Adroid开发之解析Json数据格式

前言

相比较 XML，JSON 的主要优势在于它的体积更小，在网络上传输的时候可以更省流量。但缺点在于，它的语义性较差，看起来不如 XML 直观。

各有所长，这篇主要学习如何解析json,常用的解析方式有

JSONObject (*)

GSON (*)

Jackson

FastJson

…

这里我们主要来学习一下前两种方式。

同样的，在服务器新建一个get_data.json文件。内容格式如下：

通过JSONObject

@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.send_req:
sendRequestWithHttpClient();
break;

default:
break;
}
}

// The code that request is Success
private static final int REQUEST_SUCCESS = 200;

// Encoding format
private static final String UTF_8 = "UTF-8";

/**
* HttpClient
*
* The HttpClient was supported by Apache
*
*/
private void sendRequestWithHttpClient() {

new Thread(new Runnable() {

@Override
public void run() {
// this is a GET request
try {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet("http://127.0.0.1/get_data.json");
HttpResponse httpResponse = httpClient.execute(httpGet);

if (httpResponse.getStatusLine().getStatusCode() == REQUEST_SUCCESS) {
HttpEntity entity = httpResponse.getEntity();
String response = EntityUtils.toString(entity, UTF_8);

// Parse json data by JSONObject method
parseJSONWithJSONObject(response);

}
} catch (Exception e) {
e.printStackTrace();
}
}
}).start();

}

/**
* 通过JSONObject来解析json数据
*
* @param jsonData
*/
private void parseJSONWithJSONObject(String jsonData) {
try {
JSONArray jsonArray = new JSONArray(jsonData);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
String id = jsonObject.getString("id");
String name = jsonObject.getString("name");
String version = jsonObject.getString("version");

Log.d("MainActivity", "id is " + id);
Log.d("MainActivity", "name is " + name);
Log.d("MainActivity", "version is " + version);
}
} catch (Exception e) {
e.printStackTrace();
}
}

通过GSON

首先要导入GSON的jar包到libs文件夹中：



GSON库有何神奇之处？

GSON可以将一段JSON格式的字符串自动映射成一个对象，从而不需要我们再手动去编写代码进行解析了.

比如说一段 JSON 格式的数据如下所示：

{"name":"Tom","age":20}

那我们就可以定义一个 Person 类，并加入 name 和 age 这两个字段，然后只需简单地调用如下代码就可以将 JSON 数据自动解析成一个 Person 对象了：

Gson gson = new Gson();
Person person = gson.fromJson(jsonData, Person.class);

如果需要解析的是一段 JSON 数组会稍微麻烦一点，我们需要借助 TypeToken 将期望解析成的数据类型传入到 fromJson()方法中，如下所示：

List<Person> people = gson.fromJson(jsonData, new TypeToken<List<Person>>()
{}.getType());

接下来，我们来解析服务器上的get_data.json,新建个app类：

public class App {

private String id;

private String name;

private String version;

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public String getName() {
return name;
}

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

public String getVersion() {
return version;
}

public void setVersion(String version) {
this.version = version;
}

}

MainActivity.java

/**
* HttpClient
*
* The HttpClient was supported by Apache
*
*/
private void sendRequestWithHttpClient() {

new Thread(new Runnable() {

@Override
public void run() {
// this is a GET request
try {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet("http://127.0.0.1/get_data.json");
HttpResponse httpResponse = httpClient.execute(httpGet);

if (httpResponse.getStatusLine().getStatusCode() == REQUEST_SUCCESS) {
HttpEntity entity = httpResponse.getEntity();
String response = EntityUtils.toString(entity, UTF_8);

// Parse json data by Gson method
parseJSONWithGson(response);

}
} catch (Exception e) {
e.printStackTrace();
}
}
}).start();

}

/**
* 通过Gson来解析json数据
*
* @param jsonData
*/
private void parseJSONWithGson(String jsonData) {
Gson gson = new Gson();
List<App> appList = gson.fromJson(jsonData, new TypeToken<List<App>>(){}.getType());
for (App app : appList) {
Log.d("MainActivity", app.getId());
Log.d("MainActivity", app.getName());
Log.d("MainActivity", app.getVersion());
}
}