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General data-binding functionality for Jackson: works on core streaming API
There is a newer version: 2.18.1
package com.fasterxml.jackson.databind;

import java.io.*;
import java.lang.reflect.Type;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.text.DateFormat;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicReference;

import com.fasterxml.jackson.annotation.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.core.io.CharacterEscapes;
import com.fasterxml.jackson.core.io.SegmentedStringWriter;
import com.fasterxml.jackson.core.type.ResolvedType;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.core.util.*;
import com.fasterxml.jackson.databind.cfg.*;
import com.fasterxml.jackson.databind.deser.*;
import com.fasterxml.jackson.databind.exc.MismatchedInputException;
import com.fasterxml.jackson.databind.introspect.*;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitorWrapper;
import com.fasterxml.jackson.databind.jsontype.*;
import com.fasterxml.jackson.databind.jsontype.impl.LaissezFaireSubTypeValidator;
import com.fasterxml.jackson.databind.jsontype.impl.StdSubtypeResolver;
import com.fasterxml.jackson.databind.jsontype.impl.StdTypeResolverBuilder;
import com.fasterxml.jackson.databind.node.*;
import com.fasterxml.jackson.databind.ser.*;
import com.fasterxml.jackson.databind.type.*;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.RootNameLookup;
import com.fasterxml.jackson.databind.util.StdDateFormat;
import com.fasterxml.jackson.databind.util.TokenBuffer;

/**
 * ObjectMapper provides functionality for reading and writing JSON,
 * either to and from basic POJOs (Plain Old Java Objects), or to and from
 * a general-purpose JSON Tree Model ({@link JsonNode}), as well as
 * related functionality for performing conversions.
 * It is also highly customizable to work both with different styles of JSON
 * content, and to support more advanced Object concepts such as
 * polymorphism and Object identity.
 * ObjectMapper also acts as a factory for more advanced {@link ObjectReader}
 * and {@link ObjectWriter} classes.
 * Mapper (and {@link ObjectReader}s, {@link ObjectWriter}s it constructs) will
 * use instances of {@link JsonParser} and {@link JsonGenerator}
 * for implementing actual reading/writing of JSON.
 * Note that although most read and write methods are exposed through this class,
 * some of the functionality is only exposed via {@link ObjectReader} and
 * {@link ObjectWriter}: specifically, reading/writing of longer sequences of
 * values is only available through {@link ObjectReader#readValues(InputStream)}
 * and {@link ObjectWriter#writeValues(OutputStream)}.
 *
Simplest usage is of form:
  final ObjectMapper mapper = new ObjectMapper(); // can use static singleton, inject: just make sure to reuse!
  MyValue value = new MyValue();
  // ... and configure
  File newState = new File("my-stuff.json");
  mapper.writeValue(newState, value); // writes JSON serialization of MyValue instance
  // or, read
  MyValue older = mapper.readValue(new File("my-older-stuff.json"), MyValue.class);

  // Or if you prefer JSON Tree representation:
  JsonNode root = mapper.readTree(newState);
  // and find values by, for example, using a {@link com.fasterxml.jackson.core.JsonPointer} expression:
  int age = root.at("/personal/age").getValueAsInt(); 

 *
 * The main conversion API is defined in {@link ObjectCodec}, so that
 * implementation details of this class need not be exposed to
 * streaming parser and generator classes. Usage via {@link ObjectCodec} is,
 * however, usually only for cases where dependency to {@link ObjectMapper} is
 * either not possible (from Streaming API), or undesireable (when only relying
 * on Streaming API).
 *
 
 * Mapper instances are fully thread-safe provided that ALL configuration of the
 * instance occurs before ANY read or write calls. If configuration of a mapper instance
 * is modified after first usage, changes may or may not take effect, and configuration
 * calls themselves may fail.
 * If you need to use different configuration, you have two main possibilities:
 *

