学习笔记：Android里JSON解析的几种方法

一、解析方法：

　Android解析json有很多种方法，下面介绍三种方法：Android自带的org.json解析、Gson解析和Jackson解析。

优缺点对比：

　Android自带的方法有点像xml的dom解析，遍历之后根据需要的key值去取数据，操作比较复杂，而且速度比较慢；Gson方法只需要建立一个对应json的javaBean类，就可以通过简单的操作解析出数据，而且速度比较快，还可以按需去取数据；Jackson方法是三种方法里面最快的一种，在数据量的的情况优势尤为明显，也是像Gson一样要建立对应的javaBean，但是缺点是一定要读取所有key，如果要按需解析的话可以拆分json来读取，操作比较麻烦。

　PS:从服务器或从本地读取的json数据有可能含有BOM头，读入的话会导致json数据解析失败，所以需要去除BOM头,因为java在读取Unicode文件的时候，会统一把BOM变成“\uFEFF”，所以可以：

       if(line.startsWith("\uFEFF")){              line = line.replace("\uFEFF", "");//去除BOM头         }

　　下面请看我学习json解析中运用到3个方法的例子（以下例子使用Android Studio编译）

二、Android Studio自带org.json解析：

1.解析一个json数据：

{"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"}

2.读入本地assets文件夹里面的student.json并解析

package scut.learngson;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 {            InputStreamReader isr = new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream("assets/" + "student.json"));            //从assets获取json文件，和eclipse里面的方法不同，我搞了好久才发现            BufferedReader bfr = new BufferedReader(isr);//字节流转字符流            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());            System.out.println("root:"+root.getString("cat"));//根据键名获取键值信息            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();        }    }}

输出

System.out: ------------------System.out: id=1,name=小明,sex=男,age=18,height=175,System.out: id=2,name=小红,sex=女,age=19,height=165,System.out: id=3,name=小强,sex=男,age=20,height=185,

三、Gson解析

1.Gson简单解析

一个JavaBean（json用gson转化的时候要有一个实体类对应）:
　PS：用Gson解析的话，JavaBean里面的属性不一定要全部和json数据里面的所有key对应，可以按需取数据。

package scut.learngson;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 + ",");    }}

输出

System.out: id=1,name=小明,sex=男,age=18,height=175,System.out: id=2,name=小红,sex=女,age=19,height=165,System.out: id=3,name=小强,sex=男,age=20,height=185,

用gson进行简单的转换

package scut.learngson;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import com.google.gson.Gson;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);        Gson gson = new Gson();        EntityStudent student = new EntityStudent();        String json = "{\"id\":1,\"name\":\"小明\",\"sex\":\"男\",\"age\":18,\"height\":175}";        student = gson.fromJson(json,EntityStudent.class);//json数据转为单个类实体        student.show();        String json1 = gson.toJson(student);//转化为json        System.out.println(json1);    }}

带泛型的List装类实体数组数据

package scut.learngson;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import com.google.gson.Gson;import com.google.gson.reflect.TypeToken;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;import java.util.ArrayList;import java.util.List;import com.google.gson.reflect.TypeToken;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Gson gson = new Gson();        String json = "[{\"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}]";        List<EntityStudent> List = gson.fromJson(json, new TypeToken<List<EntityStudent>>(){}.getType());        //将JSON解析为带泛型的list        for (int i= 0;i<List.size();i++) {            EntityStudent stu = List.get(i);            stu.show();        }//显示实体数据        String json2 = gson.toJson(List);//转换为json        System.out.println(json2);    }}

