Support for array delegate creator

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

@@ -1225,7 +1225,7 @@ public Object deserializeFromArray(JsonParser p, DeserializationContext ctxt) th
     {
         if (_delegateDeserializer != null) {
             try {
-                Object bean = _valueInstantiator.createUsingDelegate(ctxt, _delegateDeserializer.deserialize(p, ctxt));
+                Object bean = _valueInstantiator.createUsingArrayDelegate(ctxt, _delegateDeserializer.deserialize(p, ctxt));
                 if (_injectables != null) {
                     injectValues(ctxt, bean);
                 }

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

@@ -171,6 +171,15 @@ public Object createUsingDelegate(DeserializationContext ctxt, Object delegate)
                 getValueTypeDesc());
     }
 
+    /**
+     * Method to called to create value instance from JSON Array using
+     * an intermediate "delegate" value to pass to createor method
+     */
+    public Object createUsingArrayDelegate(DeserializationContext ctxt, Object delegate) throws IOException {
+        throw ctxt.mappingException("Can not instantiate value of type %s using delegate",
+                getValueTypeDesc());
+    }
+
     /*
     /**********************************************************
     /* Instantiation methods for JSON scalar types

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

@@ -28,6 +28,7 @@ public class CreatorCollector
     protected final static int C_BOOLEAN = 5;
     protected final static int C_DELEGATE = 6;
     protected final static int C_PROPS = 7;
+    protected final static int C_ARRAY_DELEGATE = 8;
 
     protected final static String[] TYPE_DESCS = new String[] {
         "default",
@@ -50,7 +51,7 @@ public class CreatorCollector
      * 
      * @since 2.5
      */
-    protected final AnnotatedWithParams[] _creators = new AnnotatedWithParams[8];
+    protected final AnnotatedWithParams[] _creators = new AnnotatedWithParams[9];
 
     /**
      * Bitmask of creators that were explicitly marked as creators; false for auto-detected
@@ -65,6 +66,8 @@ public class CreatorCollector
     // when there are injectable values along with delegate:
     protected SettableBeanProperty[] _delegateArgs;
 
+    protected SettableBeanProperty[] _arrayDelegateArgs;
+
     protected SettableBeanProperty[] _propertyBasedArgs;
 
     protected AnnotatedParameter _incompleteParameter;
@@ -84,32 +87,13 @@ public CreatorCollector(BeanDescription beanDesc, MapperConfig<?> config)
 
     public ValueInstantiator constructValueInstantiator(DeserializationConfig config)
     {
-        JavaType delegateType;
-        boolean maybeVanilla = !_hasNonDefaultCreator;
-
-        if (maybeVanilla || (_creators[C_DELEGATE] == null)) {
-            delegateType = null;
-        } else {
-            // need to find type...
-            int ix = 0;
-            if (_delegateArgs != null) {
-                for (int i = 0, len = _delegateArgs.length; i < len; ++i) {
-                    if (_delegateArgs[i] == null) { // marker for delegate itself
-                        ix = i;
-                        break;
-                    }
-                }
-            }
-            delegateType = _creators[C_DELEGATE].getParameterType(ix);
-        }
-
+        final JavaType delegateType = _computeDelegateType(_creators[C_DELEGATE], _delegateArgs);
+        final JavaType arrayDelegateType = _computeDelegateType(_creators[C_ARRAY_DELEGATE], _arrayDelegateArgs);
         final JavaType type = _beanDesc.getType();
 
