- java.lang.Object
-
- com.google.gson.Gson
-
public final class Gson extends Object
This is the main class for using Gson. Gson is typically used by first constructing a Gson instance and then invokingtoJson(Object)
orfromJson(String, Class)
methods on it. Gson instances are Thread-safe so you can reuse them freely across multiple threads.You can create a Gson instance by invoking
new Gson()
if the default configuration is all you need. You can also useGsonBuilder
to build a Gson instance with various configuration options such as versioning support, pretty printing, custom newline, custom indent, customJsonSerializer
s,JsonDeserializer
s, andInstanceCreator
s.Here is an example of how Gson is used for a simple Class:
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
If the type of the object that you are converting is a
ParameterizedType
(i.e. has at least one type argument, for exampleList<MyType>
) then for deserialization you must use afromJson
method withType
orTypeToken
parameter to specify the parameterized type. For serialization specifying aType
orTypeToken
is optional, otherwise Gson will use the runtime type of the object.TypeToken
is a class provided by Gson which helps creating parameterized types. Here is an example showing how this can be done: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);
See the Gson User Guide for a more complete set of examples.
JSON Strictness handling
For legacy reasons most of theGson
methods allow JSON data which does not comply with the JSON specification when no explicit strictness is set (the default). To specify the strictness of aGson
instance, you should set it throughGsonBuilder.setStrictness(Strictness)
.For older Gson versions, which don't have the strictness mode API, the following workarounds can be used:
Serialization
- Use
getAdapter(Class)
to obtain the adapter for the type to be serialized - When using an existing
JsonWriter
, manually apply the writer settings of thisGson
instance listed bynewJsonWriter(Writer)
.
Otherwise, when not using an existingJsonWriter
, usenewJsonWriter(Writer)
to construct one. - Call
TypeAdapter.write(JsonWriter, Object)
Deserialization
- Use
getAdapter(Class)
to obtain the adapter for the type to be deserialized - When using an existing
JsonReader
, manually apply the reader settings of thisGson
instance listed bynewJsonReader(Reader)
.
Otherwise, when not using an existingJsonReader
, usenewJsonReader(Reader)
to construct one. - Call
TypeAdapter.read(JsonReader)
- Call
JsonReader.peek()
and verify that the result isJsonToken.END_DOCUMENT
to make sure there is no trailing data
JsonReader
created this way is only 'legacy strict', it mostly adheres to the JSON specification but allows small deviations. SeeJsonReader.setStrictness(Strictness)
for details.- Author:
- Inderjeet Singh, Joel Leitch, Jesse Wilson
- See Also:
TypeToken
- Use
-
-
Constructor Summary
Constructors Constructor Description Gson()
Constructs a Gson object with default configuration.
-
Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description com.google.gson.internal.Excluder
excluder()
Deprecated.This method by accident exposes an internal Gson class; it might be removed in a future version.FieldNamingStrategy
fieldNamingStrategy()
Returns the field naming strategy used by this Gson instance.<T> T
fromJson(JsonElement json, TypeToken<T> typeOfT)
This method deserializes the JSON read from the specified parse tree into an object of the specified type.<T> T
fromJson(JsonElement json, Class<T> classOfT)
This method deserializes the JSON read from the specified parse tree into an object of the specified type.<T> T
fromJson(JsonElement json, Type typeOfT)
This method deserializes the JSON read from the specified parse tree into an object of the specified type.<T> T
fromJson(JsonReader reader, TypeToken<T> typeOfT)
Reads the next JSON value fromreader
and converts it to an object of typetypeOfT
.<T> T
fromJson(JsonReader reader, Type typeOfT)
Reads the next JSON value fromreader
and converts it to an object of typetypeOfT
.<T> T
fromJson(Reader json, TypeToken<T> typeOfT)
This method deserializes the JSON read from the specified reader into an object of the specified type.<T> T
fromJson(Reader json, Class<T> classOfT)
This method deserializes the JSON read from the specified reader into an object of the specified class.<T> T
fromJson(Reader json, Type typeOfT)
This method deserializes the JSON read from the specified reader into an object of the specified type.<T> T
fromJson(String json, TypeToken<T> typeOfT)
This method deserializes the specified JSON into an object of the specified type.<T> T
