Re: Difference in Template Rendering Between Velocity 2.3 and 2.4.1 for Map with List

This PR(https://github.com/apache/velocity-engine/pull/45) is the route
cause for this issue.

Because of this change, in *UberspectImpl.getPropertyGet()* method the
*executor* value is *PropertyExecutor* instead of *MapGetExecutor*

*to replicate this issue sample program:*

import com.fasterxml.jackson.core.JsonProcessingException;
> import com.fasterxml.jackson.databind.ObjectMapper;
> import org.apache.velocity.VelocityContext;
> import org.apache.velocity.app.VelocityEngine;
> import org.apache.velocity.runtime.VelocityEngineVersion;
>
> import java.io.StringWriter;
> import java.util.Map;
>
> public class TestVelocity {
>     public static final String studentData = "{ \"student\": { \"values\":
> [ " +
>             "{ \"id\": 1, \"name\": \"Alice\", \"age\": 20, \"grade\":
> \"A\" }, " +
>             "{ \"id\": 2, \"name\": \"Bob\", \"age\": 21, \"grade\": \"B\"
> } ] } }";
>     public static final String editorContent = "{\n" +
>             "    \"students\" :  $student.values\n" +
>             "}\n";
>     public static final String LOG_LABEL = "TemplateParser";
>     public static void main(String[] args) throws JsonProcessingException {
>         VelocityEngine velocityEngine = new VelocityEngine();
>         StringWriter writer = new StringWriter();
>         Map studentsMap = new ObjectMapper().readValue(studentData,
> Map.class);
>         VelocityContext context = new VelocityContext(studentsMap);
>         velocityEngine.init();
>         velocityEngine.evaluate(context,writer,LOG_LABEL,editorContent);
>         System.out.println("Velocity Version: " +
> VelocityEngineVersion.VERSION);
>         System.out.println(writer.toString());
>     }
> }


*output in v2.3: *
Velocity Version: 2.3
{
    "students" :  [{id=1, name=Alice, age=20, grade=A}, {id=2, name=Bob,
age=21, grade=B}]
}
*output in v 2.4.1:*
Velocity Version: 2.4.1
{
    "students" :  [[{id=1, name=Alice, age=20, grade=A}, {id=2, name=Bob,
age=21, grade=B}]]
}


*Screenshots:*
*Java program in version 2.3:*
https://github.com/mergurishaan/VelocityIssue/blob/main/jpv23.png?raw=true
*vg.executor value in 2.3:*
https://github.com/mergurishaan/VelocityIssue/blob/main/vg_23.png?raw=true
*java program In version 2.4.1:*
https://github.com/mergurishaan/VelocityIssue/blob/main/jpv241.png?raw=true
*vg.executor value in 2.4.1: *
https://github.com/mergurishaan/VelocityIssue/blob/main/vg_241.png?raw=true

On Tue, Jul 22, 2025 at 7:08 PM Mergu Ravi <[email protected]>
wrote:

> Dear Velocity Team,
>
> I hope this message finds you well.
>
> I'm currently using Apache Velocity in my Java application, and I noticed
> a behavioral difference in template rendering when upgrading from version
> *2.3* to *2.4.1*.
> Template:
>
> {
>   "students" :  $student.values
> }
>
> Sample JSON (studentData):
>
> {
>   "student": {
>     "values": [
>       { "id": 1, "name": "Alice", "age": 20, "grade": "A" },
>       { "id": 2, "name": "Bob", "age": 21, "grade": "B" }
>     ]
>   }
> }
>
> Output in Velocity 2.3:
>
> {
>   "students" : [{id=1, name=Alice, age=20, grade=A}, {id=2, name=Bob, age=21, grade=B}]
> }
>
> Output in Velocity 2.4.1:
>
> {
>   "students" : [[{id=1, name=Alice, age=20, grade=A}, {id=2, name=Bob, age=21, grade=B}]]
> }
>
> Concern:
>
> In *2.4.1*, the result includes an extra set of brackets, indicating that
> Velocity is now treating the .values object as a list containing a list
> instead of a list itself.
>
> This change in behavior breaks backward compatibility in my use case. I'm
> unsure if this change was intentional or a regression.
> Screenshots:
>
> I’ve attached screenshots of the same Java code executed with both
> versions:
>
>    -
>
>    *velocity-2.3*
>    - [image: Screenshot from 2025-07-22 18-38-28.png]
>
>    -
>
>    *velocity-2.4.1*
>    - [image: Screenshot from 2025-07-22 18-39-00.png]
>
>
> Request:
>
> Could you please clarify if this is:
>
>    -
>
>    An intended change in how Velocity handles map values, or
>    -
>
>    A bug introduced in the recent release?
>
> Additionally, if there's a recommended workaround or best practice for
> handling this in 2.4.1, I’d greatly appreciate the guidance.
>
> Thanks for maintaining such a helpful project!
>
> Best regards,
> *Ravi Mergu*
> ------------------------------
>