Improve Maven cache architecture for better memory efficiency and performance

This comprehensive enhancement to Maven's caching system addresses memory issues
and significantly improves performance through several key improvements:

## Key Features:
- Enhanced DefaultRequestCache with configurable reference types and CSS-like selectors
- Pluggable ModelObjectPool service architecture with configurable object types
- Comprehensive cache statistics with eviction tracking
- Improved InputLocation and InputSource with ImmutableCollections
- Custom equality strategy for Dependency pooling
- Enhanced parent request matching with interface checking
- Configurable cache statistics display

## Performance Results:
- Maven 3: Requires -Xmx1536m, runs in 45 seconds
- Maven 4.0.0-rc-4: Runs with -Xmx1024m in 2'32" (cannot run with -Xmx512m)
- Maven 4.0.0-rc-4 with -Xmx1536m: 2'5"
- Maven 4.0.0-rc-4 + maven3Personality with -Xmx1536m: 1'14"
- Maven 4 + this PR: Runs with -Xmx512m in 3'42" (more memory does not help)
- Maven 4 + this PR + maven3Personality: Runs with -Xmx512m in 1'0"

## Memory Improvements:
- Reduced minimum memory requirement from 1024m to 512m
- Eliminated memory scaling issues - additional memory beyond 512m provides no benefit
- Significant reduction in memory pressure through improved caching strategies

This PR definitively solves memory problems while maintaining or improving performance.

Author: gnodet

.github/release-drafter-3.x.yml

@@ -16,4 +16,3 @@
 # under the License.
 
 _extends: maven-gh-actions-shared:.github/release-drafter.yml
-tag-template: maven-$RESOLVED_VERSION

.github/release-drafter.yml

@@ -16,7 +16,6 @@
 # under the License.
 
 _extends: maven-gh-actions-shared
-tag-template: maven-$RESOLVED_VERSION
 
 include-pre-releases: true
 prerelease: true

api/maven-api-core/src/main/java/org/apache/maven/api/Artifact.java

@@ -39,7 +39,7 @@
 @Immutable
 public interface Artifact {
     /**
-     * {@return a unique identifier for this artifact}.
+     * {@return a unique identifier for this artifact}
      * The identifier is composed of groupId, artifactId, extension, classifier, and version.
      *
      * @see ArtifactCoordinates#getId()
@@ -58,23 +58,23 @@ default String key() {
     }
 
     /**
-     * {@return the group identifier of the artifact}.
+     * {@return the group identifier of the artifact}
      *
      * @see ArtifactCoordinates#getGroupId()
      */
     @Nonnull
     String getGroupId();
 
     /**
-     * {@return the identifier of the artifact}.
+     * {@return the identifier of the artifact}
      *
      * @see ArtifactCoordinates#getArtifactId()
      */
     @Nonnull
     String getArtifactId();
 
     /**
-     * {@return the version of the artifact}.
+     * {@return the version of the artifact}
      * Contrarily to {@link ArtifactCoordinates},
      * each {@code Artifact} is associated to a specific version instead of a range of versions.
      * If the {@linkplain #getBaseVersion() base version} contains a meta-version such as {@code SNAPSHOT},
@@ -86,7 +86,7 @@ default String key() {
     Version getVersion();
 
     /**
-     * {@return the version or meta-version of the artifact}.
+     * {@return the version or meta-version of the artifact}
      * A meta-version is a version suffixed with the {@code SNAPSHOT} keyword.
      * Meta-versions are represented in a base version by their symbols (e.g., {@code SNAPSHOT}),
      * while they are replaced by, for example, the actual timestamp in the {@linkplain #getVersion() version}.
@@ -122,7 +122,7 @@ default String key() {
     boolean isSnapshot();
 
     /**
-     * {@return coordinates with the same identifiers as this artifact}.
+     * {@return coordinates with the same identifiers as this artifact}
      * This is a shortcut for {@code session.createArtifactCoordinates(artifact)}.
      *
      * @see org.apache.maven.api.Session#createArtifactCoordinates(Artifact)

api/maven-api-core/src/main/java/org/apache/maven/api/ArtifactCoordinates.java

@@ -33,13 +33,13 @@
 @Immutable
 public interface ArtifactCoordinates {
     /**
-     * {@return the group identifier of the artifact}.
+     * {@return the group identifier of the artifact}
      */
     @Nonnull
     String getGroupId();
 
     /**
-     * {@return the identifier of the artifact}.
+     * {@return the identifier of the artifact}
      */
     @Nonnull
     String getArtifactId();
@@ -53,7 +53,7 @@ public interface ArtifactCoordinates {
     String getClassifier();
 
     /**
-     * {@return the specific version, range of versions, or meta-version of the artifact}.
+     * {@return the specific version, range of versions or meta-version of the artifact}
      * A meta-version is a version suffixed with the {@code SNAPSHOT} keyword.
      */
     @Nonnull
@@ -69,7 +69,7 @@ public interface ArtifactCoordinates {
     String getExtension();
 
     /**
-     * {@return a unique string identifying this artifact}.
+     * {@return a unique string representation identifying this artifact}
      *
      * The default implementation returns a colon-separated list of group
      * identifier, artifact identifier, extension, classifier and version.

api/maven-api-core/src/main/java/org/apache/maven/api/Constants.java

@@ -622,5 +622,66 @@ public final class Constants {
      */
     public static final String MAVEN_LOGGER_LOG_PREFIX = MAVEN_LOGGER_PREFIX + "log.";
 
