2

I'm trying to create a proxy component for AEM Core Component with custom Sling Model which delegates part of functionality back to the Core Component's Sling Model.

I'm following the example from https://github.com/adobe/aem-core-wcm-components/wiki/Delegation-Pattern-for-Sling-Models but it results in java.lang.IllegalArgumentException: Can not set com.example.core.models.Title field.

Setup

  • AEM version 6.4.4
  • core.wcm.components.content version 2.4.0

Sources

/apps/myproject/components/pageHeadline/.content.xml

<?xml version="1.0" encoding="UTF-8"?>
<jcr:root xmlns:sling="http://sling.apache.org/jcr/sling/1.0" xmlns:cq="http://www.day.com/jcr/cq/1.0" xmlns:jcr="http://www.jcp.org/jcr/1.0"
    jcr:primaryType="cq:Component"
    jcr:title="Page Headline"
    jcr:description="Display Page Heading"
    sling:resourceSuperType="core/wcm/components/title/v2/title"
    componentGroup="My Project"/>

com.example.core.models.PageHeadline

package com.example.core.models;

import com.adobe.cq.wcm.core.components.models.Title;
import com.day.cq.wcm.api.Page;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.models.annotations.Model;
import org.apache.sling.models.annotations.Via;
import org.apache.sling.models.annotations.injectorspecific.ScriptVariable;
import org.apache.sling.models.annotations.injectorspecific.Self;
import org.apache.sling.models.annotations.via.ResourceSuperType;

@Model(adaptables = SlingHttpServletRequest.class, adapters = Title.class, resourceType = "myproject/components/pageHeadline")
public class PageHeadline implements Title {

    @ScriptVariable
    private Page currentPage;

    @Self @Via(type = ResourceSuperType.class)
    private Title delegate;

    @Override
    public String getText() {
        return currentPage.getTitle();
    }

    @Override
    public String getType() {
        return delegate.getType();
    }
}