fromJson(String json, Class<T> classOfT)
This method deserializes the specified JSON into an object of the specified class.<T> T
fromJson(String json, Type typeOfT)
This method deserializes the specified JSON into an object of the specified type.<T> TypeAdapter<T>
getAdapter(TypeToken<T> type)
Returns the type adapter fortype
.<T> TypeAdapter<T>
getAdapter(Class<T> type)
Returns the type adapter fortype
.<T> TypeAdapter<T>
getDelegateAdapter(TypeAdapterFactory skipPast, TypeToken<T> type)
This method is used to get an alternate type adapter for the specified type.boolean
htmlSafe()
Returns whether this Gson instance produces JSON output which is HTML-safe, that means all HTML characters are escaped.GsonBuilder
newBuilder()
Returns a new GsonBuilder containing all custom factories and configuration used by the current instance.JsonReader
newJsonReader(Reader reader)
Returns a new JSON reader configured for the settings on this Gson instance.JsonWriter
newJsonWriter(Writer writer)
Returns a new JSON writer configured for the settings on this Gson instance.boolean
serializeNulls()
Returns whether this Gson instance is serializing JSON object properties withnull
values, or just omits them.String
toJson(JsonElement jsonElement)
Converts a tree ofJsonElement
s into its equivalent JSON representation.void
toJson(JsonElement jsonElement, JsonWriter writer)
Writes the JSON forjsonElement
towriter
.void
toJson(JsonElement jsonElement, Appendable writer)
Writes out the equivalent JSON for a tree ofJsonElement
s.String
toJson(Object src)
This method serializes the specified object into its equivalent JSON representation.void
toJson(Object src, Appendable writer)
This method serializes the specified object into its equivalent JSON representation and writes it to the writer.String
toJson(Object src, Type typeOfSrc)
This method serializes the specified object, including those of generic types, into its equivalent JSON representation.void
toJson(Object src, Type typeOfSrc, JsonWriter writer)
Writes the JSON representation ofsrc
of typetypeOfSrc
towriter
.void
toJson(Object src, Type typeOfSrc, Appendable writer)
This method serializes the specified object, including those of generic types, into its equivalent JSON representation and writes it to the writer.JsonElement
toJsonTree(Object src)
This method serializes the specified object into its equivalent representation as a tree ofJsonElement
s.JsonElement
toJsonTree(Object src, Type typeOfSrc)
This method serializes the specified object, including those of generic types, into its equivalent representation as a tree ofJsonElement
s.String
toString()
-
-
-
Constructor Detail
-
Gson
public Gson()
Constructs a Gson object with default configuration. The default configuration has the following settings:- The JSON generated by
toJson
methods is in compact representation. This means that all the unneeded white-space is removed. You can change this behavior withGsonBuilder.setPrettyPrinting()
. - When the JSON generated contains more than one line, the kind of newline and indent to
use can be configured with
GsonBuilder.setFormattingStyle(FormattingStyle)
. - 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
GsonBuilder.serializeNulls()
. - Gson provides default serialization and deserialization for Enums,
Map
,URL
,URI
,Locale
,Date
,BigDecimal
, andBigInteger
classes. If you would prefer to change the default representation, you can do so by registering a type adapter throughGsonBuilder.registerTypeAdapter(Type, Object)
. - The default Date format is same as
DateFormat.DEFAULT
. This format ignores the millisecond portion of the date during serialization. You can change this by invokingGsonBuilder.setDateFormat(int, int)
orGsonBuilder.setDateFormat(String)
. - By default, Gson ignores the
Expose
annotation. You can enable Gson to serialize/deserialize only those fields marked with this annotation throughGsonBuilder.excludeFieldsWithoutExposeAnnotation()
. - By default, Gson ignores the
Since
annotation. You can enable Gson to use this annotation throughGsonBuilder.setVersion(double)
. - The default field naming policy for the output JSON is same as in Java. So, a Java class
field
versionNumber
will be output as"versionNumber"
in JSON. The same rules are applied for mapping incoming JSON to the Java classes. You can change this policy throughGsonBuilder.setFieldNamingPolicy(FieldNamingPolicy)
. - By default, Gson excludes
transient
orstatic
fields from consideration for serialization and deserialization. You can change this behavior throughGsonBuilder.excludeFieldsWithModifiers(int...)
