amazon web services - AWS Lambda NoClassDefFoundError

Question

I am having difficulty with a Java based Lambda function setup to receive messages from SNS. My function looks like the below:

package com.mycompany;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.LambdaLogger;
import com.amazonaws.services.lambda.runtime.events.SNSEvent;

public class LambdaHandler {  
    public void Handler(SNSEvent event, Context context) {
        //Process the event
    }
}

It compiles just fine and I don't have any problems uploading the jar file to Lambda (via the web console).

However, when I publish to it (via SNS through to the subscribed Lambda function) with JSON representing the SNSEvent model, the Lambda function throws the following exception:

Error loading method handler on class com.mycompany.LambdaHandler: class java.lang.NoClassDefFoundError java.lang.NoClassDefFoundError: com/amazonaws/services/lambda/runtime/events/SNSEvent at

java.lang.Class.getDeclaredMethods0(Native Method) at java.lang.Class.privateGetDeclaredMethods(Class.java:2701) at java.lang.Class.privateGetPublicMethods(Class.java:2902) at java.lang.Class.getMethods(Class.java:1615) Caused by: java.lang.ClassNotFoundException: com.amazonaws.services.lambda.runtime.events.SNSEvent at java.net.URLClassLoader.findClass(URLClassLoader.java:381) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

I use Maven + Netbeans and it's a Maven Java Application project. I downloaded the function from the Lambda console and confirmed, the jar has a lib/ directory with all of the jar's for the imports, including aws-lambda-java-events-1.1.0.jar, which itself includes the /com/amazonaws/services/lambda/runtime/events/SNSEvent.class file.

Why is the runtime unable to find the class when it's definitely in the jar file? Is there anything else I need to do, set any environment variables, etc?

Any help would be appreciated!

EDIT 1 I tried downgrading to aws-lambda-java-events 1.0.0 and it's still reporting the same exception. As requested, below is my POM file (with just project name changed). I don't know how to tell Maven to put the libraries in a tree structure.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.app</groupId>
    <artifactId>Handler</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <dependencies>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-java-sdk-lambda</artifactId>
            <version>1.10.6</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-lambda-java-core</artifactId>
            <version>1.0.0</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-lambda-java-events</artifactId>
            <version>1.0.0</version>
        </dependency>
    </dependencies>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
</project>

Answer 1

Use the maven-shade plugin so that the JAR contains the dependencies in an uber-jar.

So, add this to your pom.xml

<build>
<plugins>
  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>2.3</version>
    <configuration>
      <createDependencyReducedPom>false</createDependencyReducedPom>
    </configuration>
    <executions>
      <execution>
        <phase>package</phase>
        <goals>
          <goal>shade</goal>
        </goals>
      </execution>
    </executions>
  </plugin>
</plugins>

Source: http://docs.aws.amazon.com/lambda/latest/dg/java-create-jar-pkg-maven-no-ide.html

Potentially you may have this issue https://github.com/aws/aws-lambda-java-libs/issues/2 which requires a downgrade to aws-lambda-java-events-1.0.0.jar