/
Gson.java
1535 lines (1446 loc) · 66.9 KB
/
Gson.java
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/*
* Copyright (C) 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.gson;
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.LazilyParsedNumber;
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;
import com.google.gson.stream.JsonWriter;
import com.google.gson.stream.MalformedJsonException;
import java.io.EOFException;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.reflect.Type;
import java.math.BigDecimal;
import java.math.BigInteger;
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
* instance and then invoking {@link #toJson(Object)} or {@link #fromJson(String, Class)} methods on
* it. Gson instances are Thread-safe so you can reuse them freely across multiple threads.
*
* <p>You can create a Gson instance by invoking {@code new Gson()} if the default configuration is
* all you need. You can also use {@link GsonBuilder} to build a Gson instance with various
* configuration options such as versioning support, pretty printing, custom newline, custom indent,
* custom {@link JsonSerializer}s, {@link JsonDeserializer}s, and {@link InstanceCreator}s.
*
* <p>Here is an example of how Gson is used for a simple Class:
*
* <pre>
* Gson gson = new Gson(); // Or use new GsonBuilder().create();
* MyType target = new MyType();
* String json = gson.toJson(target); // serializes target to JSON
* MyType target2 = gson.fromJson(json, MyType.class); // deserializes json into target2
* </pre>
*
* <p>If the type of the object that you are converting is a {@code ParameterizedType} (i.e. has at
* least one type argument, for example {@code List<MyType>}) then for deserialization you must use
* a {@code fromJson} method with {@link Type} or {@link TypeToken} parameter to specify the
* parameterized type. For serialization specifying a {@code Type} or {@code TypeToken} is optional,
* otherwise Gson will use the runtime type of the object. {@link TypeToken} is a class provided by
* Gson which helps creating parameterized types. Here is an example showing how this can be done:
*
* <pre>
* TypeToken<List<MyType>> listType = new TypeToken<List<MyType>>() {};
* List<MyType> target = new LinkedList<MyType>();
* target.add(new MyType(1, "abc"));
*
* Gson gson = new Gson();
* // For serialization you normally do not have to specify the type, Gson will use
* // the runtime type of the objects, however you can also specify it explicitly
* String json = gson.toJson(target, listType.getType());
*
* // But for deserialization you have to specify the type
* List<MyType> target2 = gson.fromJson(json, listType);
* </pre>
*
* <p>See the <a href="https://github.com/google/gson/blob/main/UserGuide.md">Gson User Guide</a>
* for a more complete set of examples.
*
* <h2 id="default-lenient">JSON Strictness handling</h2>
*
* For legacy reasons most of the {@code Gson} methods allow JSON data which does not comply with
* the JSON specification when no explicit {@linkplain Strictness strictness} is set (the default).
* To specify the strictness of a {@code Gson} instance, you should set it through {@link
* GsonBuilder#setStrictness(Strictness)}.
*
* <p>For older Gson versions, which don't have the strictness mode API, the following workarounds
* can be used:
*
* <h3>Serialization</h3>
*
* <ol>
* <li>Use {@link #getAdapter(Class)} to obtain the adapter for the type to be serialized
* <li>When using an existing {@code JsonWriter}, manually apply the writer settings of this
* {@code Gson} instance listed by {@link #newJsonWriter(Writer)}.<br>
* Otherwise, when not using an existing {@code JsonWriter}, use {@link
* #newJsonWriter(Writer)} to construct one.
* <li>Call {@link TypeAdapter#write(JsonWriter, Object)}
* </ol>
*
* <h3>Deserialization</h3>
*
* <ol>
* <li>Use {@link #getAdapter(Class)} to obtain the adapter for the type to be deserialized
* <li>When using an existing {@code JsonReader}, manually apply the reader settings of this
* {@code Gson} instance listed by {@link #newJsonReader(Reader)}.<br>
* Otherwise, when not using an existing {@code JsonReader}, use {@link
* #newJsonReader(Reader)} to construct one.
