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Optimize new Gson() #2864

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4560d87
Optimize `new Gson()`
MukjepScarlet Oct 29, 2025
4b68d63
revert ConstructorConstructor
MukjepScarlet Jan 12, 2026
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206 changes: 32 additions & 174 deletions gson/src/main/java/com/google/gson/Gson.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,28 +16,18 @@

package com.google.gson;

import static com.google.gson.internal.bind.TypeAdapters.atomicLongAdapter;
import static com.google.gson.internal.bind.TypeAdapters.atomicLongArrayAdapter;
import static com.google.gson.GsonBuilder.newImmutableList;

import com.google.gson.annotations.JsonAdapter;
import com.google.gson.internal.ConstructorConstructor;
import com.google.gson.internal.Excluder;
import com.google.gson.internal.GsonBuildConfig;
import com.google.gson.internal.Primitives;
import com.google.gson.internal.Streams;
import com.google.gson.internal.bind.ArrayTypeAdapter;
import com.google.gson.internal.bind.CollectionTypeAdapterFactory;
import com.google.gson.internal.bind.DefaultDateTypeAdapter;
import com.google.gson.internal.bind.JsonAdapterAnnotationTypeAdapterFactory;
import com.google.gson.internal.bind.JsonTreeReader;
import com.google.gson.internal.bind.JsonTreeWriter;
import com.google.gson.internal.bind.MapTypeAdapterFactory;
import com.google.gson.internal.bind.NumberTypeAdapter;
import com.google.gson.internal.bind.ObjectTypeAdapter;
import com.google.gson.internal.bind.ReflectiveTypeAdapterFactory;
import com.google.gson.internal.bind.SerializationDelegatingTypeAdapter;
import com.google.gson.internal.bind.TypeAdapters;
import com.google.gson.internal.sql.SqlTypesSupport;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
Expand All @@ -49,17 +39,12 @@
import java.io.StringReader;
import java.io.Writer;
import java.lang.reflect.Type;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicLongArray;

/**
* This is the main class for using Gson. Gson is typically used by first constructing a Gson
Expand Down Expand Up @@ -149,21 +134,6 @@
*/
public final class Gson {

static final boolean DEFAULT_JSON_NON_EXECUTABLE = false;
// Strictness of `null` is the legacy mode where some Gson APIs are always lenient
static final Strictness DEFAULT_STRICTNESS = null;
static final FormattingStyle DEFAULT_FORMATTING_STYLE = FormattingStyle.COMPACT;
static final boolean DEFAULT_ESCAPE_HTML = true;
static final boolean DEFAULT_SERIALIZE_NULLS = false;
static final boolean DEFAULT_COMPLEX_MAP_KEYS = false;
static final boolean DEFAULT_SPECIALIZE_FLOAT_VALUES = false;
static final boolean DEFAULT_USE_JDK_UNSAFE = true;
static final String DEFAULT_DATE_PATTERN = null;
static final FieldNamingStrategy DEFAULT_FIELD_NAMING_STRATEGY = FieldNamingPolicy.IDENTITY;
static final ToNumberStrategy DEFAULT_OBJECT_TO_NUMBER_STRATEGY = ToNumberPolicy.DOUBLE;
static final ToNumberStrategy DEFAULT_NUMBER_TO_NUMBER_STRATEGY =
ToNumberPolicy.LAZILY_PARSED_NUMBER;

private static final String JSON_NON_EXECUTABLE_PREFIX = ")]}'\n";

/**
Expand Down Expand Up @@ -250,144 +220,40 @@ public final class Gson {
* </ul>
*/
public Gson() {
this(
Excluder.DEFAULT,
DEFAULT_FIELD_NAMING_STRATEGY,
Collections.emptyMap(),
DEFAULT_SERIALIZE_NULLS,
DEFAULT_COMPLEX_MAP_KEYS,
DEFAULT_JSON_NON_EXECUTABLE,
DEFAULT_ESCAPE_HTML,
DEFAULT_FORMATTING_STYLE,
DEFAULT_STRICTNESS,
DEFAULT_SPECIALIZE_FLOAT_VALUES,
DEFAULT_USE_JDK_UNSAFE,
LongSerializationPolicy.DEFAULT,
DEFAULT_DATE_PATTERN,
DateFormat.DEFAULT,
DateFormat.DEFAULT,
Collections.emptyList(),
Collections.emptyList(),
Collections.emptyList(),
DEFAULT_OBJECT_TO_NUMBER_STRATEGY,
DEFAULT_NUMBER_TO_NUMBER_STRATEGY,
Collections.emptyList());
this(GsonBuilder.DEFAULT);
}

