Fix #963: Add JsonPropertyNamingStrategy.KEBAB_CASE for hyphen-delimited (List-style) names

Author: cowtowncoder

release-notes/CREDITS

@@ -359,19 +359,23 @@ Miles Kaufmann (milesk-amzn@github)
   * Reported #432: `StdValueInstantiator` unwraps exceptions, losing context
    (2.7.0)
 
+Thomas Mortagne (tmortagne@github)
+  * Suggested #857: Add support for java.beans.Transient
+   (2.7.0)
+
+Jonas Konrad (yawkat@github)
+  * Suggested #905: Add support for `@ConstructorProperties`
+   (2.7.0)
+
 Jirka Kremser (Jiri-Kremser@github)
   * Suggested #924: SequenceWriter.writeAll() could accept Iterable
    (2.7.0)
 
-Thomas Mortagne (tmortagne@github)
-  * Suggested #857: Add support for java.beans.Transient
+Daniel Mischler (danielmischler@github)
+  * Requested #963: Add PropertyNameStrategy `KEBAB_CASE`
    (2.7.0)
 
 Shumpei Akai (flexfrank@github)
   * Reported #978: ObjectMapper#canSerialize(Object.class) returns false even though
    FAIL_ON_EMPTY_BEANS is disabled
    (2.7.0)
-
-Jonas Konrad (yawkat@github)
-  * Suggested #905: Add support for `@ConstructorProperties`
-   (2.7.0)

release-notes/VERSION

@@ -36,6 +36,8 @@ Project: jackson-databind
  (contributed by Jesse W)
 #957: Merge `datatype-jdk7` stuff in (java.nio.file.Path handling)
 #959: Schema generation: consider active view, discard non-included properties
+#963: Add PropertyNameStrategy `KEBAB_CASE`
+ (requested by Daniel M)
 #978: ObjectMapper#canSerialize(Object.class) returns false even though FAIL_ON_EMPTY_BEANS is disabled
  (reported by Shumpei A)
 #997: Add `MapperFeature.OVERRIDE_PUBLIC_ACCESS_MODIFIERS`

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

@@ -13,7 +13,7 @@
  * Methods are passed information about POJO member for which name is needed,
  * as well as default name that would be used if no custom strategy was used.
  *<p>
- * Default implementation returns suggested ("default") name unmodified.
+ * Default (empty) implementation returns suggested ("default") name unmodified.
  *<p>
  * Note that the strategy is guaranteed to be called once per logical property
  * (which may be represented by multiple members; such as pair of a getter and
@@ -66,7 +66,16 @@ public class PropertyNamingStrategy // NOTE: was abstract until 2.7
      * @since 2.4
      */
     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.
+     * 
+     * @since 2.7
+     */
+    public static final PropertyNamingStrategy KEBAB_CASE = new KebabCaseStrategy();
+
     /*
     /**********************************************************
     /* API
@@ -341,6 +350,53 @@ public String translate(String input) {
         }
     }
 
+    /**
+     * Naming strategy similar to {@link SnakeCaseStrategy}, but instead of underscores
+     * as separators, uses hyphens. Naming convention traditionally used for languages
+     * like Lisp.
+     *
+     * @since 2.7
+     */
+    public static class KebabCaseStrategy extends PropertyNamingStrategyBase
+    {
+        @Override
+        public String translate(String input)
+        {
+            if (input == null) return input; // garbage in, garbage out
+            int length = input.length();
+            if (length == 0) {
+                return input;
+            }
+
+            StringBuilder result = new StringBuilder(length + (length >> 1));
+
+            int upperCount = 0;
+
+            for (int i = 0; i < length; ++i) {
+                char ch = input.charAt(i);
+                char lc = Character.toLowerCase(ch);
+                
+                if (lc == ch) { // lower-case letter means we can get new word
+                    // but need to check for multi-letter upper-case (acronym), where assumption
+                    // is that the last upper-case char is start of a new word
+                    if (upperCount > 1) {
+                        // so insert hyphen before the last character now
+                        result.insert(result.length() - 1, '-');
+                    }
+                    upperCount = 0;
+                } else {
+                    // Otherwise starts new word, unless beginning of string
+                    if ((upperCount == 0) && (i > 0)) {
+                        result.append('-');
+                    }
+                    ++upperCount;
+                }
+                result.append(lc);
+            }
+            return result.toString();
+        }
+    }
+    
     /*
     /**********************************************************
     /* Deprecated variants, aliases

src/test/java/com/fasterxml/jackson/databind/creators/TestCreatorWithNamingStrategy556.java

@@ -58,7 +58,7 @@ public String findImplicitPropertyName(AnnotatedMember param) {
     }
 
     private final ObjectMapper MAPPER = new ObjectMapper()
-            .setPropertyNamingStrategy(PropertyNamingStrategy.PASCAL_CASE_TO_CAMEL_CASE)
+            .setPropertyNamingStrategy(PropertyNamingStrategy.UPPER_CAMEL_CASE)
             ;
     {
         MAPPER.setAnnotationIntrospector(new MyParamIntrospector());

src/test/java/com/fasterxml/jackson/databind/introspect/TestNamingStrategyStd.java