* <li>Call {@link TypeAdapter#read(JsonReader)}
* <li>Call {@link JsonReader#peek()} and verify that the result is {@link JsonToken#END_DOCUMENT}
* to make sure there is no trailing data
* </ol>
*
* Note that the {@code JsonReader} created this way is only 'legacy strict', it mostly adheres to
* the JSON specification but allows small deviations. See {@link
* JsonReader#setStrictness(Strictness)} for details.
*
* @see TypeToken
* @author Inderjeet Singh
* @author Joel Leitch
* @author Jesse Wilson
*/
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";
/**
* This thread local guards against reentrant calls to {@link #getAdapter(TypeToken)}. In certain
* object graphs, creating an adapter for a type may recursively require an adapter for the same
* type! Without intervention, the recursive lookup would stack overflow. We cheat by returning a
* proxy type adapter, {@link FutureTypeAdapter}, which is wired up once the initial adapter has
* been created.
*
* <p>The map stores the type adapters for ongoing {@code getAdapter} calls, with the type token
* provided to {@code getAdapter} as key and either {@code FutureTypeAdapter} or a regular {@code
* TypeAdapter} as value.
*/
@SuppressWarnings("ThreadLocalUsage")
private final ThreadLocal<Map<TypeToken<?>, TypeAdapter<?>>> threadLocalAdapterResults =
new ThreadLocal<>();
private final ConcurrentMap<TypeToken<?>, TypeAdapter<?>> typeTokenCache =
new ConcurrentHashMap<>();
private final ConstructorConstructor constructorConstructor;
private final JsonAdapterAnnotationTypeAdapterFactory jsonAdapterFactory;
final List<TypeAdapterFactory> factories;
final Excluder excluder;
final FieldNamingStrategy fieldNamingStrategy;
final Map<Type, InstanceCreator<?>> instanceCreators;
final boolean serializeNulls;
final boolean complexMapKeySerialization;
final boolean generateNonExecutableJson;
final boolean htmlSafe;
final FormattingStyle formattingStyle;
final Strictness strictness;
final boolean serializeSpecialFloatingPointValues;
final boolean useJdkUnsafe;
final String datePattern;
final int dateStyle;
final int timeStyle;
final LongSerializationPolicy longSerializationPolicy;
final List<TypeAdapterFactory> builderFactories;
final List<TypeAdapterFactory> builderHierarchyFactories;
final ToNumberStrategy objectToNumberStrategy;
final ToNumberStrategy numberToNumberStrategy;
final List<ReflectionAccessFilter> reflectionFilters;
/**
* Constructs a Gson object with default configuration. The default configuration has the
* following settings:
*
* <ul>
* <li>The JSON generated by {@code toJson} methods is in compact representation. This means
* that all the unneeded white-space is removed. You can change this behavior with {@link
* GsonBuilder#setPrettyPrinting()}.
* <li>When the JSON generated contains more than one line, the kind of newline and indent to
* use can be configured with {@link GsonBuilder#setFormattingStyle(FormattingStyle)}.
* <li>The generated JSON omits all the fields that are null. Note that nulls in arrays are kept
* as is since an array is an ordered list. Moreover, if a field is not null, but its
* generated JSON is empty, the field is kept. You can configure Gson to serialize null
* values by setting {@link GsonBuilder#serializeNulls()}.
* <li>Gson provides default serialization and deserialization for Enums, {@link Map}, {@link
* java.net.URL}, {@link java.net.URI}, {@link java.util.Locale}, {@link java.util.Date},
* {@link java.math.BigDecimal}, and {@link java.math.BigInteger} classes. If you would
* prefer to change the default representation, you can do so by registering a type adapter
* through {@link GsonBuilder#registerTypeAdapter(Type, Object)}.
* <li>The default Date format is same as {@link java.text.DateFormat#DEFAULT}. This format
* ignores the millisecond portion of the date during serialization. You can change this by
* invoking {@link GsonBuilder#setDateFormat(int, int)} or {@link
* GsonBuilder#setDateFormat(String)}.
