configuration

aepp-sdk-java

Under the hood the plugin as well as the generated classes make use of the aepp-sdk-java to implement the interaction with the aeternity node. Therefore the dependency needs to be declared in the corresponding section - please make sure to always use the latest version of the SDK.

<dependency>
    <groupId>com.kryptokrauts</groupId>
    <artifactId>aepp-sdk-java</artifactId>
    <version>3.0.0</version
</dependency>