Gson(
Excluder excluder,
FieldNamingStrategy fieldNamingStrategy,
Map<Type, InstanceCreator<?>> instanceCreators,
boolean serializeNulls,
boolean complexMapKeySerialization,
boolean generateNonExecutableGson,
boolean htmlSafe,
FormattingStyle formattingStyle,
Strictness strictness,
boolean serializeSpecialFloatingPointValues,
boolean useJdkUnsafe,
LongSerializationPolicy longSerializationPolicy,
String datePattern,
int dateStyle,
int timeStyle,
List<TypeAdapterFactory> builderFactories,
List<TypeAdapterFactory> builderHierarchyFactories,
List<TypeAdapterFactory> factoriesToBeAdded,
ToNumberStrategy objectToNumberStrategy,
ToNumberStrategy numberToNumberStrategy,
List<ReflectionAccessFilter> reflectionFilters) {
this.excluder = excluder;
this.fieldNamingStrategy = fieldNamingStrategy;
this.instanceCreators = instanceCreators;
this.constructorConstructor =
new ConstructorConstructor(instanceCreators, useJdkUnsafe, reflectionFilters);
this.serializeNulls = serializeNulls;
this.complexMapKeySerialization = complexMapKeySerialization;
this.generateNonExecutableJson = generateNonExecutableGson;
this.htmlSafe = htmlSafe;
this.formattingStyle = formattingStyle;
this.strictness = strictness;
this.serializeSpecialFloatingPointValues = serializeSpecialFloatingPointValues;
this.useJdkUnsafe = useJdkUnsafe;
this.longSerializationPolicy = longSerializationPolicy;
this.datePattern = datePattern;
this.dateStyle = dateStyle;
this.timeStyle = timeStyle;
this.builderFactories = builderFactories;
this.builderHierarchyFactories = builderHierarchyFactories;
this.objectToNumberStrategy = objectToNumberStrategy;
this.numberToNumberStrategy = numberToNumberStrategy;
this.reflectionFilters = reflectionFilters;

List<TypeAdapterFactory> factories = new ArrayList<>();

// built-in type adapters that cannot be overridden
factories.add(TypeAdapters.JSON_ELEMENT_FACTORY);
factories.add(ObjectTypeAdapter.getFactory(objectToNumberStrategy));

// the excluder must precede all adapters that handle user-defined types
factories.add(excluder);

// users' type adapters
factories.addAll(factoriesToBeAdded);

