fix(reporter): handle binary metadata in v4 message logs

[ErwinSupp]

Issue

gravitee-io/issues#11220

Description

This PR fixes a FreeMarker template error in v4-message-log.ftl that occurred when processing binary metadata (e.g., from Kafka).

The issue was that byte[] metadata values were being treated as sequences by FreeMarker, causing the ?j_string and ?string built-ins to fail with UnexpectedTypeException.

Changes:

• Updated v4-message-log.ftl in es7x, es8x, and es9x reporter configurations.
• Refined the metadata iteration logic to first filter printable metadata (non-sequence values) into a temporary map, then render it using <#sep>. This approach is cleaner and more maintainable than manual comma handling.
• Ensured metadata values are rendered as strings for backward compatibility.

Additional context

Refined Implementation

<#assign printable_metadata = {}>
<#list log.getMessage().getMetadata() as metadataKey, metadataValue>
    <#if metadataValue?? && !metadataValue?is_sequence>
        <#assign printable_metadata = printable_metadata + {metadataKey: metadataValue}>
    </#if>
</#list>
<#list printable_metadata as metadataKey, metadataValue>
  "${metadataKey}": "${metadataValue?string?j_string}"<#sep>,</#sep>
</#list>

All 99 tests in gravitee-apim-reporter-common passed.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical FreeMarker template error that previously caused UnexpectedTypeException when the reporter processed binary metadata, such as byte[] from Kafka. By introducing robust conditional logic within the v4-message-log.ftl templates, the system now gracefully handles various metadata types, ensuring message logs are generated correctly without data loss or processing failures.

Highlights

• FreeMarker Template Fix: Resolved an UnexpectedTypeException in v4-message-log.ftl that occurred when processing binary metadata, such as byte[] values.
• Robust Metadata Handling: Implemented conditional logic to safely process various metadata types within the FreeMarker template, preventing errors.
• Type-Specific Formatting: Ensured strings are JSON escaped, numbers and booleans are rendered as strings for backward compatibility, and sequences (including byte[]) are safely skipped.
• Template Updates: Applied the necessary changes to v4-message-log.ftl across the es7x, es8x, and es9x reporter configurations.

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[gemini-code-assist]

Code Review

This pull request correctly addresses a FreeMarker template error that occurs when processing binary metadata by adding logic to skip sequence types like byte[]. The fix is applied consistently across all relevant Elasticsearch reporter configurations. I've added one suggestion to refactor the template logic for improved readability and maintainability, which applies to all three modified files.

[gemini-code-assist]

While the current implementation with manual comma handling is correct, it can be simplified and made more readable by separating the filtering of metadata from the rendering. You could first build a new map containing only the printable metadata, and then iterate over that new map using <#sep> for cleaner comma separation. This approach is generally less error-prone and easier to maintain.

This comment also applies to the identical changes in es8x/index/v4-message-log.ftl and es9x/index/v4-message-log.ftl.

    <#assign printable_metadata = {}>
    <#list log.getMessage().getMetadata() as metadataKey, metadataValue>
        <#if metadataValue?? && !metadataValue?is_sequence>
            <#assign printable_metadata = printable_metadata + {metadataKey: metadataValue}>
        </#if>
    </#list>
    <#list printable_metadata as metadataKey, metadataValue>
      "${metadataKey}": "${metadataValue?string?j_string}"<#sep>,</#sep>
    </#list>

[sonarqubecloud]

Quality Gate passed for 'Gravitee.io APIM - Reporter'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud