Gson是一个可用于将Java对象转换为JSON表示形式的Java库。也可用于将JSON字符串转换为等效的Java对象。
Gson目标
- 提供简单的toJson()和fromJson()方法将Java对象转换为JSON，反之亦然.
- 允许将先前存在的不可修改对象转换为JSON或从JSON转换。
- 支持Java泛型
- 允许对象的自定义表示
- 支持任意复杂的对象
以上内容来自官网
现在，我们自定义一个class类
public class Student {
public int id;
public String nickName;
public int age;
public ArrayList<String> books;
public HashMap<String, String> booksMap;
}
接下来的三个例子都是把Java的Class对象使用Gson转换成Json的字符串
- 包含基本数据类型的数据结构
Gson gson = new Gson();
Student student = new Student();
student.id = 1;
student.nickName = "乔晓松";
student.age = 22;
Log.e("MainActivity", gson.toJson(student));
输出结果：
{"nickName":"乔晓松","id":1,"age":22}
- 包含List集合
Gson gson = new Gson();
Student student = new Student();
student.id = 1;
student.nickName = "乔晓松";
student.age = 22;
ArrayList<String> books = new ArrayList<String>();
books.add("数学");
books.add("语文");
books.add("英语");
books.add("物理");
books.add("化学");
books.add("生物");
student.books = books;
Log.e("MainActivity", gson.toJson(student));
输出结果：
{"books":["数学","语文","英语","物理","化学","生物"],"nickName":"乔晓松","id":1,"age":22}
- List和Map集合同时存在
Gson gson = new Gson();
Student student = new Student();
student.id = 1;
student.nickName = "乔晓松";
student.age = 22;
ArrayList<String> books = new ArrayList<String>();
books.add("数学");
books.add("语文");
books.add("英语");
books.add("物理");
books.add("化学");
books.add("生物");
student.books = books;
HashMap<String, String> booksMap = new HashMap<String, String>();
booksMap.put("1", "数学");
booksMap.put("2", "语文");
booksMap.put("3", "英语");
booksMap.put("4", "物理");
booksMap.put("5", "化学");
booksMap.put("6", "生物");
student.booksMap = booksMap;
Log.e("MainActivity", gson.toJson(student));
输出结果：
{"books":["数学","语文","英语","物理","化学","生物"],"booksMap":{"3":"英语","2":"语文","1":"数学","6":"生物","5":"化学","4":"物理"},"nickName":"乔晓松","id":1,"age":22}
- 使用Gson，将字符串转换为Student对象
Gson gson = new Gson();
Student student = new Student();
student.id = 1;
student.nickName = "乔晓松";
student.age = 22;
ArrayList<String> books = new ArrayList<String>();
books.add("数学");
books.add("语文");
books.add("英语");
books.add("物理");
books.add("化学");
books.add("生物");
student.books = books;
HashMap<String, String> booksMap = new HashMap<String, String>();
booksMap.put("1", "数学");
booksMap.put("2", "语文");
booksMap.put("3", "英语");
booksMap.put("4", "物理");
booksMap.put("5", "化学");
booksMap.put("6", "生物");
student.booksMap = booksMap;
String result = gson.toJson(student);
Student studentG = gson.fromJson(result, Student.class);
Log.e("MainActivity", "id:" + studentG.id);
Log.e("MainActivity", "nickName:" + studentG.nickName);
Log.e("MainActivity", "age:" + studentG.age);
Log.e("MainActivity", "books size:" + studentG.books.size());
Log.e("MainActivity", "booksMap size:" + studentG.booksMap.size());
输出结果：
id:1
nickName:乔晓松
age:22
books size:6
booksMap size:6
- 泛型的使用
public HashMap<String,Book> booksMap;
public class Book{
public int id;
public String name;
}
把booksMap转换成字符串和上面的举例一样，但是booksMap的Json字符串转换成booksMap的实例对象就有点不同，因为booksMap有自定义的房型
HashMap<String, Book> booksMap = gson.fromJson(result, new TypeToken<HashMap<String, Book>>() { }.getType());
参考：http://blog.csdn.net/qxs965266509/article/details/42774691
