写在前面：开发中经常用到json和对象的相互转换，下面将列出FastJson中ObjectMapper对象的API的使用

一、maven工程中pom导入
<dependency>

<groupId>com.fasterxml.jackson.core</groupId>

<artifactId>jackson-databind</artifactId>

<version>2.8.3</version>

</dependency>
二、使用
1、创建对象
public static ObjectMapper mapper = new ObjectMapper();
2、初始化
static {
// 转换为格式化的json
mapper.enable(SerializationFeature.INDENT_OUTPUT);
// 如果json中有新增的字段并且是实体类类中不存在的，不报错
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
//修改日期格式
mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
}
3、对象转为字符串
String jsonStr = mapper.writeValueAsString(user);

System.out.println("对象转为字符串：" + jsonStr);
4、对象转为byte数组
byte[] byteArr = mapper.writeValueAsBytes(user);

System.out.println("对象转为byte数组：" + byteArr);
5、json字符串转为对象
ObjectClass obj = mapper.readValue(jsonStr, ObjectClass.class);

System.out.println("json字符串转为对象：" + obj);
6、byte数组转为对象
ObjectClass obj = mapper.readValue(byteArr,ObjectClass.class);

System.out.println("byte数组转为对象：" + obj);
7、集合转为字符串
String jsonStr = mapper.writeValueAsString(userList);

System.out.println("集合转为字符串：" + jsonStr);
8、字符串转集合
List list = null;
try {
list = mapper.readValue(jsonStr, List.class);
} catch (IOException e1) {
e1.printStackTrace();
}
9、Map转为字符串
String jsonStr = mapper.writeValueAsString(testMap);

System.out.println("Map转为字符串：" + jsonStr);
10、字符串转Map
Map map = null;
try {
map = mapper.readValue(jsonStr, Map.class);
} catch (IOException e1) {
e1.printStackTrace();
}
三、JsonUtils工具类
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.List;
import java.util.Map;

/**
* @Author Guixing
* @Date 2019/1/7 11:10
* @Description
*/
public class JsonUtils {

public static ObjectMapper mapper = new ObjectMapper();

static {
// 转换为格式化的json
mapper.enable(SerializationFeature.INDENT_OUTPUT);
// 如果json中有新增的字段并且是实体类类中不存在的，不报错
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
//修改日期格式
mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
}

/**
* 对象转为字符串
*
* @param obj
* @return
*/
public static String Object2Json(Object obj) {
String jsonStr = null;
try {
jsonStr = mapper.writeValueAsString(obj);
} catch (JsonProcessingException e1) {
e1.printStackTrace();
}
return jsonStr;
}

/**
* 对象转为byte数组
*
* @param obj
* @return
*/
public static byte[] object2ByteArray(Object obj) {
byte[] byteArr = new byte[0];
try {
byteArr = mapper.writeValueAsBytes(obj);
} catch (JsonProcessingException e1) {
e1.printStackTrace();
}
return byteArr;
}

/**
* json字符串转为对象
*
* @param jsonStr
* @param beanType
* @param <T>
* @return
*/
public static <T> T json2Object(String jsonStr, Class<T> beanType) {
T t = null;
try {
t = mapper.readValue(jsonStr, beanType);
} catch (IOException e1) {
e1.printStackTrace();
}
return t;
}

/**
* byte数组转为对象
*
* @param byteArr
* @param beanType
* @param <T>
* @return
*/
public static <T> T byteArr2Object(byte[] byteArr, Class<T> beanType) {
T t = null;
try {
t = mapper.readValue(byteArr, beanType);
} catch (Exception e) {
e.printStackTrace();
}
return t;
}

/**
* 集合转为字符串
*
* @param list
* @return
*/
public static String list2String(List list) {
String jsonStr = null;
try {
jsonStr = mapper.writeValueAsString(list);
} catch (JsonProcessingException e1) {
e1.printStackTrace();
}
return jsonStr;
}

/**
* 字符串转集合
*
* @param jsonStr
* @return
*/
public static List json2List(String jsonStr) {
List list = null;
try {
list = mapper.readValue(jsonStr, List.class);
} catch (IOException e1) {
e1.printStackTrace();
}
return list;
}

/**
* Map转为字符串
*
* @param map
* @return
*/
public static String map2String(Map map) {
String jsonStr = null;
try {
jsonStr = mapper.writeValueAsString(map);
} catch (JsonProcessingException e1) {
e1.printStackTrace();
}
return jsonStr;
}

/**
* 字符串转Map
*
* @param jsonStr
* @return
*/
public static Map json2Map(String jsonStr) {
Map map = null;
try {
map = mapper.readValue(jsonStr, Map.class);
} catch (IOException e1) {
e1.printStackTrace();
}
return map;
}

}

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原文链接：https://blog.csdn.net/qq_37394874/article/details/85992380