Add XmlProcessor initial implementation

[marc-gr]

This PR creates a new XML processor that achieves feature parity with Logstash's XML filter.

⚙️ Configuration Options

processors:
  - xml:
      field: "xml_data"
      target_field: "parsed"
      to_lower: false
      # Logstash-compatible options
      xpath:
        "/root/item/@id": "item_id"
        "//product/name/text()": "product_name"
      namespaces:
        "ns": "http://example.com/namespace"
      force_array: true
      force_content: false
      remove_namespaces: false
      ignore_empty_value: true
      parse_options: "strict"

🏗️ Architecture

• Streaming SAX Parser: Optimal memory usage for large XML documents
• Selective DOM Building: Only builds DOM when XPath expressions are configured
• Pre-compiled XPath: XPath expressions compiled at processor creation for performance
• Security: Enhanced XXE protection with secure parser factory configurations

📚 Documentation

Documentation includes:

• Complete configuration reference
• XPath expression examples
• Namespace configuration guide

Logstash differences

• ignore_empty_value behaves a bit different than suppress_empty, but I think it matches better with other processors behavior. It could be adapted, or even add both, but I found it confusing.

Closes #97364

[github-actions]

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• docs/reference/enrich-processor/index.md
• docs/reference/enrich-processor/xml-processor.md

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[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[elasticsearchmachine]

Hi @marc-gr, I've created a changelog YAML for you.

[github-actions]

🔍 Preview links for changed docs

• docs/reference/enrich-processor/xml-processor.md
• docs/reference/enrich-processor/index.md

[Copilot]

Pull Request Overview

Adds an initial implementation of a new XmlProcessor to parse XML input into JSON-like structures with feature parity to Logstash’s XML filter, alongside configuration options, factory validation, and documentation.

• Introduce XmlProcessor with streaming SAX parsing, optional DOM building for XPath, and secure defaults.
• Add end-to-end tests (XmlProcessorTests) and factory validation tests (XmlProcessorFactoryTests).
• Register the processor in the plugin, update module-info, documentation, and changelog.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/XmlProcessor.java	New XML parsing processor implementation
modules/ingest-common/src/test/java/org/elasticsearch/ingest/common/XmlProcessorTests.java	End-to-end tests for XML parsing behavior
modules/ingest-common/src/test/java/org/elasticsearch/ingest/common/XmlProcessorFactoryTests.java	Tests for factory config and validation
modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/IngestCommonPlugin.java	Register XmlProcessor in the plugin registry
modules/ingest-common/src/main/java/module-info.java	Add requires java.xml for XML APIs
docs/reference/enrich-processor/xml-processor.md	Documentation for XML processor
docs/reference/enrich-processor/toc.yml	Add entry for xml-processor.md
docs/reference/enrich-processor/index.md	Include xml processor in the index
docs/changelog/130337.yaml	Changelog entry for PR

Comments suppressed due to low confidence (1)

docs/reference/enrich-processor/xml-processor.md:9

• The implementation actually uses a streaming SAX parser with optional DOM building for XPath. Update this description to reflect the streaming-based approach for accurate documentation.

Parses XML documents and converts them to JSON objects using a DOM parser. This processor efficiently handles XML data with a single-parse architecture that supports both structured output and XPath extraction for optimal performance.