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 following:

Tools and libraries

Lambda provides the following libraries for Java functions:

These libraries are available through Maven Central Repository. Add them 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

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

You can upload a deployment package to any existing function using the Lambda console.

Uploading a deployment package with the Lambda API

To update a function's code with the Amazon Command Line Interface (Amazon CLI) or Amazon SDK, use the UpdateFunctionCode API operation. For the Amazon CLI, use the update-function-code command. The following command uploads a deployment package named my-function.zip in the current directory:

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

You should see the following output:

{
    "FunctionName": "my-function",
    "FunctionArn": "arn:aws-cn:lambda:us-east-2:123456789012:function:my-function",
    "Runtime": "java8",
    "Role": "arn:aws-cn:iam::123456789012:role/lambda-role",
    "Handler": "example.Handler",
    "CodeSha256": "Qf0hMc1I2di6YFMi9aXm3JtGTmcDbjniEuiYonYptAk=",
    "Version": "$LATEST",
    "TracingConfig": {
        "Mode": "Active"
    },
    "RevisionId": "983ed1e3-ca8e-434b-8dc1-7d72ebadd83d",
    ...
}

If your deployment package is larger than 50 MB, you can't upload it directly. Upload it to an Amazon Simple Storage Service (Amazon S3) bucket and point Lambda to the object. The following example commands upload a deployment package to an S3 bucket named my-bucket and use it to update a function's code:

aws s3 cp my-function.zip s3://my-bucket

You should see the following output:

upload: my-function.zip to s3://my-bucket/my-function

aws lambda update-function-code --function-name my-function \
 --s3-bucket my-bucket --s3-key my-function.zip

You should see the following output:

{
    "FunctionName": "my-function",
    "FunctionArn": "arn:aws-cn:lambda:us-east-2:123456789012:function:my-function",
    "Runtime": "java8",
    "Role": "arn:aws-cn:iam::123456789012:role/lambda-role",
    "Handler": "example.Handler",
    "CodeSha256": "Qf0hMc1I2di6YFMi9aXm3JtGTmcDbjniEuiYonYptAk=",
    "Version": "$LATEST",
    "TracingConfig": {
        "Mode": "Active"
    },
    "RevisionId": "983ed1e3-ca8e-434b-8dc1-7d72ebadd83d",
    ...
}

You can use this method to upload function packages up to 250 MB (decompressed).

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: java8
      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: