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Add LowerCamelCase EnumNamingStrategy
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@lbenedetto
lbenedetto committed Aug 13, 2024
1 parent 5e0deda commit 8342429
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Showing 2 changed files with 102 additions and 22 deletions.
112 changes: 96 additions & 16 deletions src/main/java/com/fasterxml/jackson/databind/EnumNamingStrategies.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,18 +9,53 @@ public class EnumNamingStrategies {

private EnumNamingStrategies() {}

/**
* Words other than first are capitalized and no separator is used between words.
* See {@link EnumNamingStrategies.LowerCamelCaseStrategy} for details.
*<p>
* Example external property names would be "numberValue", "namingStrategy", "theDefiniteProof".
*/
public static final EnumNamingStrategy LOWER_CAMEL_CASE = LowerCamelCaseStrategy.INSTANCE;

/**
* Words are capitalized and no separator is used between words.
* See {@link EnumNamingStrategies.UpperCamelCaseStrategy} for details.
*<p>
* Example external property names would be "NumberValue", "NamingStrategy", "TheDefiniteProof".
*/
public static final EnumNamingStrategy UPPER_CAMEL_CASE = UpperCamelCaseStrategy.INSTANCE;

/**
* @since 2.15
* @deprecated Since 2.19 use {@link LowerCamelCaseStrategy} instead.
*/
@Deprecated(since = "2.19", forRemoval = true)
public static class CamelCaseStrategy implements EnumNamingStrategy {
/**
* An instance of {@link LowerCamelCaseStrategy} for reuse.
*
* @since 2.15
*/
public static final LowerCamelCaseStrategy INSTANCE = new LowerCamelCaseStrategy();

@Override
public String convertEnumToExternalName(String enumName) {
return LOWER_CAMEL_CASE.convertEnumToExternalName(enumName);
}
}

/**
* <p>
* An implementation of {@link EnumNamingStrategy} that converts enum names in the typical upper
* snake case format to camel case format. This implementation follows three rules
* snake case format to lower camel case format. This implementation follows three rules
* described below.
*
* <ol>
* <li>converts any character preceded by an underscore into upper case character,
* regardless of its original case (upper or lower).</li>
* <li>converts any character NOT preceded by an underscore into a lower case character,
* regardless of its original case (upper or lower).</li>
* <li>converts contiguous sequence of underscores into a single underscore.</li>
* <li>removes all underscores.</li>
* </ol>
*
* WARNING: Naming conversion conflicts caused by underscore usage should be handled by client.
Expand All @@ -29,7 +64,7 @@ private EnumNamingStrategies() {}
*
* <p>
* These rules result in the following example conversions from upper snakecase names
* to camelcase names.
* to lower camelcase names.
* <ul>
* <li>"USER_NAME" is converted into "userName"</li>
* <li>"USER______NAME" is converted into "userName"</li>
Expand All @@ -43,19 +78,19 @@ private EnumNamingStrategies() {}
* <li>"Username" is converted into "username"</li>
* </ul>
*
* @since 2.15
* @since 2.19
*/
public static class CamelCaseStrategy implements EnumNamingStrategy {
public static class LowerCamelCaseStrategy implements EnumNamingStrategy {

/**
* An intance of {@link CamelCaseStrategy} for reuse.
* An instance of {@link LowerCamelCaseStrategy} for reuse.
*
* @since 2.15
* @since 2.19
*/
public static final CamelCaseStrategy INSTANCE = new CamelCaseStrategy();
public static final LowerCamelCaseStrategy INSTANCE = new LowerCamelCaseStrategy();

/**
* @since 2.15
* @since 2.19
*/
@Override
public String convertEnumToExternalName(String enumName) {
Expand Down Expand Up @@ -104,7 +139,7 @@ private static String normalizeWord(String word) {
return word;
}
return new StringBuilder(length)
.append(charToUpperCaseIfLower(word.charAt(0)))
.append(Character.toUpperCase(word.charAt(0)))
.append(toLowerCase(word.substring(1)))
.toString();
}
Expand All @@ -113,17 +148,62 @@ private static String toLowerCase(String string) {
int length = string.length();
StringBuilder builder = new StringBuilder(length);
for (int i = 0; i < length; i++) {
builder.append(charToLowerCaseIfUpper(string.charAt(i)));
builder.append(Character.toLowerCase(string.charAt(i)));
}
return builder.toString();
}
}

private static char charToUpperCaseIfLower(char c) {
return Character.isLowerCase(c) ? Character.toUpperCase(c) : c;
}
/**
* <p>
* An implementation of {@link EnumNamingStrategy} that converts enum names in the typical upper
* snake case format to upper camel case format. This implementation follows three rules
* described below.
*
* <ol>
* <li>converts any character preceded by an underscore into upper case character,
* regardless of its original case (upper or lower).</li>
* <li>converts any character NOT preceded by an underscore into a lower case character,
* regardless of its original case (upper or lower).</li>
* <li>converts the first char in the string, regardless of any underscores, to uppercase</li>
* <li>removes all underscores.</li>
* </ol>
*
* WARNING: Naming conversion conflicts caused by underscore usage should be handled by client.
* e.g. Both <code>PEANUT_BUTTER</code>, <code>PEANUT__BUTTER</code> are converted into "PeanutButter".
* And "PeanutButter" will be deserialized into enum with smaller <code>Enum.ordinal()</code> value.
*
* <p>
* These rules result in the following example conversions from upper snakecase names
* to upper camelcase names.
* <ul>
* <li>"USER_NAME" is converted into "UserName"</li>
* <li>"USER______NAME" is converted into "UserName"</li>
* <li>"USERNAME" is converted into "Username"</li>
* <li>"User__Name" is converted into "UserName"</li>
* <li>"_user_name" is converted into "UserName"</li>
* <li>"_user_name_s" is converted into "UserNameS"</li>
* <li>"__Username" is converted into "Username"</li>
* <li>"__username" is converted into "Username"</li>
* <li>"username" is converted into "Username"</li>
* <li>"Username" is converted into "Username"</li>
* </ul>
*
* @since 2.19
*/
public static class UpperCamelCaseStrategy implements EnumNamingStrategy {

private static char charToLowerCaseIfUpper(char c) {
return Character.isUpperCase(c) ? Character.toLowerCase(c) : c;
/**
* An instance of {@link LowerCamelCaseStrategy} for reuse.
*
* @since 2.19
*/
public static final UpperCamelCaseStrategy INSTANCE = new UpperCamelCaseStrategy();

@Override
public String convertEnumToExternalName(String enumName) {
var lowerCamelCase = LOWER_CAMEL_CASE.convertEnumToExternalName(enumName);
return PropertyNamingStrategies.UpperCamelCaseStrategy.INSTANCE.translate(lowerCamelCase);
}
}
}
12 changes: 6 additions & 6 deletions src/test/java/com/fasterxml/jackson/databind/introspect/EnumNamingStrategiesTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,14 +20,14 @@
public class EnumNamingStrategiesTest extends DatabindTestUtil {

/**
* Test casess for {@link com.fasterxml.jackson.databind.EnumNamingStrategies.CamelCaseStrategy}.
* Test cases for {@link com.fasterxml.jackson.databind.EnumNamingStrategies.LowerCamelCaseStrategy}.
*
* <p>
* Each <code>Object[]</code> element is composed of <code>{input, expectedOutput}</code>.
*
* @since 2.15
*/
final static List<String[]> CAMEL_CASE_NAME_TRANSLATIONS = Arrays.asList(new String[][]{
final static List<String[]> LOWER_CAMEL_CASE_NAME_TRANSLATIONS = Arrays.asList(new String[][]{
// Empty values
{null, null},
{"", ""},
Expand Down Expand Up @@ -116,18 +116,18 @@ public class EnumNamingStrategiesTest extends DatabindTestUtil {

/**
* Unit test to verify the implementation of
* {@link com.fasterxml.jackson.databind.EnumNamingStrategies.CamelCaseStrategy#convertEnumToExternalName(String)}
* {@link com.fasterxml.jackson.databind.EnumNamingStrategies.LowerCamelCaseStrategy#convertEnumToExternalName(String)}
* without the context of an ObjectMapper.
*
* @since 2.15
*/
@Test
public void testCamelCaseStrategyStandAlone() {
for (String[] pair : CAMEL_CASE_NAME_TRANSLATIONS) {
public void testLowerCamelCaseStrategyStandAlone() {
for (String[] pair : LOWER_CAMEL_CASE_NAME_TRANSLATIONS) {
final String input = pair[0];
final String expected = pair[1];

String actual = EnumNamingStrategies.CamelCaseStrategy.INSTANCE
String actual = EnumNamingStrategies.LOWER_CAMEL_CASE
.convertEnumToExternalName(input);

assertEquals(expected, actual);
Expand Down

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