Fix #5152: support "iPhone" style properties -- add MapperFeature.FIX_FIELD_NAME_UPPER_CASE_PREFIX (#5187)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -18,6 +18,8 @@ Project: jackson-databind
   serialization
 #5151: Add new exception type, `MissingInjectValueException`, to be used
   for failed `@JacksonInject`
+#5152: Support "iPhone" style capitalized properties (add
+  `MapperFeature.FIX_FIELD_NAME_CASE_MISMATCH`)
 #5179: Add "current token" info into `MismatchedInputException`
 #5192: Record types are broken on Android when using R8
  (reported by @HelloOO7)

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

@@ -218,6 +218,17 @@ public enum MapperFeature implements ConfigFeature
      */
     INFER_CREATOR_FROM_CONSTRUCTOR_PROPERTIES(true),
 
+    /**
+     * Feature that when enabled will allow getters with is-Prefix also for
+     * non-boolean return types; if disabled only methods that return
+     * {@code boolean} or {@code Boolean} qualify as "is getters".
+     * <p>
+     * Feature is disabled by default for backwards compatibility.
+     *
+     * @since 2.14
+     */
+    ALLOW_IS_GETTERS_FOR_NON_BOOLEAN(false),
+
     /**
      * Feature that determines whether nominal property type of {@link Void} is
      * allowed for Getter methods to indicate {@code null} valued pseudo-property
@@ -541,15 +552,20 @@ public enum MapperFeature implements ConfigFeature
     ALLOW_EXPLICIT_PROPERTY_RENAMING(false),
 
     /**
-     * Feature that when enabled will allow getters with is-Prefix also for
-     * non-boolean return types; if disabled only methods that return
-     * {@code boolean} or {@code Boolean} qualify as "is getters".
+     * Feature that can be enabled to solve problem where an upper-case letter in
+     * the first 2 characters of Java field name (like {@code "IPhone"} or {@code "iPhone"})
+     * prevents match with property name derived from accessors (getter like
+     * {@code getIPhone()} becomes {@code "iphone"}).
+     * If enabled, additional checking is done with case-insensitive comparison (for
+     * cases of the first or second letter of Field name being upper-case) to merge
+     * accessors. If disabled, no special processing is done.
      * <p>
-     * Feature is disabled by default for backwards compatibility.
+     * Feature is disabled by default in 2.x for backwards-compatibility.
+     * It will be enabled by default in 3.0.
      *
-     * @since 2.14
+     * @since 2.20
      */
-    ALLOW_IS_GETTERS_FOR_NON_BOOLEAN(false),
+    FIX_FIELD_NAME_UPPER_CASE_PREFIX(false),
 
     /*
     /******************************************************

src/main/java/com/fasterxml/jackson/databind/introspect/POJOPropertiesCollector.java

@@ -433,20 +433,23 @@ protected void collectAll()
         _potentialCreators = new PotentialCreators();
 
         // First: gather basic accessors
-        LinkedHashMap<String, POJOPropertyBuilder> props = new LinkedHashMap<String, POJOPropertyBuilder>();
+        LinkedHashMap<String, POJOPropertyBuilder> props = new LinkedHashMap<>();
 
         // 14-Nov-2024, tatu: Previously skipped checking fields for Records; with 2.18+ won't
         //    (see [databind#3628], [databind#3895], [databind#3992], [databind#4626])
         _addFields(props); // note: populates _fieldRenameMappings
-
         _addMethods(props);
         // 25-Jan-2016, tatu: Avoid introspecting (constructor-)creators for non-static
         //    inner classes, see [databind#1502]
         // 14-Nov-2024, tatu: Similarly need Creators for Records too (2.18+)
         if (!_classDef.isNonStaticInnerClass()) {
             _addCreators(props);
         }
-
+        // 11-Jun-2025, tatu: [databind#5152] May need to "fix" mis-matching leading case
+        //    wrt Fields vs Accessors
+        if (_config.isEnabled(MapperFeature.FIX_FIELD_NAME_UPPER_CASE_PREFIX)) {
+             _fixLeadingFieldNameCase(props);
+        }
         // Remove ignored properties, first; this MUST precede annotation merging
         // since logic relies on knowing exactly which accessor has which annotation
         _removeUnwantedProperties(props);
@@ -547,10 +550,9 @@ private Map<String, POJOPropertyBuilder> _putAnyGettersInTheEnd(
     protected void _addFields(Map<String, POJOPropertyBuilder> props)
     {
         final AnnotationIntrospector ai = _annotationIntrospector;
-        /* 28-Mar-2013, tatu: For deserialization we may also want to remove
-         *   final fields, as often they won't make very good mutators...
-         *   (although, maybe surprisingly, JVM _can_ force setting of such fields!)
-         */
+        // 28-Mar-2013, tatu: For deserialization we may also want to remove
+        //   final fields, as often they won't make very good mutators...
+        //  (although, maybe surprisingly, JVM _can_ force setting of such fields!)
         final boolean pruneFinalFields = !_forSerialization && !_config.isEnabled(MapperFeature.ALLOW_FINAL_FIELDS_AS_MUTATORS);
         final boolean transientAsIgnoral = _config.isEnabled(MapperFeature.PROPAGATE_TRANSIENT_MARKER);
 