@@ -3,25 +3,16 @@
 import java.util.Arrays;
 import java.util.List;
 
-import org.junit.Test;
-
 import com.fasterxml.jackson.annotation.*;
-import com.fasterxml.jackson.databind.BaseMapTest;
-import com.fasterxml.jackson.databind.MapperFeature;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.databind.PropertyNamingStrategy;
+
+import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import com.fasterxml.jackson.databind.introspect.TestNamingStrategyCustom.PersonBean;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 
 /**
- * Unit tests to verify functioning of 
- * {@link PropertyNamingStrategy#CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES} 
- * and
- * {@link PropertyNamingStrategy#PASCAL_CASE_TO_CAMEL_CASE } 
- * inside the context of an ObjectMapper.
- * PASCAL_CASE_TO_CAMEL_CASE was added in Jackson 2.1,
- * as per [JACKSON-63].
+ * Unit tests to verify functioning of standard {@link PropertyNamingStrategy}
+ * implementations Jackson includes out of the box.
  */
 public class TestNamingStrategyStd extends BaseMapTest
 {
@@ -110,14 +101,21 @@ static class ExplicitBean {
     static class DefaultNaming {
         public int someValue = 3;
     }
-    
+
+    static class FirstNameBean {
+        public String firstName;
+
+        protected FirstNameBean() { }
+        public FirstNameBean(String n) { firstName = n; }
+    }
+
     /*
     /**********************************************************
     /* Set up
     /**********************************************************
      */
 
-    public static List<Object[]> NAME_TRANSLATIONS = Arrays.asList(new Object[][] {
+    public static List<Object[]> SNAKE_CASE_NAME_TRANSLATIONS = Arrays.asList(new Object[][] {
                 {null, null},
                 {"", ""},
                 {"a", "a"},
@@ -176,32 +174,29 @@ public void setUp() throws Exception
     {
         super.setUp();
         _lcWithUndescoreMapper = new ObjectMapper();
-        _lcWithUndescoreMapper.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
+        _lcWithUndescoreMapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
     }
 
     /*
     /**********************************************************
-    /* Test methods for CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES
+    /* Test methods for SNAKE_CASE
     /**********************************************************
      */
 
     /**
      * Unit test to verify translations of 
-     * {@link PropertyNamingStrategy#CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES} 
+     * {@link PropertyNamingStrategy#SNAKE_CASE} 
      * outside the context of an ObjectMapper.
-     * CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES was added in Jackson 1.9, 
-     * as per [JACKSON-598].
      */
-    @Test
     public void testLowerCaseStrategyStandAlone()
     {
-        for (Object[] pair : NAME_TRANSLATIONS) {
-            String translatedJavaName = PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES.nameForField(null, null,
+        for (Object[] pair : SNAKE_CASE_NAME_TRANSLATIONS) {
+            String translatedJavaName = PropertyNamingStrategy.SNAKE_CASE.nameForField(null, null,
                     (String) pair[0]);
             assertEquals((String) pair[1], translatedJavaName);
         }
     }
-    
+
     public void testLowerCaseTranslations() throws Exception
     {
         // First serialize
@@ -256,34 +251,32 @@ public void testLowerCaseUnchangedNames() throws Exception
         assertEquals("from7user", result.from7user);
         assertEquals("_x", result._x);
     }
-    
+
     /*
     /**********************************************************
-    /* Test methods for PASCAL_CASE_TO_CAMEL_CASE (added in 2.1)
+    /* Test methods for UPPER_CAMEL_CASE
     /**********************************************************
      */
 
     /**
      * Unit test to verify translations of 
-     * {@link PropertyNamingStrategy#PASCAL_CASE_TO_CAMEL_CASE } 
+     * {@link PropertyNamingStrategy#UPPER_CAMEL_CASE } 
      * outside the context of an ObjectMapper.
-     * PASCAL_CASE_TO_CAMEL_CASE was added in Jackson 2.1.0, 
-     * as per [JACKSON-63].
      */
     public void testPascalCaseStandAlone()
     {
-        String translatedJavaName = PropertyNamingStrategy.PASCAL_CASE_TO_CAMEL_CASE.nameForField
+        String translatedJavaName = PropertyNamingStrategy.UPPER_CAMEL_CASE.nameForField
     	        (null, null, "userName");
         assertEquals("UserName", translatedJavaName);
 
-        translatedJavaName = PropertyNamingStrategy.PASCAL_CASE_TO_CAMEL_CASE.nameForField
+        translatedJavaName = PropertyNamingStrategy.UPPER_CAMEL_CASE.nameForField
                 (null, null, "User");
         assertEquals("User", translatedJavaName);
 
