Fixed #2715

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -43,6 +43,9 @@ Project: jackson-databind
 #2707: Improve description included in by `DeserializationContext.handleUnexpectedToken()`
 #2709: Support for JDK 14 record types (`java.lang.Record`)
  (contributed by Youri B)
+#2715: `PropertyNamingStrategy` class initialization depends on its subclass, this can
+  lead to class loading deadlock
+ (reported by fangwentong@github)
 #2719: `FAIL_ON_IGNORED_PROPERTIES` does not throw on `READONLY` properties with
   an explicit name
  (reported, fix contributed by David B)

src/main/java/com/fasterxml/jackson/databind/PropertyNamingStrategies.java

@@ -30,41 +30,53 @@ public abstract class PropertyNamingStrategies
      * and no separator is used between words. Since this is the native Java naming convention,
      * naming strategy will not do any transformation between names in data (JSON) and
      * POJOS.
+     *<p>
+     * Example external property names would be "numberValue", "namingStrategy", "theDefiniteProof".
      */
-    public static final PropertyNamingStrategy LOWER_CAMEL_CASE = new PropertyNamingStrategy();
+    public static final PropertyNamingStrategy LOWER_CAMEL_CASE = new LowerCamelCaseStrategy();
 
     /**
-     * Naming convention used in languages like Pascal, where words are capitalized
+     * Naming convention used in languages like Pascal, where all words are capitalized
      * and no separator is used between words.
      * See {@link UpperCamelCaseStrategy} for details.
+     *<p>
+     * Example external property names would be "NumberValue", "NamingStrategy", "TheDefiniteProof".
      */
     public static final PropertyNamingStrategy UPPER_CAMEL_CASE = new UpperCamelCaseStrategy();
 
     /**
      * Naming convention used in languages like C, where words are in lower-case
      * letters, separated by underscores.
      * See {@link SnakeCaseStrategy} for details.
+     *<p>
+     * Example external property names would be "number_value", "naming_strategy", "the_definite_proof".
      */
     public static final PropertyNamingStrategy SNAKE_CASE = new SnakeCaseStrategy();
 
     /**
      * Naming convention in which all words of the logical name are in lower case, and
      * no separator is used between words.
      * See {@link LowerCaseStrategy} for details.
+     *<p>
+     * Example external property names would be "numbervalue", "namingstrategy", "thedefiniteproof".
      */
     public static final PropertyNamingStrategy LOWER_CASE = new LowerCaseStrategy();
 
     /**
      * Naming convention used in languages like Lisp, where words are in lower-case
      * letters, separated by hyphens.
      * See {@link KebabCaseStrategy} for details.
+     *<p>
+     * Example external property names would be "number-value", "naming-strategy", "the-definite-proof".
      */
     public static final PropertyNamingStrategy KEBAB_CASE = new KebabCaseStrategy();
 
     /**
      * Naming convention widely used as configuration properties name, where words are in
      * lower-case letters, separated by dots.
      * See {@link LowerDotCaseStrategy} for details.
+     *<p>
+     * Example external property names would be "number.value", "naming.strategy", "the.definite.proof".
      */
     public static final PropertyNamingStrategy LOWER_DOT_CASE = new LowerDotCaseStrategy();
 
@@ -77,7 +89,7 @@ public abstract class PropertyNamingStrategies
     /**
      * Intermediate base class for simple implementations
      */
-    static abstract class NamingBase
+    public static abstract class NamingBase
         extends PropertyNamingStrategy
     {
         private static final long serialVersionUID = 2L;
@@ -152,39 +164,39 @@ protected String translateLowerCaseWithSeparator(final String input, final char
      */
 
     /**
-     * A {@link PropertyNamingStrategy} that translates typical camel case Java 
-     * property names to lower case JSON element names, separated by 
-     * underscores.  This implementation is somewhat lenient, in that it 
-     * provides some additional translations beyond strictly translating from 
-     * camel case only.  In particular, the following translations are applied 
+     * A {@link PropertyNamingStrategy} that translates typical camel case Java
+     * property names to lower case JSON element names, separated by
+     * underscores.  This implementation is somewhat lenient, in that it
+     * provides some additional translations beyond strictly translating from
+     * camel case only.  In particular, the following translations are applied
      * by this PropertyNamingStrategy.
      * 
-     * <ul><li>Every upper case letter in the Java property name is translated 
-     * into two characters, an underscore and the lower case equivalent of the 
+     * <ul><li>Every upper case letter in the Java property name is translated
+     * into two characters, an underscore and the lower case equivalent of the
      * target character, with three exceptions.
      * <ol><li>For contiguous sequences of upper case letters, characters after
-     * the first character are replaced only by their lower case equivalent, 
+     * the first character are replaced only by their lower case equivalent,
      * and are not preceded by an underscore.
-     * <ul><li>This provides for reasonable translations of upper case acronyms, 
-     * e.g., &quot;theWWW&quot; is translated to &quot;the_www&quot;.</li></ul></li>
-     * <li>An upper case character in the first position of the Java property 
-     * name is not preceded by an underscore character, and is translated only 
+     * <ul><li>This provides for reasonable translations of upper case acronyms,
+     * e.g., &quot;theWWW&quot; is translated to &quot;the_www&quot;.</li></ul></li
+     * <li>An upper case character in the first position of the Java property
+     * name is not preceded by an underscore character, and is translated only
      * to its lower case equivalent.
-     * <ul><li>For example, &quot;Results&quot; is translated to &quot;results&quot;, 
+     * <ul><li>For example, &quot;Results&quot; is translated to &quot;results&quot;,
      * and not to &quot;_results&quot;.</li></ul></li>
-     * <li>An upper case character in the Java property name that is already 
-     * preceded by an underscore character is translated only to its lower case 
+     * <li>An upper case character in the Java property name that is already
+     * preceded by an underscore character is translated only to its lower case
      * equivalent, and is not preceded by an additional underscore.
-     * <ul><li>For example, &quot;user_Name&quot; is translated to 
-     * &quot;user_name&quot;, and not to &quot;user__name&quot; (with two 
+     * <ul><li>For example, &quot;user_Name&quot; is translated to
+     * &quot;user_name&quot;, and not to &quot;user__name&quot; (with two
      * underscore characters).</li></ul></li></ol></li>
-     * <li>If the Java property name starts with an underscore, then that 
-     * underscore is not included in the translated name, unless the Java 
-     * property name is just one character in length, i.e., it is the 
-     * underscore character.  This applies only to the first character of the 
+     * <li>If the Java property name starts with an underscore, then that
+     * underscore is not included in the translated name, unless the Java
+     * property name is just one character in length, i.e., it is the
+     * underscore character.  This applies only to the first character of the
      * Java property name.</li></ul>
-     * 
-     * These rules result in the following additional example translations from 
+     *<p>
+     * These rules result in the following additional example translations from
      * Java property names to JSON element names.
      * <ul><li>&quot;userName&quot; is translated to &quot;user_name&quot;</li>
      * <li>&quot;UserName&quot; is translated to &quot;user_name&quot;</li>
@@ -239,6 +251,20 @@ public String translate(String input)
         }
     }
 
+    /**
+     * "No-operation" strategy that is equivalent to not specifying any
+     * strategy: will simply return suggested standard bean naming as-is.
+     */
+    public static class LowerCamelCaseStrategy extends NamingBase
+    {
+        private static final long serialVersionUID = 2L;
+
+        @Override
+        public String translate(String input) {
+            return input;
+        }
+    }
+
     /**
      * A {@link PropertyNamingStrategy} that translates typical camelCase Java 
      * property names to PascalCase JSON element names (i.e., with a capital