1 Introduction
2. Grammar
- JSON file containing a plurality of data, which in
JSONthe form of value
// JSON实例
｛"skill":{
"web":[
{
"name":"html",
"year":"5"
},
{
"name":"ht",
"year":"4"
}],
"database":[
{
"name":"h",
"year":"2"
}]
`}}
JSONThe content form of a value can be: "name-value" pair, array or object, which will be explained in detail below
3. Analysis method
-
AndroidParsingJSONa similar manner to dataXMLparsing, mainly divided into two categories: -
Below, I will describe each method in detail
3.1 Android Studio comes with org.json parsing
- Analysis principle: based on document-driven
Similar to
XMLtheDOManalytical methods
- Parsing process: read all files into the memory ->> traverse all data ->> retrieve the desired data as needed
- Specific use
// 创建需解析的JSON数据：student.json
// 将该文件放入到本地assets文件夹里
{
"student":[
{"id":1,"name":"小明","sex":"男","age":18,"height":175},
{"id":2,"name":"小红","sex":"女","age":19,"height":165},
{"id":3,"name":"小强","sex":"男","age":20,"height":185}
],
"cat":"it"
}
// 具体解析
import android.os.Bundle;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
EntityStudent student = new EntityStudent();
try {
//从assets获取json文件
InputStreamReader isr = new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream("assets/" + "student.json"));
//字节流转字符流
BufferedReader bfr = new BufferedReader(isr);
String line ;
StringBuilder stringBuilder = new StringBuilder();
while ((line = bfr.readLine())!=null){
stringBuilder.append(line);
}//将JSON数据转化为字符串
JSONObject root = new JSONObject(stringBuilder.toString());
//根据键名获取键值信息
System.out.println("root:"+root.getString("cat"));
JSONArray array = root.getJSONArray("student");
for (int i = 0;i < array.length();i++)
{
JSONObject stud = array.getJSONObject(i);
System.out.println("------------------");
System.out.print("id="+stud.getInt("id")+ ","));
System.out.print("name="+stud.getString("name")+ ","));
System.out.print("sex="+stud.getString("sex")+ ","));
System.out.print("age="+stud.getInt("age")+ ","));
System.out.println("height="+stud.getInt("height")+ ","));
bfr.close();
isr.close();
is.close();//依次关闭流
}
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
}
}
3.2 Gson analysis
- Analysis principle: based on event-driven
- Analysis process: According to the required
JSONdata, aJavaBeanclass corresponding to the data is established , and the required data can be parsed through simple operations - Specific use
Step 1: Create a JavaBean class corresponding to the JSON data (used to store the data that needs to be parsed)Gson . The key to parsing = JSONWrite a corresponding based on the data JavaBean. The rules are:
The following two examples illustrate how to JSONcreate a JavaBeanclass through the document
/**
* 简单转换
*/
// JSON数据1
String json = "{\"id\":1,\"name\":\"小明\",\"sex\":\"男\",\"age\":18,\"height\":175}";
// 对应的JavaBean类
public class EntityStudent {
private int id;
private String name;
private String sex;
private int age;
private int height;
public void setId(int id){
this.id = id;
}
public void setName(String name){
this.name = name;
}
public void setSex(String sex){
this.sex = sex;
}
public void setAge(int age){
this.age = age;
}
public void setHeight(int height){
this.height = height;
}
public int getId(){
return id;
}
public String getName(){
return name;
}
public String getSex(){
return sex;
}
public int getAge(){
return age;
}
public int getHeight(){
return height;
}
public void show(){
System.out.print("id=" + id + ",");
System.out.print("name=" + name+",");
System.out.print("sex=" + sex+",");
System.out.print("age=" + age+",");
System.out.println("height=" + height + ",");
}
}
/**
* 复杂转换
*/
// JSON数据2（具备嵌套）
{"translation":["车"],
"basic":
{
"phonetic":"kɑː",
"explains":["n. 汽车；车厢","n. (Car)人名；(土)贾尔；(法、西)卡尔；(塞)察尔"]},
"query":"car",
"errorCode":0,
"web":[{"value":["汽车","车子","小汽车"],"key":"Car"},
{"value":["概念车","概念车","概念汽车"],"key":"concept car"},
{"value":["碰碰车","碰撞用汽车","碰碰汽车"],"key":"bumper car"}]
}
// 对应的复杂的JSON数据对应的JavaBean类
public class student {
public String[] translation; //["车"]数组
public basic basic; //basic对象里面嵌套着对象，创建一个basic内部类对象
public static class basic{ //建立内部类
public String phonetic;
public String[] explains;
}
public String query;
public int errorCode;
public List<wb> web; //web是一个对象数组，创建一个web内部类对象
public static class wb{