@@ -1318,6 +1320,97 @@ private String _checkRenameByField(String implName) {
         return implName;
     }
 
+    /*
+    /**********************************************************
+    /* Internal methods; merging/fixing case-differences
+    /**********************************************************
+     */
+
+    // @since 2.20
+    protected void _fixLeadingFieldNameCase(Map<String, POJOPropertyBuilder> props)
+    {
+        // 11-Jun-2025, tatu: [databind#5152] May need to "fix" mis-matching leading case
+        //    wrt Fields vs Accessors
+
+        // First: find possible candidates where:
+        //
+        // 1. Property only has Field
+        // 2. Field does NOT have explicit name (renaming)
+        // 3. Implicit name has upper-case for first and/or second character
+
+        Map<String, POJOPropertyBuilder> fieldsToCheck = null;
+        for (Map.Entry<String, POJOPropertyBuilder> entry : props.entrySet()) {
+            POJOPropertyBuilder  prop = entry.getValue();
+
+            // First: (1) and (2)
+            if (!prop.hasFieldAndNothingElse()
+                    || prop.isExplicitlyNamed()) {
+                continue;
+            }
+            // Second: (3)
+            if (!_firstOrSecondCharUpperCase(entry.getKey())) {
+                continue;
+            }
+            if (fieldsToCheck == null) {
+                fieldsToCheck = new HashMap<>();
+            }
+            fieldsToCheck.put(entry.getKey(), prop);
+        }
+        /*// DEBUGGING
+        if (fieldsToCheck == null) {
+            System.err.println("_fixLeadingCase, candidates -> null; props -> "+props.keySet());
+        } else {
+            System.err.println("_fixLeadingCase, candidates -> "+fieldsToCheck);
+        }
+        */
+
+        if (fieldsToCheck == null) {
+            return;
+        }
+
+        for (Map.Entry<String, POJOPropertyBuilder> fieldEntry : fieldsToCheck.entrySet()) {
+            Iterator<Map.Entry<String, POJOPropertyBuilder>> it = props.entrySet().iterator();
+            final POJOPropertyBuilder fieldProp = fieldEntry.getValue();
+            final String fieldName = fieldEntry.getKey();
+
+            while (it.hasNext()) {
+                Map.Entry<String, POJOPropertyBuilder> propEntry = it.next();
+                final POJOPropertyBuilder prop = propEntry.getValue();
+
+                // Skip anything that has Field (can't merge)
+                if (prop == fieldProp || prop.hasField()) {
+                    continue;
+                }
+                if (fieldName.equalsIgnoreCase(propEntry.getKey())) {
+                    // Remove non-Field property; add its accessors to Field one
+                    it.remove();
+                    fieldProp.addAll(prop);
+                    // Should we continue with possible other accessors?
+                    // For now assume only one merge needed/desired
+                    break;
+                }
+            }
+        }
+    }
+
+    // @since 2.20
+    private boolean _firstOrSecondCharUpperCase(String name) {
+         switch (name.length()) {
+         case 0:
+             return false;
+         default:
+             if (!Character.isLowerCase(name.charAt(1))) {
+                 return true;
+             }
+             // fall through
+         case 1:
+             if (!Character.isLowerCase(name.charAt(0))) {
+                 return true;
+             }
+             return false;
+         }
+    }
+
     /*
     /**********************************************************
     /* Internal methods; removing ignored properties
@@ -1420,6 +1513,7 @@ protected void _renameProperties(Map<String, POJOPropertyBuilder> props)
         // With renaming need to do in phases: first, find properties to rename
         Iterator<Map.Entry<String,POJOPropertyBuilder>> it = props.entrySet().iterator();
         LinkedList<POJOPropertyBuilder> renamed = null;
+
         while (it.hasNext()) {
             Map.Entry<String, POJOPropertyBuilder> entry = it.next();
             POJOPropertyBuilder prop = entry.getValue();

src/main/java/com/fasterxml/jackson/databind/introspect/POJOPropertyBuilder.java

@@ -385,6 +385,12 @@ public Class<?> getRawPrimaryType() {
     @Override
     public boolean hasField() { return _fields != null; }
 