. - No explicit strictness is set. You can change this by calling
GsonBuilder.setStrictness(Strictness)
.
- The JSON generated by
-
-
Method Detail
-
newBuilder
public GsonBuilder newBuilder()
Returns a new GsonBuilder containing all custom factories and configuration used by the current instance.- Returns:
- a GsonBuilder instance.
- Since:
- 2.8.3
-
excluder
@Deprecated public com.google.gson.internal.Excluder excluder()
Deprecated.This method by accident exposes an internal Gson class; it might be removed in a future version.
-
fieldNamingStrategy
public FieldNamingStrategy fieldNamingStrategy()
Returns the field naming strategy used by this Gson instance.
-
serializeNulls
public boolean serializeNulls()
Returns whether this Gson instance is serializing JSON object properties withnull
values, or just omits them.- See Also:
GsonBuilder.serializeNulls()
-
htmlSafe
public boolean htmlSafe()
Returns whether this Gson instance produces JSON output which is HTML-safe, that means all HTML characters are escaped.- See Also:
GsonBuilder.disableHtmlEscaping()
-
getAdapter
public <T> TypeAdapter<T> getAdapter(TypeToken<T> type)
Returns the type adapter fortype
.When calling this method concurrently from multiple threads and requesting an adapter for the same type this method may return different
TypeAdapter
instances. However, that should normally not be an issue becauseTypeAdapter
implementations are supposed to be stateless.- Throws:
IllegalArgumentException
- if this Gson instance cannot serialize and deserializetype
.
-
getAdapter
public <T> TypeAdapter<T> getAdapter(Class<T> type)
Returns the type adapter fortype
.- Throws:
IllegalArgumentException
- if this Gson instance cannot serialize and deserializetype
.
-
getDelegateAdapter
public <T> TypeAdapter<T> getDelegateAdapter(TypeAdapterFactory skipPast, TypeToken<T> 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 aTypeAdapterFactory
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: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
getDelegateAdapter
method:
This factory can now be used like this: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); } }; } }
Note that this call will skip all factories registered beforeStatsTypeAdapterFactory 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);
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, seeGsonBuilder.registerTypeAdapter(Type, Object)
, our stats factory will not count the number of instances of those types that will be read or written.If
skipPast
is a factory which has neither been registered on theGsonBuilder
nor specified with the@JsonAdapter
annotation on a class, then this method behaves as ifgetAdapter(TypeToken)
had been called. This also means that for fields with@JsonAdapter
annotation this method behaves normally likegetAdapter
(except for corner cases where a customInstanceCreator
is used to create an instance of the factory).- Parameters:
skipPast
- The type adapter factory that needs to be skipped while searching for a matching type adapter. In most cases, you should just pass this (the type adapter factory from wheregetDelegateAdapter
method is being invoked).type
- Type for which the delegate adapter is being searched for.- Since:
- 2.2
-
toJsonTree
public JsonElement toJsonTree(Object src)
This method serializes the specified object into its equivalent representation as a tree ofJsonElement
s. This method should be used when the specified object is not a generic type. This method usesObject.getClass()
to get the type for the specified object, but thegetClass()
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, usetoJsonTree(Object, Type)
instead.- Parameters:
src
- the object for which JSON representation is to be created- Returns:
- JSON representation of
src
. - Since:
- 1.4
- See Also:
toJsonTree(Object, Type)
-
toJsonTree
public JsonElement toJsonTree(Object src, Type typeOfSrc)
This method serializes the specified object, including those of generic types, into its equivalent representation as a tree ofJsonElement
