Add support for Java Record deserialization

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

@@ -14,6 +14,9 @@ public class BeanConstructors
 
     protected Constructor<?> _noArgsCtor;
 
+    // @since 2.18
+    protected Constructor<?> _recordCtor;
+
     protected Constructor<?> _intCtor;
     protected Constructor<?> _longCtor;
     protected Constructor<?> _stringCtor;
@@ -27,6 +30,12 @@ public BeanConstructors addNoArgsConstructor(Constructor<?> ctor) {
         return this;
     }
 
+    // @since 2.18
+    public BeanConstructors addRecordConstructor(Constructor<?> ctor) {
+        _recordCtor = ctor;
+        return this;
+    }
+
     public BeanConstructors addIntConstructor(Constructor<?> ctor) {
         _intCtor = ctor;
         return this;
@@ -46,6 +55,9 @@ public void forceAccess() {
         if (_noArgsCtor != null) {
             _noArgsCtor.setAccessible(true);
         }
+        if (_recordCtor != null) {
+            _recordCtor.setAccessible(true);
+        }
         if (_intCtor != null) {
             _intCtor.setAccessible(true);
         }
@@ -63,6 +75,14 @@ protected Object create() throws Exception {
         }
         return _noArgsCtor.newInstance((Object[]) null);
     }
+
+    // @since 2.18
+    protected Object createRecord(Object[] components) throws Exception {
+        if (_recordCtor == null) {
+            throw new IllegalStateException("Class "+_valueType.getName()+" does not have record constructor to use");
+        }
+        return _recordCtor.newInstance(components);
+    }
 
     protected Object create(String str) throws Exception {
         if (_stringCtor == null) {

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

@@ -68,6 +68,8 @@ private POJODefinition _introspectDefinition(Class<?> beanType,
                     } else if (argType == Long.class || argType == Long.TYPE) {
                         constructors.addLongConstructor(ctor);
                     }
+                } else if (RecordsHelpers.isRecordConstructor(beanType, ctor, propsByName)) {
+                    constructors.addRecordConstructor(ctor);
                 }
             }
         }

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

@@ -36,6 +36,8 @@ public class BeanReader
      */
     protected final BeanConstructors _constructors;
 
+    protected final boolean _isRecordType;
+
     /**
      * Constructors used for deserialization use case
      *
@@ -56,6 +58,7 @@ public BeanReader(Class<?> type, Map<String, BeanPropertyReader> props,
             aliasMapping = Collections.emptyMap();
         }
         _aliasMapping = aliasMapping;
+        _isRecordType = RecordsHelpers.isRecordType(type);
     }
 
     @Deprecated // since 2.17
@@ -155,6 +158,22 @@ public Object read(JSONReader r, JsonParser p) throws IOException
                 return _constructors.create(p.getLongValue());
             case START_OBJECT:
                 {
+                    // [jackson-jr#148] Record deser support (2.18)
+                    if (_isRecordType) {
+                        final List<Object> values = new ArrayList<>();
+
+                        String propName;
+                        for (; (propName = p.nextFieldName()) != null;) {
+                            BeanPropertyReader prop = findProperty(propName);
+                            if (prop == null) {
+                                handleUnknown(r, p, propName);
+                                continue;
+                            }
+                            values.add(prop.getReader().readNext(r, p));
+                        }
+                        return _constructors.createRecord(values.toArray());
+                    }
+                    // If not Record, need to use default (no-args) Constructors
                     Object bean = _constructors.create();
                     String propName;
                     final Object[] valueBuf = r._setterBuffer;

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

@@ -0,0 +1,76 @@
+package com.fasterxml.jackson.jr.ob.impl;
+
+import com.fasterxml.jackson.jr.ob.impl.POJODefinition.PropBuilder;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Map;
+
+/**
+ * Helper class to get Java Record metadata, from Java 8 (not using
+ * JDK 17 methods)
+ *
+ * @since 2.18
+ */
+public final class RecordsHelpers {
+    private static boolean supportsRecords;
+
+    private static Method getRecordComponentsMethod;
+    private static Method getTypeMethod;
+
+    static {
+        Method getRecordComponentsMethod;
+        Method getTypeMethod;
+
+        try {
+            getRecordComponentsMethod = Class.class.getMethod("getRecordComponents");
+            Class<?> recordComponentClass = Class.forName("java.lang.reflect.RecordComponent");
+            getTypeMethod = recordComponentClass.getMethod("getType");
+            supportsRecords = true;
+        } catch (Throwable t) {
+            getRecordComponentsMethod = null;
+            getTypeMethod = null;
+            supportsRecords = false;
+        }
+
+        RecordsHelpers.getRecordComponentsMethod = getRecordComponentsMethod;
+        RecordsHelpers.getTypeMethod = getTypeMethod;
+    }
+    private RecordsHelpers() {}
+
+    static boolean isRecordConstructor(Class<?> beanClass, Constructor<?> ctor, Map<String, PropBuilder> propsByName) {
+        if (!supportsRecords || !isRecordType(beanClass)) {
+            return false;
+        }
+
+        Class<?>[] parameterTypes = ctor.getParameterTypes();
+        if (parameterTypes.length != propsByName.size()) {
+            return false;
+        }
+
+        try {
+            Object[] recordComponents = (Object[]) getRecordComponentsMethod.invoke(beanClass);
+            Class<?>[] componentTypes = new Class<?>[recordComponents.length];
+            for (int i = 0; i < recordComponents.length; i++) {
+                Object recordComponent = recordComponents[i];
+                Class<?> type = (Class<?>) getTypeMethod.invoke(recordComponent);
+                componentTypes[i] = type;
+            }
+
+            for (int i = 0; i < parameterTypes.length; i++) {
+                if (parameterTypes[i] != componentTypes[i]) {
+                    return false;
+                }
+            }
+        } catch (IllegalAccessException | InvocationTargetException e) {
+            return false;
+        }
+        return true;
+    }
+
+    static boolean isRecordType(Class<?> cls) {
+        Class<?> parent = cls.getSuperclass();
+        return (parent != null) && "java.lang.Record".equals(parent.getName());
+    }
+}

