Spring Cloud Function with AWS API Gateway and AWS Lambda

Question

Using the handler org.springframework.cloud.function.adapter.aws.FunctionInvoker::handleRequest I'm receiving the following error when calling my API Gateway endpoint with the payload below. The function is found and it runs the business logic correctly until it returns and throws this NullPointerException:

Cannot invoke "java.util.Map.size()" because "m" is null: java.lang.NullPointerException
java.lang.NullPointerException: Cannot invoke "java.util.Map.size()" because "m" is null
at java.base/java.util.HashMap.putMapEntries(HashMap.java:495)
at java.base/java.util.HashMap.<init>(HashMap.java:484)
at org.springframework.cloud.function.context.catalog.SimpleFunctionRegistry$FunctionInvocationWrapper.enrichInvocationResultIfNecessary(SimpleFunctionRegistry.java:757)
at org.springframework.cloud.function.context.catalog.SimpleFunctionRegistry$FunctionInvocationWrapper.invokeFunctionAndEnrichResultIfNecessary(SimpleFunctionRegistry.java:914)
at org.springframework.cloud.function.context.catalog.SimpleFunctionRegistry$FunctionInvocationWrapper.invokeFunction(SimpleFunctionRegistry.java:863)
at org.springframework.cloud.function.context.catalog.SimpleFunctionRegistry$FunctionInvocationWrapper.doApply(SimpleFunctionRegistry.java:716)
at org.springframework.cloud.function.context.catalog.SimpleFunctionRegistry$FunctionInvocationWrapper.apply(SimpleFunctionRegistry.java:559)
at org.springframework.cloud.function.adapter.aws.FunctionInvoker.handleRequest(FunctionInvoker.java:85)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
END

However, according to the documentation I should be using the handler org.springframework.cloud.function.adapter.aws.SpringBootApiGatewayRequestHandler::handleRequest but when I do so it does not find the function. I have set both FUNCTION_NAME and MAIN_CLASS environment variables to their respective values.

Class not found: org.springframework.cloud.function.adapter.aws.SpringBootApiGatewayRequestHandler: java.lang.ClassNotFoundException
java.lang.ClassNotFoundException: org.springframework.cloud.function.adapter.aws.SpringBootApiGatewayRequestHandler
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:587)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:467)
END RequestId: 83965357-a424-4c0f-b846-7486245380c7

Function

public class Makeuser implements Function<Message<APIGatewayRequest>, Message<User>> {

    @Override
    public Message<User> apply(Message<APIGatewayRequest> request) {

    ...
    }
}

Application

@SpringBootApplication
public class DemoApplication{

    public static void main(String[] args) {
    }

}

Request Payload

{
  "userRequest": {
    "firstName": "userfirst",
    "lastName": "userlast",
    "email": "user@gmail.com",
    "age": 21
  }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>4.0.0.RELEASE</version>
    <packaging>jar</packaging>
    <name>demo</name>
    <description>Non-native demo application</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.0.0-SNAPSHOT</version>
        <relativePath/>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <wrapper.version>1.0.28.RELEASE</wrapper.version>
        <aws-lambda-events.version>3.11.0</aws-lambda-events.version>
        <spring-cloud-function.version>4.0.0-SNAPSHOT</spring-cloud-function.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-function-adapter-aws</artifactId>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-lambda-java-events</artifactId>
            <version>${aws-lambda-events.version}</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-lambda-java-core</artifactId>
            <version>1.2.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.modelmapper</groupId>
            <artifactId>modelmapper</artifactId>
            <version>3.1.0</version>
        </dependency>
        <dependency>
            <groupId>com.github.derjust</groupId>
            <artifactId>spring-data-dynamodb</artifactId>
            <version>5.1.0</version>
        </dependency>
        <dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-java-sdk-dynamodb</artifactId>
            <version>1.12.272</version>
        </dependency>

