Fix #1498

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -175,6 +175,8 @@ Fernando Otero (zeitos@github)
 Lovro Pandžić (lpandzic@github)
   * Reported #421: @JsonCreator not used in case of multiple creators with parameter names
    (2.5.0)
+  * Requested #1498: Allow handling of single-arg constructor as property based by default
+   (2.12.0)
 
 Adam Stroud (adstro@github)
   * Contributed	#576: Add fluent API for adding mixins

release-notes/VERSION-2.x

@@ -16,6 +16,8 @@ Project: jackson-databind
  (reported by Mike G; fix contributed by Ville K)
 #1296: Add `@JsonIncludeProperties(propertyNames)` (reverse of `@JsonIgnoreProperties`)
  (contributed Baptiste P)
+#1498: Allow handling of single-arg constructor as property based by default
+ (requested by Lovro P)
 #1852: Allow case insensitive deserialization of String value into
   `boolean`/`Boolean` (esp for Excel)
  (requested by Patrick J)

src/main/java/com/fasterxml/jackson/databind/cfg/ConstructorDetector.java

@@ -1,5 +1,7 @@
 package com.fasterxml.jackson.databind.cfg;
 
+import com.fasterxml.jackson.databind.util.ClassUtil;
+
 /**
  * Configurable handler used to select aspects of selecting
  * constructor to use as "Creator" for POJOs.
@@ -143,17 +145,17 @@ protected ConstructorDetector(SingleArgConstructor singleArgMode) {
         this(singleArgMode, false, false);
     }
 
-    protected ConstructorDetector withSingleArgMode(SingleArgConstructor singleArgMode) {
+    public ConstructorDetector withSingleArgMode(SingleArgConstructor singleArgMode) {
         return new ConstructorDetector(singleArgMode,
                 _requireCtorAnnotation, _allowJDKTypeCtors);
     }
 
-    protected ConstructorDetector withRequireAnnotation(boolean state) {
+    public ConstructorDetector withRequireAnnotation(boolean state) {
         return new ConstructorDetector(_singleArgMode,
                 state, _allowJDKTypeCtors);
     }
 
-    protected ConstructorDetector withAllowJDKTypes(boolean state) {
+    public ConstructorDetector withAllowJDKTypes(boolean state) {
         return new ConstructorDetector(_singleArgMode,
                 _requireCtorAnnotation, state);
     }
@@ -183,4 +185,13 @@ public boolean singleArgCreatorDefaultsToDelegating() {
     public boolean singleArgCreatorDefaultsToProperties() {
         return _singleArgMode == SingleArgConstructor.PROPERTIES;
     }
+
+    public boolean allowImplicitCreators(Class<?> rawType) {
+        // May not allow implicit creator introspection at all:
+        if (_requireCtorAnnotation) {
+            return false;
+        }
+        // But if it is allowed, may further limit use for JDK types
+        return _allowJDKTypeCtors || !ClassUtil.isJDKClass(rawType);
+    }
 }

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

@@ -252,12 +252,16 @@ protected ValueInstantiator _constructDefaultValueInstantiator(DeserializationCo
         throws JsonMappingException
     {
         final CreatorCollectionState ccState;
+        final boolean findImplicit;
 
         {
             final DeserializationConfig config = ctxt.getConfig();
             // need to construct suitable visibility checker:
             final VisibilityChecker<?> vchecker = config.getDefaultVisibilityChecker(beanDesc.getBeanClass(),
                     beanDesc.getClassInfo());
+            // 18-Sep-2020, tatu: Although by default implicit introspection is allowed, 2.12
+            //   has settings to prevent that either generally, or at least for JDK types
+            findImplicit = config.getConstructorDetector().allowImplicitCreators(beanDesc.getBeanClass());
 
             // 24-Sep-2014, tatu: Tricky part first; need to merge resolved property information
             //  (which has creator parameters sprinkled around) with actual creator
@@ -274,7 +278,7 @@ protected ValueInstantiator _constructDefaultValueInstantiator(DeserializationCo
         }
 
         // Start with explicitly annotated factory methods
-        _addExplicitFactoryCreators(ctxt, ccState);
+        _addExplicitFactoryCreators(ctxt, ccState, findImplicit);
 
