A fix for #1498 implementation to prevent regression failures wrt Exc…

…eption deserialization

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

@@ -155,7 +155,7 @@ public ConstructorDetector withRequireAnnotation(boolean state) {
  state, _allowJDKTypeCtors);
  }
 
- public ConstructorDetector withAllowJDKTypes(boolean state) {
+ public ConstructorDetector withAllowJDKTypeConstructors(boolean state) {
  return new ConstructorDetector(_singleArgMode,
  _requireCtorAnnotation, state);
  }
@@ -186,12 +186,31 @@ public boolean singleArgCreatorDefaultsToProperties() {
  return _singleArgMode == SingleArgConstructor.PROPERTIES;
  }
 
- public boolean allowImplicitCreators(Class<?> rawType) {
+ /**
+ * Accessor that combines calls to {@link #allowImplicitCreators} and
+ * {@link #allowJDKTypeConstructors} to determine whether implicit constructor
+ * detection should be enabled or not.
+ * 
+ * @param rawType Value type to consider
+ *
+ * @return True if implicit constructor detection should be enabled; false if not
+ */
+ public boolean shouldIntrospectorImplicitConstructors(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);
+ if (!_allowJDKTypeCtors) {
+ if (ClassUtil.isJDKClass(rawType)) {
+ // 18-Sep-2020, tatu: Looks like must make an exception for Exception
+ // types (ha!) -- at this point, single-String-arg constructor
+ // is to be auto-detected
+ if (!Throwable.class.isAssignableFrom(rawType)) {
+ return false;
+ }
+ }
+ }
+ return true;
  }
 }

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

@@ -252,16 +252,14 @@ protected ValueInstantiator _constructDefaultValueInstantiator(DeserializationCo
  throws JsonMappingException
  {
  final CreatorCollectionState ccState;
- final boolean findImplicit;
+ final ConstructorDetector ctorDetector;
 
  {
  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());
+ ctorDetector = config.getConstructorDetector();
 
  // 24-Sep-2014, tatu: Tricky part first; need to merge resolved property information
  // (which has creator parameters sprinkled around) with actual creator
@@ -278,7 +276,7 @@ protected ValueInstantiator _constructDefaultValueInstantiator(DeserializationCo
  }
 
  // Start with explicitly annotated factory methods
- _addExplicitFactoryCreators(ctxt, ccState, findImplicit);
+ _addExplicitFactoryCreators(ctxt, ccState, !ctorDetector.requireCtorAnnotation());
 
  // constructors only usable on concrete types:
  if (beanDesc.getType().isConcrete()) {
@@ -300,6 +298,9 @@ protected ValueInstantiator _constructDefaultValueInstantiator(DeserializationCo
  // TODO: look for `@JsonCreator` annotated ones, throw explicit exception?
  ;
  } else {
+ // 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
+ final boolean findImplicit = ctorDetector.shouldIntrospectorImplicitConstructors(beanDesc.getBeanClass());
  _addExplicitConstructorCreators(ctxt, ccState, findImplicit);
  if (ccState.hasImplicitConstructorCandidates()
  && !ccState.hasExplicitFactories() && !ccState.hasExplicitConstructors()) {

src/test/java/com/fasterxml/jackson/databind/exc/ExceptionDeserializationTest.java

@@ -56,7 +56,8 @@ static class MyNoArgException extends Exception
  public void testIOException() throws IOException
  {
  IOException ioe = new IOException("TEST");
- String json = MAPPER.writeValueAsString(ioe);
+ String json = MAPPER.writerWithDefaultPrettyPrinter()
+ .writeValueAsString(ioe);
  IOException result = MAPPER.readValue(json, IOException.class);
  assertEquals(ioe.getMessage(), result.getMessage());
  }