Fix #4659: remove TypeFactory.defaultInstance() (#4747)

Author: cowtowncoder

release-notes/VERSION

@@ -68,6 +68,7 @@ Versions: 3.x (for earlier see VERSION-2.x)
  (contributed by Joo-Hyuk K)
 #4589: Remove `MapperFeature.SORT_CREATOR_PROPERTIES_BY_DECLARATION_ORDER` from 3.0;
   make logic default
+#4659: Remove use of global static `TypeFactory` singleton from 3.0
 #4664: Change `EnumNamingStrategy.convertEnumToExternalName()` to take `MapperConfig` argument-
  (contributed by Joo-Hyuk K)
 - Remove `MappingJsonFactory`

src/main/java/tools/jackson/databind/cfg/MapperBuilder.java

@@ -550,10 +550,10 @@ public TypeFactory typeFactory() {
     }
 
     /**
-     * Overridable method for changing default {@link SubtypeResolver} instance to use
+     * Overridable method for changing default {@link TypeFactory} instance to use
      */
     protected TypeFactory _defaultTypeFactory() {
-        return TypeFactory.defaultInstance();
+        return TypeFactory.createDefaultInstance();
     }
 
     public ClassIntrospector classIntrospector() {

src/main/java/tools/jackson/databind/ser/jdk/JDKArraySerializers.java

@@ -44,10 +44,8 @@ public static ValueSerializer<?> findStandardImpl(Class<?> cls) {
         return _arraySerializers.get(cls.getName());
     }
 
-    // @since 2.19
-    @SuppressWarnings("deprecation")
     static JavaType simpleElementType(Class<?> elemClass) {
-        return TypeFactory.defaultInstance().uncheckedSimpleType(elemClass);
+        return TypeFactory.unsafeSimpleType(elemClass);
     }
 
     /*

src/main/java/tools/jackson/databind/ser/jdk/StringArraySerializer.java

@@ -25,8 +25,7 @@ public class StringArraySerializer
     /* Note: not clean in general, but we are betting against
      * anyone re-defining properties of String.class here...
      */
-    @SuppressWarnings("deprecation")
-    private final static JavaType VALUE_TYPE = TypeFactory.defaultInstance().uncheckedSimpleType(String.class);
+    private final static JavaType VALUE_TYPE = TypeFactory.unsafeSimpleType(String.class);
 
     public final static StringArraySerializer instance = new StringArraySerializer();
 

src/main/java/tools/jackson/databind/type/TypeFactory.java

@@ -75,13 +75,6 @@ public final class TypeFactory
 
     private final static JavaType[] NO_TYPES = new JavaType[0];
 
-    /**
-     * Globally shared singleton. Not accessed directly; non-core
-     * code should use per-ObjectMapper instance (via configuration objects).
-     * Core Jackson code uses {@link #defaultInstance} for accessing it.
-     */
-    protected final static TypeFactory instance = new TypeFactory();
-
     protected final static TypeBindings EMPTY_BINDINGS = TypeBindings.emptyBindings();
 
     /*
@@ -161,7 +154,10 @@ public final class TypeFactory
     protected final TypeModifier[] _modifiers;
 
     /**
-     * ClassLoader used by this factory [databind#624].
+     * ClassLoader used by this factory.
+     *<p>
+     * See <a href="https://github.com/FasterXML/jackson-databind/issues/624">[databind#624]</a>
+     * for details.
      */
     protected final ClassLoader _classLoader;
 
@@ -171,8 +167,9 @@ public final class TypeFactory
     /**********************************************************************
      */
 
-    private TypeFactory() {
-        this(new SimpleLookupCache<Object,JavaType>(16, DEFAULT_MAX_CACHE_SIZE));
+    // NOTE: was private in Jackson 2.x
+    public TypeFactory() {
+        this(new SimpleLookupCache<>(16, DEFAULT_MAX_CACHE_SIZE));
     }
 
     protected TypeFactory(LookupCache<Object,JavaType> typeCache) {
@@ -187,6 +184,16 @@ protected TypeFactory(LookupCache<Object,JavaType> typeCache,
         _classLoader = classLoader;
     }
 
