JsonReader解析json文件实例

//要解析的message.json文件如下
 1 [
   {
     "id": 912345678901,
     "text": "How do I read a JSON stream in Java?",
     "geo": null,
     "user": {
       "name": "json_newb",
       "followers_count": 41
      }
   },
   {
     "id": 912345678902,
     "text": "@json_newb just use JsonReader!",
     "geo": [50.454722, -104.606667],
     "user": {
       "name": "jesse",
       "followers_count": 2
     }
   }
 ]

先写Message类和User类

import java.util.ArrayList;

public class Message {
    private long id;
    private String text;
    private ArrayList<Double> geo;
    private User user;

    public Message() {
    }

    public Message(long id, String text, ArrayList<Double> geo, User user) {
        super();
        this.id = id;
        this.text = text;
        this.geo = geo;
        this.user = user;
    }

    public long getId() {
        return id;
    }

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

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public ArrayList<Double> getGeo() {
        return geo;
    }

    public void setGeo(ArrayList<Double> geo) {
        this.geo = geo;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    @Override
    public String toString() {
        return "Message [id=" + id + ", text=" + text + ", geo=" + geo + ", user=" + user + "]";
    }

}

public class User {
    private String name;
    private int followers_count;

    public String getName() {
        return name;
    }

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

    public int getFollowers_count() {
        return followers_count;
    }

    public void setFollowers_count(int followers_count) {
        this.followers_count = followers_count;
    }

    @Override
    public String toString() {
        return "User [name=" + name + ", followers_count=" + followers_count + "]";
    }

}

接下来就是解析部分的代码了

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;

public class Jsontest2 {
    public static void main(String[] args) {
        InputStream iStream = Thread.currentThread().getContextClassLoader().getResourceAsStream("message.json");
        InputStreamReader in = new InputStreamReader(iStream);
        JsonReader reader = new JsonReader(in);
        ArrayList<Message> list = readMessageArray(reader);
        for (Message m : list) {
            System.out.println(m);
        }
    }

    // 解析数组
    public static ArrayList<Message> readMessageArray(JsonReader reader) {
        ArrayList<Message> list = new ArrayList<>();
        try {
            reader.beginArray();
            while (reader.hasNext()) {
                list.add(readMessage(reader));
            }
            reader.endArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return list;
    }

    // 解析对象
    public static Message readMessage(JsonReader reader) {
        Message message = new Message();
        try {
            reader.beginObject();
            while (reader.hasNext()) {
                String name = reader.nextName();
                if ("id".equals(name)) {
                    message.setId(reader.nextLong());
                } else if ("text".equals(name)) {
                    message.setText(reader.nextString());
                } else if ("geo".equals(name) && reader.peek() != JsonToken.NULL) {
                    message.setGeo(readGeo(reader));
                } else if ("user".equals(name)) {
                    message.setUser(readUser(reader));
                } else {
                    reader.skipValue();
                }
            }
            reader.endObject();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return message;
    }

    // 解析Geo数组
    public static ArrayList<Double> readGeo(JsonReader reader) {
        ArrayList<Double> list = new ArrayList<>();
        try {
            reader.beginArray();
            while (reader.hasNext()) {
                // 直接读数据就可以
                double nextDouble = reader.nextDouble();
                list.add(nextDouble);
            }
            reader.endArray();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }

    // 解析user对象
    public static User readUser(JsonReader reader) {
        User user = new User();
        try {
            reader.beginObject();
            while (reader.hasNext()) {
                String name = reader.nextName();
                if ("name".equals(name)) {
                    user.setName(reader.nextString());
                } else if ("followers_count".equals(name)) {
                    user.setFollowers_count(reader.nextInt());
                } else {
                    reader.skipValue();
                }
            }
            reader.endObject();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return user;
    }
}