JsonUtils工具类学习记录

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.lang.Nullable;

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

/**
 * @author: HuYi.Zhang
 * @create: 2018-04-24 17:20
 **/
public class JsonUtils {

    public static final ObjectMapper mapper = new ObjectMapper();

    private static final Logger logger = LoggerFactory.getLogger(JsonUtils.class);

    /**
     * 转换成json
     * @param obj
     * @return
     */
    @Nullable
    public static String serialize(Object obj) {
        if (obj == null) {
            return null;
        }
        if (obj.getClass() == String.class) {
            return (String) obj;
        }
        try {
            return mapper.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            logger.error("json序列化出错：" + obj, e);
            return null;
        }
    }

    @Nullable
    public static <T> T parse(String json, Class<T> tClass) {
        try {
            return mapper.readValue(json, tClass);
        } catch (IOException e) {
            logger.error("json解析出错：" + json, e);
            return null;
        }
    }

    @Nullable
    public static <E> List<E> parseList(String json, Class<E> eClass) {
        try {
            return mapper.readValue(json, mapper.getTypeFactory().constructCollectionType(List.class, eClass));
        } catch (IOException e) {
            logger.error("json解析出错：" + json, e);
            return null;
        }
    }

    @Nullable
    public static <K, V> Map<K, V> parseMap(String json, Class<K> kClass, Class<V> vClass) {
        try {
            return mapper.readValue(json, mapper.getTypeFactory().constructMapType(Map.class, kClass, vClass));
        } catch (IOException e) {
            logger.error("json解析出错：" + json, e);
            return null;
        }
    }

    @Nullable
    public static <T> T nativeRead(String json, TypeReference<T> type) {
        try {
            return mapper.readValue(json, type);
        } catch (IOException e) {
            logger.error("json解析出错：" + json, e);
            return null;
        }
    }


    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    static class Usert {
        String name;
        Integer age;
    }

    public static void main(String[] args) {
        Usert usert = new Usert("zhangshang", 343);
        usert.setAge(23);
        usert.setName("zhagns");

        usert.setName("qingchu");
        usert.setAge(233);

       String json =  serialize(usert);
        System.out.println("json输出："+json);
        Usert parse = parse(json, Usert.class);
        System.out.println("tostring 输出："+parse);

     /*   String  json = "[2,3,43,54,45,34]";
        List<Integer> list = parseList(json, Integer.class);
        list.stream().forEach(n-> System.out.print(n+" "));
        System.out.println(list);*/
      /*  Map<String, String> map = parseMap(json, String.class, String.class);
        System.out.println("map-->"+map);*/

        String newlist = "[{\"name\":\"qingchu\",\"age\":233},{\"name\":\"guxiang\",\"age\":54},{\"name\":\"beijing\",\"age\":23553}]";
        List<Map<String, String>> maps = nativeRead(newlist, new TypeReference<List<Map<String, String>>>() {});
        for (Map<String, String> map : maps) {
            System.out.println("new_map::"+map);
        }


    }