结果：

2.用Gson解析复杂json数据

重点是要根据json数据里面的结构写出一个对应的javaBean，规则是：
　　1.json的大括号对应一个对象，对象里面有key和value(值)。在Bean里面的类属性要和key同名。
　　2.json的方括号对应一个数组，所以在Bean里面对应的也是数组，数据里面可以有值或者对象。
　　3.如果数组里面只有值没有key，就说明它只是一个纯数组，如果里面有值有key，则说明是对象数组。纯数组对应Bean里面的数组，对象数组要在Bean里面建立一个内部类，类属性就是对应的对象里面的key，建立了之后要创建一个这个内部类的对象，名字对应数组名。
　　4.对象里面嵌套对象时候，也要建立一个内部类，和对象数组一样，这个内部类对象的名字就是父对象的key

json数据（从有道API获取到的）：

{"translation":["车"],  "basic":    { "us-phonetic":"kɑr",      "phonetic":"kɑː",      "uk-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"}]}

URL: http://fanyi.youdao.com/openapi.do?keyfrom=Yanzhikai&key=2032414398&type=data&doctype=json&version=1.1&q=car

根据json数据的结构和key值写的一个简略的javabean
PS：这里的javaBean不是一个正规的javaBean，因为类属性都是public声明的，这样用来测试的话还可以，但是在实际应用中不安全，正规的javaBean可以参考下面Jackson解析复杂json数据的javaBean.

package scut.httpgson;import java.util.List;public class fanyi {    public String[] translation;    public basic basic;    public  static class basic{        public String phonetic;        public String[] explains;    }    public String query;    public int errorCode;    public List<wb> web;    public static class wb{            public String[] value;            public String key;        }    public void show(){        for (int i = 0;i<translation.length;i++)        {        System.out.println(translation[i]);        }        System.out.println(basic.phonetic);        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);        }    }    }

fanyi.java:

package scut.httpgson;import java.util.List;public class fanyi {    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(){        for (int i = 0;i<translation.length;i++)        {        System.out.println(translation[i]);}        System.out.println(basic.phonetic);        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);        }    }    }

MainActivity:

package scut.httpgson;import android.os.AsyncTask;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.TextView;import com.google.gson.Gson;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;public class MainActivity extends AppCompatActivity {    private TextView tv;    private String json;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        tv = (TextView) findViewById(R.id.tv);        findViewById(R.id.btnstart).setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                new AsyncTask<String, Void, String>() {                    @Override                    protected String doInBackground(String... params) {                        try {                            URL url = new URL(params[0]);                            URLConnection connection = url.openConnection();                            InputStream is = connection.getInputStream();                            InputStreamReader isr = new InputStreamReader(is,"utf-8");                            BufferedReader bfr = new BufferedReader(isr);                            json = bfr.readLine();                               System.out.println(json);                            Gson gson = new Gson();                            fanyi fan = gson.fromJson(json,fanyi.class);                            fan.show();                            bfr.close();                            isr.close();                            is.close();                        } catch (MalformedURLException e) {                        } catch (IOException e) {                            e.printStackTrace();                        }                        return null;                    }                }.execute("http://fanyi.youdao.com/openapi.do?keyfrom=Yanzhikai&key=2032414398&type=data&doctype=json&version=1.1&q=car");            }        });    }

输出结果：

System.out: {"translation":["车"],"basic":{"us-phonetic":"kɑr","phonetic":"kɑː","uk-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","小汽车","轿车"],"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"}]}System.out: 车System.out: kɑːSystem.out: n. 汽车；车厢System.out: n. (Car)人名；(土)贾尔；(法、西)卡尔；(塞)察尔System.out: carSystem.out: 0System.out: 汽车System.out: 小汽车System.out: 轿车System.out: CarSystem.out: 概念车System.out: 概念车System.out: 概念汽车System.out: concept carSystem.out: 碰碰车System.out: 碰撞用汽车System.out: 碰碰汽车System.out: bumper car

