Fix #2692 (#5256)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -6,6 +6,8 @@ Project: jackson-databind
 
 Not yet released
 
+#2692: Should never call `set()` on setterless property during deserialization
+ (reported by @lbonco)
 #5237: Failing `@JsonMerge` with a custom Map with a `@JsonCreator` constructor
  (reported by @nlisker)
 #5242: Support "binary vectors": `@JsonFormat(shape = Shape.BINARY)` for

src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializer.java

@@ -480,7 +480,7 @@ protected Object _deserializeUsingPropertyBased(final JsonParser p, final Deseri
                 // 12-Aug-2025, tatu: [databind#5237] Mergeable properties need
                 //    special handling: must defer deserialization until POJO
                 //    is constructed.
-                if (prop instanceof MergingSettableBeanProperty) {
+                if (prop.isMerging()) {
                     TokenBuffer tb = ctxt.bufferForInputBuffering(p);
                     tb.copyCurrentStructure(p);
                     buffer.bufferMergingProperty(prop, tb);

src/main/java/com/fasterxml/jackson/databind/deser/SettableBeanProperty.java

@@ -342,6 +342,16 @@ public void markAsIgnorable() { /* nop */ }
      */
     public boolean isIgnorable() { return false; }
 
+    /**
+     * Whether this property requires merging of values (read-then-write)
+     *
+     * @since 2.20
+     */
+    public boolean isMerging() {
+        // Most are not merging so default to this implementation
+        return false;
+    }
+
     /*
     /**********************************************************
     /* BeanProperty impl

src/main/java/com/fasterxml/jackson/databind/deser/impl/MergingSettableBeanProperty.java

@@ -60,6 +60,11 @@ protected SettableBeanProperty withDelegate(SettableBeanProperty d) {
         return new MergingSettableBeanProperty(d, _accessor);
     }
 
+    @Override // since 2.20
+    public boolean isMerging() {
+        return true;
+    }
+
     /*
     /**********************************************************
     /* Deserialization methods

src/main/java/com/fasterxml/jackson/databind/deser/impl/SetterlessProperty.java

@@ -79,6 +79,11 @@ public void fixAccess(DeserializationConfig config) {
                 config.isEnabled(MapperFeature.OVERRIDE_PUBLIC_ACCESS_MODIFIERS));
     }
 
+    @Override // since 2.20
+    public boolean isMerging() {
+        return true;
+    }
+
     /*
     /**********************************************************
     /* BeanProperty impl

src/test/java/com/fasterxml/jackson/databind/deser/SetterlessPropertiesDeserTest.java

@@ -8,19 +8,17 @@
 
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.exc.MismatchedInputException;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
 
 import static org.junit.jupiter.api.Assertions.*;
 
-import static com.fasterxml.jackson.databind.testutil.DatabindTestUtil.jsonMapperBuilder;
-import static com.fasterxml.jackson.databind.testutil.DatabindTestUtil.verifyException;
-
 /**
- * Unit tests for verifying that feature requested
- * via [JACKSON-88] ("setterless collections") work as
+ * Unit tests for verifying that "setterless collections" work as
  * expected, similar to how Collections and Maps work
  * with JAXB.
  */
 public class SetterlessPropertiesDeserTest
+    extends DatabindTestUtil
 {
     static class CollectionBean
     {
@@ -48,17 +46,43 @@ public List<Integer> getList() {
         }
     }
 
+    static class DataBean2692
+    {
+        final String val;
+
+        @JsonCreator
+        public DataBean2692(@JsonProperty(value = "val") String val) {
+            super();
+            this.val = val;
+        }
+
+        public String getVal() {
+            return val;
+        }
+
+        public List<String> getList() {
+            return new ArrayList<>();
+        }
+
+        @Override
+        public String toString() {
+            return "DataBean [val=" + val + "]";
+        }
+    }
+    
     /*
     /**********************************************************
     /* Unit tests
     /**********************************************************
      */
 
+    private final ObjectMapper MAPPER = newJsonMapper();
+
     @Test
     public void testSimpleSetterlessCollectionOk()
         throws Exception
     {
-        CollectionBean result = new ObjectMapper().readValue
+        CollectionBean result = MAPPER.readValue
             ("{\"values\":[ \"abc\", \"def\" ]}", CollectionBean.class);
         List<String> l = result._values;
         assertEquals(2, l.size());
@@ -74,10 +98,9 @@ public void testSimpleSetterlessCollectionOk()
     public void testSimpleSetterlessCollectionFailure()
         throws Exception
     {
-        ObjectMapper m = new ObjectMapper();
         // by default, it should be enabled
-        assertTrue(m.isEnabled(MapperFeature.USE_GETTERS_AS_SETTERS));
-        m = jsonMapperBuilder()
+        assertTrue(MAPPER.isEnabled(MapperFeature.USE_GETTERS_AS_SETTERS));
+        ObjectMapper m = jsonMapperBuilder()
                 .configure(MapperFeature.USE_GETTERS_AS_SETTERS, false)
                 .build();
         assertFalse(m.isEnabled(MapperFeature.USE_GETTERS_AS_SETTERS));
@@ -98,7 +121,7 @@ public void testSimpleSetterlessCollectionFailure()
     public void testSimpleSetterlessMapOk()
         throws Exception
     {
-        MapBean result = new ObjectMapper().readValue
+        MapBean result = MAPPER.readValue
             ("{\"values\":{ \"a\": 15, \"b\" : -3 }}", MapBean.class);
         Map<String,Integer> m = result._values;
         assertEquals(2, m.size());
@@ -136,4 +159,14 @@ public void testSetterlessPrecedence() throws Exception
         assertNotNull(value);
         assertEquals(3, value.values.size());
     }
+
+    // [databind#2692]
+    @Test
+    void issue2692() throws Exception {
+        ObjectMapper om = newJsonMapper();
+        String json = "{\"list\":[\"11\"],\"val\":\"VAL2\"}";
+        DataBean2692 out = om.readerFor(DataBean2692.class).readValue(json);
+        // System.out.println("this is ko" + out);
+        assertNotNull(out);
+    }
 }