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

@@ -462,31 +462,40 @@ protected BeanReader _resolveBeanForDeser(Class<?> raw, POJODefinition beanDef)
             final boolean useFields = JSON.Feature.USE_FIELDS.isEnabled(_features);
             for (int i = 0; i < len; ++i) {
                 POJODefinition.Prop rawProp = rawProps.get(i);
-                Method m = rawProp.setter;
-                Field f = useFields ? rawProp.field : null;
+                Method setter = rawProp.setter;
+                Field field = useFields ? rawProp.field : null;
 
-                if (m != null) {
+                if (setter != null) {
                     if (forceAccess) {
-                        m.setAccessible(true);
-                    } else if (!Modifier.isPublic(m.getModifiers())) {
+                        setter.setAccessible(true);
+                    } else if (!Modifier.isPublic(setter.getModifiers())) {
                         // access to non-public setters must be forced to be usable:
-                        m = null;
+                        setter = null;
                     }
                 }
-                // if no setter, field would do as well
-                if (m == null) {
-                    if (f == null) {
-                        continue;
+                if (RecordsHelpers.isRecordType(raw)) {
+                    try {
+                        field = raw.getDeclaredField(rawProp.name);
+                    } catch (NoSuchFieldException e) {
+                        throw new IllegalStateException("Cannot access field '" + rawProp.name
+                                + "' of record class `" + raw.getName() + "`", e);
                     }
-                    // fields should always be public, but let's just double-check
-                    if (forceAccess) {
-                        f.setAccessible(true);
-                    } else if (!Modifier.isPublic(f.getModifiers())) {
-                        continue;
+                } else {
+                    // if no setter, field would do as well
+                    if (setter == null) {
+                        if (field == null) {
+                            continue;
+                        }
+                        // fields should always be public, but let's just double-check
+                        if (forceAccess) {
+                            field.setAccessible(true);
+                        } else if (!Modifier.isPublic(field.getModifiers())) {
+                            continue;
+                        }
                     }
                 }
 
-                propMap.put(rawProp.name, new BeanPropertyReader(rawProp.name, f, m));
+                propMap.put(rawProp.name, new BeanPropertyReader(rawProp.name, field, setter));
 
                 // 25-Jan-2020, tatu: Aliases are bit different because we can not tie them into
                 //   specific reader instance, due to resolution of cyclic dependencies. Instead,

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

@@ -1,4 +1,5 @@
 import com.fasterxml.jackson.jr.ob.JSON;
+import com.fasterxml.jackson.jr.ob.JSON.Feature;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -12,9 +13,15 @@ public class Java17RecordTest {
 
     @Test
     public void testJava14RecordSupport() throws IOException {
+        JSON jsonParser = JSON.builder().enable(Feature.USE_FIELD_MATCHING_GETTERS).build();
         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")));
+        Cow expectedObject = new Cow("MOO", Map.of("Foo", "Bar"));
+
+        var json = jsonParser.asString(expectedObject);
         Assert.assertEquals(expectedString, json);
+
+        Cow object = jsonParser.beanFrom(Cow.class, json);
+        Assert.assertEquals(expectedObject, object);
     }
 
     record Cow(String message, Map<String, String> object) {

release-notes/CREDITS-2.x

@@ -65,3 +65,7 @@ Julian Honnen (@jhonnen)
   when using `JSON.treeFrom()`
  (2.17.1)
 
+Tomasz Gawęda (@TomaszGaweda)
+
+* Contributed #148: Add support for Java Record deserialization
+ (2.18.0)

release-notes/VERSION-2.x

@@ -13,7 +13,8 @@ Modules:
 
 2.18.0 (not yet released)
 
-No changes since 2.17
+#148: Add support for Java Record deserialization
+ (contributed by Tomasz G)
 
 2.17.1 (04-May-2024)