什么是JSON:
JSON即JavaScript Object Natation, 它是一种轻量级的数据交换格式, 与XML一样, 是广泛被采用的客户端和服务端交互的解决方案.
JSON对象:
JSON中对象(Object)以"{"开始, 以"}"结束. 对象中的每一个item都是一个key-value对, 表现为"key:value"的形式, key-value对之间使用逗号分隔. 如:{"name":"coolxing", "age"=24, "male":true, "address":{"street":"huiLongGuan", "city":"beijing", "country":"china"}}. JSON对象的key只能是string类型的, 而value可以是string, number, false, true, null, Object对象甚至是array数组, 也就是说可以存在嵌套的情况.
JSON数组:
JSON数组(array)以"["开始, 以"]"结束, 数组中的每一个元素可以是string, number, false, true, null, Object对象甚至是array数组, 数组间的元素使用逗号分隔. 如["coolxing", 24, {"street":"huiLongGuan", "city":"beijing", "country":"china"}].
JSON数据的解析:
解析JSON数据, 首先需要明确待解析的是JSON Object还是JSON array, 然后需要确定采用哪种解析技术. android平台上一般有2种解析技术可供选择:android内置的org.json包和google的开源gson库. 以下将分别采用这两种技术解析JSON对象和JSON数组.
1. 采用android内置的org.json包解析JSON对象. 假设待解析的JSON数据为json = "{\"name\":\"coolxing\", \"age\"=24, \"male\":true, \"address\":{\"street\":\"huiLongGuan\", \"city\":\"beijing\", \"country\":\"china\"}}", 其中\用于转义表达式中的双引号. 首先定义2个JavaBean:
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package text.com.bean;
public class Address {
private String street;
private String city;
private String country;
public Address() {
super();
}
public Address(String street, String city, String country) {
super();
this.street = street;
this.city = city;
this.country = country;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
@Override
public String toString() {
return "Address [street=" + street + ", city=" + city + ", country="
+ country + "]";
}
}
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package text.com.bean;
public class Person {
private String name;
private int age;
private boolean male;
private Address address;
public Person() {
super();
}
public Person(String name, int age, boolean male, Address address) {
super();
this.name = name;
this.age = age;
this.male = male;
this.address = 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 boolean isMale() {
return male;
}
public void setMale(boolean male) {
this.male = male;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
@Override
public String toString() {
return "Person [name=" + name + ", age=" + age + ", male=" + male
+ ", address=" + address + "]";
}
}
首先使用方法一解析代码如下：
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JSONObject jsonObject = new JSONObject(json);
String name = jsonObject.getString("name");
int age = jsonObject.getInt("age");
boolean male = jsonObject.getBoolean("male");
JSONObject addressJSON = jsonObject.getJSONObject("address");
String street = addressJSON.getString("street");
String city = addressJSON.getString("city");
String country = addressJSON.getString("country");
Address address = new Address(street, city, country);
Person person = new Person(name, age, male, address);
System.out.println(person);
LogCat的输出为Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], 说明已经正确解析了JSON对象.
2. 采用gson库解析JSON对象. 假设带解析的JSON数据是json = "{\"name\":\"coolxing\", \"age\"=24, \"male\":true, \"address\":{\"street\":\"huiLongGuan\", \"city\":\"beijing\", \"country\":\"china\"}}", 首先需要到http://code.google.com/p/google-gson/下载jar包, 并将其添加到项目中. 具体的解析代码如下:
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Gson gson = new Gson();
Person person = gson.fromJson(json, Person.class);
System.out.println(person);
LogCat的输出为Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], 说明已经正确解析了JSON对象, 是不是很简单?