         // Any non-standard creator will prevent; with one exception: int-valued constructor
         // that standard containers have can be ignored
-        maybeVanilla &= !_hasNonDefaultCreator;
-
-        if (maybeVanilla) {
+        if (!_hasNonDefaultCreator) {
             /* 10-May-2014, tatu: If we have nothing special, and we are dealing with one
              *   of "well-known" types, can create a non-reflection-based instantiator.
              */
@@ -129,6 +113,7 @@ public ValueInstantiator constructValueInstantiator(DeserializationConfig config
         inst.configureFromObjectSettings(_creators[C_DEFAULT],
                 _creators[C_DELEGATE], delegateType, _delegateArgs,
                 _creators[C_PROPS], _propertyBasedArgs);
+        inst.configureFromArraySettings(_creators[C_ARRAY_DELEGATE], arrayDelegateType, _arrayDelegateArgs);
         inst.configureFromStringCreator(_creators[C_STRING]);
         inst.configureFromIntCreator(_creators[C_INT]);
         inst.configureFromLongCreator(_creators[C_LONG]);
@@ -176,8 +161,13 @@ public void addBooleanCreator(AnnotatedWithParams creator, boolean explicit) {
     public void addDelegatingCreator(AnnotatedWithParams creator, boolean explicit,
             SettableBeanProperty[] injectables)
     {
-        verifyNonDup(creator, C_DELEGATE, explicit);
-        _delegateArgs = injectables;
+        if (creator.getParameterType(0).isCollectionLikeType()) {
+            verifyNonDup(creator, C_ARRAY_DELEGATE, explicit);
+            _arrayDelegateArgs = injectables;
+        } else {
+            verifyNonDup(creator, C_DELEGATE, explicit);
+            _delegateArgs = injectables;
+        }
     }
 
     public void addPropertyCreator(AnnotatedWithParams creator, boolean explicit,
@@ -276,6 +266,25 @@ public boolean hasPropertyBasedCreator() {
     /**********************************************************
      */
 
+    private JavaType _computeDelegateType(AnnotatedWithParams creator, SettableBeanProperty[] delegateArgs)
+    {
+        if (!_hasNonDefaultCreator || (creator == null)) {
+            return null;
+        } else {
+            // need to find type...
+            int ix = 0;
+            if (delegateArgs != null) {
+                for (int i = 0, len = delegateArgs.length; i < len; ++i) {
+                    if (delegateArgs[i] == null) { // marker for delegate itself
+                        ix = i;
+                        break;
+                    }
+                }
+            }
+            return creator.getParameterType(ix);
+        }
+    }
+
     private <T extends AnnotatedMember> T _fixAccess(T member)
     {
         if (member != null && _canFixAccess) {

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

@@ -45,6 +45,12 @@ public class StdValueInstantiator
     protected JavaType _delegateType;
     protected AnnotatedWithParams _delegateCreator;
     protected SettableBeanProperty[] _delegateArguments;
+
+    // // // Array delegate construction
+
+    protected JavaType _arrayDelegateType;
+    protected AnnotatedWithParams _arrayDelegateCreator;
+    protected SettableBeanProperty[] _arrayDelegateArguments;
 
     // // // Scalar construction
 
@@ -87,6 +93,10 @@ protected StdValueInstantiator(StdValueInstantiator src)
         _delegateType = src._delegateType;
         _delegateCreator = src._delegateCreator;
         _delegateArguments = src._delegateArguments;
+
+        _arrayDelegateType = src._arrayDelegateType;
+        _arrayDelegateCreator = src._arrayDelegateCreator;
+        _arrayDelegateArguments = src._arrayDelegateArguments;
 
         _fromStringCreator = src._fromStringCreator;
         _fromIntCreator = src._fromIntCreator;
@@ -112,6 +122,16 @@ public void configureFromObjectSettings(AnnotatedWithParams defaultCreator,
         _constructorArguments = constructorArgs;
     }
 
+    public void configureFromArraySettings(
+            AnnotatedWithParams arrayDelegateCreator,
+            JavaType arrayDelegateType,
+            SettableBeanProperty[] arrayDelegateArgs)
+    {
+        _arrayDelegateCreator = arrayDelegateCreator;
+        _arrayDelegateType = arrayDelegateType;
+        _arrayDelegateArguments = arrayDelegateArgs;
+    }
+
     public void configureFromStringCreator(AnnotatedWithParams creator) {
         _fromStringCreator = creator;
     }
@@ -232,30 +252,17 @@ public Object createFromObjectWith(DeserializationContext ctxt, Object[] args) t
     @Override
     public Object createUsingDelegate(DeserializationContext ctxt, Object delegate) throws IOException
     {
-        if (_delegateCreator == null) { // sanity-check; caller should check
-            throw new IllegalStateException("No delegate constructor for "+getValueTypeDesc());
-        }
-        try {
-            // First simple case: just delegate, no injectables
-            if (_delegateArguments == null) {
-                return _delegateCreator.call1(delegate);
-            }
-            // And then the case with at least one injectable...
-            final int len = _delegateArguments.length;
-            Object[] args = new Object[len];
-            for (int i = 0; i < len; ++i) {
-                SettableBeanProperty prop = _delegateArguments[i];
-                if (prop == null) { // delegate
-                    args[i] = delegate;
-                } else { // nope, injectable:
-                    args[i] = ctxt.findInjectableValue(prop.getInjectableValueId(), prop, null);
-                }
-            }
-            // and then try calling with full set of arguments
-            return _delegateCreator.call(args);
-        } catch (Throwable t) {
-            throw rewrapCtorProblem(ctxt, t);
+        return _createUsingDelegate(_delegateCreator, _delegateArguments, ctxt, delegate);
+    }
+
+    @Override
+    public Object createUsingArrayDelegate(DeserializationContext ctxt, Object delegate) throws IOException
+    {
+        if (_arrayDelegateCreator == null) { // sanity-check; caller should check
+            // fallback to the classic delegate creator
+            return createUsingDelegate(ctxt, delegate);
         }
+        return _createUsingDelegate(_arrayDelegateCreator, _arrayDelegateArguments, ctxt, delegate);
     }
 