    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-function-dependencies</artifactId>
                <version>${spring-cloud-function.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-deploy-plugin</artifactId>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <dependencies>
                    <dependency>
                        <groupId>org.springframework.boot.experimental</groupId>
                        <artifactId>spring-boot-thin-layout</artifactId>
                        <version>${wrapper.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.3.0</version>
                <configuration>
                    <createDependencyReducedPom>false</createDependencyReducedPom>
                    <shadedArtifactAttached>true</shadedArtifactAttached>
                    <shadedClassifierName>aws</shadedClassifierName>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>


</project>

This is the documentation I'm working from: https://docs.spring.io/spring-cloud-function/docs/4.0.0-SNAPSHOT/reference/html/aws.html

Update

I switched the spring-cloud-function version from 4.0.0.RELEASE to 3.2.6 and updated the Function class to remove the Message types. The lambda succeeds in test but fails when making the request from Postman to the API Gateway.

Function

public class Makeuser implements Function<APIGatewayRequest, User> {

    @Override
    public Message<User> apply(APIGatewayRequest request) {
    ...
    return user;
    }
}

Stacktrace

Successfully saved user to database 2d1ed481-999e-4e2d-afc0-62f5315c8f4b user1first user1last user1@gmail.com 21
org/springframework/http/HttpStatus: java.lang.NoClassDefFoundError
java.lang.NoClassDefFoundError: org/springframework/http/HttpStatus
at org.springframework.cloud.function.adapter.aws.AWSLambdaUtils.generateOutput(AWSLambdaUtils.java:196)
at org.springframework.cloud.function.adapter.aws.FunctionInvoker.buildResult(FunctionInvoker.java:147)
at org.springframework.cloud.function.adapter.aws.FunctionInvoker.handleRequest(FunctionInvoker.java:114)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
Caused by: java.lang.ClassNotFoundException: org.springframework.http.HttpStatus
... 7 more
END RequestId: 3811dd35-342c-4088-7ef4-f3ed86798b9f

Can you please update/refresh your s-c-function snapshot? Based on your stacktrace it appears it is still using the old code that relies on reflection. That has been addressed few weeks ago — Oleg Zhurakousky, Aug 12 '22 at 13:31
I removed .m2 and the jar files in /target before running mvn -U clean install and uploading the new image to ECR. The same error is still occurring, should I try a different version of spring-cloud-function? — henry sneed, Aug 12 '22 at 14:48
Also, @OlegZhurakousky could you clarify which handler should be used with AWS API Gateway? The documentation is clear about using SpringBootApiGatewayHandler but my function is only found when using the FunctionInvoker handler. — henry sneed, Aug 12 '22 at 14:52
Always FunctionInvoker. What documentation you are referring to? Seems like something outdated. Anyway here - https://docs.spring.io/spring-cloud-function/docs/current/reference/html/aws.html. Also, the latest version is 3.2.6 — Oleg Zhurakousky, Aug 15 '22 at 08:10
Ok, I added the updates to the question. The reason I was unsure which handler to use is because the documentation says "to deploy behind an API Gateway, use --handler org.springframework.cloud.function.adapter.aws.SpringBootApiGatewayRequestHandler". The section HTTP and API Gateway also says to wrap the business data classes in the Message interface but it seems this is intended as a possible optimization rather than a requirement. I am not sure. — henry sneed, Aug 16 '22 at 01:10
Henry, thank you, I will review. Also, your original issue is indeed a bug (after a second look). - https://github.com/spring-cloud/spring-cloud-function/issues/917 Basically I have reviewed what was there before the refactoring and indeed there was a mistake. So it's being fixed and you should have new snapshot shortly — Oleg Zhurakousky, Aug 16 '22 at 10:15
Thank you @OlegZhurakousky , it's working without issue now. — henry sneed, Aug 17 '22 at 20:21

Spring Cloud Function with AWS API Gateway and AWS Lambda

Function

Application

Request Payload

pom.xml

Update

Function

Stacktrace

0 Answers0