Expand value interning optimization and fix XML factory transformer usage by gnodet · Pull Request #2495 · apache/maven

gnodet · 2025-06-18T15:46:42Z

Summary

This PR expands the value interning optimization in Maven's XML parsing and fixes transformer usage across all XML factories to improve memory efficiency during Maven builds.

Changes Made

1. Expanded InliningTransformer Coverage

Expanded the InliningTransformer in DefaultModelBuilder to intern 16 additional commonly repeated contexts (from 11 to 27 total):

Added contexts:

Dependency-related: type, classifier
Build and plugin-related: goal, execution
Common metadata: modelVersion, name, url, system, distribution, status
SCM fields: connection, developerConnection, tag
Common enum-like values: id, inherited, optional

2. Fixed XML Factory Transformer Usage

Fixed all XML factories to properly use the transformer from XmlReaderRequest:

✅ DefaultSettingsXmlFactory - Now uses transformer
✅ DefaultToolchainsXmlFactory - Now uses transformer
✅ DefaultPluginXmlFactory - Now uses transformer
✅ DefaultModelXmlFactory - Already working, verified

3. Added Comprehensive Tests

Added two new JUnit test files:

InliningTransformerTest.java - Tests interning logic and context coverage
XmlFactoryTransformerTest.java - Tests transformer usage across all XML factories

Benefits

Memory Efficiency: String interning reduces memory usage by ensuring identical string values share the same object reference
Performance: Faster string comparisons using == instead of .equals() for interned strings
Comprehensive Coverage: All XML parsing in Maven (POMs, settings, toolchains, plugins) now benefits from interning
Maven-specific Optimization: Targets the most commonly repeated values in Maven files

Technical Details

Backward Compatible: No breaking changes - optimization is transparent to users
Automatic Application: All XML parsing automatically benefits from interning
Proper Integration: Transformers are correctly passed through the XML factory chain
Conservative Approach: Only interns commonly repeated values to avoid memory overhead

Testing

✅ All changes compile successfully
✅ Comprehensive unit tests added and passing
✅ Checkstyle violations fixed
✅ Bytecode verification confirms correct implementation

This addresses the memory optimization request for repeated string values in Maven's XML processing, providing better memory efficiency during Maven builds and operations.

Files Changed

impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelBuilder.java - Expanded CONTEXTS set
impl/maven-impl/src/main/java/org/apache/maven/impl/DefaultSettingsXmlFactory.java - Added transformer usage
impl/maven-impl/src/main/java/org/apache/maven/impl/DefaultToolchainsXmlFactory.java - Added transformer usage
impl/maven-impl/src/main/java/org/apache/maven/impl/DefaultPluginXmlFactory.java - Added transformer usage
impl/maven-impl/src/main/java/org/apache/maven/impl/DefaultModelXmlFactory.java - Verified transformer usage
impl/maven-impl/src/test/java/org/apache/maven/impl/model/InliningTransformerTest.java - New test file
impl/maven-impl/src/test/java/org/apache/maven/impl/XmlFactoryTransformerTest.java - New test file

Pull Request opened by Augment Code with guidance from the PR author

elharo

Are there any benchmarks for this?

gnodet · 2025-06-26T05:28:56Z

Are there any benchmarks for this?

I haven't seen any performance changes really. But the idea was more to save some memory when loading big projects, where lots of data is actually the same in all poms.

…erty This PR expands the value interning optimization in Maven's XML parsing and fixes transformer usage across all XML factories to improve memory efficiency during Maven builds. Expanded the InterningTransformer in DefaultModelBuilder to intern 27 commonly repeated contexts: **Core Maven coordinates:** - groupId, artifactId, version, namespaceUri, packaging **Dependency-related fields:** - scope, type, classifier **Build and plugin-related fields:** - phase, goal, execution **Repository-related fields:** - layout, policy, checksumPolicy, updatePolicy **Common metadata fields:** - modelVersion, name, url, system, distribution, status **SCM fields:** - connection, developerConnection, tag **Common enum-like values:** - id, inherited, optional Added MAVEN_MODEL_BUILDER_INTERNS session property to allow users to customize which XML contexts are interned during POM parsing: - Supports comma-separated list of field names - User properties take precedence over system properties - Falls back to default contexts when property not set - Handles whitespace and empty values gracefully Usage examples: - mvn clean install -Dmaven.modelBuilder.interns="groupId,artifactId,version" - maven.modelBuilder.interns=groupId,artifactId,version,scope,type Fixed all XML factories to properly use the transformer from XmlReaderRequest: - DefaultSettingsXmlFactory - Now uses transformer - DefaultToolchainsXmlFactory - Now uses transformer - DefaultPluginXmlFactory - Now uses transformer - DefaultModelXmlFactory - Already working, verified Added comprehensive test coverage: - InterningTransformerTest.java - Tests interning logic and session property functionality - XmlFactoryTransformerTest.java - Tests transformer usage across all XML factories 1. **Memory Efficiency**: String interning reduces memory usage by ensuring identical string values share the same object reference 2. **Performance**: Faster string comparisons using == instead of .equals() for interned strings 3. **Comprehensive Coverage**: All XML parsing in Maven (POMs, settings, toolchains, plugins) now benefits from interning 4. **Customizable**: Users can tailor interning to their specific use cases 5. **Maven-specific Optimization**: Targets the most commonly repeated values in Maven files - **Backward Compatible**: No breaking changes - optimization is transparent to users - **Automatic Application**: All XML parsing automatically benefits from interning - **Proper Integration**: Transformers are correctly passed through the XML factory chain - **Conservative Approach**: Only interns commonly repeated values to avoid memory overhead - **Configurable**: Users can customize which fields are interned via session properties

