(Serialization)Gson gson = new Gson();gson.toJson(1);==> prints 1gson.toJson("abcd");==> prints "abcd"gson.toJson(new Long(10)); ==> prints 10int[] values = { 1 };gson.toJson(values);==> prints [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);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. (Deserialization)BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class); ==> obj2 is just like objNested Classes (including Inner Classes)
Gson可以很容易地序列化静态static的内部类（但是非静态的这不能）
Array Examples
Gson gson = new Gson();int[] ints = {1, 2, 3, 4, 5};String[] strings = {"abc", "def", "ghi"};(Serialization)gson.toJson(ints);==> prints [1,2,3,4,5]gson.toJson(strings); ==> prints ["abc", "def", "ghi"](Deserialization)int[] ints2 = gson.fromJson("[1,2,3,4,5]", int[].class); Collections ExamplesGson 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);Serializing and Deserializing Generic TypesType fooType = new TypeToken<Foo<Bar>>() {}.getType();gson.toJson(foo, fooType);gson.fromJson(json, fooType);Serializing and Deserializing Collection with Objects of Arbitrary Types
Sometimes you are dealing with JSON array that contains mixed types. For example:
[‘hello’,5,{name:’GREETINGS’,source:’guest’}]
public class RawCollectionsExample { static class Event {private String name;private String source;private Event(String name, String source) {this.name = name;this.source = source;}@Overridepublic String toString() {return String.format("(name=%s, source=%s)", name, source);} } @SuppressWarnings({ "unchecked", "rawtypes" }) public static void main(String[] args) {Gson gson = new Gson();Collection collection = new ArrayList();collection.add("hello");collection.add(5);collection.add(new Event("GREETINGS", "guest"));String json = gson.toJson(collection);System.out.println("Using Gson.toJson() on a raw collection: " + json);JsonParser parser = new JsonParser();JsonArray array = parser.parse(json).getAsJsonArray();String message = gson.fromJson(array.get(0), String.class);int number = gson.fromJson(array.get(1), int.class);Event event = gson.fromJson(array.get(2), Event.class);System.out.printf("Using Gson.fromJson() to get: %s, %d, %s", message, number, event); }}Compact Vs. Pretty Printing for JSON Output Format默认情况下Gson的json输出是没有空格与忽略null值得，，所以不是很友好。我们可以采用pretty输出,同时输出null
Gson gson = new GsonBuilder().setPrettyPrinting().serialzeNulls().create();NOTE: when serializing nulls with Gson, it will add a JsonNull element to the JsonElement structure. Therefore, this object can be used in custom serialization/deserialization.
Versioning Support
本文不做介绍
Excluding Fields From Serialization and Deserialization
默认情况下transient 和static field是被忽略的。但是如果你想包含某些transient域可以采取如下形式：
import java.lang.reflect.Modifier;Gson gson = new GsonBuilder().excludeFieldsWithModifiers(Modifier.STATIC).create();NOTE: you can use any number of the Modifier constants to "excludeFieldsWithModifiers" method. For example:Gson gson = new GsonBuilder().excludeFieldsWithModifiers(Modifier.STATIC, Modifier.TRANSIENT, Modifier.VOLATILE).create();不过有更好的形式可以采取@Expose注解：然后调用 new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create()创建Gson凡是被@Expose注解的域都会被包括，没有被注解的都被忽略。
JSON Field Naming Support @SerializedNameprivate class SomeObject { @SerializedName("custom_naming") private final String someField; private final String someOtherField; public SomeObject(String a, String b) {this.someField = a;this.someOtherField = b; }}SomeObject someObject = new SomeObject("first", "second");Gson gson = new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE).create();String jsonRepresentation = gson.toJson(someObject);System.out.println(jsonRepresentation);======== OUTPUT ========{"custom_naming":"first","SomeOtherField":"second"}Gson2.3新的功能
New Methods in JsonArray
@TypeAdapter AnnotationJsonPath Support
参考：
https://sites.google.com/site/gson/gson-user-guide
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