* <li>By default, Gson ignores the {@link com.google.gson.annotations.Expose} annotation. You
* can enable Gson to serialize/deserialize only those fields marked with this annotation
* through {@link GsonBuilder#excludeFieldsWithoutExposeAnnotation()}.
* <li>By default, Gson ignores the {@link com.google.gson.annotations.Since} annotation. You
* can enable Gson to use this annotation through {@link GsonBuilder#setVersion(double)}.
* <li>The default field naming policy for the output JSON is same as in Java. So, a Java class
* field {@code versionNumber} will be output as {@code "versionNumber"} in JSON. The same
* rules are applied for mapping incoming JSON to the Java classes. You can change this
* policy through {@link GsonBuilder#setFieldNamingPolicy(FieldNamingPolicy)}.
* <li>By default, Gson excludes {@code transient} or {@code static} fields from consideration
* for serialization and deserialization. You can change this behavior through {@link
* GsonBuilder#excludeFieldsWithModifiers(int...)}.
* <li>No explicit strictness is set. You can change this by calling {@link
* GsonBuilder#setStrictness(Strictness)}.
* </ul>
*/
public Gson() {
this(
Excluder.DEFAULT,
DEFAULT_FIELD_NAMING_STRATEGY,
Collections.<Type, InstanceCreator<?>>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.<TypeAdapterFactory>emptyList(),
Collections.<TypeAdapterFactory>emptyList(),
Collections.<TypeAdapterFactory>emptyList(),
DEFAULT_OBJECT_TO_NUMBER_STRATEGY,
DEFAULT_NUMBER_TO_NUMBER_STRATEGY,
Collections.<ReflectionAccessFilter>emptyList());
}
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 = longAdapter(longSerializationPolicy);
factories.add(TypeAdapters.newFactory(long.class, Long.class, longAdapter));
factories.add(
TypeAdapters.newFactory(
double.class, Double.class, doubleAdapter(serializeSpecialFloatingPointValues)));
factories.add(
TypeAdapters.newFactory(
float.class, Float.class, floatAdapter(serializeSpecialFloatingPointValues)));
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.newFactory(BigDecimal.class, TypeAdapters.BIG_DECIMAL));
factories.add(TypeAdapters.newFactory(BigInteger.class, TypeAdapters.BIG_INTEGER));
// Add adapter for LazilyParsedNumber because user can obtain it from Gson and then try to
// serialize it again
factories.add(
TypeAdapters.newFactory(LazilyParsedNumber.class, TypeAdapters.LAZILY_PARSED_NUMBER));
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);
if (SqlTypesSupport.SUPPORTS_SQL_TYPES) {
factories.add(SqlTypesSupport.TIME_FACTORY);
factories.add(SqlTypesSupport.DATE_FACTORY);
factories.add(SqlTypesSupport.TIMESTAMP_FACTORY);
}
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);
}
/**
* Returns a new GsonBuilder containing all custom factories and configuration used by the current
* instance.
*
* @return a GsonBuilder instance.
* @since 2.8.3
*/
public GsonBuilder newBuilder() {
return new GsonBuilder(this);
}
/**
* @deprecated This method by accident exposes an internal Gson class; it might be removed in a
* future version.
*/
@Deprecated
public Excluder excluder() {
return excluder;
}
/**
* Returns the field naming strategy used by this Gson instance.
*
* @see GsonBuilder#setFieldNamingStrategy(FieldNamingStrategy)
*/
public FieldNamingStrategy fieldNamingStrategy() {
return fieldNamingStrategy;
}
/**
* Returns whether this Gson instance is serializing JSON object properties with {@code null}
* values, or just omits them.
*
* @see GsonBuilder#serializeNulls()
*/
public boolean serializeNulls() {
return serializeNulls;
}
/**
* Returns whether this Gson instance produces JSON output which is HTML-safe, that means all HTML
* characters are escaped.
