Deploy Java Lambda functions with .zip or JAR file archives

Your Amazon Lambda function's code consists of scripts or compiled programs and their dependencies. You use a deployment package to deploy your function code to Lambda. Lambda supports two types of deployment packages: container images and .zip file archives.

This page describes how to create your deployment package as a .zip file or Jar file, and then use the deployment package to deploy your function code to Amazon Lambda using the Amazon Command Line Interface (Amazon CLI).

Prerequisites

The Amazon CLI is an open-source tool that enables you to interact with Amazon services using commands in your command line shell. To complete the steps in this section, you must have the Amazon CLI version 2.

Tools and libraries

Amazon provides the following libraries for Java functions. These libraries are available through Maven Central Repository.

Add these libraries to your build definition as follows:

To create a deployment package, compile your function code and dependencies into a single .zip file or Java Archive (JAR) file. For Gradle, use the Zip build type. For Apache Maven, use the Maven Shade plugin. To upload your deployment package, use the Lambda console, the Lambda API, or Amazon Serverless Application Model (Amazon SAM).

Building a deployment package with Gradle

To create a deployment package with your function's code and dependencies in Gradle, use the Zip build type. Here's an example from a complete sample build.gradle file:

task buildZip(type: Zip) {
    into('lib') {
        from(jar)
        from(configurations.runtimeClasspath)
    }
}

This build configuration produces a deployment package in the build/distributions directory. Within the into('lib') statement, the jar task assembles a jar archive containing your main classes into a folder named lib. Additionally, the configurations.runtimeClassPath task copies dependency libraries from the build's classpath into the same lib folder.

dependencies {
    ...
    implementation 'com.amazonaws:aws-lambda-java-core:1.2.2'
    implementation 'com.amazonaws:aws-lambda-java-events:3.11.1'
    implementation 'org.apache.logging.log4j:log4j-api:2.17.1'
    implementation 'org.apache.logging.log4j:log4j-core:2.17.1'
    runtimeOnly 'org.apache.logging.log4j:log4j-slf4j18-impl:2.17.1'
    runtimeOnly 'com.amazonaws:aws-lambda-java-log4j2:1.5.1'
    ...
}

Lambda loads JAR files in Unicode alphabetical order. If multiple JAR files in the lib directory contain the same class, the first one is used. You can use the following shell script to identify duplicate classes:

mkdir -p expanded
unzip path/to/my/function.zip -d expanded
find ./expanded/lib -name '*.jar' | xargs -n1 zipinfo -1 | grep '.*.class' | sort | uniq -c | sort

Creating a Java layer for your dependencies

The instructions in this section show you how to include your dependencies in a layer. For instructions on how to include your dependencies in your deployment package, see Building a deployment package with Gradle or Building a deployment package with Maven.

When you add a layer to a function, Lambda loads the layer content into the /opt directory of that execution environment. For each Lambda runtime, the PATH variable already includes specific folder paths within the /opt directory. To ensure that Lambda picks up your layer content, your layer .zip file should have its dependencies in the following folder paths:

For example, your layer .zip file structure might look like the following:

jackson.zip
└ java/lib/jackson-core-2.2.3.jar

In addition, Lambda automatically detects any libraries in the /opt/lib directory, and any binaries in the /opt/bin directory. To ensure that Lambda properly finds your layer content, you can also create a layer with the following structure:

custom-layer.zip
└ lib
    | lib_1
    | lib_2
└ bin
    | bin_1
    | bin_2

After you package your layer, see Creating and deleting layers in Lambda and Adding layers to functions to complete your layer setup.

Building a deployment package with Maven

To build a deployment package with Maven, use the Maven Shade plugin. The plugin creates a JAR file that contains the compiled function code and all of its dependencies.

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.2.2</version>
        <configuration>
          <createDependencyReducedPom>false</createDependencyReducedPom>
        </configuration>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

To build the deployment package, use the mvn package command.

[INFO] Scanning for projects...
[INFO] -----------------------< com.example:java-maven >-----------------------
[INFO] Building java-maven-function 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
...
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ java-maven ---
[INFO] Building jar: target/java-maven-1.0-SNAPSHOT.jar
[INFO]
[INFO] --- maven-shade-plugin:3.2.2:shade (default) @ java-maven ---
[INFO] Including com.amazonaws:aws-lambda-java-core:jar:1.2.2 in the shaded jar.
[INFO] Including com.amazonaws:aws-lambda-java-events:jar:3.11.1 in the shaded jar.
[INFO] Including joda-time:joda-time:jar:2.6 in the shaded jar.
[INFO] Including com.google.code.gson:gson:jar:2.8.6 in the shaded jar.
[INFO] Replacing original artifact with shaded artifact.
[INFO] Replacing target/java-maven-1.0-SNAPSHOT.jar with target/java-maven-1.0-SNAPSHOT-shaded.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  8.321 s
[INFO] Finished at: 2020-03-03T09:07:19Z
[INFO] ------------------------------------------------------------------------

This command generates a JAR file in the target directory.