3. 采用android内置的org.json包解析JSON数组. 假设待解析的JSON数据为json = "[{\"name\":\"coolxing\", \"age\"=24, \"male\":true, \"address\":{\"street\":\"huiLongGuan\", \"city\":\"beijing\", \"country\":\"china\"}}, {\"name\":\"min\", \"age\"=20, \"male\":false, \"address\":{\"street\":\"heiShiJiao\", \"city\":\"daLian\", \"country\":\"china\"}}]", 解析代码如下:
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List<Person> persons = new ArrayList<Person>();
JSONArray jsonArray = new JSONArray(json);
for(int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
String name = jsonObject.getString("name");
int age = jsonObject.getInt("age");
boolean male = jsonObject.getBoolean("male");
JSONObject addressJSON = jsonObject.getJSONObject("address");
String street = addressJSON.getString("street");
String city = addressJSON.getString("city");
String country = addressJSON.getString("country");
Address address = new Address(street, city, country);
Person person = new Person(name, age, male, address);
persons.add(person);
}
System.out.println(persons);
LogCat的输出为[Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], Person [name=min, age=20, male=false, address=Address [street=heiShiJiao, city=daLian, country=china]]], 说明已经正确解析了JSON数组.
4. 采用gson库解析JSON数组. 待解析的JSON数据同上, 具体代码为:
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Gson gson = new Gson();
Type listType = new TypeToken<List<Person>>(){}.getType();
List<Person> persons = gson.fromJson(json, listType);
LogCat的输出为[Person [name=coolxing, age=24, male=true, address=Address [street=huiLongGuan, city=beijing, country=china]], Person [name=min, age=20, male=false, address=Address [street=heiShiJiao, city=daLian, country=china]]], 说明已经正确解析了JSON数组.
new TypeToken<List<Person>>(){}.getType(); 这句代码表示创建一个TypeToken的匿名子类对象, 并调用对象的getType()方法.
org.json包和gson库还有很多其他有用的API, 需要的时候可查看文档. 比如有的时候需要通过java对象或java集合和数组生成json数据上传给服务器, 当然你可以自我构造json字符串, 但会很麻烦. 这个时候就可以使用其中的有关API, 方便的完成这项工作.
测试用例：
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package text.com;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.lang.reflect.Type;
import java.util.List;
import text.com.bean.Address;
import text.com.bean.Person;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
public class JsonTest {
String jsonString = "";
public static void main(String[] args) {
// Person p1 = new Person("zhangsan", 12, true, new Address("北京", "海淀区",
// "30号"));
// Person p2 = new Person("zhangsan", 12, true, new Address("北京", "海淀区",
// "30号"));
// Person p3 = new Person("zhangsan", 12, true, new Address("北京", "海淀区",
// "30号"));
// List<Person> list = new ArrayList<Person>();
// list.add(p1);
// list.add(p2);
// list.add(p3);
// Gson gson = new Gson();
// Type typeOfT = new TypeToken<List<Person>>(){}.getType();
// String json = gson.toJson(list, typeOfT);
// System.out.println("json:"+json);
// String str = readTxtFile("D:\\cjjworkspace\\Test\\json.txt");
// System.out.println("文件内容：" + str);
Gson gson = new Gson();
// Type typeOfT = new TypeToken<List<Person>>(){}.getType();
// List<Person> personList = gson.fromJson(str, typeOfT);
Person p1 = new Person("zhangsan", 12, true, new Address("北京", "海淀区", "30号"));
Type typeOfT = new TypeToken<Person>(){}.getType();
String str = gson.toJson(p1, typeOfT);
System.out.println(str);
}
public static String readTxtFile(String filePath) {
String encoding = "utf-8";
StringBuilder sb = new StringBuilder();
try {
File file = new File(filePath);
if (file.isFile() && file.exists()) { // 判断文件是否存在
InputStreamReader read = new InputStreamReader(new FileInputStream(file), encoding);// 考虑到编码格式
BufferedReader bufferedReader = new BufferedReader(read);
String str = "";
while ((str = bufferedReader.readLine()) != null) {
sb.append(str);
}
read.close();
return sb.toString();
} else {
System.out.println("找不到指定的文件");
return null;
}
} catch (Exception e) {
System.out.println("读取文件内容出错");
e.printStackTrace();
}
return sb.toString();
}
Google的GSON框架解析JSON数据
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转载自caoyu-google.iteye.com/blog/2001062
周排行