Deadlock when many threads invoke CodeList.valueOf(Class, String, Function) for the same class in same time.

This is caused by the lock on the `WeakHashMap` which can be taken before the class initialization is finished.
This bug was introduced by #91

The fix is to simplify `CodeList` by removing the `WeakHashMap`.
Instead, a `VALUES` static field is declared in each `CodeList` subclass.
This is a more traditional approach as the cost of being more cumbersome for subclasses.
The advantage is that the list of values can not longer be accessed before class initialization is finished.
As a side effect, garbage collection of classes may work better because we no longer keep references to them.

The `Vocabulary` internal annotation is no longer needed after this change and is removed.

Author: desruisseaux

geoapi-conformance/src/main/java/org/opengis/test/Configuration.java

@@ -18,6 +18,7 @@
 package org.opengis.test;
 
 import java.util.Map;
+import java.util.List;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Objects;
@@ -251,8 +252,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.util.NameTest#isMultiLocaleSupported
          */
-        public static final Key<Boolean> isMultiLocaleSupported =
-                new Key<>(Boolean.class, "isMultiLocaleSupported");
+        public static final Key<Boolean> isMultiLocaleSupported;
 
         /**
          * Whether the {@link GenericName} instances can apply different syntax rules in different
@@ -264,35 +264,30 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.util.NameTest#isMixedNameSyntaxSupported
          */
-        public static final Key<Boolean> isMixedNameSyntaxSupported =
-                new Key<>(Boolean.class, "isMixedNameSyntaxSupported");
+        public static final Key<Boolean> isMixedNameSyntaxSupported;
 
         /**
          * Whether the {@link IdentifiedObject} instances have {@linkplain IdentifiedObject#getName()
          * names} matching the names declared in the EPSG database.
          */
-        public static final Key<Boolean> isStandardNameSupported =
-                new Key<>(Boolean.class, "isStandardNameSupported");
+        public static final Key<Boolean> isStandardNameSupported;
 
         /**
          * Whether the {@link IdentifiedObject} instances have at least the
          * {@linkplain IdentifiedObject#getAlias() aliases} declared in the EPSG database.
          */
-        public static final Key<Boolean> isStandardAliasSupported =
-                new Key<>(Boolean.class, "isStandardAliasSupported");
+        public static final Key<Boolean> isStandardAliasSupported;
 
         /**
          * Whether the {@link IdentifiedObject} instances created indirectly by the factories
          * are expected to have correct identification information.
          */
-        public static final Key<Boolean> isDependencyIdentificationSupported =
-                new Key<>(Boolean.class, "isDependencyIdentificationSupported");
+        public static final Key<Boolean> isDependencyIdentificationSupported;
 
         /**
          * Whether the authority factory supports creation of deprecated {@link IdentifiedObject} instances.
          */
-        public static final Key<Boolean> isDeprecatedObjectCreationSupported =
-                new Key<>(Boolean.class, "isDeprecatedObjectCreationSupported");
+        public static final Key<Boolean> isDeprecatedObjectCreationSupported;
 
         /**
          * Whether {@link MathTransform#transform(double[], int, double[], int, int)} is supported.
@@ -301,8 +296,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.TransformTestCase#isDoubleToDoubleSupported
          */
-        public static final Key<Boolean> isDoubleToDoubleSupported =
-                new Key<>(Boolean.class, "isDoubleToDoubleSupported");
+        public static final Key<Boolean> isDoubleToDoubleSupported;
 
         /**
          * Whether {@link MathTransform#transform(float[], int, float[], int, int)} is supported.
@@ -311,8 +305,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.TransformTestCase#isFloatToFloatSupported
          */
-        public static final Key<Boolean> isFloatToFloatSupported =
-                new Key<>(Boolean.class, "isFloatToFloatSupported");
+        public static final Key<Boolean> isFloatToFloatSupported;
 
         /**
          * Whether {@link MathTransform#transform(double[], int, float[], int, int)} is supported.
@@ -321,8 +314,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.TransformTestCase#isDoubleToFloatSupported
          */
-        public static final Key<Boolean> isDoubleToFloatSupported =
-                new Key<>(Boolean.class, "isDoubleToFloatSupported");
+        public static final Key<Boolean> isDoubleToFloatSupported;
 
         /**
          * Whether {@link MathTransform#transform(float[], int, double[], int, int)} is supported.
@@ -331,8 +323,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.TransformTestCase#isFloatToDoubleSupported
          */
-        public static final Key<Boolean> isFloatToDoubleSupported =
-                new Key<>(Boolean.class, "isFloatToDoubleSupported");
+        public static final Key<Boolean> isFloatToDoubleSupported;
 
