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>
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
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>
=== 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.
In the plugins section of your pom.xml, add the Apache Maven Shade Plugin.It is used during the build process. This plugin is used for packaging jars to create a standalone .jar.The maven-shade-plugin will take artifacts (jars) produced by the package goal , and created a standalone .jar that contains the compiled code, and the resolved dependencies from the pom.xml.
<dependency>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.0.0</version>
来源：https://stackoverflow.com/questions/32782980/aws-lambda-noclassdeffounderror