to #3789, toJavaObject IgnoreSetNullValue

core/src/main/java/com/alibaba/fastjson2/reader/ObjectReaderAdapter.java

@@ -578,8 +578,10 @@ public class ObjectReaderAdapter<T>
                 FieldReader fieldReader = fieldReaders[i];
                 Object fieldValue = map.get(fieldReader.fieldName);
                 if (fieldValue == null) {
+                    if ((features2 & JSONReader.Feature.IgnoreSetNullValue.mask) != 0 || !map.containsKey(fieldReader.fieldName)) {
                         continue;
                     }
+                }
 
                 if (fieldReader.field != null && Modifier.isFinal(fieldReader.field.getModifiers())) {
                     try {
@@ -592,7 +594,7 @@ public class ObjectReaderAdapter<T>
                     }
                 }
 
-                if (fieldValue.getClass() == fieldReader.fieldType) {
+                if (fieldValue == null || fieldValue.getClass() == fieldReader.fieldType) {
                     fieldReader.accept(object, fieldValue);
                 } else {
                     if ((fieldReader instanceof FieldReaderList)

core/src/test/java/com/alibaba/fastjson2/issues_3700/Issue3789.java

@@ -0,0 +1,35 @@
+package com.alibaba.fastjson2.issues_3700;
+
+import com.alibaba.fastjson2.JSONException;
+import com.alibaba.fastjson2.JSONObject;
+import com.alibaba.fastjson2.JSONReader;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class Issue3789 {
+    @Test
+    public void test() {
+        String name = "abc";
+
+        assertThrows(JSONException.class,
+                () -> JSONObject.of("name", null).to(Bean.class));
+
+        assertNull(JSONObject.of("name", null).to(Bean.class, JSONReader.Feature.IgnoreSetNullValue).name);
+        assertNull(JSONObject.of().to(Bean.class).name);
+
+        assertEquals(name,
+                JSONObject.of("name", name).to(Bean.class).name);
+    }
+
+    public static class Bean {
+        private String name;
+
+        public void setName(String name) {
+            if (name == null) {
+                throw new IllegalArgumentException();
+            }
+            this.name = name;
+        }
+    }
+}