         /**
          * Whether source and destination arrays can overlap in {@link MathTransform} operations.
@@ -351,8 +342,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.TransformTestCase#isOverlappingArraySupported
          */
-        public static final Key<Boolean> isOverlappingArraySupported =
-                new Key<>(Boolean.class, "isOverlappingArraySupported");
+        public static final Key<Boolean> isOverlappingArraySupported;
 
         /**
          * Whether {@link MathTransform#inverse()} is supported.
@@ -361,8 +351,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.TransformTestCase#isInverseTransformSupported
          */
-        public static final Key<Boolean> isInverseTransformSupported =
-                new Key<>(Boolean.class, "isInverseTransformSupported");
+        public static final Key<Boolean> isInverseTransformSupported;
 
         /**
          * Whether {@link MathTransform#derivative(DirectPosition)} is supported.
@@ -371,16 +360,14 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.TransformTestCase#isDerivativeSupported
          */
-        public static final Key<Boolean> isDerivativeSupported =
-                new Key<>(Boolean.class, "isDerivativeSupported");
+        public static final Key<Boolean> isDerivativeSupported;
 
         /**
          * Whether {@link MathTransformFactory#createAffineTransform(Matrix)} accepts non-square matrixes.
          *
          * @see org.opengis.test.referencing.AffineTransformTest#isNonSquareMatrixSupported
          */
-        public static final Key<Boolean> isNonSquareMatrixSupported =
-                new Key<>(Boolean.class, "isNonSquareMatrixSupported");
+        public static final Key<Boolean> isNonSquareMatrixSupported;
 
         /**
          * Whether {@link MathTransformFactory} can create transforms between spaces that are
@@ -389,8 +376,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.AffineTransformTest#isNonBidimensionalSpaceSupported
          */
-        public static final Key<Boolean> isNonBidimensionalSpaceSupported =
-                new Key<>(Boolean.class, "isNonBidimensionalSpaceSupported");
+        public static final Key<Boolean> isNonBidimensionalSpaceSupported;
 
         /**
          * Whether (<var>y</var>,<var>x</var>) axis order is supported. This axis swapping is not
@@ -400,8 +386,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.AuthorityFactoryTest#isAxisSwappingSupported
          */
-        public static final Key<Boolean> isAxisSwappingSupported =
-                new Key<>(Boolean.class, "isAxisSwappingSupported");
+        public static final Key<Boolean> isAxisSwappingSupported;
 
         /**
          * Whether the test methods can invoke a <code>{@linkplain TestCase#validators validators}.validate(…)}</code>
@@ -417,46 +402,41 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * @see org.opengis.test.referencing.WKTParserTest#isValidationEnabled
          */
-        public static final Key<Boolean> isValidationEnabled =
-                new Key<>(Boolean.class, "isValidationEnabled");
+        public static final Key<Boolean> isValidationEnabled;
 
         /**
          * Whether the tolerance threshold of a {@link org.opengis.test.referencing.TransformTestCase}
          * has been relaxed. This information is determined after test execution.
          */
-        public static final Key<Boolean> isToleranceRelaxed =
-                new Key<>(Boolean.class, "isToleranceRelaxed");
+        public static final Key<Boolean> isToleranceRelaxed;
 
         /**
          * The provider of {@linkplain Units units} to use for tests. If this configuration hint
          * is not specified, then the {@linkplain Units#getDefault() default instance} is used.
          */
-        public static final Key<Units> units = new Key<>(Units.class, "units");
+        public static final Key<Units> units;
 
         /**
          * The {@linkplain MathTransformFactory Math Transform factory} instance used for a test.
          *
          * @see org.opengis.test.referencing.AffineTransformTest#mtFactory
          * @see org.opengis.test.referencing.ParameterizedTransformTest#mtFactory
          */
-        public static final Key<MathTransformFactory> mtFactory =
-                new Key<>(MathTransformFactory.class, "mtFactory");
+        public static final Key<MathTransformFactory> mtFactory;
 
         /**
          * The {@linkplain CRSFactory Coordinate Reference System factory} instance used for a test.
          * This is used mostly for parsing of documents in <abbr>WKT</abbr> or <abbr>XML</abbr> formats.
          *
          * @see org.opengis.test.referencing.WKTParserTest#crsFactory
          */
-        public static final Key<CRSFactory> crsFactory =
-                new Key<>(CRSFactory.class, "crsFactory");
+        public static final Key<CRSFactory> crsFactory;
 