         // constructors only usable on concrete types:
         if (beanDesc.getType().isConcrete()) {
@@ -296,16 +300,16 @@ protected ValueInstantiator _constructDefaultValueInstantiator(DeserializationCo
                 // TODO: look for `@JsonCreator` annotated ones, throw explicit exception?
                 ;
             } else {
-                _addExplicitConstructorCreators(ctxt, ccState);
-                if (!ccState.hasExplicitFactories() && !ccState.hasExplicitConstructors()
-                        && ccState.hasImplicitConstructorCandidates()) {
+                _addExplicitConstructorCreators(ctxt, ccState, findImplicit);
+                if (ccState.hasImplicitConstructorCandidates()
+                        && !ccState.hasExplicitFactories() && !ccState.hasExplicitConstructors()) {
                     _addImplicitConstructorCreators(ctxt, ccState, ccState.implicitConstructorCandidates());
                 }
             }
         }
         // and finally, implicitly found factory methods if nothing explicit found
-        if (!ccState.hasExplicitFactories() && !ccState.hasExplicitConstructors()
-                && ccState.hasImplicitFactoryCandidates()) {
+        if (ccState.hasImplicitFactoryCandidates()
+                && !ccState.hasExplicitFactories() && !ccState.hasExplicitConstructors()) {
             _addImplicitFactoryCreators(ctxt, ccState, ccState.implicitFactoryCandidates());
         }
         return ccState.creators.constructValueInstantiator(ctxt);
@@ -418,7 +422,7 @@ protected void _addRecordConstructor(DeserializationContext ctxt, CreatorCollect
      */
 
     protected void _addExplicitConstructorCreators(DeserializationContext ctxt,
-            CreatorCollectionState ccState)
+            CreatorCollectionState ccState, boolean findImplicit)
                     throws JsonMappingException
     {
         final BeanDescription beanDesc = ccState.beanDesc;
@@ -444,7 +448,7 @@ protected void _addExplicitConstructorCreators(DeserializationContext ctxt,
             }
             if (creatorMode == null) {
                 // let's check Visibility here, to avoid further processing for non-visible?
-                if (vchecker.isCreatorVisible(ctor)) {
+                if (findImplicit && vchecker.isCreatorVisible(ctor)) {
                     ccState.addImplicitConstructorCandidate(CreatorCandidate.construct(intr,
                             ctor, creatorParams.get(ctor)));
                 }
@@ -623,7 +627,7 @@ protected void _addImplicitConstructorCreators(DeserializationContext ctxt,
      */
 
     protected void _addExplicitFactoryCreators(DeserializationContext ctxt,
-            CreatorCollectionState ccState)
+            CreatorCollectionState ccState, boolean findImplicit)
         throws JsonMappingException
     {
         final BeanDescription beanDesc = ccState.beanDesc;
@@ -638,7 +642,7 @@ protected void _addExplicitFactoryCreators(DeserializationContext ctxt,
             final int argCount = factory.getParameterCount();
             if (creatorMode == null) {
                 // Only potentially accept 1-argument factory methods
-                if ((argCount == 1) && vchecker.isCreatorVisible(factory)) {
+                if (findImplicit && (argCount == 1) && vchecker.isCreatorVisible(factory)) {
                     ccState.addImplicitFactoryCandidate(CreatorCandidate.construct(intr, factory, null));
                 }
                 continue;

src/main/java/com/fasterxml/jackson/databind/util/ClassUtil.java

@@ -1131,14 +1131,21 @@ public static boolean isJacksonStdImpl(Class<?> implClass) {
     }
 
     /**
-     * Some aspects of handling need to be changed for JDK types (and possibly
-     * some extensions under {@code javax.}?): for example, forcing of access
+     * Accessor for checking whether given {@code Class} is under Java package
+     * of {@code java.*} or {@code javax.*} (including all sub-packages).
+     *<p>
+     * Added since some aspects of handling need to be changed for JDK types (and
+     * possibly some extensions under {@code javax.}?): for example, forcing of access
      * will not work well for future JDKs (12 and later).
+     *<p>
+     * Note: in Jackson 2.11 only returned true for {@code java.*} (and not {@code javax.*});
+     * was changed in 2.12.
      *
      * @since 2.11
      */
     public static boolean isJDKClass(Class<?> rawType) {
-        return rawType.getName().startsWith("java.");
+        final String clsName = rawType.getName();
+        return clsName.startsWith("java.") || clsName.startsWith("javax.");
     }
 