*
* @see GsonBuilder#disableHtmlEscaping()
*/
public boolean htmlSafe() {
return htmlSafe;
}
private TypeAdapter<Number> doubleAdapter(boolean serializeSpecialFloatingPointValues) {
if (serializeSpecialFloatingPointValues) {
return TypeAdapters.DOUBLE;
}
return new TypeAdapter<Number>() {
@Override
public Double read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
return in.nextDouble();
}
@Override
public void write(JsonWriter out, Number value) throws IOException {
if (value == null) {
out.nullValue();
return;
}
double doubleValue = value.doubleValue();
checkValidFloatingPoint(doubleValue);
out.value(doubleValue);
}
};
}
private TypeAdapter<Number> floatAdapter(boolean serializeSpecialFloatingPointValues) {
if (serializeSpecialFloatingPointValues) {
return TypeAdapters.FLOAT;
}
return new TypeAdapter<Number>() {
@Override
public Float read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
return (float) in.nextDouble();
}
@Override
public void write(JsonWriter out, Number value) throws IOException {
if (value == null) {
out.nullValue();
return;
}
float floatValue = value.floatValue();
checkValidFloatingPoint(floatValue);
// For backward compatibility don't call `JsonWriter.value(float)` because that method has
// been newly added and not all custom JsonWriter implementations might override it yet
Number floatNumber = value instanceof Float ? value : floatValue;
out.value(floatNumber);
}
};
}
static void checkValidFloatingPoint(double value) {
if (Double.isNaN(value) || Double.isInfinite(value)) {
throw new IllegalArgumentException(
value
+ " is not a valid double value as per JSON specification. To override this"
+ " behavior, use GsonBuilder.serializeSpecialFloatingPointValues() method.");
}
}
private static TypeAdapter<Number> longAdapter(LongSerializationPolicy longSerializationPolicy) {
if (longSerializationPolicy == LongSerializationPolicy.DEFAULT) {
return TypeAdapters.LONG;
}
return new TypeAdapter<Number>() {
@Override
public Number read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
return in.nextLong();
}
@Override
public void write(JsonWriter out, Number value) throws IOException {
if (value == null) {
out.nullValue();
return;
}
out.value(value.toString());
}
};
}
private static TypeAdapter<AtomicLong> atomicLongAdapter(final TypeAdapter<Number> longAdapter) {
return new TypeAdapter<AtomicLong>() {
@Override
public void write(JsonWriter out, AtomicLong value) throws IOException {
longAdapter.write(out, value.get());
}
@Override
public AtomicLong read(JsonReader in) throws IOException {
Number value = longAdapter.read(in);
return new AtomicLong(value.longValue());
}
}.nullSafe();
}
private static TypeAdapter<AtomicLongArray> atomicLongArrayAdapter(
final TypeAdapter<Number> longAdapter) {
return new TypeAdapter<AtomicLongArray>() {
@Override
public void write(JsonWriter out, AtomicLongArray value) throws IOException {
out.beginArray();
for (int i = 0, length = value.length(); i < length; i++) {
longAdapter.write(out, value.get(i));
}
out.endArray();
}
@Override
public AtomicLongArray read(JsonReader in) throws IOException {
List<Long> list = new ArrayList<>();
in.beginArray();
while (in.hasNext()) {
long value = longAdapter.read(in).longValue();
list.add(value);
}
in.endArray();
int length = list.size();
AtomicLongArray array = new AtomicLongArray(length);
for (int i = 0; i < length; ++i) {
array.set(i, list.get(i));
}
return array;
}
}.nullSafe();
}
/**
* Returns the type adapter for {@code type}.
*
* <p>When calling this method concurrently from multiple threads and requesting an adapter for
* the same type this method may return different {@code TypeAdapter} instances. However, that
* should normally not be an issue because {@code TypeAdapter} implementations are supposed to be
* stateless.
