Ming
0%

JSON

Posted on Edited on In

JSON

地位

数据传输的一种格式

特点

UTF-8 Only

语法简单，key只能是字符串

浏览器认识JSON，可以转为js对象

  • 开发web应用的不二之选

支持的数据类型

键值对

数组

字符串

数值

布尔值

空值null

用java读写JSON

测试函数

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
package eternal.fire;

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

import java.io.IOException;
import java.io.InputStream;

public class Main {
    public static void main(String[] args) throws IOException {
        InputStream inputStream = Main.class.getResourceAsStream("/book.json");
        ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule());
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        Book book = objectMapper.readValue(inputStream, Book.class);
        System.out.println(book.pubDate);
        System.out.println(book.price);
        System.out.println(book.isbn);
        String json = objectMapper.writeValueAsString(book);
        System.out.println(json);
    }
}

自定义解析规则

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
package eternal.fire;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;

import java.io.IOException;
import java.math.BigInteger;

public class IsbnDeserializer extends JsonDeserializer<BigInteger> {
    @Override
    public BigInteger deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
        String str = jsonParser.getValueAsString();
        if (str != null) {
            return new BigInteger(str.replace('-', ' '));
        }
        return null;
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Java Bean

package eternal.fire;

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.time.LocalDate;
import java.util.List;

public class Book {
    public long id;
    public String name;
    public String author;
    @JsonDeserialize(using = IsbnDeserializer.class)
    public BigInteger isbn;
    public List<String> tags;
    public LocalDate pubDate;
    public BigDecimal price;
}

要解析的JSON

1
2
3
4
5
6
7
8
9
{
  "id": 1,
  "name": "Java核心技术",
  "author": "Cay S. Horstmann",
  "isbn": "978-7-111-54742-6",
  "tags": ["Java", "Network"],
  "pubDate": "2016-09-01",
  "price": 119.5
}

反序列化

  • JSON转化为一般的java对象
  • JSON转化为特殊的java对象，例如LocalTime
  • 自定义解析规则

序列化

  • 自定义解析规则