集合转换为Jsoin存入redis

重温复习redis，要将对象集合存入redis作为缓存，上网找了个json串转集合的工具类，这里记录一下。

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

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.CollectionType;


public class JsonUtil {
    private static ObjectMapper objectMapper = new ObjectMapper();
    static {
        //忽略属性为null
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        //忽略多余属性
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    }

    public static String objectToString(Object object)  {

        try {
            return objectMapper.writeValueAsString(object);

        } catch (JsonProcessingException e) {
            // TODO: handle exception
        }
        return null;
    }

    public static <T> T stringToObject(String json,Class<T> object) throws IOException {
        return objectMapper.readValue(json,object);
    }

    public static <T> List<T>   stringToList(String json,Class<T> object){
        try {
            CollectionType listType = objectMapper.getTypeFactory().constructCollectionType(ArrayList.class, object);
            List<T> list = objectMapper.readValue(json, listType);
            return list;
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        return null;
    }
}

一个很简单的示例，先从redis中去找集合。若不存在就从数据库中读取集合，并将数据写入redis。

public List<ShopType> queryTypeList() {
        String key=CACHE_SHOP_TYPE;
        String typeListJson = stringRedisTemplate.opsForValue().get(key);
        List<ShopType> typeList=null;
        if(typeListJson!=null){//redis中存有集合，直接获取
            typeList= JsonUtil.stringToList(typeListJson,ShopType.class);
        }else {
            //从数据库查找集合
            typeList = this.query().orderByAsc("sort").list();
            //将集合存入redis
            String json = JsonUtil.objectToString(typeList);
            stringRedisTemplate.opsForValue().set(key,json);
        }

        return typeList;

    }