         /**
          * The {@linkplain RegisterOperations register operations} instance used for a test.
          * Provides also factories for building CRS components from authority codes.
          */
-        public static final Key<RegisterOperations> registerOperations =
-                new Key<>(RegisterOperations.class, "registerOperations");
+        public static final Key<RegisterOperations> registerOperations;
 
         /**
          * Whether the objects created by the tested {@link org.opengis.referencing.ObjectFactory} use the
@@ -475,8 +455,7 @@ public static final class Key<T> extends CodeList<Key<?>> {
          *
          * If the factory does not perform any of the above conversions, then this flag can be {@code true}.
          */
-        public static final Key<Boolean> isFactoryPreservingUserValues =
-                new Key<>(Boolean.class, "isFactoryPreservingUserValues");
+        public static final Key<Boolean> isFactoryPreservingUserValues;
 
         /**
          * The set of {@link Validator} instances to use for validating objects.
@@ -488,6 +467,35 @@ public static final class Key<T> extends CodeList<Key<?>> {
         public static final Key<ValidatorContainer> validators =
                 new Key<>(ValidatorContainer.class, "validators");
 
+        /**
+         * All code list values created in the currently running <abbr>JVM</abbr>.
+         */
+        private static final List<Key<?>> VALUES = initialValues(
+            // Inline assignments for getting compiler error if a field is missing or duplicated.
+            isMultiLocaleSupported              = new Key<>(Boolean.class, "isMultiLocaleSupported"),
+            isMixedNameSyntaxSupported          = new Key<>(Boolean.class, "isMixedNameSyntaxSupported"),
+            isStandardNameSupported             = new Key<>(Boolean.class, "isStandardNameSupported"),
+            isStandardAliasSupported            = new Key<>(Boolean.class, "isStandardAliasSupported"),
+            isDependencyIdentificationSupported = new Key<>(Boolean.class, "isDependencyIdentificationSupported"),
+            isDeprecatedObjectCreationSupported = new Key<>(Boolean.class, "isDeprecatedObjectCreationSupported"),
+            isDoubleToDoubleSupported           = new Key<>(Boolean.class, "isDoubleToDoubleSupported"),
+            isFloatToFloatSupported             = new Key<>(Boolean.class, "isFloatToFloatSupported"),
+            isDoubleToFloatSupported            = new Key<>(Boolean.class, "isDoubleToFloatSupported"),
+            isFloatToDoubleSupported            = new Key<>(Boolean.class, "isFloatToDoubleSupported"),
+            isOverlappingArraySupported         = new Key<>(Boolean.class, "isOverlappingArraySupported"),
+            isInverseTransformSupported         = new Key<>(Boolean.class, "isInverseTransformSupported"),
+            isDerivativeSupported               = new Key<>(Boolean.class, "isDerivativeSupported"),
+            isNonSquareMatrixSupported          = new Key<>(Boolean.class, "isNonSquareMatrixSupported"),
+            isNonBidimensionalSpaceSupported    = new Key<>(Boolean.class, "isNonBidimensionalSpaceSupported"),
+            isAxisSwappingSupported             = new Key<>(Boolean.class, "isAxisSwappingSupported"),
+            isValidationEnabled                 = new Key<>(Boolean.class, "isValidationEnabled"),
+            isToleranceRelaxed                  = new Key<>(Boolean.class, "isToleranceRelaxed"),
+            units                               = new Key<>(Units.class, "units"),
+            mtFactory                           = new Key<>(MathTransformFactory.class, "mtFactory"),
+            crsFactory                          = new Key<>(CRSFactory.class, "crsFactory"),
+            registerOperations                  = new Key<>(RegisterOperations.class, "registerOperations"),
+            isFactoryPreservingUserValues       = new Key<>(Boolean.class, "isFactoryPreservingUserValues"));
+
         /**
          * The type of values associated to this key.
          */
@@ -520,7 +528,7 @@ private Key(final Class<T> type, final String name) {
         public static <T> Key<? extends T> valueOf(final String name, final Class<T> type) {
             Objects.requireNonNull(type, "type");
             @SuppressWarnings("rawtypes")
-            final Key<?> key = (Key<?>) valueOf(Key.class, name, (n) -> new Key(type, n)).get();
+            final Key<?> key = (Key<?>) valueOf(VALUES, name, (n) -> new Key(type, n));
             if (type.isAssignableFrom(key.type)) {
                 return (Key<? extends T>) key;
             }
@@ -534,7 +542,7 @@ public static <T> Key<? extends T> valueOf(final String name, final Class<T> typ
          */
         @SuppressWarnings("unchecked")
         public static Key<?>[] values() {
-            return values(Key.class);
+            return VALUES.toArray(Key[]::new);
         }
 