     /*

src/test/java/com/fasterxml/jackson/databind/deser/creators/ConstructorDetector1498Test.java

@@ -67,7 +67,7 @@ public SingleArg2CtorsNotAnnotated(@ImplicitName("value") long value) {
             v = (int) (value * 2);
         }
     }
-    
+
     static class SingleArg1498 {
         final int _bar;
 
@@ -77,10 +77,22 @@ static class SingleArg1498 {
         }
     }
 
+    static class TwoArgsNotAnnotated {
+        protected int _a, _b;
+
+        public TwoArgsNotAnnotated(@ImplicitName("a") int a, @ImplicitName("b") int b) {
+            _a = a;
+            _b = b;
+        }
+    }
+
     private final ObjectMapper MAPPER_PROPS = mapperFor(ConstructorDetector.USE_PROPERTIES_BASED);
     private final ObjectMapper MAPPER_DELEGATING = mapperFor(ConstructorDetector.USE_DELEGATING);
     private final ObjectMapper MAPPER_EXPLICIT = mapperFor(ConstructorDetector.EXPLICIT_ONLY);
 
+    private final ObjectMapper MAPPER_MUST_ANNOTATE = mapperFor(ConstructorDetector.DEFAULT
+            .withRequireAnnotation(true));
+
     /*
     /**********************************************************************
     /* Test methods, selecting from 1-arg constructors, properties-based
@@ -96,7 +108,6 @@ public void test1ArgDefaultsToPropertiesNonAnnotated() throws Exception
 
     public void test1ArgDefaultsToPropertiesNoMode() throws Exception
     {
-        // and similarly for mode-less
         SingleArgNoMode value = MAPPER_PROPS.readValue(a2q("{'value' : 137 }"),
                 SingleArgNoMode.class);
         assertEquals(137, value.v);
@@ -105,12 +116,20 @@ public void test1ArgDefaultsToPropertiesNoMode() throws Exception
     // And specific test for original [databind#1498]
     public void test1ArgDefaultsToPropertiesIssue1498() throws Exception
     {
-        // and similarly for mode-less
         SingleArg1498 value = MAPPER_PROPS.readValue(a2q("{'bar' : 404 }"),
                 SingleArg1498.class);
         assertEquals(404, value._bar);
     }
 
+    // This was working already but verify
+    public void testMultiArgAsProperties() throws Exception
+    {
+        TwoArgsNotAnnotated value = MAPPER_PROPS.readValue(a2q("{'a' : 3, 'b':4 }"),
+                TwoArgsNotAnnotated.class);
+        assertEquals(3, value._a);
+        assertEquals(4, value._b);
+    }
+
     // 18-Sep-2020, tatu: For now there is a problematic case of multiple eligible
     //   choices; not cleanly solvable for 2.12
     public void test1ArgDefaultsToPropsMultipleCtors() throws Exception
@@ -166,7 +185,7 @@ public void test1ArgDefaultsToHeuristics() throws Exception
 
     /*
     /**********************************************************************
-    /* Test methods, selecting from 1-arg constructors, explicit fail
+    /* Test methods, selecting from 1-arg constructors, explicit fails
     /**********************************************************************
      */
 
@@ -197,6 +216,32 @@ public void test1ArgFailsNoMode() throws Exception
         }
     }
 
+    public void test1ArgRequiresAnnotation() throws Exception
+    {
+        // First: if there is a 0-arg ctor, fine, must use that
+        SingleArgNotAnnotated value = MAPPER_MUST_ANNOTATE.readValue("{ }",
+                SingleArgNotAnnotated.class);
+        assertEquals(new SingleArgNotAnnotated().v, value.v);
+
+        // But if no such ctor, will fail
+        try {
+            MAPPER_MUST_ANNOTATE.readValue(" { } ", SingleArg1498.class);
+            fail("Should not pass");
+        } catch (InvalidDefinitionException e) {
+            verifyException(e, "no Creators, like default constructor");
+        }
+    }
+
+    public void testMultiArgRequiresAnnotation() throws Exception
+    {
+        try {
+            MAPPER_MUST_ANNOTATE.readValue(" { } ", TwoArgsNotAnnotated.class);
+            fail("Should not pass");
+        } catch (InvalidDefinitionException e) {
+            verifyException(e, "no Creators, like default constructor");
+        }
+    }
+
     /*
     /**********************************************************************
     /* Helper methods