If you use the appender library (aws-lambda-java-log4j2), you must also configure a transformer for the Maven Shade plugin. The transformer library combines versions of a cache file that appear in both the appender library and in Log4j.

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.2.2</version>
        <configuration>
          <createDependencyReducedPom>false</createDependencyReducedPom>
        </configuration>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
            <configuration>
              <transformers>
                <transformer implementation="com.github.edwgiz.maven_shade_plugin.log4j2_cache_transformer.PluginsCacheFileTransformer">
                </transformer>
              </transformers>
            </configuration>
          </execution>
        </executions>
        <dependencies>
          <dependency>
            <groupId>com.github.edwgiz</groupId>
            <artifactId>maven-shade-plugin.log4j2-cachefile-transformer</artifactId>
            <version>2.13.0</version>
          </dependency>
        </dependencies>
      </plugin>

Uploading a deployment package with the Lambda console

To create a new function, you must first create the function in the console, then upload your .zip or JAR file. To update an existing function, open the page for your function, then follow the same procedure to add your updated .zip or JAR file.

If your deployment package file is less than 50MB, you can create or update a function by uploading the file directly from your local machine. For .zip or JAR files greater than 50MB, you must upload your package to an Amazon S3 bucket first. For instructions on how to upload a file to an Amazon S3 bucket using the Amazon Web Services Management Console, see Getting started with Amazon S3. To upload files using the Amazon CLI, see Move objects in the Amazon CLI User Guide.

Uploading a deployment package with the Amazon CLI

You can can use the Amazon CLI to create a new function or to update an existing one using a .zip or JAR file. Use the create-function and update-function-code commands to deploy your .zip or JAR package. If your file is smaller than 50MB, you can upload the package from a file location on your local build machine. For larger files, you must upload your .zip or JAR package from an Amazon S3 bucket. For instructions on how to upload a file to an Amazon S3 bucket using the Amazon CLI, see Move objects in the Amazon CLI User Guide.

To create a new function using a .zip or JAR file with the Amazon CLI, you must specify the following:

You must also specify the location of your .zip or JAR file. If your .zip or JAR file is located in a folder on your local build machine, use the --zip-file option to specify the file path, as shown in the following example command.

aws lambda create-function --function-name myFunction \
--runtime java21 --handler example.handler \
--role arn:aws:iam::123456789012:role/service-role/my-lambda-role \
--zip-file fileb://myFunction.zip

To specify the location of .zip file in an Amazon S3 bucket, use the --code option as shown in the following example command. You only need to use the S3ObjectVersion parameter for versioned objects.

aws lambda create-function --function-name myFunction \
--runtime java21 --handler example.handler \
--role arn:aws:iam::123456789012:role/service-role/my-lambda-role \
--code S3Bucket=amzn-s3-demo-bucket,S3Key=myFileName.zip,S3ObjectVersion=myObjectVersion

To update an existing function using the CLI, you specify the the name of your function using the --function-name parameter. You must also specify the location of the .zip file you want to use to update your function code. If your .zip file is located in a folder on your local build machine, use the --zip-file option to specify the file path, as shown in the following example command.

aws lambda update-function-code --function-name myFunction \
--zip-file fileb://myFunction.zip

To specify the location of .zip file in an Amazon S3 bucket, use the --s3-bucket and --s3-key options as shown in the following example command. You only need to use the --s3-object-version parameter for versioned objects.

aws lambda update-function-code --function-name myFunction \
--s3-bucket amzn-s3-demo-bucket --s3-key myFileName.zip --s3-object-version myObject Version

Uploading a deployment package with Amazon SAM

You can use Amazon SAM to automate deployments of your function code, configuration, and dependencies. Amazon SAM is an extension of Amazon CloudFormation that provides a simplified syntax for defining serverless applications. The following example template defines a function with a deployment package in the build/distributions directory that Gradle uses:

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: An Amazon Lambda application that calls the Lambda API.
Resources:
  function:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: build/distributions/java-basic.zip
      Handler: example.Handler
      Runtime: java21
      Description: Java function
      MemorySize: 512
      Timeout: 10
      # Function's execution role
      Policies:
        - AWSLambdaBasicExecutionRole
        - AWSLambda_ReadOnlyAccess
        - AWSXrayWriteOnlyAccess
        - AWSLambdaVPCAccessExecutionRole
      Tracing: Active

To create the function, use the package and deploy commands. These commands are customizations to the Amazon CLI. They wrap other commands to upload the deployment package to Amazon S3, rewrite the template with the object URI, and update the function's code.

The following example script runs a Gradle build and uploads the deployment package that it creates. It creates an Amazon CloudFormation stack the first time you run it. If the stack already exists, the script updates it.

#!/bin/bash
set -eo pipefail
aws cloudformation package --template-file template.yml --s3-bucket MY_BUCKET --output-template-file out.yml
aws cloudformation deploy --template-file out.yml --stack-name java-basic --capabilities CAPABILITY_NAMED_IAM

For a complete working example, see the following sample applications: