add short date formatter

CHANGELOG.md

@@ -20,6 +20,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 to the page field for cases where the page numbers are missing. [#7019](https://github.com/JabRef/jabref/issues/7019)
 - We added a new fetcher to enable users to search jstor.org [#6627](https://github.com/JabRef/jabref/issues/6627)
 - We added an error message in the New Entry dialog that is shown in case the fetcher did not find anything . [#7000](https://github.com/JabRef/jabref/issues/7000)
+- We added a new formatter to output shorthand month format. [#6579](https://github.com/JabRef/jabref/issues/6579)
 
 ### Changed
 

src/main/java/org/jabref/logic/layout/LayoutEntry.java

@@ -74,6 +74,7 @@
 import org.jabref.logic.layout.format.RisAuthors;
 import org.jabref.logic.layout.format.RisKeywords;
 import org.jabref.logic.layout.format.RisMonth;
+import org.jabref.logic.layout.format.ShortMonthFormatter;
 import org.jabref.logic.layout.format.ToLowerCase;
 import org.jabref.logic.layout.format.ToUpperCase;
 import org.jabref.logic.layout.format.WrapContent;
@@ -542,6 +543,8 @@ private LayoutFormatter getLayoutFormatterByName(String name) {
                 return new MarkdownFormatter();
             case "CSLType":
                 return new CSLType();
+            case "ShortMonth":
+                return new ShortMonthFormatter();
             default:
                 return null;
         }

src/main/java/org/jabref/logic/layout/format/ShortMonthFormatter.java

@@ -0,0 +1,15 @@
+package org.jabref.logic.layout.format;
+
+import java.util.Optional;
+
+import org.jabref.logic.layout.LayoutFormatter;
+import org.jabref.model.entry.Month;
+
+public class ShortMonthFormatter implements LayoutFormatter {
+
+    @Override
+    public String format(String fieldText) {
+        Optional<Month> month = Month.parse(fieldText);
+        return month.map(Month::getShortName).orElse("");
+    }
+}

src/test/java/org/jabref/logic/layout/format/ShortMonthFormatterTest.java

@@ -0,0 +1,24 @@
+package org.jabref.logic.layout.format;
+
+import org.jabref.logic.layout.LayoutFormatter;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ShortMonthFormatterTest {
+
+    private LayoutFormatter formatter;
+
+    @BeforeEach
+    public void setUp() {
+        formatter = new ShortMonthFormatter();
+    }
+
+    @Test
+    public void testFormat() {
+        assertEquals("jan", formatter.format("01"));
+        assertEquals("jan", formatter.format("Januar"));
+    }
+}