s. This method must be used if the specified object is a generic type. For non-generic objects, usetoJsonTree(Object)
instead.- Parameters:
src
- the object for which JSON representation is to be createdtypeOfSrc
- The specific genericized type of src. You can obtain this type by using theTypeToken
class. For example, to get the type forCollection<Foo>
, you should use:Type typeOfSrc = new TypeToken<Collection<Foo>>(){}.getType();
- Returns:
- JSON representation of
src
. - Since:
- 1.4
- See Also:
toJsonTree(Object)
-
toJson
public String toJson(Object src)
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 usesObject.getClass()
to get the type for the specified object, but thegetClass()
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, usetoJson(Object, Type)
instead. If you want to write out the object to aWriter
, usetoJson(Object, Appendable)
instead.- Parameters:
src
- the object for which JSON representation is to be created- Returns:
- JSON representation of
src
. - See Also:
toJson(Object, Appendable)
,toJson(Object, Type)
-
toJson
public String toJson(Object src, Type typeOfSrc)
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, usetoJson(Object)
instead. If you want to write out the object to aAppendable
, usetoJson(Object, Type, Appendable)
instead.- Parameters:
src
- the object for which JSON representation is to be createdtypeOfSrc
- The specific genericized type of src. You can obtain this type by using theTypeToken
class. For example, to get the type forCollection<Foo>
, you should use:Type typeOfSrc = new TypeToken<Collection<Foo>>(){}.getType();
- Returns:
- JSON representation of
src
. - See Also:
toJson(Object, Type, Appendable)
,toJson(Object)
-
toJson
public void toJson(Object src, Appendable writer) throws JsonIOException
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 usesObject.getClass()
to get the type for the specified object, but thegetClass()
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, usetoJson(Object, Type, Appendable)
instead.- Parameters:
src
- the object for which JSON representation is to be createdwriter
- 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 Also:
toJson(Object)
,toJson(Object, Type, Appendable)
-
toJson
public void toJson(Object src, Type typeOfSrc, Appendable writer) throws JsonIOException
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, usetoJson(Object, Appendable)
instead.- Parameters:
src
- the object for which JSON representation is to be createdtypeOfSrc
- The specific genericized type of src. You can obtain this type by using theTypeToken
class. For example, to get the type forCollection<Foo>
, you should use:Type typeOfSrc = new TypeToken<Collection<Foo>>(){}.getType();
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 Also:
toJson(Object, Type)
,toJson(Object, Appendable)
-
toJson
public void toJson(Object src, Type typeOfSrc, JsonWriter writer) throws JsonIOException
Writes the JSON representation ofsrc
of typetypeOfSrc
towriter
.If the
Gson
instance has an explicit strictness setting, this setting will be used for writing the JSON regardless of the strictness of the providedJsonWriter
. For legacy reasons, if theGson
instance has no explicit strictness setting and the writer does not have the strictnessStrictness.STRICT
, the JSON will be written inStrictness.LENIENT
mode.
Note that in all cases the old strictness setting of the writer will be restored when this method returns.The 'HTML-safe' and 'serialize
null
' settings of thisGson
instance (configured by theGsonBuilder
) are applied, and the original settings of the writer are restored once this method returns.- Parameters:
src
- the object for which JSON representation is to be createdtypeOfSrc
- the type of the object to be writtenwriter
- Writer to which the JSON representation of src needs to be written- Throws:
JsonIOException
- if there was a problem writing to the writer
-
toJson
public String toJson(JsonElement jsonElement)
Converts a tree ofJsonElement
s into its equivalent JSON representation.- Parameters:
jsonElement
- root of a tree ofJsonElement
s- Returns:
- JSON String representation of the tree.
