Adding support for Java 17 & Groovy Records (#130)

Author: Shounaks

jr-objects/src/main/java/com/fasterxml/jackson/jr/ob/JSON.java

@@ -261,6 +261,17 @@ public enum Feature
          */
         USE_IS_GETTERS(true, true),
 
+        /**
+         * Feature that provides serialization support for Groovy & Java 17 records, by allowing
+         * reading of "non-get-getters" in a class, (like for a field named <code>amount</code>
+         * the getter would be <code>amount()</code>).
+         *
+         * @implNote <p>Feature is disabled by default for backward compatibility.</p>
+         *
+         * @since 2.17
+         */
+        USE_FIELD_MATCHING_GETTERS(false,true),
+
         /**
          * Feature that enables use of public fields instead of setters and getters,
          * in cases where no setter/getter is available.

jr-objects/src/main/java/com/fasterxml/jackson/jr/ob/impl/BeanPropertyIntrospector.java

@@ -1,9 +1,7 @@
 package com.fasterxml.jackson.jr.ob.impl;
 
-import java.lang.reflect.Constructor;
-import java.lang.reflect.Field;
-import java.lang.reflect.Method;
-import java.lang.reflect.Modifier;
+import java.lang.reflect.*;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.TreeMap;
 
@@ -98,17 +96,22 @@ private static void _introspect(Class<?> currType, Map<String, PropBuilder> prop
         _introspect(currType.getSuperclass(), props, features);
 
         final boolean noStatics = JSON.Feature.INCLUDE_STATIC_FIELDS.isDisabled(features);
+        final boolean isFieldNameGettersEnabled = JSON.Feature.USE_FIELD_MATCHING_GETTERS.isEnabled(features);
+
+        final Map<String, Field> fieldNameMap = isFieldNameGettersEnabled ? new HashMap<>() : null;
+
         // then public fields (since 2.8); may or may not be ultimately included
         // but at this point still possible
         for (Field f : currType.getDeclaredFields()) {
-            if (!Modifier.isPublic(f.getModifiers())
-                    || f.isEnumConstant() || f.isSynthetic()) {
+            if (fieldNameMap != null) {
+                fieldNameMap.put(f.getName(), f);
+            }
+            if (!Modifier.isPublic(f.getModifiers()) || f.isEnumConstant() || f.isSynthetic()) {
                 continue;
             }
             // Only include static members if (a) inclusion feature enabled and
             // (b) not final (cannot deserialize final fields)
-            if (Modifier.isStatic(f.getModifiers())
-                    && (noStatics || Modifier.isFinal(f.getModifiers()))) {
+            if (Modifier.isStatic(f.getModifiers()) && (noStatics || Modifier.isFinal(f.getModifiers()))) {
                 continue;
             }
             _propFrom(props, f.getName()).withField(f);
@@ -145,6 +148,17 @@ private static void _introspect(Class<?> currType, Map<String, PropBuilder> prop
                         name = decap(name.substring(2));
                         _propFrom(props, name).withIsGetter(m);
                     }
+                } else if (isFieldNameGettersEnabled) {
+                    // 10-Mar-2024: [jackson-jr#94]:
+                    //  This will allow getters with field name as their getters,
+                    // like the ones generated by Groovy (or JDK 17 for Records).
+                    // If method name matches with field name, & method return
+                    // type matches the field type only then it can be considered a getter.
+                    Field field = fieldNameMap.get(name);
+                    if (field != null && Modifier.isPublic(m.getModifiers()) && m.getReturnType().equals(field.getType())) {
+                        // NOTE: do NOT decap, field name should be used as-is
+                        _propFrom(props, name).withGetter(m);
+                    }
                 }
             } else if (argTypes.length == 1) { // setter?
                 // Non-public setters are fine if we can force access, don't yet check

jr-objects/src/test/java/com/fasterxml/jackson/jr/ob/ReadRecordLikeTest.java

@@ -0,0 +1,37 @@
+package com.fasterxml.jackson.jr.ob;
+
+// For [jackson-jr#94]: support for Serializing JDK 17/Groovy records
+// (minimal one; full test in separate test package)
+//
+// @since 2.17
+public class ReadRecordLikeTest extends TestBase
+{
+    static class RecordLike94 {
+        int count = 3;
+        int STATUS = 500;
+        int foobar;
+
+        // should be discovered:
+        public int count() { return count; }
+        // likewise:
+        public int STATUS() { return STATUS; }
+
+        // should NOT be discovered (takes argument(s))
+        public int foobar(int value) {
+            foobar = value;
+            return value;
+        }
+
+        // also not to be discovered
+        public int mismatched() { return 42; }
+    }
+
+    public void testRecordLikePOJO() throws Exception
+    {
+        // By default, do not auto-detect "record-style" accessors
+        assertEquals("{}", JSON.std.asString(new RecordLike94()));
+
+        assertEquals(a2q("{'STATUS':500,'count':3}"), JSON.std.with(JSON.Feature.USE_FIELD_MATCHING_GETTERS)
+                .asString(new RecordLike94()));
+    }
+}

jr-test-module/src/test/groovy/GroovyObjectSupportTest.groovy

@@ -2,6 +2,11 @@ import com.fasterxml.jackson.jr.ob.JSON
 import org.junit.Assert
 import org.junit.Test
 