public String[] value;
public String key;
}
public void show(){
//输出数组
for (int i = 0;i<translation.length;i++)
{
System.out.println(translation[i]);
}
//输出内部类对象
System.out.println(basic.phonetic);
//输出内部类数组
for (int i = 0;i<basic.explains.length;i++){
System.out.println(basic.explains[i]);
}
System.out.println(query);
System.out.println(errorCode);
for (int i = 0;i<web.size();i++){
for(int j = 0; j<web.get(i).value.length;j++)
{
System.out.println(web.get(i).value[j]);
}
System.out.println(web.get(i).key);
}
}
}
If you think the conversion is too complicated, please use the tool directly: JSON string to Java entity class
Step 2: Import the GSON library
, Android Gradleimport dependencies
dependencies {
compile 'com.google.code.gson:gson:2.3.1'
}
Step 3: Use Gson for analysis
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// 1. 创建Gson对象
Gson gson = new Gson();
// 2. 创建JavaBean类的对象
Student student = new EntityStudent();
// 3. 使用Gson解析：将JSON数据转为单个类实体
String json = "{\"id\":1,\"name\":\"小明\",\"sex\":\"男\",\"age\":18,\"height\":175}";
student = gson.fromJson(json,Student.class);
// 解析：JavaBean对象 = gson.fromJson(son,javaBean类类名.class);
// 4. 调用student方法展示解析的数据
student.show();
// 5. 将Java集合转换为json
String json2 = gson.toJson(List);
System.out.println(json2);
}
}
3.3 Jackson analysis
- Analysis principle: based on event-driven
- Analysis process:
- Similarly
GSON, first createJSONa JavaBeanclass corresponding to the data , and then analyze it through simple operations - And
Gsonparsing different:GSONon-demand resolution, i.e., to create theJavaBeanclass may not be covered completely parsedJSONdata, attributes created on demand; butJacksonresolved correspondingJavaBeanto be theJsondata of which allkeyhave corresponding, i.e., it must beJSONdata in All parsed out, unable to parse on demand
- Similarly
But Jackson’s analysis speed and efficiency are higher than GSON
- Specific use
Step 1: Establish Jsonthe javaBean corresponding to the data (the rules are the same as GSON)
// 创建需解析的JSON数据：student.json
// 将该文件放入到本地assets文件夹里
{"student":
[
{"id":1,"name":"小明","sex":"男","age":18,"height":175,"date":[2013,8,11]},
{"id":2,"name":"小红","sex":"女","age":19,"height":165,"date":[2013,8,23]},
{"id":3,"name":"小强","sex":"男","age":20,"height":185,"date":[2013,9,1]}
],
"grade":"2"
}
// JavaBean类
class test {
private List<stu> student = new ArrayList<stu>();
private int grade;
public void setStudent(List<stu> student){
this.student = student;
}
public List<stu> getStudent(){
return student;
}
public void setGrade(int grade){
this.grade = grade;
}
public int getGrade(){
return grade;
}
private static class stu {
private int id;
private String name;
private String sex;
private int age;
private int height;
private int[] date;
public void setId(int id){
this.id = id;
}
public int getId(){
return id;
}
public void setName(String name){
this.name = name;
}
public String getName(){
return name;
}
public void setSex(String sex){
this.sex = sex;
}
public String getSex(){
return sex;
}
public void setAge(int age){
this.age = age;
}
public int getAge(){
return age;
}
public void setHeight(int height){
this.height = height;
}
public int getHeight(){
return height;
}
public void setDate(int[] date){
this.date = date;
}
public int[] getDate(){
return date;
}
}
public String tostring(){
String str = "";
for (int i = 0;i<student.size();i++){
str += student.get(i).getId() + " " + student.get(i).getName() + " " + student.get(i).getSex() + " " + student.get(i).getAge() + " " + student.get(i).getHeight() ;
for (int j = 0;j<student.get(i).getDate().length;j++) {
str += student.get(i).getDate()[j]+ " " ;
}
str += "\n";
}
str += "\n"+getGrade();
return str;
}
}
Step 2: Analyze using Jackson method
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ObjectMapper objectMapper = new ObjectMapper();
try {
// 1. //从assets获取json文件
InputStreamReader isr = new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream("assets/" + "student.json"),"utf-8");
BufferedReader bfr = new BufferedReader(isr);
String line;
StringBuilder stringBuilder = new StringBuilder();
while ((line = bfr.readLine())!=null){
stringBuilder.append(line);
}
// 2. 将JSON数据转化为字符串
System.out.println(stringBuilder.toString());
System.out.println(tes.tostring());
} catch (IOException e) {
e.printStackTrace();
}
}
}