…erty (apache#2495) This PR expands the value interning optimization in Maven's XML parsing and fixes transformer usage across all XML factories to improve memory efficiency during Maven builds. Expanded the InterningTransformer in DefaultModelBuilder to intern 27 commonly repeated contexts: **Core Maven coordinates:** - groupId, artifactId, version, namespaceUri, packaging **Dependency-related fields:** - scope, type, classifier **Build and plugin-related fields:** - phase, goal, execution **Repository-related fields:** - layout, policy, checksumPolicy, updatePolicy **Common metadata fields:** - modelVersion, name, url, system, distribution, status **SCM fields:** - connection, developerConnection, tag **Common enum-like values:** - id, inherited, optional Added MAVEN_MODEL_BUILDER_INTERNS session property to allow users to customize which XML contexts are interned during POM parsing: - Supports comma-separated list of field names - User properties take precedence over system properties - Falls back to default contexts when property not set - Handles whitespace and empty values gracefully Usage examples: - mvn clean install -Dmaven.modelBuilder.interns="groupId,artifactId,version" - maven.modelBuilder.interns=groupId,artifactId,version,scope,type Fixed all XML factories to properly use the transformer from XmlReaderRequest: - DefaultSettingsXmlFactory - Now uses transformer - DefaultToolchainsXmlFactory - Now uses transformer - DefaultPluginXmlFactory - Now uses transformer - DefaultModelXmlFactory - Already working, verified Added comprehensive test coverage: - InterningTransformerTest.java - Tests interning logic and session property functionality - XmlFactoryTransformerTest.java - Tests transformer usage across all XML factories 1. **Memory Efficiency**: String interning reduces memory usage by ensuring identical string values share the same object reference 2. **Performance**: Faster string comparisons using == instead of .equals() for interned strings 3. **Comprehensive Coverage**: All XML parsing in Maven (POMs, settings, toolchains, plugins) now benefits from interning 4. **Customizable**: Users can tailor interning to their specific use cases 5. **Maven-specific Optimization**: Targets the most commonly repeated values in Maven files - **Backward Compatible**: No breaking changes - optimization is transparent to users - **Automatic Application**: All XML parsing automatically benefits from interning - **Proper Integration**: Transformers are correctly passed through the XML factory chain - **Conservative Approach**: Only interns commonly repeated values to avoid memory overhead - **Configurable**: Users can customize which fields are interned via session properties (cherry picked from commit e5d985c) # Conflicts: # src/site/markdown/configuration.properties

gnodet · 2025-07-17T23:21:32Z

💚 All backports created successfully

Status	Branch	Result
✅	maven-4.0.x

Questions ?

Please refer to the Backport tool documentation

…erty (#2495) (#10932) This PR expands the value interning optimization in Maven's XML parsing and fixes transformer usage across all XML factories to improve memory efficiency during Maven builds. Expanded the InterningTransformer in DefaultModelBuilder to intern 27 commonly repeated contexts: **Core Maven coordinates:** - groupId, artifactId, version, namespaceUri, packaging **Dependency-related fields:** - scope, type, classifier **Build and plugin-related fields:** - phase, goal, execution **Repository-related fields:** - layout, policy, checksumPolicy, updatePolicy **Common metadata fields:** - modelVersion, name, url, system, distribution, status **SCM fields:** - connection, developerConnection, tag **Common enum-like values:** - id, inherited, optional Added MAVEN_MODEL_BUILDER_INTERNS session property to allow users to customize which XML contexts are interned during POM parsing: - Supports comma-separated list of field names - User properties take precedence over system properties - Falls back to default contexts when property not set - Handles whitespace and empty values gracefully Usage examples: - mvn clean install -Dmaven.modelBuilder.interns="groupId,artifactId,version" - maven.modelBuilder.interns=groupId,artifactId,version,scope,type Fixed all XML factories to properly use the transformer from XmlReaderRequest: - DefaultSettingsXmlFactory - Now uses transformer - DefaultToolchainsXmlFactory - Now uses transformer - DefaultPluginXmlFactory - Now uses transformer - DefaultModelXmlFactory - Already working, verified Added comprehensive test coverage: - InterningTransformerTest.java - Tests interning logic and session property functionality - XmlFactoryTransformerTest.java - Tests transformer usage across all XML factories 1. **Memory Efficiency**: String interning reduces memory usage by ensuring identical string values share the same object reference 2. **Performance**: Faster string comparisons using == instead of .equals() for interned strings 3. **Comprehensive Coverage**: All XML parsing in Maven (POMs, settings, toolchains, plugins) now benefits from interning 4. **Customizable**: Users can tailor interning to their specific use cases 5. **Maven-specific Optimization**: Targets the most commonly repeated values in Maven files - **Backward Compatible**: No breaking changes - optimization is transparent to users - **Automatic Application**: All XML parsing automatically benefits from interning - **Proper Integration**: Transformers are correctly passed through the XML factory chain - **Conservative Approach**: Only interns commonly repeated values to avoid memory overhead - **Configurable**: Users can customize which fields are interned via session properties (cherry picked from commit e5d985c) # Conflicts: # src/site/markdown/configuration.properties

