<!-- 根据自己需要引入相关版本依赖。 -->
<dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>2.9.10</version>
</dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.9.10</version>
</dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId><version>2.9.10</version>
</dependency>

1、反序列化（字符串转对象）

// 创建 ObjectMapper 对象
ObjectMapper objectMapper = new ObjectMapper();// 将 JSON 字符串反序列化为 Java 对象
MyClass myObj = objectMapper.readValue(jsonString, MyClass.class);

2、序列化（对象转字符串）

// 创建 ObjectMapper 对象
ObjectMapper objectMapper = new ObjectMapper();// 将 Java 对象序列化为 JSON 字符串
String jsonString = objectMapper.writeValueAsString(obj);

ObjectMapper mapper = new ObjectMapper();
String jsonString = "{\"name\":\"Hyl\", \"age\":20}";//将字符串转换为对象
Student student = mapper.readValue(jsonString, Student.class);
System.out.println(student);//将对象转换为json字符串
jsonString = mapper.writeValueAsString(student);
System.out.println(jsonString);结果：
Student [ name: Hyl, age: 20 ]{"name" : "Hyl","age" : 20
}

//对象转为byte数组
byte[] byteArr = mapper.writeValueAsBytes(student);
System.out.println(byteArr);//byte数组转为对象
Student student= mapper.readValue(byteArr, Student.class);
System.out.println(student);结果：
[B@3327bd23Student [ name: Hyl, age: 20 ]

List<Student> studentList= new ArrayList<>();
studentList.add(new Student("hyl1" ,20 , new Date()));
studentList.add(new Student("hyl2" ,21 , new Date()));
studentList.add(new Student("hyl3" ,22 , new Date()));
studentList.add(new Student("hyl4" ,23 , new Date()));String jsonStr = mapper.writeValueAsString(studentList);
System.out.println(jsonStr);List<Student> studentList2 = mapper.readValue(jsonStr, List.class);
System.out.println("字符串转集合：" + studentList2 );结果：
[ {"name" : "hyl1","age" : 20,"sendTime" : 1525164212803
}, {"name" : "hyl2","age" : 21,"sendTime" : 1525164212803
}, {"name" : "hyl3","age" : 22,"sendTime" : 1525164212803
}, {"name" : "hyl4","age" : 23,"sendTime" : 1525164212803
} ]
[{name=hyl1, age=20, sendTime=1525164212803}, {name=hyl2, age=21, sendTime=1525164212803}, {name=hyl3, age=22, sendTime=1525164212803}, {name=hyl4, age=23, sendTime=1525164212803}]

Map<String, Object> testMap = new HashMap<>();
testMap.put("name", "22");
testMap.put("age", 20);
testMap.put("date", new Date());
testMap.put("student", new Student("hyl", 20, new Date()));String jsonStr = mapper.writeValueAsString(testMap);
System.out.println(jsonStr);
Map<String, Object> testMapDes = mapper.readValue(jsonStr, Map.class);
System.out.println(testMapDes);结果：
{"date" : 1525164212803,"name" : "22","student" : {"name" : "hyl","age" : 20,"sendTime" : 1525164212803,"intList" : null},"age" : 20
}
{date=1525164212803, name=22, student={name=hyl, age=20, sendTime=1525164212803, intList=null}, age=20}

// 修改时间格式
mapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
Student student = new Student ("hyl",21, new Date());
student.setIntList(Arrays.asList(1, 2, 3));String jsonStr = mapper.writeValueAsString(student);
System.out.println(jsonStr);结果：
{"name" : "hyl","age" : 21,"sendTime" : "2020-07-23 13:14:36","intList" : [ 1, 2, 3 ]
}