the latest version is 2.8.0. If you're using Gradle, add the following line:html
compile 'com.google.code.gson:gson:2.8.0'
If you're using Maven, you can add the following dependency:java
<dependencies> <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.8.0</version> <scope>compile</scope> </dependency> </dependencie>
Primitives Examples
// Serialization Gson gson = new Gson(); gson.toJson(1); // ==> 1 gson.toJson("abcd"); // ==> "abcd" gson.toJson(new Long(10)); // ==> 10 int[] values = { 1 }; gson.toJson(values); // ==> [1] // Deserialization int one = gson.fromJson("1", int.class); Integer one = gson.fromJson("1", Integer.class); Long one = gson.fromJson("1", Long.class); Boolean false = gson.fromJson("false", Boolean.class); String str = gson.fromJson("\"abc\"", String.class); String[] anotherStr = gson.fromJson("[\"abc\"]", String[].class);
Object Examples
class BagOfPrimitives { private int value1 = 1; private String value2 = "abc"; private transient int value3 = 3; BagOfPrimitives() { // no-args constructor } } // Serialization BagOfPrimitives obj = new BagOfPrimitives(); Gson gson = new Gson(); String json = gson.toJson(obj); // ==> json is {"value1":1,"value2":"abc"}
Note that you can not serialize objects with circular references since that will result in infinite recursion.git
// Deserialization BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class); // ==> obj2 is just like obj
Nested Classes (including Inner Classes)
Gson can serialize static nested classes quite easily.github
Gson can also deserialize static nested classes. However, Gson can not automatically deserialize the pure inner classes since their no-args constructor also need a reference to the containing Object which is not available at the time of deserialization. You can address this problem by either making the inner class static or by providing a custom InstanceCreator for it. Here is an example:json
public class A { public String a; class B { public String b; public B() { // No args constructor for B } } }
NOTE: The above class B can not (by default) be serialized with Gson.bash
Gson can not deserialize {"b":"abc"} into an instance of B since the class B is an inner class. If it was defined as static class B then Gson would have been able to deserialize the string. Another solution is to write a custom instance creator for B.ide
public class InstanceCreatorForB implements InstanceCreator<A.B> { private final A a; public InstanceCreatorForB(A a) { this.a = a; } public A.B createInstance(Type type) { return a.new B(); } }
The above is possible, but not recommended.post
Array Examples
Gson gson = new Gson(); int[] ints = {1, 2, 3, 4, 5}; String[] strings = {"abc", "def", "ghi"}; // Serialization gson.toJson(ints); // ==> [1,2,3,4,5] gson.toJson(strings); // ==> ["abc", "def", "ghi"] // Deserialization int[] ints2 = gson.fromJson("[1,2,3,4,5]", int[].class); // ==> ints2 will be same as ints
We also support multi-dimensional arrays, with arbitrarily complex element types.學習
Collections Examples
Gson gson = new Gson(); Collection<Integer> ints = Lists.immutableList(1,2,3,4,5); // Serialization String json = gson.toJson(ints); // ==> json is [1,2,3,4,5] // Deserialization Type collectionType = new TypeToken<Collection<Integer>>(){}.getType(); Collection<Integer> ints2 = gson.fromJson(json, collectionType); // ==> ints2 is same as ints
gson/UserGuide.md at master · google/gson
https://github.com/google/gson/blob/master/UserGuide.md#TOC-Gson-Users
Gson — Getting Started with Java-JSON Serialization & Deserialization
https://futurestud.io/tutorials/gson-getting-started-with-java-json-serialization-deserializationui
google/gson: A Java serialization/deserialization library that can convert Java Objects into JSON and back.
https://github.com/google/gson