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Validation

This utility provides JSON Schema validation for payloads held within events and response used in AWS Lambda.

Key features

  • Validate incoming events and responses
  • Built-in validation for most common events (API Gateway, SNS, SQS, ...)
  • JMESPath support validate only a sub part of the event

Install

To install this utility, add the following dependency to your project.

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<dependencies>
...
<dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>powertools-validation</artifactId>
    <version>1.12.3</version>
</dependency>
...
</dependencies>
<!-- configure the aspectj-maven-plugin to compile-time weave (CTW) the aws-lambda-powertools-java aspects into your project -->
<build>
    <plugins>
        ...
        <plugin>
             <groupId>org.codehaus.mojo</groupId>
             <artifactId>aspectj-maven-plugin</artifactId>
             <version>1.14.0</version>
             <configuration>
                 <source>1.8</source>
                 <target>1.8</target>
                 <complianceLevel>1.8</complianceLevel>
                 <aspectLibraries>
                     <aspectLibrary>
                         <groupId>software.amazon.lambda</groupId>
                         <artifactId>powertools-validation</artifactId>
                     </aspectLibrary>
                 </aspectLibraries>
             </configuration>
             <executions>
                 <execution>
                     <goals>
                         <goal>compile</goal>
                     </goals>
                 </execution>
             </executions>
        </plugin>
        ...
    </plugins>
</build>
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plugins{
    id 'java'
    id 'io.freefair.aspectj.post-compile-weaving' version '6.3.0'
}

repositories {
    mavenCentral()
}

dependencies {
    aspect 'software.amazon.lambda:powertools-validation:1.12.3'
}

Validating events

You can validate inbound and outbound events using @Validation annotation.

You can also use the Validator#validate() methods, if you want more control over the validation process such as handling a validation error.

We support JSON schema version 4, 6, 7 and 201909 (from jmespath-jackson library).

Validation annotation

@Validation annotation is used to validate either inbound events or functions' response.

It will fail fast with ValidationException if an event or response doesn't conform with given JSON Schema.

While it is easier to specify a json schema file in the classpath (using the notation "classpath:/path/to/schema.json"), you can also provide a JSON String containing the schema.

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import software.amazon.lambda.powertools.validation.Validation;

public class MyFunctionHandler implements RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> {

    @Override
    @Validation(inboundSchema = "classpath:/schema_in.json", outboundSchema = "classpath:/schema_out.json")
    public APIGatewayProxyResponseEvent handleRequest(APIGatewayProxyRequestEvent input, Context context) {
        // ...
        return something;
    }
}

NOTE: It's not a requirement to validate both inbound and outbound schemas - You can either use one, or both.

Validate function

Validate standalone function is used within the Lambda handler, or any other methods that perform data validation.

You can also gracefully handle schema validation errors by catching ValidationException.

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import static software.amazon.lambda.powertools.validation.ValidationUtils.*;

public class MyFunctionHandler implements RequestHandler<APIGatewayProxyRequestEvent, APIGatewayProxyResponseEvent> {

    @Override
    public APIGatewayProxyResponseEvent handleRequest(APIGatewayProxyRequestEvent input, Context context) {
        try {
            validate(input, "classpath:/schema.json");
        } catch (ValidationException ex) {
            // do something before throwing it
            throw ex;
        }

        // ...
        return something;
    }
}

NOTE: Schemas are stored in memory for reuse, to avoid loading them from file each time.

Built-in events and responses

For the following events and responses, the Validator will automatically perform validation on the content.

Events

Type of event Class Path to content
API Gateway REST APIGatewayProxyRequestEvent body
API Gateway HTTP APIGatewayV2HTTPEvent body
Application Load Balancer ApplicationLoadBalancerRequestEvent body
Cloudformation Custom Resource CloudFormationCustomResourceEvent resourceProperties
CloudWatch Logs CloudWatchLogsEvent awslogs.powertools_base64_gzip(data)
EventBridge / Cloudwatch ScheduledEvent detail
Kafka KafkaEvent records[*][*].value
Kinesis KinesisEvent Records[*].kinesis.powertools_base64(data)
Kinesis Firehose KinesisFirehoseEvent Records[*].powertools_base64(data)
Kinesis Analytics from Firehose KinesisAnalyticsFirehoseInputPreprocessingEvent Records[*].powertools_base64(data)
Kinesis Analytics from Streams KinesisAnalyticsStreamsInputPreprocessingEvent Records[*].powertools_base64(data)
SNS SNSEvent Records[*].Sns.Message
SQS SQSEvent Records[*].body

Responses

Type of response Class Path to content (envelope)
API Gateway REST APIGatewayProxyResponseEvent} body
API Gateway HTTP APIGatewayV2HTTPResponse} body
API Gateway WebSocket APIGatewayV2WebSocketResponse} body
Load Balancer ApplicationLoadBalancerResponseEvent} body
Kinesis Analytics KinesisAnalyticsInputPreprocessingResponse} `Records[*].powertools_base64(data)``

Custom events and responses

You can also validate any Event or Response type, once you have the appropriate schema.

Sometimes, you might want to validate only a portion of it - This is where the envelope parameter is for.

Envelopes are JMESPath expressions to extract a portion of JSON you want before applying JSON Schema validation.

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import software.amazon.lambda.powertools.validation.Validation;

public class MyCustomEventHandler implements RequestHandler<MyCustomEvent, String> {

    @Override
    @Validation(inboundSchema = "classpath:/my_custom_event_schema.json",
                envelope = "basket.products[*]")
    public String handleRequest(MyCustomEvent input, Context context) {
        return "OK";
    }
}
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{
  "basket": {
    "products" : [
      {
        "id": 43242,
        "name": "FooBar XY",
        "price": 258
      },
      {
        "id": 765,
        "name": "BarBaz AB",
        "price": 43.99
      }
    ]
  }
}

This is quite powerful because you can use JMESPath Query language to extract records from arrays, slice and dice, to pipe expressions and function expressions, where you'd extract what you need before validating the actual payload.

Change the schema version

By default, powertools-validation is configured with V7. You can use the ValidationConfig to change that behaviour.

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...
import software.amazon.lambda.powertools.validation.ValidationConfig;
import software.amazon.lambda.powertools.validation.Validation;

static {
    ValidationConfig.get().setSchemaVersion(SpecVersion.VersionFlag.V4);
}

public class MyXMLEventHandler implements RequestHandler<MyEventWithXML, String> {

    @Override
    @Validation(inboundSchema="classpath:/schema.json", envelope="powertools_xml(path.to.xml_data)")
    public String handleRequest(MyEventWithXML myEvent, Context context) {
        return "OK";
   }
}

Advanced ObjectMapper settings

If you need to configure the Jackson ObjectMapper, you can use the ValidationConfig:

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...
import software.amazon.lambda.powertools.validation.ValidationConfig;
import software.amazon.lambda.powertools.validation.Validation;

static {
    ObjectMapper objectMapper= ValidationConfig.get().getObjectMapper();
    // update (de)serializationConfig or other properties
}

public class MyXMLEventHandler implements RequestHandler<MyEventWithXML, String> {

    @Override
    @Validation(inboundSchema="classpath:/schema.json", envelope="powertools_xml(path.to.xml_data)")
    public String handleRequest(MyEventWithXML myEvent, Context context) {
        return "OK";
   }
}