Add treeToValue(TreeNode, JavaType) overload in ObjectMapper

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java

@@ -3256,7 +3256,7 @@ public <T> T treeToValue(TreeNode n, Class<T> valueType)
             // 25-Jan-2019, tatu: [databind#2220] won't prevent existing coercions here
             // Simple cast when we just want to cast to, say, ObjectNode
             if (TreeNode.class.isAssignableFrom(valueType)
-                    && valueType.isAssignableFrom(n.getClass())) {
+                     && valueType.isAssignableFrom(n.getClass())) {
                 return (T) n;
             }
             final JsonToken tt = n.asToken();
@@ -3286,6 +3286,45 @@ public <T> T treeToValue(TreeNode n, Class<T> valueType)
         }
     }
 
+    /**
+     * Same as {@link #treeToValue(TreeNode, Class)} but target type specified
+     * using fully resolved {@link JavaType}.
+     *
+     * @since 2.13
+     */
+    @SuppressWarnings("unchecked")
+    public <T> T treeToValue(TreeNode n, JavaType valueType)
+        throws IllegalArgumentException,
+            JsonProcessingException
+    {
+        // Implementation copied from the type-erased variant
+        if (n == null) {
+            return null;
+        }
+        try {
+            if (valueType.isTypeOrSubTypeOf(TreeNode.class)
+                    && valueType.isTypeOrSuperTypeOf(n.getClass())) {
+                return (T) n;
+            }
+            final JsonToken tt = n.asToken();
+            if (tt == JsonToken.VALUE_EMBEDDED_OBJECT) {
+                if (n instanceof POJONode) {
+                    Object ob = ((POJONode) n).getPojo();
+                    if ((ob == null) || valueType.isTypeOrSuperTypeOf(ob.getClass())) {
+                        return (T) ob;
+                    }
+                }
+            }
+            return (T) readValue(treeAsTokens(n), valueType);
+        } catch (JsonProcessingException e) {
+            // 12-Nov-2020, tatu: These can legit happen, during conversion, especially
+            //   with things like Builders that validate arguments.
+            throw e;
+        } catch (IOException e) { // should not occur, no real i/o...
+            throw new IllegalArgumentException(e.getMessage(), e);
+        }
+    }
+
     /**
      * Method that is reverse of {@link #treeToValue}: it
      * will convert given Java value (usually bean) into its

src/main/java/com/fasterxml/jackson/databind/ObjectReader.java

@@ -1975,7 +1975,11 @@ public <T> T treeToValue(TreeNode n, Class<T> valueType) throws JsonProcessingEx
         }
     }
 
-    // @since 2.13
+    /**
+     * Same as {@link #treeToValue(TreeNode, Class)} but with type-resolved target value type.
+     *
+     * @since 2.13
+     */
     public <T> T treeToValue(TreeNode n, JavaType valueType) throws JsonProcessingException
     {
         _assertNotNull("n", n);

src/main/java/com/fasterxml/jackson/databind/deser/std/ReferenceTypeDeserializer.java

@@ -126,6 +126,11 @@ public Object getEmptyValue(DeserializationContext ctxt) throws JsonMappingExcep
         return getNullValue(ctxt);
     }
 
+    @Override
+    public Object getAbsentValue(DeserializationContext ctxt) throws JsonMappingException {
+        return null;
+    }
+
     public abstract T referenceValue(Object contents);
 
     /**

src/test/java/com/fasterxml/jackson/databind/convert/TestBeanConversions.java

@@ -4,14 +4,12 @@
 import java.util.Map;
 
 import com.fasterxml.jackson.core.JsonParser;
-import com.fasterxml.jackson.core.TreeNode;
 
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
 import com.fasterxml.jackson.databind.exc.InvalidFormatException;
 import com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException;
-import com.fasterxml.jackson.databind.node.ObjectNode;
 import com.fasterxml.jackson.databind.util.StdConverter;
 
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
@@ -197,17 +195,7 @@ public void testConvertUsingCast() throws Exception
         // should just cast...
         assertSame(str, result);
     }
-    
-    // [Issue-11]: simple cast, for Tree
-    public void testNodeConvert() throws Exception
-    {
-        ObjectNode src = (ObjectNode) MAPPER.readTree("{}");
-        TreeNode node = src;
-        ObjectNode result = MAPPER.treeToValue(node, ObjectNode.class);
-        // should just cast...
-        assertSame(src, result);
-    }
-    
+
     private void _convertAndVerifyPoint(ObjectMapper m)
     {
         final PointZ input = new PointZ(1, 2, 3);

src/test/java/com/fasterxml/jackson/databind/node/TestConversions.java

@@ -166,16 +166,23 @@ public void testTreeToValue() throws Exception
         Root r1 = mapper.treeToValue(root, Root.class);
         assertNotNull(r1);
         assertEquals(13, r1.leaf.value);
+
+        // ... also JavaType
+        r1 = mapper.treeToValue(root, mapper.constructType(Root.class));
+        assertEquals(13, r1.leaf.value);
     }
 
     // [databind#1208]: should coerce POJOs at least at root level
     public void testTreeToValueWithPOJO() throws Exception
     {
         Calendar c = Calendar.getInstance();
         c.setTime(new java.util.Date(0));
-        ValueNode pojoNode = MAPPER.getNodeFactory().pojoNode(c);        
+        final ValueNode pojoNode = MAPPER.getNodeFactory().pojoNode(c);
         Calendar result = MAPPER.treeToValue(pojoNode, Calendar.class);
-        assertNotNull(result);
+        assertEquals(result.getTimeInMillis(), c.getTimeInMillis());
+
+        // and same with JavaType
+        result = MAPPER.treeToValue(pojoNode, MAPPER.constructType(Calendar.class));
         assertEquals(result.getTimeInMillis(), c.getTimeInMillis());
     }
 
@@ -328,10 +335,32 @@ public void testConversionsOfNull() throws Exception
         Object pojo = MAPPER.treeToValue(n, Root.class);
         assertNull(pojo);
 
+        pojo = MAPPER.treeToValue(n, MAPPER.constructType(Root.class));
+        assertNull(pojo);
+        
         // [databind#2972]
         AtomicReference<?> result = MAPPER.treeToValue(NullNode.instance,
                 AtomicReference.class);
         assertNotNull(result);
         assertNull(result.get());
+
+        result = MAPPER.treeToValue(NullNode.instance,
+                MAPPER.constructType(AtomicReference.class));
+        assertNotNull(result);
+        assertNull(result.get());
+    }
+
+    // Simple cast, for Tree
+    public void testNodeConvert() throws Exception
+    {
+        ObjectNode src = (ObjectNode) MAPPER.readTree("{}");
+        TreeNode node = src;
+        ObjectNode result = MAPPER.treeToValue(node, ObjectNode.class);
+        // should just cast...
+        assertSame(src, result);
+
+        // ditto w/ JavaType
+        result = MAPPER.treeToValue(node, MAPPER.constructType(ObjectNode.class));
+        assertSame(src, result);
     }
 }