利用Jackson封装常用的JsonUtil工具类

在实际开发中，我们对于 JSON 数据的处理，通常有这么几个第三方工具包可以使用：

gson：谷歌的
fastjson：阿里巴巴的
jackson：美国FasterXML公司的，Spring框架默认用的

由于以前一直用习惯了阿里的 fastjson，最近突然改为 jackson ，不是太习惯，所以手写一个工具类，应付一下工作中常用的一些方法。

1. 引入依赖包

在 pom.xml 文件中加入以下依赖

<!-- 引入jackson依赖包-->
<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.14.2</version>
</dependency>

2. 编写 JsonUtil 工具类

package com.yuhuofei.utils;import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import lombok.extern.slf4j.Slf4j;import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;/*** @Description 由于习惯了用fastjson处理JSON数据，突然改成用jackson，有些不适应，所以打算用jackson封装出类似fastjson里的方法进行使用* @ClassName JsonUtil* @Author yuhuofei* @Date 2023/8/19 14:36* @Version 1.0*/
@Slf4j
public class JsonUtil {private static ObjectMapper objectMapper = new ObjectMapper();// 时间日期格式private static final String STANDARD_FORMAT = "yyyy-MM-dd HH:mm:ss";//以静态代码块初始化static {//对象的所有字段全部列入序列化objectMapper.setSerializationInclusion(JsonInclude.Include.ALWAYS);//取消默认转换timestamps形式objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);//忽略空Bean转json的错误objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);//所有的日期格式都统一为以下的格式，即yyyy-MM-dd HH:mm:ssobjectMapper.setDateFormat(new SimpleDateFormat(STANDARD_FORMAT));//忽略 在json字符串中存在，但在java对象中不存在对应属性的情况。防止错误objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);}/**===========================以下是从JSON中获取对象====================================*/public static <T> T parseObject(String jsonString, Class<T> object) {T t = null;try {t = objectMapper.readValue(jsonString, object);} catch (JsonProcessingException e) {log.error("JsonString转为自定义对象失败：{}", e.getMessage());}return t;}public static <T> T parseObject(File file, Class<T> object) {T t = null;try {t = objectMapper.readValue(file, object);} catch (IOException e) {log.error("从文件中读取json字符串转为自定义对象失败：{}", e.getMessage());}return t;}//将json数组字符串转为指定对象List列表或者Map集合public static <T> T parseJSONArray(String jsonArray, TypeReference<T> reference) {T t = null;try {t = objectMapper.readValue(jsonArray, reference);} catch (JsonProcessingException e) {log.error("JSONArray转为List列表或者Map集合失败：{}", e.getMessage());}return t;}/**=================================以下是将对象转为JSON=====================================*/public static String toJSONString(Object object) {String jsonString = null;try {jsonString = objectMapper.writeValueAsString(object);} catch (JsonProcessingException e) {log.error("Object转JSONString失败：{}", e.getMessage());}return jsonString;}public static byte[] toByteArray(Object object) {byte[] bytes = null;try {bytes = objectMapper.writeValueAsBytes(object);} catch (JsonProcessingException e) {log.error("Object转ByteArray失败：{}", e.getMessage());}return bytes;}public static void objectToFile(File file, Object object) {try {objectMapper.writeValue(file, object);} catch (JsonProcessingException e) {log.error("Object写入文件失败：{}", e.getMessage());} catch (IOException e) {e.printStackTrace();}}/**=============================以下是与JsonNode相关的=======================================*///JsonNode和JSONObject一样，都是JSON树形模型，只不过在jackson中，存在的是JsonNodepublic static JsonNode parseJSONObject(String jsonString) {JsonNode jsonNode = null;try {jsonNode = objectMapper.readTree(jsonString);} catch (JsonProcessingException e) {log.error("JSONString转为JsonNode失败：{}", e.getMessage());}return jsonNode;}public static JsonNode parseJSONObject(Object object) {JsonNode jsonNode = objectMapper.valueToTree(object);return jsonNode;}public static String toJSONString(JsonNode jsonNode) {String jsonString = null;try {jsonString = objectMapper.writeValueAsString(jsonNode);} catch (JsonProcessingException e) {log.error("JsonNode转JSONString失败：{}", e.getMessage());}return jsonString;}//JsonNode是一个抽象类，不能实例化，创建JSON树形模型，得用JsonNode的子类ObjectNode，用法和JSONObject大同小异public static ObjectNode newJSONObject() {return objectMapper.createObjectNode();}//创建JSON数组对象，就像JSONArray一样用public static ArrayNode newJSONArray() {return objectMapper.createArrayNode();}/**===========以下是从JsonNode对象中获取key值的方法，个人觉得有点多余，直接用JsonNode自带的取值方法会好点，出于纠结症，还是补充进来了*/public static String getString(JsonNode jsonObject, String key) {String s = jsonObject.get(key).asText();return s;}public static Integer getInteger(JsonNode jsonObject, String key) {Integer i = jsonObject.get(key).asInt();return i;}public static Boolean getBoolean(JsonNode jsonObject, String key) {Boolean bool = jsonObject.get(key).asBoolean();return bool;}public static JsonNode getJSONObject(JsonNode jsonObject, String key) {JsonNode json = jsonObject.get(key);return json;}
}

3. 测试

新建一个 User 类

package com.yuhuofei.entity;import lombok.Data;import java.io.Serializable;/*** @Description* @ClassName User* @Author yuhuofei* @Date 2023/8/19 14:49* @Version 1.0*/
@Data
public class User implements Serializable {private static final long serialVersionUID = 1L;private Integer id;private String name;private String passWord;
}

新建一个测试类

import com.yuhuofei.entity.User;
import com.yuhuofei.utils.JsonUtil;/*** @Description* @ClassName TestJsonUtil* @Author yuhuofei* @Date 2023/8/19 14:58* @Version 1.0*/
public class TestJsonUtil {public static void main(String[] args) {String jsonString = "{\"id\":11,\"name\":\"小明\",\"passWord\":\"123456\"}";User user = JsonUtil.parseObject(jsonString, User.class);System.out.println(user);}
}