JsonReader解析json文件实例

冷不防 2021-12-03 11:25 548阅读 0赞

//要解析的message.json文件如下
     1 [
     2    {
     3      "id": 912345678901,
     4      "text": "How do I read a JSON stream in Java?",
     5      "geo": null,
     6      "user": {
     7        "name": "json_newb",
     8        "followers_count": 41
     9       }
    10    },
    11    {
    12      "id": 912345678902,
    13      "text": "@json_newb just use JsonReader!",
    14      "geo": [50.454722, -104.606667],
    15      "user": {
    16        "name": "jesse",
    17        "followers_count": 2
    18      }
    19    }
    20  ]

先写Message类和User类

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 import java.util.ArrayList;
     2 
     3 public class Message {
     4     private long id;
     5     private String text;
     6     private ArrayList<Double> geo;
     7     private User user;
     8 
     9     public Message() {
    10     }
    11 
    12     public Message(long id, String text, ArrayList<Double> geo, User user) {
    13         super();
    14         this.id = id;
    15         this.text = text;
    16         this.geo = geo;
    17         this.user = user;
    18     }
    19 
    20     public long getId() {
    21         return id;
    22     }
    23 
    24     public void setId(long id) {
    25         this.id = id;
    26     }
    27 
    28     public String getText() {
    29         return text;
    30     }
    31 
    32     public void setText(String text) {
    33         this.text = text;
    34     }
    35 
    36     public ArrayList<Double> getGeo() {
    37         return geo;
    38     }
    39 
    40     public void setGeo(ArrayList<Double> geo) {
    41         this.geo = geo;
    42     }
    43 
    44     public User getUser() {
    45         return user;
    46     }
    47 
    48     public void setUser(User user) {
    49         this.user = user;
    50     }
    51 
    52     @Override
    53     public String toString() {
    54         return "Message [id=" + id + ", text=" + text + ", geo=" + geo + ", user=" + user + "]";
    55     }
    56 
    57 }

Message

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 public class User {
     2     private String name;
     3     private int followers_count;
     4 
     5     public String getName() {
     6         return name;
     7     }
     8 
     9     public void setName(String name) {
    10         this.name = name;
    11     }
    12 
    13     public int getFollowers_count() {
    14         return followers_count;
    15     }
    16 
    17     public void setFollowers_count(int followers_count) {
    18         this.followers_count = followers_count;
    19     }
    20 
    21     @Override
    22     public String toString() {
    23         return "User [name=" + name + ", followers_count=" + followers_count + "]";
    24     }
    25 
    26 }

User

接下来就是解析部分的代码了

1 import java.io.IOException;
     2 import java.io.InputStream;
     3 import java.io.InputStreamReader;
     4 import java.util.ArrayList;
     5 
     6 import com.google.gson.stream.JsonReader;
     7 import com.google.gson.stream.JsonToken;
     8 
     9 public class Jsontest2 {
    10     public static void main(String[] args) {
    11         InputStream iStream = Thread.currentThread().getContextClassLoader().getResourceAsStream("message.json");
    12         InputStreamReader in = new InputStreamReader(iStream);
    13         JsonReader reader = new JsonReader(in);
    14         ArrayList<Message> list = readMessageArray(reader);
    15         for (Message m : list) {
    16             System.out.println(m);
    17         }
    18     }
    19 
    20     // 解析数组
    21     public static ArrayList<Message> readMessageArray(JsonReader reader) {
    22         ArrayList<Message> list = new ArrayList<>();
    23         try {
    24             reader.beginArray();
    25             while (reader.hasNext()) {
    26                 list.add(readMessage(reader));
    27             }
    28             reader.endArray();
    29         } catch (IOException e) {
    30             e.printStackTrace();
    31         }
    32         return list;
    33     }
    34 
    35     // 解析对象
    36     public static Message readMessage(JsonReader reader) {
    37         Message message = new Message();
    38         try {
    39             reader.beginObject();
    40             while (reader.hasNext()) {
    41                 String name = reader.nextName();
    42                 if ("id".equals(name)) {
    43                     message.setId(reader.nextLong());
    44                 } else if ("text".equals(name)) {
    45                     message.setText(reader.nextString());
    46                 } else if ("geo".equals(name) && reader.peek() != JsonToken.NULL) {
    47                     message.setGeo(readGeo(reader));
    48                 } else if ("user".equals(name)) {
    49                     message.setUser(readUser(reader));
    50                 } else {
    51                     reader.skipValue();
    52                 }
    53             }
    54             reader.endObject();
    55         } catch (Exception e) {
    56             e.printStackTrace();
    57         }
    58         return message;
    59     }
    60 
    61     // 解析Geo数组
    62     public static ArrayList<Double> readGeo(JsonReader reader) {
    63         ArrayList<Double> list = new ArrayList<>();
    64         try {
    65             reader.beginArray();
    66             while (reader.hasNext()) {
    67                 // 直接读数据就可以
    68                 double nextDouble = reader.nextDouble();
    69                 list.add(nextDouble);
    70             }
    71             reader.endArray();
    72         } catch (Exception e) {
    73             e.printStackTrace();
    74         }
    75         return list;
    76     }
    77 
    78     // 解析user对象
    79     public static User readUser(JsonReader reader) {
    80         User user = new User();
    81         try {
    82             reader.beginObject();
    83             while (reader.hasNext()) {
    84                 String name = reader.nextName();
    85                 if ("name".equals(name)) {
    86                     user.setName(reader.nextString());
    87                 } else if ("followers_count".equals(name)) {
    88                     user.setFollowers_count(reader.nextInt());
    89                 } else {
    90                     reader.skipValue();
    91                 }
    92             }
    93             reader.endObject();
    94         } catch (Exception e) {
    95             e.printStackTrace();
    96         }
    97         return user;
    98     }
    99 }

转载于:https://www.cnblogs.com/glittergirl/p/10756304.html

[ContractedBlock.gif]: https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
[ExpandedBlockStart.gif]: /images/20211203/691a4866fa384dfea355b6b73b8fdf91.png