- Since:
- 1.4
-
toJson
public void toJson(JsonElement jsonElement, Appendable writer) throws JsonIOException
Writes out the equivalent JSON for a tree ofJsonElement
s.- Parameters:
jsonElement
- root of a tree ofJsonElement
swriter
- Writer to which the JSON representation needs to be written- Throws:
JsonIOException
- if there was a problem writing to the writer- Since:
- 1.4
-
toJson
public void toJson(JsonElement jsonElement, JsonWriter writer) throws JsonIOException
Writes the JSON forjsonElement
towriter
.If the
Gson
instance has an explicit strictness setting, this setting will be used for writing the JSON regardless of the strictness of the providedJsonWriter
. For legacy reasons, if theGson
instance has no explicit strictness setting and the writer does not have the strictnessStrictness.STRICT
, the JSON will be written inStrictness.LENIENT
mode.
Note that in all cases the old strictness setting of the writer will be restored when this method returns.The 'HTML-safe' and 'serialize
null
' settings of thisGson
instance (configured by theGsonBuilder
) are applied, and the original settings of the writer are restored once this method returns.- Parameters:
jsonElement
- the JSON element to be writtenwriter
- the JSON writer to which the provided element will be written- Throws:
JsonIOException
- if there was a problem writing to the writer
-
newJsonWriter
public JsonWriter newJsonWriter(Writer writer) throws IOException
Returns a new JSON writer configured for the settings on this Gson instance.The following settings are considered:
GsonBuilder.disableHtmlEscaping()
GsonBuilder.generateNonExecutableJson()
GsonBuilder.serializeNulls()
GsonBuilder.setStrictness(Strictness)
. If no explicit strictness has been set the created writer will have a strictness ofStrictness.LEGACY_STRICT
. Otherwise, the strictness of theGson
instance will be used for the created writer.GsonBuilder.setPrettyPrinting()
GsonBuilder.setFormattingStyle(FormattingStyle)
- Throws:
IOException
-
newJsonReader
public JsonReader newJsonReader(Reader reader)
Returns a new JSON reader configured for the settings on this Gson instance.The following settings are considered:
GsonBuilder.setStrictness(Strictness)
. If no explicit strictness has been set the created reader will have a strictness ofStrictness.LEGACY_STRICT
. Otherwise, the strictness of theGson
instance will be used for the created reader.
-
fromJson
public <T> T fromJson(String json, Class<T> classOfT) throws JsonSyntaxException
This method deserializes the specified JSON into an object of the specified class. It is not suitable to use if the specified class is a generic type since it will not have the generic type information because of the Type Erasure feature of Java. Therefore, this method should not be used if the desired type is a generic type. Note that this method works fine if any of the fields of the specified object are generics, just the object itself should not be a generic type. For the cases when the object is of generic type, invokefromJson(String, TypeToken)
. If you have the JSON in aReader
instead of a String, usefromJson(Reader, Class)
instead.An exception is thrown if the JSON string has multiple top-level JSON elements, or if there is trailing data. Use
fromJson(JsonReader, Type)
if this behavior is not desired.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the string from which the object is to be deserializedclassOfT
- the class of T- Returns:
- an object of type T from the string. Returns
null
ifjson
isnull
or ifjson
is empty. - Throws:
JsonSyntaxException
- if json is not a valid representation for an object of type classOfT- See Also:
fromJson(Reader, Class)
,fromJson(String, TypeToken)
-
fromJson
public <T> T fromJson(String json, Type typeOfT) throws JsonSyntaxException
This method deserializes the specified JSON into an object of the specified type. This method is useful if the specified object is a generic type. For non-generic objects, usefromJson(String, Class)
instead. If you have the JSON in aReader
instead of a String, usefromJson(Reader, Type)
instead.Since
Type
is not parameterized by T, this method is not type-safe and should be used carefully. If you are creating theType
from aTypeToken
, prefer usingfromJson(String, TypeToken)
