Hey folks i trying to use Grails JSON feature for generating json from a domain class.
And i am facing many issues in this one after another.

If someone can help me here it would be great. I have following grails configuration

grailsVersion=5.3.2
grailsGradlePluginVersion=5.3.0
groovyVersion=3.0.11
gorm.version=7.3.3

I have following 3 domain classes.

Company.groovy

class Company{

    String name

    String contactName

    String agentId // If businessType = Accountant
    String status  = "Active"


    User owner
    User lastUpdatedBy


    static hasMany = [apps: ZApp]
    static embedded = ['address']
}

User.groovy

class User {

    Long id

    String fullName
    String username
    User owner
    User lastUpdatedBy
}

And ** ZApp.groovy**

class ZucoduApp{

    String appName

    String appDescription
}

I have added following line in my application.groovy file for deep domain marshaller.

grails.converters.json.default.deep = true

And than i tried to generate json for company instance as following

company as JSON

I am getting following error

Caused by: org.grails.web.converters.exceptions.ConverterException: java.lang.StringIndexOutOfBoundsException: start 0, end -1, length 0

When i check error trails it giving me error in JSON.java file in following line

I thought this should handle it automatically gracefully. but no, than i adding following line in application.groovy

grails.converters.json.circular.reference.behaviour=’PATH’

And error solved but now error comes whenever any field has null value. In my case agentId of company class is null

Caused by: org.grails.web.converters.exceptions.ConverterException: org.grails.web.json.JSONException: Value out of sequence: expected mode to be OBJECT or ARRAY
when writing ‘org.grails.web.json.JSONWriter$NullWritable@1a1fd03d’ but was INIT

Error coming at following code from DomainClassMarshaller.java

if ( !(property instanceof Association) ) {
                // Write non-relation property
                Object val = beanWrapper.getPropertyValue(property.getName());
                json.convertAnother(val); // **here it throws error**
            }

To By pass this error i created my own CustomDomainMarshaller class and in place of

json.convertAnother(val); i used

if (val == null) {
   writer.value(null)
} else {
   json.convertAnother(val);
}

And it worked.
But now i got another error for apps (Hasmany relation for ZApp)

Caused by: java.lang.ClassCastException: class org.grails.web.json.PathCapturingJSONWriterWrapper$PropertyElement cannot be cast to class org.grails.web.json.PathCapturingJSONWriterWrapper$IndexElement (org.grails.web.json.PathCapturingJSONWriterWrapper$PropertyElement and org.grails.web.json.PathCapturingJSONWriterWrapper$IndexElement are in unnamed module of loader ‘app’)

This error is coming when we have 2 item in apps. and when call second item.
Error is coming in following code.

    @SuppressWarnings(["unchecked", "rawtypes"])
    public void marshalObject(Object value, JSON json) throws ConverterException {
        JSONWriter writer = json.getWriter();
        value = proxyHandler.unwrapIfProxy(value);
        Class<?> clazz = value.getClass();

        List<String> excludes = json.getExcludes(clazz);
        List<String> includes = json.getIncludes(clazz);
        IncludeExcludeSupport<String> includeExcludeSupport = new IncludeExcludeSupport<String>();

        BeanWrapper beanWrapper = new BeanWrapperImpl(value);

        writer.object(); // **here it throws error**

And in postmen following json response coming.

{
    "data": [
        {
            "id": 72050630615,
            "lastUpdatedBy": {
                "id": 59396476865
            },
            "dateCreated": "2024-03-30 18:07:42",
            "contactName": "Chetan",
            "lastUpdated": "2024-05-22 18:54:21",
            "agentId": null,
            "apps": [
                {
                    "id": 2,
                    "appName": "ZUCODU MTD SERVICES",
                    "appDescription": "Use this app to file you tax using Zucodu MTD app"
                }{
                    "message": "Internal server error",
                    "error": 500
                }