*
* @throws IllegalArgumentException if this Gson instance cannot serialize and deserialize {@code
* type}.
*/
public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
Objects.requireNonNull(type, "type must not be null");
TypeAdapter<?> cached = typeTokenCache.get(type);
if (cached != null) {
@SuppressWarnings("unchecked")
TypeAdapter<T> adapter = (TypeAdapter<T>) cached;
return adapter;
}
Map<TypeToken<?>, TypeAdapter<?>> threadCalls = threadLocalAdapterResults.get();
boolean isInitialAdapterRequest = false;
if (threadCalls == null) {
threadCalls = new HashMap<>();
threadLocalAdapterResults.set(threadCalls);
isInitialAdapterRequest = true;
} else {
// the key and value type parameters always agree
@SuppressWarnings("unchecked")
TypeAdapter<T> ongoingCall = (TypeAdapter<T>) threadCalls.get(type);
if (ongoingCall != null) {
return ongoingCall;
}
}
TypeAdapter<T> candidate = null;
try {
FutureTypeAdapter<T> call = new FutureTypeAdapter<>();
threadCalls.put(type, call);
for (TypeAdapterFactory factory : factories) {
candidate = factory.create(this, type);
if (candidate != null) {
call.setDelegate(candidate);
// Replace future adapter with actual adapter
threadCalls.put(type, candidate);
break;
}
}
} finally {
if (isInitialAdapterRequest) {
threadLocalAdapterResults.remove();
}
}
if (candidate == null) {
throw new IllegalArgumentException(
"GSON (" + GsonBuildConfig.VERSION + ") cannot handle " + type);
}
if (isInitialAdapterRequest) {
/*
* Publish resolved adapters to all threads
* Can only do this for the initial request because cyclic dependency TypeA -> TypeB -> TypeA
* would otherwise publish adapter for TypeB which uses not yet resolved adapter for TypeA
* See https://github.com/google/gson/issues/625
*/
typeTokenCache.putAll(threadCalls);
}
return candidate;
}
/**
* Returns the type adapter for {@code type}.
*
* @throws IllegalArgumentException if this Gson instance cannot serialize and deserialize {@code
* type}.
*/
public <T> TypeAdapter<T> getAdapter(Class<T> type) {
return getAdapter(TypeToken.get(type));
}
/**
* This method is used to get an alternate type adapter for the specified type. This is used to
* access a type adapter that is overridden by a {@link TypeAdapterFactory} that you may have
* registered. This feature is typically used when you want to register a type adapter that does a
* little bit of work but then delegates further processing to the Gson default type adapter. Here
* is an example:
*
* <p>Let's say we want to write a type adapter that counts the number of objects being read from
* or written to JSON. We can achieve this by writing a type adapter factory that uses the {@code
* getDelegateAdapter} method:
*
* <pre>{@code
* class StatsTypeAdapterFactory implements TypeAdapterFactory {
* public int numReads = 0;
* public int numWrites = 0;
* public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
* final TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
* return new TypeAdapter<T>() {
* public void write(JsonWriter out, T value) throws IOException {
* ++numWrites;
* delegate.write(out, value);
* }
* public T read(JsonReader in) throws IOException {
* ++numReads;
* return delegate.read(in);
* }
* };
* }
* }
* }</pre>
*
* This factory can now be used like this:
*
* <pre>{@code
* StatsTypeAdapterFactory stats = new StatsTypeAdapterFactory();
* Gson gson = new GsonBuilder().registerTypeAdapterFactory(stats).create();
* // Call gson.toJson() and fromJson methods on objects
* System.out.println("Num JSON reads: " + stats.numReads);
* System.out.println("Num JSON writes: " + stats.numWrites);
* }</pre>
*
* Note that this call will skip all factories registered before {@code skipPast}. In case of
* multiple TypeAdapterFactories registered it is up to the caller of this function to ensure that
* the order of registration does not prevent this method from reaching a factory they would
* expect to reply from this call. Note that since you can not override the type adapter factories
* for some types, see {@link GsonBuilder#registerTypeAdapter(Type, Object)}, our stats factory
* will not count the number of instances of those types that will be read or written.