 * Construct and use {@link ObjectReader} for reading, {@link ObjectWriter} for writing.
 *    Both types are fully immutable and you can freely create new instances with different
 *    configuration using either factory methods of {@link ObjectMapper}, or readers/writers
 *    themselves. Construction of new {@link ObjectReader}s and {@link ObjectWriter}s is
 *    a very light-weight operation so it is usually appropriate to create these on per-call
 *    basis, as needed, for configuring things like optional indentation of JSON.
 *  
 * If the specific kind of configurability is not available via {@link ObjectReader} and
 *   {@link ObjectWriter}, you may need to use multiple {@link ObjectMapper} instead (for example:
 *   you cannot change mix-in annotations on-the-fly; or, set of custom (de)serializers).
 *   To help with this usage, you may want to use method {@link #copy()} which creates a clone
 *   of the mapper with specific configuration, and allows configuration of the copied instance
 *   before it gets used. Note that {@link #copy} operation is as expensive as constructing
 *   a new {@link ObjectMapper} instance: if possible, you should still pool and reuse mappers
 *   if you intend to use them for multiple operations.
 *  
 * 
 *
 * Note on caching: root-level deserializers are always cached, and accessed
 * using full (generics-aware) type information. This is different from
 * caching of referenced types, which is more limited and is done only
 * for a subset of all deserializer types. The main reason for difference
 * is that at root-level there is no incoming reference (and hence no
 * referencing property, no referral information or annotations to
 * produce differing deserializers), and that the performance impact
 * greatest at root level (since it'll essentially cache the full
 * graph of deserializers involved).
 *

 * Notes on security: use "default typing" feature (see {@link #enableDefaultTyping()})
 * is a potential security risk, if used with untrusted content (content generated by
 * untrusted external parties). If so, you may want to construct a custom 
 * {@link TypeResolverBuilder} implementation to limit possible types to instantiate,
 * (using {@link #setDefaultTyping}).
 */
public class ObjectMapper
    extends ObjectCodec
    implements Versioned,
        java.io.Serializable // as of 2.1
{
    private static final long serialVersionUID = 2L; // as of 2.9

    /*
    /**********************************************************
    /* Helper classes, enums
    /**********************************************************
     */

    /**
     * Enumeration used with {@link ObjectMapper#activateDefaultTyping(PolymorphicTypeValidator)}
     * to specify what kind of types (classes) default typing should
     * be used for. It will only be used if no explicit type information
     * is found, but this enumeration further limits subset of those types.
     *

     * Since 2.4 there are special exceptions for JSON Tree model
     * types (sub-types of {@link TreeNode}: default typing is never
     * applied to them.
     * Since 2.8(.4) additional checks are made to avoid attempts at default
     * typing primitive-valued properties.
     *

     * NOTE: use of Default Typing can be a potential security risk if incoming
     * content comes from untrusted sources, and it is recommended that this
     * is either not done, or, if enabled, make sure to {@code activateDefaultTyping(...)}
     * methods that take {@link PolymorphicTypeValidator} that limits applicability
     * to known trusted types.
     */
    public enum DefaultTyping {
        /**
         * This value means that only properties that have
         * {@link java.lang.Object} as declared type (including
         * generic types without explicit type) will use default
         * typing.
         */
        JAVA_LANG_OBJECT,

        /**
         * Value that means that default typing will be used for
         * properties with declared type of {@link java.lang.Object}
         * or an abstract type (abstract class or interface).
         * Note that this does not include array types.
         *

         * Since 2.4, this does NOT apply to {@link TreeNode} and its subtypes.
         */
        OBJECT_AND_NON_CONCRETE,

        /**
         * Value that means that default typing will be used for
         * all types covered by {@link #OBJECT_AND_NON_CONCRETE}
         * plus all array types for them.
         *

         * Since 2.4, this does NOT apply to {@link TreeNode} and its subtypes.
         */
        NON_CONCRETE_AND_ARRAYS,

        /**
         * Value that means that default typing will be used for
         * all non-final types, with exception of small number of
         * "natural" types (String, Boolean, Integer, Double), which
         * can be correctly inferred from JSON; as well as for
         * all arrays of non-final types.
         *

         * Since 2.4, this does NOT apply to {@link TreeNode} and its subtypes.
         */
        NON_FINAL,

        /**
         * Value that means that default typing will be used for
         * all types, with exception of small number of
         * "natural" types (String, Boolean, Integer, Double) that
         * can be correctly inferred from JSON, and primitives (which
         * can not be polymorphic either).
         * Typing is also enabled for all array types.
         *

         * WARNING: most of the time this is NOT the setting you want
         * as it tends to add Type Ids everywhere, even in cases
         * where type can not be anything other than declared (for example
         * if declared value type of a property is {@code final} -- for example,
         * properties of type {@code long} (or wrapper {@code Long}).
         *

         * Note that this is rarely the option you should use as it results
         * in adding type information in many places where it should not be needed:
         * make sure you understand its behavior.
         * The only known use case for this setting is for serialization
         * when passing instances of final class, and base type is not
         * separately specified.
         *
         * @since 2.10
         */
        EVERYTHING
    }

