What needs to be put into the uriPath field when creating a StatementProperty in AWS CDK (Java)?

Question

We want to create a webACL for AWS WAF, using the latest version (2.51.1) of AWS CDK and Java 17 (corretto).

One of the rules we want to define contains a URI path that is to be allowed. We use the following definition:

Object emptyUriPath; // How to define this?
StatementProperty apiV1Order = StatementProperty.builder()
    .byteMatchStatement(ByteMatchStatementProperty.builder()
        .searchString("/the/path/to/allow")
        .positionalConstraint("STARTS_WITH")
        .fieldToMatch(FieldToMatchProperty.builder()
            .uriPath(emptyUriPath)
            .build())
        .textTransformations(List.of(TextTransformationProperty.builder()
            .priority(0)
            .type("LOWERCASE")
            .build()))
        .build())
    .build();

The question is: How does the uriPath need to be defined? The documentation is quite sparse about this.

The documentation says that the uriPath field shall contain an 'empty object'. In TypeScript, this seems to be quite easy. But for Java, we get various errors for the different attempts we tried:

Object emptyUriPath = new Object();
Object emptyUriPath = new JsonObject();
Object emptyUriPath = "{}";

cause errors like this:

An exception occured while executing the Java class. No serializer found for class java.lang.Object and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ImmutableCollections$List12[1]) (through reference chain: software.amazon.jsii.api.CreateRequest["args"]->java.util.Arrays$ArrayList[2])

or this:

An exception occured while executing the Java class. JsonObject (through reference chain: com.google.gson.JsonObject["asBoolean"]) (through reference chain: java.util.ImmutableCollections$List12[1]) (through reference chain: software.amazon.jsii.api.CreateRequest["args"]->java.util.Arrays$ArrayList[2])

or this:

An exception occured while executing the Java class. Error: Resolution error: Supplied properties not correct for "CfnWebACLProps"
[ERROR]   rules: element 1: supplied properties not correct for "RuleProperty"
[ERROR]     statement: supplied properties not correct for "StatementProperty"
[ERROR]       byteMatchStatement: supplied properties not correct for "ByteMatchStatementProperty"
[ERROR]         fieldToMatch: supplied properties not correct for "FieldToMatchProperty"
[ERROR]           uriPath: "{}" should be an 'object'.
[ERROR] @jsii/kernel.RuntimeError: Error: Resolution error: Supplied properties not correct for "CfnWebACLProps"
[ERROR]   rules: element 1: supplied properties not correct for "RuleProperty"
[ERROR]     statement: supplied properties not correct for "StatementProperty"
[ERROR]       byteMatchStatement: supplied properties not correct for "ByteMatchStatementProperty"
[ERROR]         fieldToMatch: supplied properties not correct for "FieldToMatchProperty"
[ERROR]           uriPath: "{}" should be an 'object'.

We would have assumed something like this:

Object emptyUriPath = UriPathProperty.builder().build();

but such a property doesn't exist (only something similar for the SDK ).

Can anyone please tell us what to do? Can also be a hint on how to create such a rule/statement in a completely different way.

Answer 1

With the help of the CDK developers we found out that emptyUriPath needs to look like this:

Map<String, String> emptyUriPath = Map.of("UriPath", "{}");

see also the documentation about generic structures here .

For those who may have the same problem:
It turned out that we had another issue in our rule property definition: an action definition was missing. The final rule property definition now looks like this:

RuleProperty.builder()
        .name("AllowValidApiCalls")
        .priority(1)
        .statement(apiV1Order)
        .action(RuleActionProperty.builder()
            .allow(AllowActionProperty.builder()
                .build())
            .build())
        .visibilityConfig(VisibilityConfigProperty.builder()
            .cloudWatchMetricsEnabled(false)
            .metricName("metricName")
            .sampledRequestsEnabled(false)
            .build())
        .build();