+    /**
+     * Method used to construct a new default/standard {@code TypeFactory}
+     * instance; an instance which has
+     * no custom configuration. Used by {@code ObjectMapper} to
+     * get the default factory when constructed.
+     *
+     * @since 3.0
+     */
+    public static TypeFactory createDefaultInstance() { return new TypeFactory(); }
+
     /**
      * Need to make a copy on snapshot() to avoid accidental leakage via cache.
      * In theory only needed if there are modifiers, but since these are lightweight
@@ -242,13 +249,6 @@ public TypeFactory withCache(LookupCache<Object,JavaType> cache)  {
         return new TypeFactory(cache, _modifiers, _classLoader);
     }
 
-    /**
-     * Method used to access the globally shared instance, which has
-     * no custom configuration. Used by <code>ObjectMapper</code> to
-     * get the default factory when constructed.
-     */
-    public static TypeFactory defaultInstance() { return instance; }
-
     /**
      * Method that will clear up any cached type definitions that may
      * be cached by this {@link TypeFactory} instance.
@@ -306,6 +306,27 @@ public static Class<?> rawClass(Type t) {
                 +ClassUtil.classNameOf(t));
     }
 
+    // 12-Oct-2024, tatu: not ideal but has to do for now -- maybe can re-factor somehow
+    //   before 3.0 release?
+    /**
+     * Method by core databind for constructing "simple" {@link JavaType}s in cases
+     * where there is no access to {@link TypeFactory} AND it is known that full
+     * resolution of the type is not needed (generally when type is just a placeholder).
+     * NOT TO BE USED by application code!
+     *
+     * @since 3.0
+     */
+    public static JavaType unsafeSimpleType(Class<?> cls) {
+        // 18-Oct-2015, tatu: Not sure how much problem missing super-type info is here
+        // Copied from `_constructSimple()`:
+        JavaType t = _findWellKnownSimple(cls);
+        if (t == null) {
+            // copied from `_newSimpleType()`
+            return new SimpleType(cls, EMPTY_BINDINGS, null, null);
+        }
+        return t;
+    }
+
     /*
     /**********************************************************************
     /* Low-level helper methods
@@ -748,22 +769,15 @@ public JavaType constructType(TypeReference<?> typeRef)
      *
      * @param type Type of a {@link java.lang.reflect.Member} to resolve
      * @param contextBindings Type bindings from the context, often class in which
-     *     member declared but may be subtype of that type (to bind actual bound
-     *     type parametrers). Not used if {@code type} is of type {@code Class<?>}.
+     *     member declared but may be sub-type of that type (to bind actual bound
+     *     type parameters). Not used if {@code type} is of type {@code Class<?>}.
      *
      * @return Fully resolved type
      */
     public JavaType resolveMemberType(Type type, TypeBindings contextBindings) {
         return _fromAny(null, type, contextBindings);
     }
 
-    // 20-Apr-2018, tatu: Really should get rid of this...
-    @Deprecated // since 2.8
-    public JavaType uncheckedSimpleType(Class<?> cls) {
-        // 18-Oct-2015, tatu: Not sure how much problem missing super-type info is here
-        return _constructSimple(cls, EMPTY_BINDINGS, null, null);
-    }
-
     /*
     /**********************************************************************
     /* Direct factory methods
@@ -1221,7 +1235,7 @@ protected JavaType _unknownType() {
      * type is one of common, "well-known" types, instances of which are
      * pre-constructed and do not need dynamic caching.
      */
-    protected JavaType _findWellKnownSimple(Class<?> clz) {
+    protected static JavaType _findWellKnownSimple(Class<?> clz) {
         if (clz.isPrimitive()) {
             if (clz == CLS_BOOL) return CORE_TYPE_BOOL;
             if (clz == CLS_INT) return CORE_TYPE_INT;

src/test/java/tools/jackson/databind/testutil/DatabindTestUtil.java

@@ -45,6 +45,8 @@ public String findImplicitPropertyName(MapperConfig<?> config,
 
     private final static Object SINGLETON_OBJECT = new Object();
 
+    private final static TypeFactory DEFAULT_TYPE_FACTORY = TypeFactory.createDefaultInstance();
+
     /*
     /**********************************************************************
     /* A sample documents
@@ -561,7 +563,7 @@ public static TimeZone getUTCTimeZone() {
     // Separated out since "default" TypeFactory instance handling differs
     // between 2.x and 3.x
     public static TypeFactory defaultTypeFactory() {
-        return TypeFactory.defaultInstance();
+        return DEFAULT_TYPE_FACTORY;
     }
 
     protected JsonParser createParserUsingReader(String input)