Jackson所有的操作都是通过ObjectMapper对象实例来操作的，可以重用这个对象实例。
首先定义一个实例：ObjectMapper mapper = new ObjectMapper();
定义一个Student类:
???package jackson; ???import java.util.Date; ???public class Student { ???????private String name; ???????private int age; ???????private String position; ???????private Date createTime; ???????public String getName() { ???????????return name; ???????} ???????public void setName(String name) { ???????????this.name = name; ???????} ???????public int getAge() { ???????????return age; ???????} ???????public void setAge(int age) { ???????????this.age = age; ???????} ???????public String getPosition() { ???????????return position; ???????} ???????public void setPosition(String position) { ???????????this.position = position; ???????} ???????public Date getCreateTime() { ???????????return createTime; ???????} ???????public void setCreateTime(Date createTime) { ???????????this.createTime = createTime; ???????} ???????@Override ???????public String toString() { ???????????return "Student [name=" + name + ", age=" + age + ", position=" ???????????????????+ position + ", createTime=" + createTime + "]"; ???????} ???}准备一个字符串：String jsonString = "{\"name\":\"king\",\"age\":21}";
常规操作: 字符串转对象
????mapper.readValue(jsonString,Student.class); ????System.out.println(student);打印输出结果：
Student [name=king, age=21, position=null, createTime=null]常规操作: 对象转字符串
???????student.setCreateTime(new Date()); ???????String json = mapper.writeValueAsString(student); ???????System.out.println(json);打印输出结果：
{"name":"king","age":21,"position":null,"createTime":1524819355361}如何改变输出的日期字段格式?
两种方式：一种SimpleDateFormat，另外一种通过在属性字段注解
在Student.java属性字段createTime注解@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
import com.fasterxml.jackson.annotation.JsonFormat;public class Student { ???private String name; ???private int age; ???private String position; ???@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss") ?????private Date createTime; ????????????//省略get,set}打印输出结果：
{"name":"king","age":21,"position":null,"createTime":"2018-04-27 09:00:56"}8小时时间差问题：上面打印结果发现，时间少8小时。
解决方法: 注解上增加时区。
public class Student { ???private String name; ???private int age; ???private String position; ???@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss", timezone = "GMT+8") ?????private Date createTime; ???????????????//省略get,set}打印输出结果：
{"name":"king","age":21,"position":null,"createTime":"2018-04-27 17:07:33"}【json】Jackson的使用
原文地址：https://www.cnblogs.com/30go/p/8963290.html