+/**
+ * A minor note on running/debugging this test on local, if you are using intellij, please
+ * change `<packaging>pom</packaging>` to `<packaging>bundle</packaging>`. this is causing
+ * some issue with the IDE.
+ */
 class GroovyObjectSupportTest {
     @Test
     void testSimpleGroovyObject() throws Exception {

jr-test-module/src/test/groovy/GroovyRecordsTest.groovy

@@ -0,0 +1,67 @@
+import com.fasterxml.jackson.jr.ob.JSON
+import org.junit.Assert
+import org.junit.Test
+
+/**
+ * A minor note on running/debugging this test on local, if you are using intellij, please
+ * change `<packaging>pom</packaging>` to `<packaging>bundle</packaging>`. this is causing
+ * some issue with the IDE.
+*/
+class GroovyRecordsTest {
+
+    @Test
+    void testRecord() throws Exception {
+        /* We need to use this since build (8, ubuntu-20.04), will fail Map.of() was added in Java 9*/
+        def map = new HashMap<String, String>()
+        map.put("foo", "bar")
+
+        def json = JSON.builder().enable(JSON.Feature.USE_FIELD_MATCHING_GETTERS).build().asString(new Cow("foo", map))
+        def expected = """{"message":"foo","object":{"foo":"bar"}}"""
+        Assert.assertEquals(expected, json)
+    }
+
+    @Test
+    void testRecordEquivalentObjects() throws Exception {
+        def expected = """{"message":"foo","object":{"foo":"bar"}}"""
+
+        /* We need to use this since build (8, ubuntu-20.04), will fail Map.of() was added in Java 9*/
+        def map = new HashMap<String, String>()
+        map.put("foo", "bar")
+
+        def json = JSON.builder().enable(JSON.Feature.USE_FIELD_MATCHING_GETTERS).build().asString(new SimpleGroovyObject("foo", map))
+        Assert.assertEquals(expected, json)
+
+        def json2 = JSON.builder().enable(JSON.Feature.USE_FIELD_MATCHING_GETTERS).build().asString(new GroovyObjectWithNamedGetters("foo", map))
+        Assert.assertEquals(expected, json2)
+    }
+}
+
+class SimpleGroovyObject {
+    public final String message
+    public final Map<String, String> object
+
+    SimpleGroovyObject(String message, Map<String, String> object) {
+        this.message = message
+        this.object = object
+    }
+}
+
+class GroovyObjectWithNamedGetters {
+    private final String message
+    private final Map<String, String> object
+
+    GroovyObjectWithNamedGetters(String message, Map<String, String> object) {
+        this.message = message
+        this.object = object
+    }
+
+    String message() {
+        return message
+    }
+
+    Map<String, String> object() {
+        return object
+    }
+}
+
+record Cow(String message, Map<String, String> object) {}

jr-test-module/src/test/java/Java17RecordTest.java

@@ -0,0 +1,22 @@
+import com.fasterxml.jackson.jr.ob.JSON;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.Map;
+
+/**
+ * This test is in test module since the JDK version to be tested is higher than other, and hence supports Records.
+ */
+public class Java17RecordTest {
+
+    @Test
+    public void testJava14RecordSupport() throws IOException {
+        var expectedString = "{\"message\":\"MOO\",\"object\":{\"Foo\":\"Bar\"}}";
+        var json = JSON.builder().enable(JSON.Feature.USE_FIELD_MATCHING_GETTERS).build().asString(new Cow("MOO", Map.of("Foo", "Bar")));
+        Assert.assertEquals(expectedString, json);
+    }
+
+    record Cow(String message, Map<String, String> object) {
+    }
+}

release-notes/CREDITS-2.x

@@ -57,5 +57,7 @@ Julian Honnen (@jhonnen)
 * Contributed fix for #93: Skip serialization of `groovy.lang.MetaClass` values
   to avoid `StackOverflowError`
  (2.17.0)
+* Constributed implementation of #94: Support for serializing Java Records
+ (2.17.0)
 * Contributed impl for #100: Add support for `java.time` (Java 8 date/time) types
  (2.17.0)

release-notes/VERSION-2.x

@@ -17,6 +17,8 @@ Not yet released
  (contributed by @Shounaks) 
 #51: Duplicate key detection does not work for (simple) Trees
  (contributed by @Shounaks) 
+#94: Support for serializing Java Records
+ (implementation contributed by @Shounaks) 
 #131: Add mechanism for `JacksonJrExtension`s to access state of `JSON.Feature`s
 
 2.17.0-rc1 (26-Feb-2024)