利用Jackson封装常用JsonUtil工具类

在日常的项目开发中，接口与接口之间、前后端之间的数据传输一般都是使用JSON格式，那必然会封装一些常用的Json数据转化的工具类，本文讲解下如何利用Jackson封装高复用性的Json转换工具类。

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import java.io.IOException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com...common.util.StringUtil;

/**
* jsonUtil工具类
*
* @author ryz
* @since 2020-05-11
*/
public class JsonUtil {

private static final Logger LOGGER = LoggerFactory.getLogger(JsonUtil.class);

private static ObjectMapper mapper = new ObjectMapper();

/**
* 对象转Json格式字符串
* @param obj 对象
* @return Json格式字符串
*/
public static <T> String obj2String(T obj) {
if (obj == null) {
return null;
}
try {
return obj instanceof String ? (String) obj : mapper.writeValueAsString(obj);
} catch (JsonProcessingException e) {
LOGGER.warn("Parse Object to String error : {}", e.getMessage());
return null;
}
}

/**
* 对象转Json格式字符串(格式化的Json字符串)
* @param obj 对象
* @return 美化的Json格式字符串
*/
public static <T> String obj2StringPretty(T obj) {
if (obj == null) {
return null;
}
try {
return obj instanceof String ? (String) obj : mapper.writerWithDefaultPrettyPrinter().writeValueAsString(obj);
} catch (JsonProcessingException e) {
LOGGER.warn("Parse Object to String error : {}", e.getMessage());
return null;
}
}

/**
* 字符串转换为自定义对象
* @param str 要转换的字符串
* @param clazz 自定义对象的class对象
* @return 自定义对象
*/
public static <T> T jsonToObj(String str, Class<T> clazz){
if(StringUtil.isEmpty(str) || clazz == null){
return null;
}
try {
return clazz.equals(String.class) ? (T) str : mapper.readValue(str, clazz);
} catch (Exception e) {
LOGGER.warn("Parse String to Object error : {}", e.getMessage());
return null;
}
}

/**
* 集合对象与Json字符串之间的转换
* @param str 要转换的字符串
* @param typeReference 集合类型如List<Object>
* @param <T>
* @return
*/
public static <T> T jsonToObj(String str, TypeReference<T> typeReference) {
if (StringUtil.isEmpty(str) || typeReference == null) {
return null;
}
try {
return (T) (typeReference.getType().equals(String.class) ? str : mapper.readValue(str, typeReference));
} catch (IOException e) {
LOGGER.warn("Parse String to Object error", e);
return null;
}
}

/**
* 集合对象与Json字符串之间的转换
* @param str 要转换的字符串
* @param collectionClazz 集合类型
* @param elementClazzes 自定义对象的class对象
* @param <T>
* @return
*/
public static <T> T string2Obj(String str, Class<?> collectionClazz, Class<?>... elementClazzes) {
JavaType javaType = mapper.getTypeFactory().constructParametricType(collectionClazz, elementClazzes);
try {
return mapper.readValue(str, javaType);
} catch (IOException e) {
LOGGER.warn("Parse String to Object error : {}" + e.getMessage());
return null;
}
}
}

User对象类

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package com...utils;

/**
* 功能描述
*
* @since 2020-05-11
*/
public class User {
private Integer id;
private String email;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getEmail() {
return email;
}

public void setEmail(String email) {
this.email = email;
}
}

测试类

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/*
* Copyright (c) Huawei Technologies Co., Ltd. 2020-2020. All rights reserved.
*/

package ....utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.List;

import com.fasterxml.jackson.core.type.TypeReference;

public class JsonUtilTest {
private static final Logger LOGGER = LoggerFactory.getLogger(JsonUtilTest.class);

public static void main(String[] args) {
User user1 = new User();
user1.setId(1);
user1.setEmail("[email protected]");
String userJsonstr = JsonUtil.obj2String(user1);
String userJsonPretty = JsonUtil.obj2StringPretty(user1);
LOGGER.info("userJson: {}", userJsonPretty);

User user2 = JsonUtil.string2Obj(userJsonstr, User.class);
user2.setId(2);
user2.setEmail("[email protected]");

List<User> userList = new ArrayList<>();
userList.add(user1);
userList.add(user2);
String userListJson = JsonUtil.obj2String(userList);
List<User> userListBean = JsonUtil.string2Obj(userListJson, new TypeReference<List<User>>() {});
if (userListBean != null) {
userListBean.forEach(user -> {
System.out.println(user.getId() + " : " + user.getEmail());
});
}
List<User> userListBean2 = JsonUtil.string2Obj(userListJson, List.class, User.class);
if (userListBean2 != null) {
userListBean2.forEach(user -> {
System.out.println(user.getId() + " : " + user.getEmail());
});
}
}
}

运行结果
在这里插入图片描述