instead since its return type is based on theTypeToken
and is therefore more type-safe.An exception is thrown if the JSON string has multiple top-level JSON elements, or if there is trailing data. Use
fromJson(JsonReader, Type)
if this behavior is not desired.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the string from which the object is to be deserializedtypeOfT
- The specific genericized type of src- Returns:
- an object of type T from the string. Returns
null
ifjson
isnull
or ifjson
is empty. - Throws:
JsonSyntaxException
- if json is not a valid representation for an object of type typeOfT- See Also:
fromJson(Reader, Type)
,fromJson(String, Class)
,fromJson(String, TypeToken)
-
fromJson
public <T> T fromJson(String json, TypeToken<T> typeOfT) throws JsonSyntaxException
This method deserializes the specified JSON into an object of the specified type. This method is useful if the specified object is a generic type. For non-generic objects, usefromJson(String, Class)
instead. If you have the JSON in aReader
instead of a String, usefromJson(Reader, TypeToken)
instead.An exception is thrown if the JSON string has multiple top-level JSON elements, or if there is trailing data. Use
fromJson(JsonReader, TypeToken)
if this behavior is not desired.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the string from which the object is to be deserializedtypeOfT
- The specific genericized type of src. You should create an anonymous subclass ofTypeToken
with the specific generic type arguments. For example, to get the type forCollection<Foo>
, you should use:new TypeToken<Collection<Foo>>(){}
- Returns:
- an object of type T from the string. Returns
null
ifjson
isnull
or ifjson
is empty. - Throws:
JsonSyntaxException
- if json is not a valid representation for an object of the type typeOfT- Since:
- 2.10
- See Also:
fromJson(Reader, TypeToken)
,fromJson(String, Class)
-
fromJson
public <T> T fromJson(Reader json, Class<T> classOfT) throws JsonSyntaxException, JsonIOException
This method deserializes the JSON read from the specified reader into an object of the specified class. It is not suitable to use if the specified class is a generic type since it will not have the generic type information because of the Type Erasure feature of Java. Therefore, this method should not be used if the desired type is a generic type. Note that this method works fine if any of the fields of the specified object are generics, just the object itself should not be a generic type. For the cases when the object is of generic type, invokefromJson(Reader, TypeToken)
. If you have the JSON in a String form instead of aReader
, usefromJson(String, Class)
instead.An exception is thrown if the JSON data has multiple top-level JSON elements, or if there is trailing data. Use
fromJson(JsonReader, Type)
if this behavior is not desired.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the reader producing the JSON from which the object is to be deserialized.classOfT
- the class of T- Returns:
- an object of type T from the Reader. Returns
null
ifjson
is at EOF. - Throws:
JsonIOException
- if there was a problem reading from the ReaderJsonSyntaxException
- if json is not a valid representation for an object of type typeOfT- Since:
- 1.2
- See Also:
fromJson(String, Class)
,fromJson(Reader, TypeToken)
-
fromJson
public <T> T fromJson(Reader json, Type typeOfT) throws JsonIOException, JsonSyntaxException
This method deserializes the JSON read from the specified reader into an object of the specified type. This method is useful if the specified object is a generic type. For non-generic objects, usefromJson(Reader, Class)
instead. If you have the JSON in a String form instead of aReader
, usefromJson(String, Type)
instead.Since
Type
is not parameterized by T, this method is not type-safe and should be used carefully. If you are creating theType
from aTypeToken
, prefer usingfromJson(Reader, TypeToken)
instead since its return type is based on theTypeToken
and is therefore more type-safe.An exception is thrown if the JSON data has multiple top-level JSON elements, or if there is trailing data. Use
fromJson(JsonReader, Type)
if this behavior is not desired.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the reader producing JSON from which the object is to be deserializedtypeOfT
