jackson/fastjson

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import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.Data;
import org.omg.Messaging.SYNC_WITH_TRANSPORT;

import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Data
class User {
    private Long id;
    private String userId;
    private String userName;

    private Address[] address;
    @Data
    public  static class Address{
        private String street;
    }
}

public class A {
    public static void main(String[] args) throws IOException {
        ObjectMapper objectMapper = new ObjectMapper();
        User user = new User();
        user.setId(1L);
        user.setUserId("123");
        user.setUserName("test");
        User.Address address = new User.Address();
        address.setStreet("BJ");
        User.Address[] list = new User.Address[]{address};
        user.setAddress(list);
        System.out.println("----jackson----");
        //转为json
        String json = objectMapper.writeValueAsString(user);
        System.out.println("Bean > json " + json);

        String jsonString = "{\"id\":1,\"userId\":\"123\",\"userName\":\"test\",\"address\":[{\"street\":\"BJ\"}]}";
        //转为Bean
        User userBean = objectMapper.readValue(jsonString, User.class);
        System.out.println("json > Bean " + userBean);

        //不转为Bean
        JsonNode rootNode = objectMapper.readTree(jsonString);
        // asInt asText
        String userName = rootNode.path("userName").asText();
        System.out.println("json > 非Bean属性 " + userName);
        int userId = rootNode.path("userId").asInt();
        System.out.println("json > 非Bean属性 " + userId);
        JsonNode childNode = rootNode.path("address");
        // get(0)用于获取列表元素
        String street = childNode.get(0).path("street").asText();
        System.out.println("json > 非Bean子属性 " + street);

        //转为Bean Map
        Map<String, Object> map = objectMapper.readValue(jsonString, new TypeReference<Map<String, Object>>(){});
        // 或者 HashMap map = objectMapper.readValue(string, HashMap.class);
        System.out.println("json > Map " + map);

        String jsonStringArray = "[{\"id\":1,\"userId\":\"123\",\"userName\":\"test\",\"address\":[{\"street\":\"street1\"}]}," +
                "{\"id\":1,\"userId\":\"123\",\"userName\":\"test\",\"address\":[{\"street\":\"street1\"}]}]";
        //转为Bean List
        List<User> userList = objectMapper.readValue(jsonStringArray, new TypeReference<List<User>>(){});
        System.out.println("json > List<Bean> " + userList);


        System.out.println("----fastjson----");
        //转为json
        String string = JSON.toJSONString(user);
        System.out.println("Bean > json " + string);

        // 转为Bean
        user = JSON.parseObject(jsonString, User.class);
        System.out.println("json > Bean " + user);


        // 转为非Bean
        JSONObject bodyJson = JSON.parseObject(jsonString);
        System.out.println(bodyJson);
        userName = bodyJson.getString("userName");
        System.out.println("json > 非Bean属性 " + userName);

        userId = bodyJson.getIntValue("userId");
        System.out.println("json > 非Bean属性 " + userId);
        street = bodyJson.getJSONArray("address").getJSONObject(0).getString("street");
        System.out.println("json > 非Bean子属性 " + street);

        // 转为Bean List
        userList = JSON.parseArray(jsonStringArray, User.class);
        System.out.println("json > List<Bean> " + userList);
        

    }
}

参考 https://itlearner.me/p/56384/

https://www.iteye.com/blog/shensy-1717776

http://kimmking.github.io/2017/06/06/json-best-practice/