*
* <p>If {@code skipPast} is a factory which has neither been registered on the {@link
* GsonBuilder} nor specified with the {@link JsonAdapter @JsonAdapter} annotation on a class,
* then this method behaves as if {@link #getAdapter(TypeToken)} had been called. This also means
* that for fields with {@code @JsonAdapter} annotation this method behaves normally like {@code
* getAdapter} (except for corner cases where a custom {@link InstanceCreator} is used to create
* an instance of the factory).
*
* @param skipPast The type adapter factory that needs to be skipped while searching for a
* matching type adapter. In most cases, you should just pass <i>this</i> (the type adapter
* factory from where {@code getDelegateAdapter} method is being invoked).
* @param type Type for which the delegate adapter is being searched for.
* @since 2.2
*/
public <T> TypeAdapter<T> getDelegateAdapter(TypeAdapterFactory skipPast, TypeToken<T> type) {
Objects.requireNonNull(skipPast, "skipPast must not be null");
Objects.requireNonNull(type, "type must not be null");
if (jsonAdapterFactory.isClassJsonAdapterFactory(type, skipPast)) {
skipPast = jsonAdapterFactory;
}
boolean skipPastFound = false;
for (TypeAdapterFactory factory : factories) {
if (!skipPastFound) {
if (factory == skipPast) {
skipPastFound = true;
}
continue;
}
TypeAdapter<T> candidate = factory.create(this, type);
if (candidate != null) {
return candidate;
}
}
if (skipPastFound) {
throw new IllegalArgumentException("GSON cannot serialize or deserialize " + type);
} else {
// Probably a factory from @JsonAdapter on a field
return getAdapter(type);
}
}
/**
* This method serializes the specified object into its equivalent representation as a tree of
* {@link JsonElement}s. This method should be used when the specified object is not a generic
* type. This method uses {@link Class#getClass()} to get the type for the specified object, but
* the {@code getClass()} loses the generic type information because of the Type Erasure feature
* of Java. Note that this method works fine if any of the object fields are of generic type, just
* the object itself should not be of a generic type. If the object is of generic type, use {@link
* #toJsonTree(Object, Type)} instead.
*
* @param src the object for which JSON representation is to be created
* @return JSON representation of {@code src}.
* @since 1.4
* @see #toJsonTree(Object, Type)
*/
public JsonElement toJsonTree(Object src) {
if (src == null) {
return JsonNull.INSTANCE;
}
return toJsonTree(src, src.getClass());
}
/**
* This method serializes the specified object, including those of generic types, into its
* equivalent representation as a tree of {@link JsonElement}s. This method must be used if the
* specified object is a generic type. For non-generic objects, use {@link #toJsonTree(Object)}
* instead.
*
* @param src the object for which JSON representation is to be created
* @param typeOfSrc The specific genericized type of src. You can obtain this type by using the
* {@link com.google.gson.reflect.TypeToken} class. For example, to get the type for {@code
* Collection<Foo>}, you should use:
* <pre>
* Type typeOfSrc = new TypeToken<Collection<Foo>>(){}.getType();
* </pre>
*
* @return JSON representation of {@code src}.
* @since 1.4
* @see #toJsonTree(Object)
*/
public JsonElement toJsonTree(Object src, Type typeOfSrc) {
JsonTreeWriter writer = new JsonTreeWriter();
toJson(src, typeOfSrc, writer);
return writer.get();
}
/**
* This method serializes the specified object into its equivalent JSON representation. This
* method should be used when the specified object is not a generic type. This method uses {@link
* Class#getClass()} to get the type for the specified object, but the {@code getClass()} loses
* the generic type information because of the Type Erasure feature of Java. Note that this method
* works fine if any of the object fields are of generic type, just the object itself should not
* be of a generic type. If the object is of generic type, use {@link #toJson(Object, Type)}
* instead. If you want to write out the object to a {@link Writer}, use {@link #toJson(Object,
* Appendable)} instead.