把有道翻译的单词car换成new，输出：

System.out: {"translation":["新"],"basic":{"us-phonetic":"nu","phonetic":"njuː","uk-phonetic":"njuː","explains":["adj. 新的，新鲜的；更新的；初见的","adv. 新近","n. (New)人名；(英)纽"]},"query":"new","errorCode":0,"web":[{"value":["新的","新建","新品"],"key":"new"},{"value":["新世纪","新世纪音乐","新纪元运动"],"key":"NEW AGE"},{"value":["新罕布什尔","新罕布什尔州","新罕布什尔州"],"key":"New Hampshire"}]}System.out: 新System.out: njuːSystem.out: adj. 新的，新鲜的；更新的；初见的System.out: adv. 新近System.out: n. (New)人名；(英)纽System.out: newSystem.out: 0System.out: 新的System.out: 新建System.out: 新品System.out: newSystem.out: 新世纪System.out: 新世纪音乐System.out: 新纪元运动System.out: NEW AGESystem.out: 新罕布什尔System.out: 新罕布什尔州System.out: 新罕布什尔州System.out: New Hampshire

四、Jackson解析json

1.用Jackson简单json的解析：

一个javaBean
和Gson解析不同，Jackson解析对应的javaBean必须把json数据里面的所有key都弄出来对应好

package scut.learnjackson;public class Student {    private int id;    private String name;    private String sex;    private int age;    private  int height;    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 String toString(){        return id+" "+name+" "+sex+" "+age+" "+height;    }}

解析简单的json对象：

package scut.learnjackson;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import org.codehaus.jackson.map.ObjectMapper;import org.codehaus.jackson.type.JavaType;import java.io.IOException;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        String json = "{\"id\":1,\"name\":\"小明\",\"sex\":\"男\",\"age\":18,\"height\":175}";        ObjectMapper objectMapper = new ObjectMapper();        try {             Student student = objectMapper.readValue(json,Student.class);            System.out.println(student.toString());        } catch (IOException e) {            e.printStackTrace();        }    }}

输出：

 1 小明 男 18 175

2.解析简单的json对象数组：

package scut.learnjackson;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import org.codehaus.jackson.map.ObjectMapper;import org.codehaus.jackson.type.JavaType;import java.io.IOException;import java.util.ArrayList;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        String json = "[{\"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}]";        ObjectMapper objectMapper = new ObjectMapper();        try {            list = objectMapper.readValue(json,list.getClass());            JavaType javaType = objectMapper.getTypeFactory().constructParametricType(ArrayList.class,Student.class);            ArrayList<Student> list = objectMapper.readValue(json, javaType);//用ArrayList装json数组数据            System.out.println(list.toString());//ArrayList的toString方法            System.out.println(list.get(0).toString());//Student类的toString        } catch (IOException e) {            e.printStackTrace();        }    }}

输出：

 [1 小明 男 18 175, 2 小红 女 19 165, 3 小强 男 20 185] 1 小明 男 18 175

3.用Jackson解析复杂的json数据

json数据：

{"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"}

建立对应的javaBean：
建立javaBean的对应规则和gson一样

package scut.learnjackson;import java.util.ArrayList;import java.util.List;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;    }}

Mainactivity

package scut.learnjackson;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import org.codehaus.jackson.map.ObjectMapper;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        ObjectMapper objectMapper = new ObjectMapper();        try {            InputStreamReader isr = new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream("assets/" + "student.json"),"utf-8");            //从assets获取json文件            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            System.out.println(stringBuilder.toString());            System.out.println(tes.tostring());        } catch (IOException e) {            e.printStackTrace();        }    }}

输出：

System.out: {"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"}System.out: 1 小明 男 18 1752013 8 11 System.out: 2 小红 女 19 1652013 8 23 System.out: 3 小强 男 20 1852013 9 1 System.out: 2

　　以上就是本人所总结的解析json数据的三种方法，如果要解析少量数据json数据的话建议使用Gson解析，方便快捷，如果解析大量json数据的话建议用Jackson解析，性能高效。

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希望我分享的经验能帮助大家，转载请注明原创地址：
炎之铠的博客：http://blog.csdn.net/totond/article/details/51077386