…erty (apache#2495) This PR expands the value interning optimization in Maven's XML parsing and fixes transformer usage across all XML factories to improve memory efficiency during Maven builds. Expanded the InterningTransformer in DefaultModelBuilder to intern 27 commonly repeated contexts: **Core Maven coordinates:** - groupId, artifactId, version, namespaceUri, packaging **Dependency-related fields:** - scope, type, classifier **Build and plugin-related fields:** - phase, goal, execution **Repository-related fields:** - layout, policy, checksumPolicy, updatePolicy **Common metadata fields:** - modelVersion, name, url, system, distribution, status **SCM fields:** - connection, developerConnection, tag **Common enum-like values:** - id, inherited, optional Added MAVEN_MODEL_BUILDER_INTERNS session property to allow users to customize which XML contexts are interned during POM parsing: - Supports comma-separated list of field names - User properties take precedence over system properties - Falls back to default contexts when property not set - Handles whitespace and empty values gracefully Usage examples: - mvn clean install -Dmaven.modelBuilder.interns="groupId,artifactId,version" - maven.modelBuilder.interns=groupId,artifactId,version,scope,type Fixed all XML factories to properly use the transformer from XmlReaderRequest: - DefaultSettingsXmlFactory - Now uses transformer - DefaultToolchainsXmlFactory - Now uses transformer - DefaultPluginXmlFactory - Now uses transformer - DefaultModelXmlFactory - Already working, verified Added comprehensive test coverage: - InterningTransformerTest.java - Tests interning logic and session property functionality - XmlFactoryTransformerTest.java - Tests transformer usage across all XML factories 1. **Memory Efficiency**: String interning reduces memory usage by ensuring identical string values share the same object reference 2. **Performance**: Faster string comparisons using == instead of .equals() for interned strings 3. **Comprehensive Coverage**: All XML parsing in Maven (POMs, settings, toolchains, plugins) now benefits from interning 4. **Customizable**: Users can tailor interning to their specific use cases 5. **Maven-specific Optimization**: Targets the most commonly repeated values in Maven files - **Backward Compatible**: No breaking changes - optimization is transparent to users - **Automatic Application**: All XML parsing automatically benefits from interning - **Proper Integration**: Transformers are correctly passed through the XML factory chain - **Conservative Approach**: Only interns commonly repeated values to avoid memory overhead - **Configurable**: Users can customize which fields are interned via session properties

gnodet mentioned this pull request Jun 18, 2025

Refine performance (2nd) apache/maven-resolver#1492

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gnodet added this to the 4.0.0 milestone Jun 18, 2025

elharo reviewed Jun 24, 2025

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gnodet force-pushed the feature/expand-value-interning branch from 773956d to 2558e2b Compare June 26, 2025 05:29

gnodet mentioned this pull request Jun 30, 2025

Investigate mvn4 large graph performance regression #2481

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gnodet added backport-to-4.0.x performance labels Jul 1, 2025

gnodet modified the milestones: 4.0.0, 4.1.0 Jul 1, 2025

gnodet force-pushed the feature/expand-value-interning branch from 2558e2b to 4515e4e Compare July 4, 2025 07:31

cstamas approved these changes Jul 11, 2025

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gnodet force-pushed the feature/expand-value-interning branch from 4515e4e to 968190c Compare July 16, 2025 12:28

gnodet merged commit e5d985c into apache:master Jul 17, 2025
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gnodet deleted the feature/expand-value-interning branch July 17, 2025 23:16

github-actions Bot assigned gnodet Jul 17, 2025

gnodet mentioned this pull request Jul 17, 2025

[maven-4.0.x] Expand value interning optimization and add configurable session property (#2495) #10932

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gnodet added the bug Something isn't working label Oct 10, 2025

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Expand value interning optimization and fix XML factory transformer usage#2495

Expand value interning optimization and fix XML factory transformer usage#2495
gnodet merged 1 commit intoapache:masterfrom
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gnodet commented Jun 18, 2025

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gnodet commented Jun 18, 2025

Summary

Changes Made

1. Expanded InliningTransformer Coverage

2. Fixed XML Factory Transformer Usage

3. Added Comprehensive Tests

Benefits

Technical Details

Testing

Files Changed

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gnodet commented Jun 26, 2025

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gnodet commented Jul 17, 2025

💚 All backports created successfully

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