How can I use AWS lambda layer by java (Layer is success in Lambda)...error is NoClassDefFoundError

Question

I built two project and added layers to AWS Lamba successfully.

And my functions use these two layers.

This is my structure of layer

When I execute the function, an error happened:

java.lang.NoClassDefFoundError

I know the location of the layer is inside/opt, but how can I use the layer's library in functions?

Answer 1

Anyone trying to figure out how to copy your dependencies (.jar) into java/lib directory, this is maven snippet from a project -

    <build>
    <plugins>
            <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>${maven.compiler.plugin.version}</version>
            <configuration>
                <source>${maven.compiler.source}</source>
                <target>${maven.compiler.target}</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <version>2.8</version>
            <executions>
                <execution>
                    <id>copy-dependencies</id>
                    <phase>prepare-package</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${project.build.directory}/classes/java/lib</outputDirectory>
                        <includeScope>runtime</includeScope>
                    </configuration>
                </execution>
            </executions>
        </plugin></plugins></build>

Hope this will come handy to someone

Answer 2

You should locate the files into a folder, in according to the language:

• Node.js –> nodejs/node_modules or nodejs/node8/node_modules (NODE_PATH)

• Python – python -> python/lib/python3.7/site-packages (site
  directories)

• Java –> java/lib (classpath)

• Ruby –> ruby/gems/2.5.0 (GEM_PATH), ruby/lib (RUBY_LIB)

• Or default All –> bin (PATH), lib (LD_LIBRARY_PATH)

For more details see: https://docs.aws.amazon.com/en_us/lambda/latest/dg/configuration-layers.html#configuration-layers-path