语法

1个JSON文件里含多个数据，这些数据以 JSON值的形式存在

// JSON实例
{
    "l1": {
        "l1_1": [
            "l1_1_1",
            "l1_1_2"
        ],
        "l1_2": {
            "l1_2_1": 121
        }
    },
    "l2": {
        "l2_1": null,
        "l2_2": true,
        "l2_3": {}
    }
}

1个JSON值的内容形式可以是：“名称 - 值对”、数组或对象，下面将详细说明

json.png

解析方式

说明：json的解析方式有很多种（Android自带org.json解析、Gson、Jackson等），这里我选择效率、依赖包最小和健壮性最好的fastjson来进行解析，比竟如果fastjson能最好的满足我们的要求，其它的都将是将就。

具体使用步骤

1、在Android Gradle导入依赖

注意：由于我是android开发者，我这里引入的针对android的fastjson，这样可以减少下载依赖包的大小，把fastjson中一些我们android端不需要的类和方法可以不导入进来。

dependencies {
    implementation 'com.alibaba:fastjson:1.1.68.android'
}

2、编写FastJson工具类

import com.alibaba.fastjson.JSON;

import java.util.List;

/**
 * FastJson工具类
 */
public class FastJsonUtil {
    /**
     * json字符串解析成对象
     * @param json
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> T json2Object(String json,Class<T> clazz) {
        return JSON.parseObject(json,clazz);
    }
    /**
     * json字符串解析成List集合
     * @param json
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> List<T> json2List(String json, Class<T> clazz) {
        return JSON.parseArray(json, clazz);
    }
    /**
     * 对象转换为json字符串
     * @param object
     * @return
     */
    public static String object2Json(Object object) {
        return JSON.toJSONString(object);
    }
}

3、创建一个与JSON数据对应的JavaBean类（用作存储需要解析的数据）

Gson解析的关键 = 根据JSON数据写出一个对应的JavaBean，规则是：

JavaBean.jpg
下面用2个例子说明如何通过JSON文档创建JavaBean类

/*
简单转换
*/
{
  "id": 1,
  "name": "小明",
  "sex": "男",
  "age": 18,
  "height": 175
}
// 对应的JavaBean类
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 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;
  }
}

/*
复杂转换（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"}]
}
// 对应的复杂数据对应的JavaBean类
public class car {
  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
  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
  class wb{
    public String[] value;
    public String key;
  }
}

注：若觉得转换过于复杂，请直接使用工具：JSON字符串在线转Java实体类工具

4、使用FastJson工具类进行解析

School对应的JavaBean类

import java.util.Arrays;
import java.util.List;

/*需解析的JSON数据：school.json
将该文件放入到项目的main\assets文件夹里（没有assets文件夹的话手动创建）
{"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"
}*/

public class School {
    private List<stu> student;

    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;
    }
    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;
        }

        @Override
        public String toString() {
            return "stu{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", sex='" + sex + '\'' +
                    ", age=" + age +
                    ", height=" + height +
                    ", date=" + Arrays.toString(date) +
                    '}';
        }
    }

    @Override
    public String toString() {
        return "School{" +
                "student=" + student +
                ", grade=" + grade +
                '}';
    }
}

具体用工具类进行解析测试代码

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //json2Object
        try {
            // 1. //从assets获取json文件
            InputStreamReader isr = new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream("assets/" + "school.json"),"utf-8");
            BufferedReader bfr = new BufferedReader(isr);
            String line;
            StringBuilder stringBuilder = new StringBuilder();
            while ((line = bfr.readLine())!=null){
                stringBuilder.append(line);
            }
            School school = FastJsonUtil.json2Object(stringBuilder.toString(), School.class);
            Log.d("FastJsonUtil",school.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
        //json2List
        // 3. 使用Gson解析：将JSON数据转为单个类实体
        String json = "[\n" +
                "  {\"id\":1,\"name\":\"小明\",\"sex\":\"男\",\"age\":18,\"height\":175,\"date\":[2013,8,11]},\n" +
                "  {\"id\":2,\"name\":\"小红\",\"sex\":\"女\",\"age\":19,\"height\":165,\"date\":[2013,8,23]},\n" +
                "  {\"id\":3,\"name\":\"小强\",\"sex\":\"男\",\"age\":20,\"height\":185,\"date\":[2013,9,1]}\n" +
                "]";
        List<School.stu> stuList = FastJsonUtil.json2List(json, School.stu.class);
        Log.d("FastJsonUtil",stuList.toString());
        //object2Json
        List<String> mList = new ArrayList<>();
        for (int i = 0; i < 6; i++) {
            mList.add("数据"+i);
        }
        Log.d("FastJsonUtil",FastJsonUtil.object2Json(mList));
    }

}

输出日志

FastJsonUtil: School{student=[stu{id=1, name='小明', sex='男', age=18, height=175, date=[2013, 8, 11]}, stu{id=2, name='小红', sex='女', age=19, height=165, date=[2013, 8, 23]}, stu{id=3, name='小强', sex='男', age=20, height=185, date=[2013, 9, 1]}], grade=2}
FastJsonUtil: [stu{id=1, name='小明', sex='男', age=18, height=175, date=[2013, 8, 11]}, stu{id=2, name='小红', sex='女', age=19, height=165, date=[2013, 8, 23]}, stu{id=3, name='小强', sex='男', age=20, height=185, date=[2013, 9, 1]}]
FastJsonUtil: ["数据0","数据1","数据2","数据3","数据4","数据5"]

好了到此为止基本就完了，json解析在实际开发中用的还是挺多的，掌握还是必须的，记不住就收藏点评论下或点个赞哦！

感谢简书作者Carson_Ho的文章作为参考，文章链接

JSON解析

JSON解析

语法

解析方式

具体使用步骤

1、在Android Gradle导入依赖

2、编写FastJson工具类

3、创建一个与JSON数据对应的JavaBean类（用作存储需要解析的数据）

注：若觉得转换过于复杂，请直接使用工具：JSON字符串在线转Java实体类工具

4、使用FastJson工具类进行解析

感谢简书作者Carson_Ho的文章作为参考，文章链接

推荐阅读更多精彩内容