Result

org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: Identifier com.example.core.models.Title cannot be correctly instantiated by the Use API
...
Caused by: org.apache.sling.scripting.sightly.SightlyException: Identifier com.example.core.models.Title cannot be correctly instantiated by the Use API
    at org.apache.sling.scripting.sightly.impl.engine.extension.use.UseRuntimeExtension.call(UseRuntimeExtension.java:78) [org.apache.sling.scripting.sightly:1.0.54.1_4_0]
    at org.apache.sling.scripting.sightly.impl.engine.runtime.RenderContextImpl.call(RenderContextImpl.java:69) [org.apache.sling.scripting.sightly:1.0.54.1_4_0]
    at org.apache.sling.scripting.sightly.apps.core.wcm.components.title.v2.title.title_html.render(title_html.java:41)
    at org.apache.sling.scripting.sightly.java.compiler.RenderUnit.render(RenderUnit.java:48) [org.apache.sling.scripting.sightly.compiler.java:1.0.26.1_4_0]
    at org.apache.sling.scripting.sightly.impl.engine.SightlyCompiledScript.eval(SightlyCompiledScript.java:61) [org.apache.sling.scripting.sightly:1.0.54.1_4_0]
    at org.apache.sling.scripting.core.impl.DefaultSlingScript.call(DefaultSlingScript.java:386) [org.apache.sling.scripting.core:2.0.54]
    at org.apache.sling.scripting.core.impl.DefaultSlingScript.eval(DefaultSlingScript.java:184) [org.apache.sling.scripting.core:2.0.54]
    at org.apache.sling.scripting.core.impl.DefaultSlingScript.service(DefaultSlingScript.java:491) [org.apache.sling.scripting.core:2.0.54]
    ... 269 common frames omitted
Caused by: org.apache.sling.models.factory.MissingElementsException: Could not inject all required fields into class com.example.core.models.PageHeadline
    at org.apache.sling.models.impl.ModelAdapterFactory.createObject(ModelAdapterFactory.java:765) [org.apache.sling.models.impl:1.4.10]
    at org.apache.sling.models.impl.ModelAdapterFactory.internalCreateModel(ModelAdapterFactory.java:448) [org.apache.sling.models.impl:1.4.10]
    at org.apache.sling.models.impl.ModelAdapterFactory.createModel(ModelAdapterFactory.java:314) [org.apache.sling.models.impl:1.4.10]
    at org.apache.sling.scripting.sightly.models.impl.SlingModelsUseProvider.provide(SlingModelsUseProvider.java:126) [org.apache.sling.scripting.sightly.models.provider:1.0.6]
    at org.apache.sling.scripting.sightly.impl.engine.extension.use.UseRuntimeExtension.call(UseRuntimeExtension.java:73) [org.apache.sling.scripting.sightly:1.0.54.1_4_0]
    ... 276 common frames omitted
    Suppressed: org.apache.sling.models.factory.MissingElementException: Could not inject private com.example.core.models.Title com.example.core.models.PageHeadline.title
        at org.apache.sling.models.impl.ModelAdapterFactory.createObject(ModelAdapterFactory.java:749) [org.apache.sling.models.impl:1.4.10]
        ... 280 common frames omitted
    Caused by: org.apache.sling.models.factory.ModelClassException: Could not inject field due to reflection issues
        at org.apache.sling.models.impl.model.InjectableField.set(InjectableField.java:48) [org.apache.sling.models.impl:1.4.10]
        at org.apache.sling.models.impl.ModelAdapterFactory.setField(ModelAdapterFactory.java:989) [org.apache.sling.models.impl:1.4.10]
        at org.apache.sling.models.impl.ModelAdapterFactory.access$200(ModelAdapterFactory.java:132) [org.apache.sling.models.impl:1.4.10]
        at org.apache.sling.models.impl.ModelAdapterFactory$SetFieldCallback.inject(ModelAdapterFactory.java:500) [org.apache.sling.models.impl:1.4.10]
        at org.apache.sling.models.impl.ModelAdapterFactory.injectElement(ModelAdapterFactory.java:595) [org.apache.sling.models.impl:1.4.10]
        at org.apache.sling.models.impl.ModelAdapterFactory.createObject(ModelAdapterFactory.java:744) [org.apache.sling.models.impl:1.4.10]
        ... 280 common frames omitted
    Caused by: java.lang.IllegalArgumentException: Can not set com.example.core.models.Title field com.example.core.models.PageHeadline.title to com.adobe.cq.wcm.core.components.internal.models.v1.TitleImpl
        at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
        at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
        at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:81)
        at java.lang.reflect.Field.set(Field.java:764)
        at org.apache.sling.models.impl.model.InjectableField.set(InjectableField.java:46) [org.apache.sling.models.impl:1.4.10]
        ... 285 common frames omitted
Community
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arkki
  • 104
  • 6
  • 1
    can you please also add the htl code? – luckyluke May 24 '19 at 08:19
  • 1
    Your code looks ok so far. No changes compared to the Github page you linked. I could imagine that you don't have core components deployed in AEM, but that is really just a shot in the dark because then I would expect some kind of "Missing class definition" exception. – Jens May 25 '19 at 20:11
  • the delegation pattern was added in the Sling API 1.3.4/1.4 (api/ impl). Im not sure about your specific version of AEM. can you confirm you use at least that version? (check the felix bundle console) – santiagozky Jun 04 '19 at 13:12
  • The specific AEM version is 6.4.4 as mentioned above. Core Components are deployed and working fine. There is no custom HTL code as it's using sling:resourceSuperType="core/wcm/components/title/v2/title. – arkki Jun 23 '19 at 23:48

1 Answers1

2

I had the same problem, where the delegation pattern was not working, specifically, the injected attribute was null if I used @Optional, or the same stack trace as posted if @Optional was left out.

The problem for me was that we are using the following Embed-Dependency code:

<Embed-Dependency>
  *;scope=compile|runtime
</Embed-Dependency>
<Embed-Transitive>true</Embed-Transitive>

in the maven-bundle-plugin. The issue was that the core components dependency got set as an embedded dependency. Once I fixed this, the delegation pattern worked fine.

<Embed-Dependency>
  *;scope=compile|runtime;artifactId=!core.wcm.components.core
</Embed-Dependency>
Bill Randall
  • 41
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  • Thanks for the tip! I'll try it out and see how it goes. – arkki Jul 18 '19 at 23:29
  • I had the similar issue and solution described here fixed it, could you please explain this as well? – Atif Jul 28 '22 at 00:09
  • It has been so long I forget now. However, it may have been a conflict of versions between transitive and imported core components. – Bill Randall Aug 01 '22 at 14:37