    /**
     * Customized {@link TypeResolverBuilder} that provides type resolver builders
     * used with so-called "default typing"
     * (see {@link ObjectMapper#activateDefaultTyping(PolymorphicTypeValidator)} for details).
     *

     * Type resolver construction is based on configuration: implementation takes care
     * of only providing builders in cases where type information should be applied.
     * This is important since build calls may be sent for any and all types, and
     * type information should NOT be applied to all of them.
     */
    public static class DefaultTypeResolverBuilder
        extends StdTypeResolverBuilder
        implements java.io.Serializable
    {
        private static final long serialVersionUID = 1L;

        /**
         * Definition of what types is this default typer valid for.
         */
        protected final DefaultTyping _appliesFor;

        /**
         * {@link PolymorphicTypeValidator} top use for validating that the subtypes
         * resolved are valid for use (usually to protect against possible
         * security issues)
         *
         * @since 2.10
         */
        protected final PolymorphicTypeValidator _subtypeValidator;

        /**
         * @deprecated Since 2.10
         */
        @Deprecated // since 2.10
        public DefaultTypeResolverBuilder(DefaultTyping t) {
            this(t, LaissezFaireSubTypeValidator.instance);
        }

        /**
         * @since 2.10
         */
        public DefaultTypeResolverBuilder(DefaultTyping t, PolymorphicTypeValidator ptv) {
            _appliesFor = _requireNonNull(t, "Can not pass `null` DefaultTyping");
            _subtypeValidator = _requireNonNull(ptv, "Can not pass `null` PolymorphicTypeValidator");
        }

        // 20-Jan-2020: as per [databind#2599] Objects.requireNonNull() from JDK7 not in all Android so
        private static  T _requireNonNull(T value, String msg) {
            // Replacement for: return Objects.requireNonNull(t, msg);
            if (value == null) {
                throw new NullPointerException(msg);
            }
            return value;
        }

        /**
         * @since 2.10
         */
        public static DefaultTypeResolverBuilder construct(DefaultTyping t,
                PolymorphicTypeValidator ptv) {
            return new DefaultTypeResolverBuilder(t, ptv);
        }

        @Override // since 2.10
        public PolymorphicTypeValidator subTypeValidator(MapperConfig config) {
            return _subtypeValidator;
        }

        @Override
        public TypeDeserializer buildTypeDeserializer(DeserializationConfig config,
                JavaType baseType, Collection subtypes)
        {
            return useForType(baseType) ? super.buildTypeDeserializer(config, baseType, subtypes) : null;
        }

        @Override
        public TypeSerializer buildTypeSerializer(SerializationConfig config,
                JavaType baseType, Collection subtypes)
        {
            return useForType(baseType) ? super.buildTypeSerializer(config, baseType, subtypes) : null;            
        }

        /**
         * Method called to check if the default type handler should be
         * used for given type.
         * Note: "natural types" (String, Boolean, Integer, Double) will never
         * use typing; that is both due to them being concrete and final,
         * and since actual serializers and deserializers will also ignore any
         * attempts to enforce typing.
         */
        public boolean useForType(JavaType t)
        {
            // 03-Oct-2016, tatu: As per [databind#1395], need to skip
            //  primitive types too, regardless
            if (t.isPrimitive()) {
                return false;
            }

            switch (_appliesFor) {
            case NON_CONCRETE_AND_ARRAYS:
                while (t.isArrayType()) {
                    t = t.getContentType();
                }
                // fall through
            case OBJECT_AND_NON_CONCRETE:
                // 19-Apr-2016, tatu: ReferenceType like Optional also requires similar handling:
                while (t.isReferenceType()) {
                    t = t.getReferencedType();
                }
                return t.isJavaLangObject()
                        || (!t.isConcrete()
                                // [databind#88] Should not apply to JSON tree models:
                                && !TreeNode.class.isAssignableFrom(t.getRawClass()));

            case NON_FINAL:
                while (t.isArrayType()) {
                    t = t.getContentType();
                }
                // 19-Apr-2016, tatu: ReferenceType like Optional also requires similar handling:
                while (t.isReferenceType()) {
                    t = t.getReferencedType();
                }
                // [databind#88] Should not apply to JSON tree models:
                return !t.isFinal() && !TreeNode.class.isAssignableFrom(t.getRawClass());
            case EVERYTHING:
                // So, excluding primitives (handled earlier) and "Natural types" (handled
                // before this method is called), applied to everything
                return true;
            default:
            case JAVA_LANG_OBJECT:
                return t.isJavaLangObject();
            }
        }
    }

