Expression in responseValidator in http:request in mule - mule4

Question

I use mule-http-connector version 1.6.0 in mule 4.4 community edition (MuleSoft 4 ce) and I get a response (aka GraphQL):
{
"success": true,
"data": ...
}
I want validate the response by cheking success field. I can made validation by use two…four components (http:response, choice, raise…), but I found in Anypoint Studio 7.11 in component properties «Reponse» → «Response validator» → «Expression or Bean reference». I don't want use «Bean reference» and write java code, but I want use «Expression». I wrote that:
%dw 2.0
output application/json
---
payload.success
But I got error:
"org.mule.weave.v2.exception.UnexpectedFunctionCallTypesException: You called the function 'Value Selector' with these arguments:
1: Binary ("" as Binary {base: "64"})
2: Name ("success")
If I write something:
%dw 2.0
output application/json
---
true
I got that error:
org.mule.weave.v2.exception.WriterExecutionException: Unable to convert 'true' with class 'java.lang.Boolean' to class 'ResponseValidator'
4| true
^^^^
Trace:
at anonymous::main (line: 4, column: 1), while writing Java at
4| true
^^^^.
4| true
^^^^
Trace:
at anonymous::main (line: 4, column: 1)
" evaluating expression: "%dw 2.0
output application/json
---
true".
How to write a dw expression in a response validation?

Answer 1

That's not how response validation should be used. By default -when using a string- it validates HTTP status codes against ranges of status codes in the string. If you want to implement your custom validation you have to extend Java class org.mule.extension.http.api.request.validator.RangeStatusCodeValidator.
Example:
public class MyValidator extends RangeStatusCodeValidator {
public MyValidator() {}
public MyValidator(String values) {
setValues(values);
}
#Override
public void validate(Result<InputStream, HttpResponseAttributes> result, HttpRequest request) {
int status = result.getAttributes().get().getStatusCode();
String method = request.getMethod();
if ((!belongs(status)) && (!method.equals("GET"))) {
throwValidationException(result, request, status);
}
}
}
Then instantiate it in you flow and reference it in the response validator:
<java:new doc:name="New" class="validator.MyValidator" constructor='MyValidator(String)' target="out">
<java:args ><![CDATA[#[{arg0:"500"}]]]></java:args>
</java:new>
<http:request method="POST" doc:name="Request" config-ref="HTTP_Request_configuration" responseValidator='#[vars.out]' path="/endpoint">
</http:request>
Alternatively you can instance the class from DataWeave:
<http:request method="POST" doc:name="Request" config-ref="HTTP_Request_configuration" responseValidator='#[%dw 2.0 import java!validator::MyValidator output application/java --- MyValidator::new("500")]' path="/endpoint">
</http:request>
Source: https://help.mulesoft.com/s/article/How-to-define-a-custom-HTTP-response-validator-in-Mule-Runtime-4-x