- The specific genericized type of src- Returns:
- an object of type T from the Reader. Returns
null
ifjson
is at EOF. - Throws:
JsonIOException
- if there was a problem reading from the ReaderJsonSyntaxException
- if json is not a valid representation for an object of type typeOfT- Since:
- 1.2
- See Also:
fromJson(String, Type)
,fromJson(Reader, Class)
,fromJson(Reader, TypeToken)
-
fromJson
public <T> T fromJson(Reader json, TypeToken<T> typeOfT) throws JsonIOException, JsonSyntaxException
This method deserializes the JSON read from the specified reader into an object of the specified type. This method is useful if the specified object is a generic type. For non-generic objects, usefromJson(Reader, Class)
instead. If you have the JSON in a String form instead of aReader
, usefromJson(String, TypeToken)
instead.An exception is thrown if the JSON data has multiple top-level JSON elements, or if there is trailing data. Use
fromJson(JsonReader, TypeToken)
if this behavior is not desired.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the reader producing JSON from which the object is to be deserializedtypeOfT
- The specific genericized type of src. You should create an anonymous subclass ofTypeToken
with the specific generic type arguments. For example, to get the type forCollection<Foo>
, you should use:new TypeToken<Collection<Foo>>(){}
- Returns:
- an object of type T from the Reader. Returns
null
ifjson
is at EOF. - Throws:
JsonIOException
- if there was a problem reading from the ReaderJsonSyntaxException
- if json is not a valid representation for an object of type of typeOfT- Since:
- 2.10
- See Also:
fromJson(String, TypeToken)
,fromJson(Reader, Class)
-
fromJson
public <T> T fromJson(JsonReader reader, Type typeOfT) throws JsonIOException, JsonSyntaxException
Reads the next JSON value fromreader
and converts it to an object of typetypeOfT
. Returnsnull
, if thereader
is at EOF.Since
Type
is not parameterized by T, this method is not type-safe and should be used carefully. If you are creating theType
from aTypeToken
, prefer usingfromJson(JsonReader, TypeToken)
instead since its return type is based on theTypeToken
and is therefore more type-safe. If the provided type is aClass
theTypeToken
can be created withTypeToken.get(Class)
.Unlike the other
fromJson
methods, no exception is thrown if the JSON data has multiple top-level JSON elements, or if there is trailing data.If the
Gson
instance has an explicit strictness setting, this setting will be used for reading the JSON regardless of the strictness of the providedJsonReader
. For legacy reasons, if theGson
instance has no explicit strictness setting and the reader does not have the strictnessStrictness.STRICT
, the JSON will be written inStrictness.LENIENT
mode.
Note that in all cases the old strictness setting of the reader will be restored when this method returns.- Type Parameters:
T
- the type of the desired object- Parameters:
reader
- the reader whose next JSON value should be deserializedtypeOfT
- The specific genericized type of src- Returns:
- an object of type T from the JsonReader. Returns
null
ifreader
is at EOF. - Throws:
JsonIOException
- if there was a problem reading from the JsonReaderJsonSyntaxException
- if json is not a valid representation for an object of type typeOfT- See Also:
fromJson(Reader, Type)
,fromJson(JsonReader, TypeToken)
-
fromJson
public <T> T fromJson(JsonReader reader, TypeToken<T> typeOfT) throws JsonIOException, JsonSyntaxException
Reads the next JSON value fromreader
and converts it to an object of typetypeOfT
. Returnsnull
, if thereader
is at EOF. This method is useful if the specified object is a generic type. For non-generic objects,fromJson(JsonReader, Type)
can be called, orTypeToken.get(Class)
can be used to create the type token.Unlike the other
fromJson
methods, no exception is thrown if the JSON data has multiple top-level JSON elements, or if there is trailing data.If the
Gson
instance has an explicit strictness setting, this setting will be used for reading the JSON regardless of the strictness of the providedJsonReader
. For legacy reasons, if theGson
instance has no explicit strictness setting and the reader does not have the strictnessStrictness.STRICT
, the JSON will be written inStrictness.LENIENT
mode.