    /*
    /**********************************************************
    /* Internal constants, singletons
    /**********************************************************
     */

    // 16-May-2009, tatu: Ditto ^^^
    protected final static AnnotationIntrospector DEFAULT_ANNOTATION_INTROSPECTOR = new JacksonAnnotationIntrospector();

    /**
     * Base settings contain defaults used for all {@link ObjectMapper}
     * instances.
     */
    protected final static BaseSettings DEFAULT_BASE = new BaseSettings(
            null, // cannot share global ClassIntrospector any more (2.5+)
            DEFAULT_ANNOTATION_INTROSPECTOR,
             null, TypeFactory.defaultInstance(),
            null, StdDateFormat.instance, null,
            Locale.getDefault(),
            null, // to indicate "use Jackson default TimeZone" (UTC since Jackson 2.7)
            Base64Variants.getDefaultVariant(),
            // Only for 2.x; 3.x will use more restrictive default
            LaissezFaireSubTypeValidator.instance,
            // Since 2.12:
            new DefaultAccessorNamingStrategy.Provider()
    );

    /*
    /**********************************************************
    /* Configuration settings, shared
    /**********************************************************
     */

    /**
     * Factory used to create {@link JsonParser} and {@link JsonGenerator}
     * instances as necessary.
     */
    protected final JsonFactory _jsonFactory;

    /**
     * Specific factory used for creating {@link JavaType} instances;
     * needed to allow modules to add more custom type handling
     * (mostly to support types of non-Java JVM languages)
     */
    protected TypeFactory _typeFactory;

    /**
     * Provider for values to inject in deserialized POJOs.
     */
    protected InjectableValues _injectableValues;

    /**
     * Thing used for registering sub-types, resolving them to
     * super/sub-types as needed.
     */
    protected SubtypeResolver _subtypeResolver;

    /**
     * Currently active per-type configuration overrides, accessed by
     * declared type of property.
     *
     * @since 2.9
     */
    protected final ConfigOverrides _configOverrides;

    /**
     * Current set of coercion configuration definitions that define allowed
     * (and not allowed) coercions from secondary shapes.
     *
     * @since 2.12
     */
    protected final CoercionConfigs _coercionConfigs;

    /*
    /**********************************************************
    /* Configuration settings: mix-in annotations
    /**********************************************************
     */

    /**
     * Mapping that defines how to apply mix-in annotations: key is
     * the type to received additional annotations, and value is the
     * type that has annotations to "mix in".
     *

     * Annotations associated with the value classes will be used to
     * override annotations of the key class, associated with the
     * same field or method. They can be further masked by sub-classes:
     * you can think of it as injecting annotations between the target
     * class and its sub-classes (or interfaces)
     * 
     * @since 2.6 (earlier was a simple {@link java.util.Map}
     */
    protected SimpleMixInResolver _mixIns;

    /*
    /**********************************************************
    /* Configuration settings, serialization
    /**********************************************************
     */

    /**
     * Configuration object that defines basic global
     * settings for the serialization process
     */
    protected SerializationConfig _serializationConfig;

    /**
     * Object that manages access to serializers used for serialization,
     * including caching.
     * It is configured with {@link #_serializerFactory} to allow
     * for constructing custom serializers.
     *

     * Note: while serializers are only exposed {@link SerializerProvider},
     * mappers and readers need to access additional API defined by
     * {@link DefaultSerializerProvider}
     */
    protected DefaultSerializerProvider _serializerProvider;

    /**
     * Serializer factory used for constructing serializers.
     */
    protected SerializerFactory _serializerFactory;

    /*
    /**********************************************************
    /* Configuration settings, deserialization
    /**********************************************************
     */

    /**
     * Configuration object that defines basic global
     * settings for the serialization process
     */
    protected DeserializationConfig _deserializationConfig;

    /**
     * Blueprint context object; stored here to allow custom
     * sub-classes. Contains references to objects needed for
     * deserialization construction (cache, factory).
     */
    protected DefaultDeserializationContext _deserializationContext;

    /*
    /**********************************************************
    /* Module-related
    /**********************************************************
     */

    /**
     * Set of module types (as per {@link Module#getTypeId()} that have been
     * registered; kept track of iff {@link MapperFeature#IGNORE_DUPLICATE_MODULE_REGISTRATIONS}
     * is enabled, so that duplicate registration calls can be ignored
     * (to avoid adding same handlers multiple times, mostly).
     * 
     * @since 2.5
     */
    protected Set