// type adapters for basic platform types
factories.add(TypeAdapters.STRING_FACTORY);
factories.add(TypeAdapters.INTEGER_FACTORY);
factories.add(TypeAdapters.BOOLEAN_FACTORY);
factories.add(TypeAdapters.BYTE_FACTORY);
factories.add(TypeAdapters.SHORT_FACTORY);
TypeAdapter<Number> longAdapter = longSerializationPolicy.typeAdapter();
factories.add(TypeAdapters.newFactory(long.class, Long.class, longAdapter));
factories.add(TypeAdapters.newFactory(double.class, Double.class, doubleAdapter()));
factories.add(TypeAdapters.newFactory(float.class, Float.class, floatAdapter()));
factories.add(NumberTypeAdapter.getFactory(numberToNumberStrategy));
factories.add(TypeAdapters.ATOMIC_INTEGER_FACTORY);
factories.add(TypeAdapters.ATOMIC_BOOLEAN_FACTORY);
factories.add(TypeAdapters.newFactory(AtomicLong.class, atomicLongAdapter(longAdapter)));
factories.add(
TypeAdapters.newFactory(AtomicLongArray.class, atomicLongArrayAdapter(longAdapter)));
factories.add(TypeAdapters.ATOMIC_INTEGER_ARRAY_FACTORY);
factories.add(TypeAdapters.CHARACTER_FACTORY);
factories.add(TypeAdapters.STRING_BUILDER_FACTORY);
factories.add(TypeAdapters.STRING_BUFFER_FACTORY);
factories.add(TypeAdapters.BIG_DECIMAL_FACTORY);
factories.add(TypeAdapters.BIG_INTEGER_FACTORY);
// Add adapter for LazilyParsedNumber because user can obtain it from Gson and then try to
// serialize it again
factories.add(TypeAdapters.LAZILY_PARSED_NUMBER_FACTORY);
factories.add(TypeAdapters.URL_FACTORY);
factories.add(TypeAdapters.URI_FACTORY);
factories.add(TypeAdapters.UUID_FACTORY);
factories.add(TypeAdapters.CURRENCY_FACTORY);
factories.add(TypeAdapters.LOCALE_FACTORY);
factories.add(TypeAdapters.INET_ADDRESS_FACTORY);
factories.add(TypeAdapters.BIT_SET_FACTORY);
factories.add(DefaultDateTypeAdapter.DEFAULT_STYLE_FACTORY);
factories.add(TypeAdapters.CALENDAR_FACTORY);
factories.addAll(SqlTypesSupport.SQL_TYPE_FACTORIES);
TypeAdapterFactory javaTimeFactory = TypeAdapters.javaTimeTypeAdapterFactory();
if (javaTimeFactory != null) {
factories.add(javaTimeFactory);
Gson(GsonBuilder builder) {
this.excluder = builder.excluder;
this.fieldNamingStrategy = builder.fieldNamingPolicy;
this.instanceCreators = new HashMap<>(builder.instanceCreators);
this.serializeNulls = builder.serializeNulls;
this.complexMapKeySerialization = builder.complexMapKeySerialization;
this.generateNonExecutableJson = builder.generateNonExecutableJson;
this.htmlSafe = builder.escapeHtmlChars;
this.formattingStyle = builder.formattingStyle;
this.strictness = builder.strictness;
this.serializeSpecialFloatingPointValues = builder.serializeSpecialFloatingPointValues;
this.useJdkUnsafe = builder.useJdkUnsafe;
this.longSerializationPolicy = builder.longSerializationPolicy;
this.datePattern = builder.datePattern;
this.dateStyle = builder.dateStyle;
this.timeStyle = builder.timeStyle;
this.builderFactories = newImmutableList(builder.factories);
this.builderHierarchyFactories = newImmutableList(builder.hierarchyFactories);
this.objectToNumberStrategy = builder.objectToNumberStrategy;
this.numberToNumberStrategy = builder.numberToNumberStrategy;
this.reflectionFilters = newImmutableList(builder.reflectionFilters);
if (builder == GsonBuilder.DEFAULT) {
this.constructorConstructor = GsonBuilder.DEFAULT_CONSTRUCTOR_CONSTRUCTOR;
this.jsonAdapterFactory = GsonBuilder.DEFAULT_JSON_ADAPTER_ANNOTATION_TYPE_ADAPTER_FACTORY;
this.factories = GsonBuilder.DEFAULT_TYPE_ADAPTER_FACTORIES;
} else {
this.constructorConstructor =
new ConstructorConstructor(instanceCreators, useJdkUnsafe, reflectionFilters);
this.jsonAdapterFactory = new JsonAdapterAnnotationTypeAdapterFactory(constructorConstructor);
this.factories = builder.createFactories(constructorConstructor, jsonAdapterFactory);
}
factories.add(ArrayTypeAdapter.FACTORY);
factories.add(TypeAdapters.CLASS_FACTORY);

// type adapters for composite and user-defined types
factories.add(new CollectionTypeAdapterFactory(constructorConstructor));
factories.add(new MapTypeAdapterFactory(constructorConstructor, complexMapKeySerialization));
this.jsonAdapterFactory = new JsonAdapterAnnotationTypeAdapterFactory(constructorConstructor);
factories.add(jsonAdapterFactory);
factories.add(TypeAdapters.ENUM_FACTORY);
factories.add(
new ReflectiveTypeAdapterFactory(
constructorConstructor,
fieldNamingStrategy,
excluder,
jsonAdapterFactory,
reflectionFilters));

this.factories = Collections.unmodifiableList(factories);
}

/**
Expand Down Expand Up @@ -439,14 +305,6 @@ public boolean htmlSafe() {
return htmlSafe;
}

private TypeAdapter<Number> floatAdapter() {
return serializeSpecialFloatingPointValues ? TypeAdapters.FLOAT : TypeAdapters.FLOAT_STRICT;
}

private TypeAdapter<Number> doubleAdapter() {
return serializeSpecialFloatingPointValues ? TypeAdapters.DOUBLE : TypeAdapters.DOUBLE_STRICT;
}

/**
* Returns the type adapter for {@code type}.
*
Expand Down
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