README.md

lambda-packaging

A collection of Maven assembly descriptors for building AWS Lambda deployment packages.

The lambda-zip descriptor supports building .zip deployment packages as described in the AWS documentation page, "Creating a ZIP Deployment Package for a Java Function". The resulting .zip file contains compiled class files and resources at the top level, and all of the required dependencies as .jar files in the lib/ directory.

Advantages of .zip over uberjar

This method of packaging Lambda deployment packages has two major advantages over the uberjar method:

1. Reduces the amount of time it takes the Lambda runtime to unpack the deployment package (see the AWS Lambda "Best Practices" page).
2. Avoids overlaying unpacked dependencies on top of each other, which leads to resource merge conflicts.

When not to use lambda-packaging

1. For Lambda functions that have no dependencies other than aws-lambda-java-core.
2. In cases where classes need to be relocated - use the maven-shade-plugin instead.

Usage

Add the following plugin configuration to your pom.xml file:

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>3.1.0</version>
                <dependencies>
                  <dependency>
                    <groupId>io.symphonia</groupId>
                    <artifactId>lambda-packaging</artifactId>
                    <version>1.0.0</version>
                  </dependency>
                </dependencies>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <descriptorRefs>
                        <descriptorRef>lambda-zip</descriptorRef>
                    </descriptorRefs>
                    <appendAssemblyId>false</appendAssemblyId>
                    <finalName>lambda</finalName>
                </configuration>
            </plugin>
            ...
        </plugins>
        ...
    </build>

With this configuration in place, running mvn package will produce a lambda.zip deployment package in the target/ directory.