*
* @param src the object for which JSON representation is to be created
* @return JSON representation of {@code src}.
* @see #toJson(Object, Appendable)
* @see #toJson(Object, Type)
*/
public String toJson(Object src) {
if (src == null) {
return toJson(JsonNull.INSTANCE);
}
return toJson(src, src.getClass());
}
/**
* This method serializes the specified object, including those of generic types, into its
* equivalent JSON representation. This method must be used if the specified object is a generic
* type. For non-generic objects, use {@link #toJson(Object)} instead. If you want to write out
* the object to a {@link Appendable}, use {@link #toJson(Object, Type, Appendable)} instead.
*
* @param src the object for which JSON representation is to be created
* @param typeOfSrc The specific genericized type of src. You can obtain this type by using the
* {@link com.google.gson.reflect.TypeToken} class. For example, to get the type for {@code
* Collection<Foo>}, you should use:
* <pre>
* Type typeOfSrc = new TypeToken<Collection<Foo>>(){}.getType();
* </pre>
*
* @return JSON representation of {@code src}.
* @see #toJson(Object, Type, Appendable)
* @see #toJson(Object)
*/
public String toJson(Object src, Type typeOfSrc) {
StringWriter writer = new StringWriter();
toJson(src, typeOfSrc, writer);
return writer.toString();
}
/**
* This method serializes the specified object into its equivalent JSON representation and writes
* it to the writer. This method should be used when the specified object is not a generic type.
* This method uses {@link Class#getClass()} to get the type for the specified object, but the
* {@code getClass()} loses the generic type information because of the Type Erasure feature of
* Java. Note that this method works fine if any of the object fields are of generic type, just
* the object itself should not be of a generic type. If the object is of generic type, use {@link
* #toJson(Object, Type, Appendable)} instead.
*
* @param src the object for which JSON representation is to be created
* @param writer Writer to which the JSON representation needs to be written
* @throws JsonIOException if there was a problem writing to the writer
* @since 1.2
* @see #toJson(Object)
* @see #toJson(Object, Type, Appendable)
*/
public void toJson(Object src, Appendable writer) throws JsonIOException {
if (src != null) {
toJson(src, src.getClass(), writer);
} else {
toJson(JsonNull.INSTANCE, writer);
}
}
/**
* This method serializes the specified object, including those of generic types, into its
* equivalent JSON representation and writes it to the writer. This method must be used if the
* specified object is a generic type. For non-generic objects, use {@link #toJson(Object,
* Appendable)} instead.
*
* @param src the object for which JSON representation is to be created
* @param typeOfSrc The specific genericized type of src. You can obtain this type by using the
* {@link com.google.gson.reflect.TypeToken} class. For example, to get the type for {@code
* Collection<Foo>}, you should use:
* <pre>
* Type typeOfSrc = new TypeToken<Collection<Foo>>(){}.getType();
* </pre>
*
* @param writer Writer to which the JSON representation of src needs to be written
* @throws JsonIOException if there was a problem writing to the writer
* @since 1.2
* @see #toJson(Object, Type)
* @see #toJson(Object, Appendable)
*/
public void toJson(Object src, Type typeOfSrc, Appendable writer) throws JsonIOException {
try {
JsonWriter jsonWriter = newJsonWriter(Streams.writerForAppendable(writer));
toJson(src, typeOfSrc, jsonWriter);
} catch (IOException e) {
throw new JsonIOException(e);
}
}
/**
* Writes the JSON representation of {@code src} of type {@code typeOfSrc} to {@code writer}.
