Json常用序列化工具

1.maven

<dependency>
     <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
     <version>2.10.0</version>
 </dependency>

2.Json序列化工具类

1.对象转Json字符串
2.Json字符串转为对象
3.json列表字符串转List对象
4.json字符串转Map对象
5.单个对象或者list的Json字符串都转换成List对象

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * 常用Json序列化
 */
public class JsonUtil {

    private static final Logger log = LoggerFactory.getLogger(JsonUtil.class);
    /**
     * 对象转Json字符
     *
     * @param obj 对象
     * @return String
     */
    public static String objToJsonStr(Object obj) {
        try {
            ObjectMapper objectMapper = new ObjectMapper();
            return objectMapper.writeValueAsString(obj);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "";

    }

    /**
     * Json字符串转为对象
     *
     * @param jsonStr
     * @param clazz
     * @param <T>     对象类型
     * @return 对象
     */
    public static <T> T jsonStrToObject(String jsonStr, Class<T> clazz) {

        try {
            if (StringUtil.isEmpty(jsonStr)) return null;
            ObjectMapper objectMapper = new ObjectMapper();
            //允许未带引号字段
            objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
            //允许使用单引号
            objectMapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
            return objectMapper.readValue(jsonStr, clazz);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;

    }

    /**
     * json列表字符串转List对象
     *
     * @param jsonStr
     * @param clszz
     * @param <T>
     * @return
     */
    public static <T> List<T> jsonToList(String jsonStr, Class<T> clszz) {
        try {
            if (StringUtil.isEmpty(jsonStr)) return null;
            ObjectMapper objectMapper = new ObjectMapper();
            //允许未带引号字段
            objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
            //允许使用单引号
            objectMapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
            return objectMapper.readValue(jsonStr, getCollectionType(objectMapper, List.class, clszz));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * Map json字符串转Map对象
     *
     * @param jsonStr
     * @return
     */
    public static Map<String, Object> jsonToMap(String jsonStr) {
        try {
            if (StringUtil.isEmpty(jsonStr)) return null;
            ObjectMapper objectMapper = new ObjectMapper();
            //允许未带引号字段
            objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
            //允许使用单引号
            objectMapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);
            return objectMapper.readValue(jsonStr, new TypeReference<Map<String, Object>>() {
            });
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 获取泛型的Collection Type
     *
     * @param collectionClass 泛型的Collection
     * @param elementClasses  实体bean
     * @return JavaType Java类型
     */
    private static JavaType getCollectionType(ObjectMapper mapper, Class<?> collectionClass, Class<?>... elementClasses) {
        return mapper.getTypeFactory().constructParametricType(collectionClass, elementClasses);
    }

    /**
     * 单个对象或者list的Json字符串都转换成List对象
     *
     * @param jsonStr
     * @param cla
     * @param <T>
     * @return
     */
    public static <T> List<T> objOrArrToList(String jsonStr, Class<T> cla) {
        if (StringUtil.isEmpty(jsonStr)) return null;

        //单个或多个、都转成list
        boolean single = jsonStr.startsWith("{");
        List<T> cList = null;
        if (single) {
            T t = jsonStrToObject(jsonStr, cla);
            cList = new ArrayList();
            cList.add(t);
        } else {
            cList = jsonToList(jsonStr, cla);
        }
        return cList;
    }

}