     /*
@@ -441,4 +448,43 @@ protected JsonMappingException rewrapCtorProblem(DeserializationContext ctxt,
         }
         return wrapAsJsonMappingException(ctxt, t);
     }
+
+    /*
+    /**********************************************************
+    /* Helper methods
+    /**********************************************************
+     */
+
+    private Object _createUsingDelegate(
+            AnnotatedWithParams delegateCreator,
+            SettableBeanProperty[] delegateArguments,
+            DeserializationContext ctxt,
+            Object delegate)
+            throws IOException
+    {
+        if (delegateCreator == null) { // sanity-check; caller should check
+            throw new IllegalStateException("No delegate constructor for "+getValueTypeDesc());
+        }
+        try {
+            // First simple case: just delegate, no injectables
+            if (delegateArguments == null) {
+                return delegateCreator.call1(delegate);
+            }
+            // And then the case with at least one injectable...
+            final int len = delegateArguments.length;
+            Object[] args = new Object[len];
+            for (int i = 0; i < len; ++i) {
+                SettableBeanProperty prop = delegateArguments[i];
+                if (prop == null) { // delegate
+                    args[i] = delegate;
+                } else { // nope, injectable:
+                    args[i] = ctxt.findInjectableValue(prop.getInjectableValueId(), prop, null);
+                }
+            }
+            // and then try calling with full set of arguments
+            return delegateCreator.call(args);
+        } catch (Throwable t) {
+            throw rewrapCtorProblem(ctxt, t);
+        }
+    }
 }

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

@@ -0,0 +1,48 @@
+package com.fasterxml.jackson.databind.deser;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.util.List;
+import java.util.Map;
+
+public class TestObjectOrArrayDeserialization extends BaseMapTest {
+
+    public static class ArrayOrObject {
+        private final List<Object> objects;
+        private final Object object;
+
+        @JsonCreator public ArrayOrObject(List<Object> objects) {
+            this.objects = objects;
+            this.object = null;
+        }
+
+        @JsonCreator public ArrayOrObject(Object object) {
+            this.objects = null;
+            this.object = object;
+        }
+    }
+
+    public void testObjectCase() throws Exception {
+        ArrayOrObject arrayOrObject = new ObjectMapper().readValue("{}", ArrayOrObject.class);
+        assertNull("expected objects field to be null", arrayOrObject.objects);
+        assertNotNull("expected object field not to be null", arrayOrObject.object);
+    }
+
+    public void testEmptyArrayCase() throws Exception {
+        ArrayOrObject arrayOrObject = new ObjectMapper().readValue("[]", ArrayOrObject.class);
+        assertNotNull("expected objects field not to be null", arrayOrObject.objects);
+        assertTrue("expected objects field to be an empty list", arrayOrObject.objects.isEmpty());
+        assertNull("expected object field to be null", arrayOrObject.object);
+    }
+
+    public void testNotEmptyArrayCase() throws Exception {
+        ArrayOrObject arrayOrObject = new ObjectMapper().readValue("[{}, {}]", ArrayOrObject.class);
+        assertNotNull("expected objects field not to be null", arrayOrObject.objects);
+        assertEquals("expected objects field to have size 2", 2, arrayOrObject.objects.size());
+        assertNull("expected object field to be null", arrayOrObject.object);
+    }
+
+}