+    // @since 2.20 additional accessor
+    public boolean hasFieldAndNothingElse() {
+        return (_fields != null)
+                && ((_getters == null) && (_setters == null) && (_ctorParameters == null));
+    }
+
     @Override
     public boolean hasConstructorParameter() { return _ctorParameters != null; }
 
@@ -416,9 +422,8 @@ public AnnotatedMethod getGetter()
         }
         // But if multiple, verify that they do not conflict...
         for (; next != null; next = next.next) {
-            /* [JACKSON-255] Allow masking, i.e. do not report exception if one
-             *   is in super-class from the other
-             */
+            // Allow masking, i.e. do not report exception if one
+            // is in super-class from the other
             Class<?> currClass = curr.value.getDeclaringClass();
             Class<?> nextClass = next.value.getDeclaringClass();
             if (currClass != nextClass) {

src/test/java/com/fasterxml/jackson/databind/tofix/IPhoneStyleProperty5152Test.java renamed to src/test/java/com/fasterxml/jackson/databind/misc/IPhoneStyleProperty5152Test.java

@@ -1,11 +1,9 @@
-package com.fasterxml.jackson.databind.tofix;
+package com.fasterxml.jackson.databind.misc;
 
 import org.junit.jupiter.api.Test;
 
-import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
-import com.fasterxml.jackson.databind.testutil.failure.JacksonTestFailureExpected;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -73,10 +71,27 @@ public void setPhone(String value) {
         }
     }
 
+    // [databind#2696]
+    static class OAuthTokenBean {
+        protected String oAuthToken;
+
+        public OAuthTokenBean(String t) {
+            oAuthToken = t;
+        }
+
+        public String getOAuthToken() {
+            return this.oAuthToken;
+        }
+
+        public void setOAuthToken(String oAuthToken) {
+            this.oAuthToken = oAuthToken;
+        }
+    }
+
     private final ObjectMapper MAPPER = jsonMapperBuilder()
+            .enable(MapperFeature.FIX_FIELD_NAME_UPPER_CASE_PREFIX)
             .build();
 
-    @JacksonTestFailureExpected
     @Test
     public void testIPhoneStyleProperty() throws Exception {
         // Test with iPhone style property
@@ -104,21 +119,19 @@ public void testRegularPojoProperty() throws Exception {
     }
 
     // [databind#2835]: "dLogHeader" property
-    @JacksonTestFailureExpected
     @Test
     public void testDLogHeaderStyleProperty() throws Exception {
         // Test with DLogHeader style property
-        String json = "{\"dLogHeader\":\"Debug Log Header\"}";
+        String json = "{\"DLogHeader\":\"Debug Log Header\"}";
         DLogHeaderBean result = MAPPER.readValue(json, DLogHeaderBean.class);
         assertNotNull(result);
         assertEquals("Debug Log Header", result.getDLogHeader());
 
         // Test serialization
         String serialized = MAPPER.writeValueAsString(result);
-        assertEquals("{\"dLogHeader\":\"Debug Log Header\"}", serialized);
+        assertEquals("{\"DLogHeader\":\"Debug Log Header\"}", serialized);
     }
 
-    @JacksonTestFailureExpected
     @Test
     public void testKBSBroadCastingStyleProperty() throws Exception {
         // Test with KBSBroadCasting style property
@@ -132,7 +145,6 @@ public void testKBSBroadCastingStyleProperty() throws Exception {
         assertEquals("{\"KBSBroadCasting\":\"Korean Broadcasting System\"}", serialized);
     }
 
-    @JacksonTestFailureExpected
     @Test
     public void testPhoneStyleProperty() throws Exception {
         // Test with Phone style property
@@ -146,4 +158,10 @@ public void testPhoneStyleProperty() throws Exception {
         assertEquals("{\"Phone\":\"iPhone 15\"}", serialized);
     }
 
-}
+    // [databind#2696]
+    @Test
+    public void testOAuthProperty() throws Exception {
+        assertEquals(a2q("{'oAuthToken':'123'}"),
+                MAPPER.writeValueAsString(new OAuthTokenBean("123")));
+    }
+}