-        translatedJavaName = PropertyNamingStrategy.PASCAL_CASE_TO_CAMEL_CASE.nameForField
+        translatedJavaName = PropertyNamingStrategy.UPPER_CAMEL_CASE.nameForField
                 (null, null, "user");
         assertEquals("User", translatedJavaName);
-        translatedJavaName = PropertyNamingStrategy.PASCAL_CASE_TO_CAMEL_CASE.nameForField
+        translatedJavaName = PropertyNamingStrategy.UPPER_CAMEL_CASE.nameForField
                 (null, null, "x");
         assertEquals("X", translatedJavaName);
     }
@@ -294,14 +287,20 @@ public void testPascalCaseStandAlone()
     public void testIssue428PascalWithOverrides() throws Exception {
 
         String json = new ObjectMapper()
-                            .setPropertyNamingStrategy(PropertyNamingStrategy.PASCAL_CASE_TO_CAMEL_CASE)
+                            .setPropertyNamingStrategy(PropertyNamingStrategy.UPPER_CAMEL_CASE)
                             .writeValueAsString(new Bean428());
 
         if (!json.contains(quote("fooBar"))) {
             fail("Should use name 'fooBar', does not: "+json);
         }
     }
 
+    /*
+    /**********************************************************
+    /* Test methods for LOWER_CASE
+    /**********************************************************
+     */
+    
     /**
      * For [databind#461]
      */
@@ -314,13 +313,52 @@ public void testSimpleLowerCase() throws Exception
                 m.writeValueAsString(input));
     }
 
+    /*
+    /**********************************************************
+    /* Test methods for KEBAB_CASE
+    /**********************************************************
+     */
+    
+    public void testKebabCaseStrategyStandAlone()
+    {
+        assertEquals("some-value",
+                PropertyNamingStrategy.KEBAB_CASE.nameForField(null, null, "someValue"));
+        assertEquals("some-value",
+                PropertyNamingStrategy.KEBAB_CASE.nameForField(null, null, "SomeValue"));
+        assertEquals("url",
+                PropertyNamingStrategy.KEBAB_CASE.nameForField(null, null, "URL"));
+        assertEquals("url-stuff",
+                PropertyNamingStrategy.KEBAB_CASE.nameForField(null, null, "URLStuff"));
+        assertEquals("some-url-stuff",
+                PropertyNamingStrategy.KEBAB_CASE.nameForField(null, null, "SomeURLStuff"));
+    }
+    
+    public void testSimpleKebabCase() throws Exception
+    {
+        final FirstNameBean input = new FirstNameBean("Bob");
+        ObjectMapper m = new ObjectMapper()
+                .setPropertyNamingStrategy(PropertyNamingStrategy.KEBAB_CASE);
+
+        assertEquals(aposToQuotes("{'first-name':'Bob'}"), m.writeValueAsString(input));
+
+        FirstNameBean result = m.readValue(aposToQuotes("{'first-name':'Billy'}"),
+                FirstNameBean.class);
+        assertEquals("Billy", result.firstName);
+    }
+
+    /*
+    /**********************************************************
+    /* Test methods, other
+    /**********************************************************
+     */
+    
     /**
      * Test [databind#815], problems with ObjectNode, naming strategy
      */
     public void testNamingWithObjectNode() throws Exception
     {
-        ObjectMapper m = new ObjectMapper();
-        m.setPropertyNamingStrategy(PropertyNamingStrategy.LOWER_CASE);
+        ObjectMapper m = new ObjectMapper()
+            .setPropertyNamingStrategy(PropertyNamingStrategy.LOWER_CASE);
         ClassWithObjectNodeField result =
             m.readValue(
                 "{ \"id\": \"1\", \"json\": { \"foo\": \"bar\", \"baz\": \"bing\" } }",
@@ -332,16 +370,17 @@ public void testNamingWithObjectNode() throws Exception
         assertEquals("bing", result.json.path("baz").asText());
     }
 
-    public void testExplicitRename() throws Exception {
+    public void testExplicitRename() throws Exception
+    {
       ObjectMapper m = new ObjectMapper();
-      m.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
+      m.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
       m.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
       // by default, renaming will not take place on explicitly named fields
       assertEquals(aposToQuotes("{'firstName':'Peter','lastName':'Venkman','user_age':'35'}"),
           m.writeValueAsString(new ExplicitBean()));
 
       m = new ObjectMapper();
-      m.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
+      m.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
       m.enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
       m.enable(MapperFeature.ALLOW_EXPLICIT_PROPERTY_RENAMING);
       // w/ feature enabled, ALL property names should get re-written

src/test/java/com/fasterxml/jackson/failing/ImplicitParamsForCreator806Test.java

@@ -42,7 +42,7 @@ public void testImplicitNameWithNamingStrategy() throws Exception
     {
         ObjectMapper mapper = new ObjectMapper()
             .setAnnotationIntrospector(new MyParamIntrospector())
-            .setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES)
+            .setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE)
             ;
         XY value = mapper.readValue(aposToQuotes("{'param_name0':1,'param_name1':2}"), XY.class);
         assertNotNull(value);