GSONJava中很常用的json库，它是google自定义的json库，功能很强大，支持泛型，它也可以实现从json到java对象的装换，也可以从java对象转换成json数据。

导入GSON包

• gardle中加入 bash $ compile 'com.google.code.gson:gson:2.3.1'
• 直接导入jar包
  下载地址http://search.maven.org/#artifactdetails%7Ccom.google.code.gson%7Cgson%7C2.3.1%7Cjar
  ### 首先定义一个Peson实体

package com.example.xuyushi.autocompletetext;

/**
 * Created by xuyushi on 15/6/22.
 */
public class Person {
    public Person() {
        super();
    }

    private String name;
    private int age;
    private String address;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

class -> json

普通对象

Person person = new Person("zhangsan", 22, "beijing");
Gson gson = new Gson();
String str = gson.toJson(person);
Log.d(TAG, str);

** LOG为**

{"address":"beijing","name":"zhangsan","age":22}

数组对象

        List<Person> persons = new ArrayList<Person>();
        Person person1 = new Person("zhangsan", 22, "beijing");
        Person person2 = new Person("lisi", 23, "shanghai");
        Person person3 = new Person("wangwu", 24, "guangzhou");
        persons.add(person1);
        persons.add(person2);
        persons.add(person3);
        Gson gson = new Gson();
        String str = gson.toJson(persons);
        Log.d(TAG, str);

** LOG为**

[{"address":"beijing","name":"zhangsan","age":22},{"address":"shanghai","name":"lisi","age":23},{"address":"guangzhou","name":"wangwu","age":24}]

json -> class

普通对象

        Person person = new Person("zhangsan", 22, "beijing");
        Gson gson = new Gson();
        String str = gson.toJson(person);
    //    Log.d(TAG, str);

        Person personFromJson = gson.fromJson(str, Person.class);
        Log.d(TAG, personFromJson.getName());
        Log.d(TAG, ""+personFromJson.getAge());
        Log.d(TAG, personFromJson.getAddress());

** LOG为**

zhangsan
22
beijing

数组对象(难点)

        List<Person> persons = new ArrayList<Person>();
        Person person1 = new Person("zhangsan", 22, "beijing");
        Person person2 = new Person("lisi", 23, "shanghai");
        Person person3 = new Person("wangwu", 24, "guangzhou");
        persons.add(person1);
        persons.add(person2);
        persons.add(person3);
        Gson gson = new Gson();
        String str = gson.toJson(persons);
//        Log.d(TAG, str);

        List<Person> personsFromJson = new ArrayList<Person>();
        //这里我们通过 Gson中的 TypeToken类是简便操作：这边typeOfT的用法是通过反射机制把T里面的对象的属性的值映射出来，然后通过将json字符串取得的值赋值上去就可以了。
        //* getType()的意思就是表示将jsonString的字符串解析出来之后封装到List集合中，然后分别从T里面取出类型将其复制。
        personsFromJson = gson.fromJson(str, new TypeToken<List<Person>>(){}.getType());
        Log.d(TAG, personsFromJson.get(0).getName());
        Log.d(TAG, personsFromJson.get(1).getName());
        Log.d(TAG, personsFromJson.get(2).getName());

** LOG为**

zhangsan
lisi
wangwu