封装类:

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.util.StringUtils;

import java.io.IOException;

/**
 * QQ:728297725
 * Created by liupeng on 2019/4/14.
 */
public class JsonUtils {

    private static ObjectMapper objectMapper = new ObjectMapper();

    //对象转字符串
    public static <T> String obj2String(T obj){
        if (obj == null){
            return null;
        }
        try {
            return obj instanceof String ? (String) obj : objectMapper.writeValueAsString(obj);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    //字符串转对象
    public static <T> T string2Obj(String str,Class<T> clazz){
        if (StringUtils.isEmpty(str) || clazz == null){
            return null;
        }
        try {
            return clazz.equals(String.class)? (T) str :objectMapper.readValue(str,clazz);
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
}

调用实例:

//返回json实例
@RequestMapping(value="/httpJson", method = {RequestMethod.GET})
public String getJson(){
    JObject object = new JObject("chengxi","970624");
    Map<String,JObject> mapObject = new HashMap<String,JObject>();
    mapObject.put("liupeng",object);
    return JsonUtils.obj2String(mapObject);
}