Note that in all cases the old strictness setting of the reader will be restored when this method returns.- Type Parameters:
T
- the type of the desired object- Parameters:
reader
- the reader whose next JSON value should be deserializedtypeOfT
- The specific genericized type of src. You should create an anonymous subclass ofTypeToken
with the specific generic type arguments. For example, to get the type forCollection<Foo>
, you should use:new TypeToken<Collection<Foo>>(){}
- Returns:
- an object of type T from the JsonReader. Returns
null
ifreader
is at EOF. - Throws:
JsonIOException
- if there was a problem reading from the JsonReaderJsonSyntaxException
- if json is not a valid representation for an object of the type typeOfT- Since:
- 2.10
- See Also:
fromJson(Reader, TypeToken)
,fromJson(JsonReader, Type)
-
fromJson
public <T> T fromJson(JsonElement json, Class<T> classOfT) throws JsonSyntaxException
This method deserializes the JSON read from the specified parse tree into an object of the specified type. It is not suitable to use if the specified class is a generic type since it will not have the generic type information because of the Type Erasure feature of Java. Therefore, this method should not be used if the desired type is a generic type. Note that this method works fine if any of the fields of the specified object are generics, just the object itself should not be a generic type. For the cases when the object is of generic type, invokefromJson(JsonElement, TypeToken)
.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the root of the parse tree ofJsonElement
s from which the object is to be deserializedclassOfT
- The class of T- Returns:
- an object of type T from the JSON. Returns
null
ifjson
isnull
or ifjson
is empty. - Throws:
JsonSyntaxException
- if json is not a valid representation for an object of type classOfT- Since:
- 1.3
- See Also:
fromJson(Reader, Class)
,fromJson(JsonElement, TypeToken)
-
fromJson
public <T> T fromJson(JsonElement json, Type typeOfT) throws JsonSyntaxException
This method deserializes the JSON read from the specified parse tree into an object of the specified type. This method is useful if the specified object is a generic type. For non-generic objects, usefromJson(JsonElement, Class)
instead.Since
Type
is not parameterized by T, this method is not type-safe and should be used carefully. If you are creating theType
from aTypeToken
, prefer usingfromJson(JsonElement, TypeToken)
instead since its return type is based on theTypeToken
and is therefore more type-safe.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the root of the parse tree ofJsonElement
s from which the object is to be deserializedtypeOfT
- The specific genericized type of src- Returns:
- an object of type T from the JSON. Returns
null
ifjson
isnull
or ifjson
is empty. - Throws:
JsonSyntaxException
- if json is not a valid representation for an object of type typeOfT- Since:
- 1.3
- See Also:
fromJson(Reader, Type)
,fromJson(JsonElement, Class)
,fromJson(JsonElement, TypeToken)
-
fromJson
public <T> T fromJson(JsonElement json, TypeToken<T> typeOfT) throws JsonSyntaxException
This method deserializes the JSON read from the specified parse tree into an object of the specified type. This method is useful if the specified object is a generic type. For non-generic objects, usefromJson(JsonElement, Class)
instead.- Type Parameters:
T
- the type of the desired object- Parameters:
json
- the root of the parse tree ofJsonElement
s from which the object is to be deserializedtypeOfT
- The specific genericized type of src. You should create an anonymous subclass ofTypeToken
with the specific generic type arguments. For example, to get the type forCollection<Foo>
, you should use:new TypeToken<Collection<Foo>>(){}
- Returns:
- an object of type T from the JSON. Returns
null
ifjson
isnull
or ifjson
is empty. - Throws:
JsonSyntaxException
- if json is not a valid representation for an object of type typeOfT- Since:
- 2.10
- See Also:
fromJson(Reader, TypeToken)
,fromJson(JsonElement, Class)
-
-