*
* <p>If the {@code Gson} instance has an {@linkplain GsonBuilder#setStrictness(Strictness)
* explicit strictness setting}, this setting will be used for writing the JSON regardless of the
* {@linkplain JsonWriter#getStrictness() strictness} of the provided {@link JsonWriter}. For
* legacy reasons, if the {@code Gson} instance has no explicit strictness setting and the writer
* does not have the strictness {@link Strictness#STRICT}, the JSON will be written in {@link
* Strictness#LENIENT} mode.<br>
* Note that in all cases the old strictness setting of the writer will be restored when this
* method returns.
*
* <p>The 'HTML-safe' and 'serialize {@code null}' settings of this {@code Gson} instance
* (configured by the {@link GsonBuilder}) are applied, and the original settings of the writer
* are restored once this method returns.
*
* @param src the object for which JSON representation is to be created
* @param typeOfSrc the type of the object to be written
* @param writer Writer to which the JSON representation of src needs to be written
* @throws JsonIOException if there was a problem writing to the writer
*/
public void toJson(Object src, Type typeOfSrc, JsonWriter writer) throws JsonIOException {
@SuppressWarnings("unchecked")
TypeAdapter<Object> adapter = (TypeAdapter<Object>) getAdapter(TypeToken.get(typeOfSrc));
Strictness oldStrictness = writer.getStrictness();
if (this.strictness != null) {
writer.setStrictness(this.strictness);
} else if (writer.getStrictness() == Strictness.LEGACY_STRICT) {
// For backward compatibility change to LENIENT if writer has default strictness LEGACY_STRICT
writer.setStrictness(Strictness.LENIENT);
}
boolean oldHtmlSafe = writer.isHtmlSafe();
boolean oldSerializeNulls = writer.getSerializeNulls();
writer.setHtmlSafe(htmlSafe);
writer.setSerializeNulls(serializeNulls);
try {
adapter.write(writer, src);
} catch (IOException e) {
throw new JsonIOException(e);
} catch (AssertionError e) {
throw new AssertionError(
"AssertionError (GSON " + GsonBuildConfig.VERSION + "): " + e.getMessage(), e);
} finally {
writer.setStrictness(oldStrictness);
writer.setHtmlSafe(oldHtmlSafe);
writer.setSerializeNulls(oldSerializeNulls);
}
}
/**
* Converts a tree of {@link JsonElement}s into its equivalent JSON representation.
*
* @param jsonElement root of a tree of {@link JsonElement}s
* @return JSON String representation of the tree.
* @since 1.4
*/
public String toJson(JsonElement jsonElement) {
StringWriter writer = new StringWriter();
toJson(jsonElement, writer);
return writer.toString();
}
/**
* Writes out the equivalent JSON for a tree of {@link JsonElement}s.
*
* @param jsonElement root of a tree of {@link JsonElement}s
* @param writer Writer to which the JSON representation needs to be written
* @throws JsonIOException if there was a problem writing to the writer
* @since 1.4
*/
public void toJson(JsonElement jsonElement, Appendable writer) throws JsonIOException {
try {
JsonWriter jsonWriter = newJsonWriter(Streams.writerForAppendable(writer));
toJson(jsonElement, jsonWriter);
} catch (IOException e) {
throw new JsonIOException(e);
}
}
/**
* Writes the JSON for {@code jsonElement} to {@code writer}.
*
* <p>If the {@code Gson} instance has an {@linkplain GsonBuilder#setStrictness(Strictness)
* explicit strictness setting}, this setting will be used for writing the JSON regardless of the
* {@linkplain JsonWriter#getStrictness() strictness} of the provided {@link JsonWriter}. For
* legacy reasons, if the {@code Gson} instance has no explicit strictness setting and the writer
* does not have the strictness {@link Strictness#STRICT}, the JSON will be written in {@link
* Strictness#LENIENT} mode.<br>
* Note that in all cases the old strictness setting of the writer will be restored when this
* method returns.
*
* <p>The 'HTML-safe' and 'serialize {@code null}' settings of this {@code Gson} instance
* (configured by the {@link GsonBuilder}) are applied, and the original settings of the writer