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>

Solution 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>
  </build>

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

Solution 2

Sometimes you have to upload your lambda again. Also I got the same issue I fixed with this pom.xml:

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

   <dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.amazonaws</groupId>
      <artifactId>aws-java-sdk-bom</artifactId>
      <version>1.11.83</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>

 </dependencyManagement>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

   <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>
 </build>
</project>

Solution 3

=== If this issue exists even after including shaded jar ===

If you have this issue even after having shaded jar then the issue should be related to aws-lambda-java-events package version (should be some incompatibility between AWS lamda version and newer aws-lambda-java-events version) . i.e. I had this issue with latest version (2.0.2) of aws-lambda-java-events package and I have to downgrade the version to 1.3.0.

Seems like newer aws-lambda-java-events version doesn't have many dependencies.

Comments

[Brooks]

Unfortunately, this did not work for me...still getting the same exception.

[Mike76]

Ah, just seen your pom.xml. Try using the maven-shade plugin as detailed here: docs.aws.amazon.com/lambda/latest/dg/…

[Brooks]

Worked! I'll accept, but you should put the URL in your answer so it can be upvoted some more.

[Mike76]

Excellent. I've edited the answer. Does it still work with aws-lambda-java-events-1.1.0.jar? If so, I'll remove that part from the answer so it doesn't mislead anyone else.

[Brooks]

I just tried it with 1.1.0 and it worked still. It was just that it couldn't find it. What's strange is that it couldn't find it, even when I had the jar's installed. In fact, someone on the AWS forums had the same problem and he had the jar's installed as well. I suggested he use the shade plugin and it worked for him as well. Thanks!

[Baradwaj Aryasomayajula]

Hi there, I tried your solution bt its still shows me some comflict with the spring dependencies and the amazon libraries...

[Lakshman Diwaakar]

Worked like a charm!! Spent hours searching for the solution!! Thank you.

[Alejandro Garcia]

Remember to include your own aws dependencies!

[Sridhar Sarnobat]

Ha, "just uploading the jar again" worked for me. Maybe I accidentally uploaded the original...jar by accident.

[Jakub Wisniewski]

Is it normal that the jar is very large after shading?

[Bishnu Das]

How to use this plugin in case of gradle ?

[Sanket Mehta]

For reducing the shaded-jar size - stackoverflow.com/questions/8817257/…