         /**

geoapi-pending/src/main/java/org/opengis/coverage/CommonPointRule.java

@@ -17,11 +17,11 @@
  */
 package org.opengis.coverage;
 
+import java.util.List;
 import java.util.Collection;                    // For javadoc
 import org.opengis.util.CodeList;
 import org.opengis.geometry.DirectPosition;
 import org.opengis.annotation.UML;
-import org.opengis.geoapi.internal.Vocabulary;
 
 import static org.opengis.annotation.Obligation.*;
 import static org.opengis.annotation.Specification.*;
@@ -45,7 +45,6 @@
  *
  * @see Coverage#getCommonPointRule
  */
-@Vocabulary(capacity=6)
 @UML(identifier="CV_CommonPointRule", specification=ISO_19123)
 public class CommonPointRule extends CodeList<CommonPointRule> {
     /**
@@ -57,41 +56,53 @@ public class CommonPointRule extends CodeList<CommonPointRule> {
      * The mean of the feature attribute values.
      */
     @UML(identifier="average", obligation=CONDITIONAL, specification=ISO_19123)
-    public static final CommonPointRule AVERAGE = new CommonPointRule("AVERAGE");
+    public static final CommonPointRule AVERAGE;
 
     /**
      * The least of the feature attribute values.
      */
     @UML(identifier="low", obligation=CONDITIONAL, specification=ISO_19123)
-    public static final CommonPointRule LOW = new CommonPointRule("LOW");
+    public static final CommonPointRule LOW;
 
     /**
      * The greatest of the feature attribute values.
      */
     @UML(identifier="high", obligation=CONDITIONAL, specification=ISO_19123)
-    public static final CommonPointRule HIGH = new CommonPointRule("HIGH");
+    public static final CommonPointRule HIGH;
 
     /**
      * All the feature attribute values that can be determined for the input direct position.
      */
     @UML(identifier="all", obligation=CONDITIONAL, specification=ISO_19123)
-    public static final CommonPointRule ALL = new CommonPointRule("ALL");
+    public static final CommonPointRule ALL;
 
     /**
      * The {@linkplain ValueSegment#getStartParameter start value} of the second
      * {@linkplain ValueSegment value segment}.
      * Applies only to segmented curve coverages.
      */
     @UML(identifier="start", obligation=CONDITIONAL, specification=ISO_19123)
-    public static final CommonPointRule START = new CommonPointRule("START");
+    public static final CommonPointRule START;
 
     /**
      * The {@linkplain ValueSegment#getEndParameter end value} of the first
      * {@linkplain ValueSegment value segment}.
      * Applies only to segmented curve coverages.
      */
     @UML(identifier="end", obligation=CONDITIONAL, specification=ISO_19123)
-    public static final CommonPointRule END = new CommonPointRule("END");
+    public static final CommonPointRule END;
+
+    /**
+     * All code list values created in the currently running <abbr>JVM</abbr>.
+     */
+    private static final List<CommonPointRule> VALUES = initialValues(
+        // Inline assignments for getting compiler error if a field is missing or duplicated.
+        AVERAGE = new CommonPointRule("AVERAGE"),
+        LOW     = new CommonPointRule("LOW"),
+        HIGH    = new CommonPointRule("HIGH"),
+        ALL     = new CommonPointRule("ALL"),
+        START   = new CommonPointRule("START"),
+        END     = new CommonPointRule("END"));
 
     /**
      * Constructs an element of the given name.
@@ -109,7 +120,7 @@ private CommonPointRule(final String name) {
      * @return the list of codes declared in the current JVM.
      */
     public static CommonPointRule[] values() {
-        return values(CommonPointRule.class);
+        return VALUES.toArray(CommonPointRule[]::new);
     }
 
     /**
@@ -134,6 +145,6 @@ public CommonPointRule[] family() {
      * @return a code matching the given name.
      */
     public static CommonPointRule valueOf(String code) {
-        return valueOf(CommonPointRule.class, code, CommonPointRule::new).get();
+        return valueOf(VALUES, code, CommonPointRule::new);
     }
 }