前言
本人学生一枚,若文章中出现错误
,请大佬
指出。
每篇格言:
不管何时何地做你想做的事永远都不嫌晚,如果你发现生活不如意,我希望你有勇气重来
一、 什么是JSON:
借用百科的介绍:
JSON(JavaScript Object Notation, JS 对象标记) 是一种轻量级的数据交换格式。
它基于 ECMAScript (w3c制定的js规范)的一个子集,采用完全独立于编程语言的文本格式来存储和表示数据。
简洁和清晰的层次结构使得 JSON 成为理想的数据交换语言。 易于人阅读和编写,同时也易于机器解析和生成,并有效地提升网络传输效率。自己的理解:本人感觉JSON相当于Java中的Map集合,通过Key-Value(键值对)的形式来保存数据。
二、JSON的特点:
-
优点:
JSON的体积更小,在网络上传输的时候可以更省流量。易于人阅读和编写,同时也易于机器解析和生成。
-
缺点:
语义性差,看起来不如XML直观。
三、JSON的数据格式:
1、JSON对象:
-
形式:
{ "firstName":"John" , "lastName":"Doe" }
key键数据类型 : String(字符串)
Value值数据类型 : String、null、JSON对象、JSON数组、数值
2、 JSON数组 :
-
形式:
{ "employees": [{ "firstName": "John", "lastName": "Doe" }, { "firstName": "Anna", "lastName": "Smith" }, { "firstName": "Peter", "lastName": "Jones" } ] }
四、JSON在不同环境中的解析
-
服务端(Java):
将Java对象转换成JSON格式的字符串
-
客户端(Android):
将JSON格式字符串转换成Java对象
五、Android原生技术解析JSON
- 缺点:Android原生技术解析JSON特别繁琐,对于复杂的JSON数据容易出错。
解析JSON对象
-
相关API:
JSONObject(String json);将Json字符串解析成Json对象;
XxxgetXxx(String name) ;根据name在json对象中得到相应的value。
案例:
服务端(Java):
public class JsonOneServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setCharacterEncoding("utf-8");
String json = "{\n" +
"\t\"id\":2, \"name\":\"WangXiaoNao\", \n" +
"\t\"age\":20, \n" +
"}\n";
response.getWriter().println(json);
}
}
移动端(Android):
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "MainActivity";
private Button mSend;
private TextView mResponse;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mSend = findViewById(R.id.send);
mSend.setOnClickListener(this);
mResponse = findViewById(R.id.response);
}
private void sendRequestWithHttpURLConnection() {
// 开启线程发起网络请求
new Thread(new Runnable() {
@Override
public void run() {
BufferedReader mReader = null;
HttpURLConnection mConnection = null;
try {
// 注意:如果这里使用的是本地的服务器,这里传入的url地址一定要用本地ip地址
URL url = new URL("http://xxx:8080/JsonOne");
mConnection = (HttpURLConnection) url.openConnection();
mConnection.setRequestMethod("GET");
mConnection.setConnectTimeout(8000);
mConnection.setReadTimeout(8000);
InputStream in = mConnection.getInputStream();
// 对获取的输入流进行读取
mReader = new BufferedReader(new InputStreamReader(in));
StringBuffer response = new StringBuffer();
String line;
while ((line = mReader.readLine()) != null) {
response.append(line);
}
showResponse(response.toString());
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (mReader != null) {
try {
mReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (mConnection != null) {
mConnection.disconnect();
}
}
}
}).start();
}
private void showResponse(final String s) {
runOnUiThread(new Runnable() {
@Override
public void run() {
mResponse.setText(s);
Log.d(TAG, "run: --->" + s);
try {
JSONObject jsonObject = new JSONObject(s);
int id = jsonObject.optInt("id");
String name = jsonObject.optString("name");
int age = jsonObject.optInt("age");
Log.d(TAG, "解析JSON字符串:" + "id=" + id + "name=" + name + "age=" + age);
} catch (JSONException e) {
e.printStackTrace();
}
}
});
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.send:
sendRequestWithHttpURLConnection();
break;
}
}
}
六、解析JSON数组
-
相关API:
JSONArray(String json);将json字符串解析成json数组;
int length();得到json数组中元素的个数;
XxxgetXxx(int s) ;根据下标得到json数组中对应的元素数据。
案例:
服务端(Java)
public class JsonTwoServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setCharacterEncoding("utf-8");
String json = "[\n" +
" {\n" +
" \"id\": 1,\n" +
" \"name\": \"路人甲\",\n" +
" \"age\": 20\n" +
" },\n" +
" {\n" +
" \"id\": 2,\n" +
" \"name\": \"路人乙\",\n" +
" \"age\": 10\n" +
" }\n" +
"]";
response.getWriter().println(json);
}
}
移动端(Android)
public class JSONActivity extends AppCompatActivity implements View.OnClickListener {
private Button mSendTwo;
private TextView mResponse;
private static final String TAG = "JSONActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_json);
mSendTwo = findViewById(R.id.sendTwo);
mSendTwo.setOnClickListener(this);
mResponse = findViewById(R.id.response);
}
@Override
public void onClick(View view) {
if (view.getId() == R.id.sendTwo) {
sendRequestWithHttpURLConnectionTwo();
}
}
private void sendRequestWithHttpURLConnectionTwo() {
// 开启线程发起网络请求
new Thread(new Runnable() {
@Override
public void run() {
BufferedReader mReader = null;
HttpURLConnection mConnection = null;
try {
URL url = new URL("http://xxx:8080/JsonTwo");
mConnection = (HttpURLConnection) url.openConnection();
mConnection.setRequestMethod("GET");
mConnection.setConnectTimeout(8000);
mConnection.setReadTimeout(8000);
InputStream in = mConnection.getInputStream();
// 对获取的输入流进行读取
mReader = new BufferedReader(new InputStreamReader(in));
StringBuffer response = new StringBuffer();
String line;
while ((line = mReader.readLine()) != null) {
response.append(line);
}
showResponse(response.toString());
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (mReader != null) {
try {
mReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (mConnection != null) {
mConnection.disconnect();
}
}
}
}).start();
}
private void showResponse(final String s) {
runOnUiThread(new Runnable() {
@Override
public void run() {
try {
JSONArray jsonArray = new JSONArray(s);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
if (jsonObject != null) {
int id = jsonObject.optInt("id");
String name = jsonObject.getString("name");
int age = jsonObject.getInt("age");
Log.d(TAG, "解析JSON字符串:" + "id=" + id + "name=" + name + "age=" + age);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
});
}
}