+    /**
+     * User property key for cache configuration.
+     *
+     * @since 4.1.0
+     */
+    public static final String MAVEN_CACHE_CONFIG_PROPERTY = "maven.cache.config";
+
+    /**
+     * User property to enable cache statistics display at the end of the build.
+     * When set to true, detailed cache statistics including hit/miss ratios,
+     * request type breakdowns, and retention policy effectiveness will be displayed
+     * when the build completes.
+     *
+     * @since 4.1.0
+     */
+    @Config(type = "java.lang.Boolean", defaultValue = "false")
+    public static final String MAVEN_CACHE_STATS = "maven.cache.stats";
+
+    /**
+     * User property to configure separate reference types for cache keys and values.
+     * Format: "key:value" where key and value can be NONE, SOFT, WEAK, or HARD.
+     * Examples:
+     * - "HARD:SOFT" - Keep keys strongly referenced, allow values to be garbage collected under memory pressure
+     * - "WEAK:WEAK" - Allow both keys and values to be garbage collected aggressively
+     * - "SOFT:HARD" - Allow keys to be GC'd under memory pressure, keep values strongly referenced
+     *
+     * This enables fine-grained analysis of cache misses caused by key vs value evictions.
+     *
+     * @since 4.1.0
+     */
+    public static final String MAVEN_CACHE_KEY_VALUE_REFS = "maven.cache.keyValueRefs";
+
+    /**
+     * User property key for configuring which object types are pooled by ModelObjectProcessor.
+     * Value should be a comma-separated list of simple class names (e.g., "Dependency,Plugin,Build").
+     * Default is "Dependency" for backward compatibility.
+     *
+     * @since 4.1.0
+     */
+    @Config(defaultValue = "Dependency")
+    public static final String MAVEN_MODEL_PROCESSOR_POOLED_TYPES = "maven.model.processor.pooledTypes";
+
+    /**
+     * User property key for configuring the default reference type used by ModelObjectProcessor.
+     * Valid values are: "SOFT", "HARD", "WEAK", "NONE".
+     * Default is "HARD" for optimal performance.
+     *
+     * @since 4.1.0
+     */
+    @Config(defaultValue = "HARD")
+    public static final String MAVEN_MODEL_PROCESSOR_REFERENCE_TYPE = "maven.model.processor.referenceType";
+
+    /**
+     * User property key prefix for configuring per-object-type reference types.
+     * Format: maven.model.processor.referenceType.{ClassName} = {ReferenceType}
+     * Example: maven.model.processor.referenceType.Dependency = SOFT
+     *
+     * @since 4.1.0
+     */
+    public static final String MAVEN_MODEL_PROCESSOR_REFERENCE_TYPE_PREFIX = "maven.model.processor.referenceType.";
+
     private Constants() {}
 }

api/maven-api-core/src/main/java/org/apache/maven/api/Dependency.java

@@ -36,7 +36,7 @@
 @Immutable
 public interface Dependency extends Artifact {
     /**
-     * {@return the type of the dependency}.
+     * {@return the type of the dependency}
      * A dependency can be a <abbr>JAR</abbr> file,
      * a modular-<abbr>JAR</abbr> if it is intended to be placed on the module path,
      * a <abbr>JAR</abbr> containing test classes, <i>etc.</i>
@@ -47,7 +47,7 @@ public interface Dependency extends Artifact {
     Type getType();
 
     /**
-     * {@return the time at which the dependency will be used}.
+     * {@return the time at which the dependency will be used}
      * It may be, for example, at compile time only, at run time or at test time.
      *
      * @see DependencyCoordinates#getScope()
@@ -66,7 +66,7 @@ public interface Dependency extends Artifact {
     boolean isOptional();
 
     /**
-     * {@return coordinates with the same identifiers as this dependency}.
+     * {@return coordinates with the same identifiers as this dependency}
      */
     @Nonnull
     @Override

api/maven-api-core/src/main/java/org/apache/maven/api/DownloadedArtifact.java

@@ -33,7 +33,7 @@
 public interface DownloadedArtifact extends Artifact {
 
     /**
-     * {@return the a path to the file that has been downloaded to the file system}.
+     * {@return the actual file that has been downloaded in the file system}
      */
     Path getPath();
 }

api/maven-api-core/src/main/java/org/apache/maven/api/JavaPathType.java

@@ -263,8 +263,8 @@ final String[] format(String moduleName, Iterable<? extends Path> paths) {
         if (option == null) {
             throw new IllegalStateException("No option is associated to this path type.");
         }
-        String prefix = (moduleName == null) ? "\"" : (moduleName + "=\"");
-        StringJoiner joiner = new StringJoiner(File.pathSeparator, prefix, "\"");
+        String prefix = (moduleName == null) ? "" : (moduleName + '=');
+        StringJoiner joiner = new StringJoiner(File.pathSeparator, prefix, "");
         joiner.setEmptyValue("");
         for (Path p : paths) {
             joiner.add(p.toString());

api/maven-api-core/src/main/java/org/apache/maven/api/SourceRoot.java

@@ -68,8 +68,9 @@ default Path directory() {
      * If no syntax is specified, or if its length is 1 character (interpreted as a Windows drive),
      * the default is a Maven-specific variation of the {@code "glob"} pattern.
      *
-     * <p>The default implementation returns an empty list, which means to apply a language-dependent pattern.
-     * For example, for the Java language, the pattern includes all files with the {@code .java} suffix.</p>
+     * <p>
+     * The default implementation returns an empty list, which means to apply a language-dependent pattern.
+     * For example, for the Java language, the pattern includes all files with the {@code .java} suffix.
      *
      * @see java.nio.file.FileSystem#getPathMatcher(String)
      */