1. 什么是 Json 序列化 和 反序列化
序列化 => 将 Java对象 转换成 json字符串反序列化 => 将 json字符串 转换成 Java对象
2. 依赖包 说明
com.fasterxml.jackson.core
jackson-databind
2.7.4
依赖包说明:
# 提供注解支持
Maven: com.fasterxml.jackson.core:jackson-annotations:2.7.0
# 核心功能支持
Maven: com.fasterxml.jackson.core:jackson-core:2.10.1
Maven: com.fasterxml.jackson.core:jackson-databind:2.7.4
3. ObjectMapper
功能:
ObjectMapper 提供了 读写Json的功能
读:
public T readValue(String content, Class valueType)
将 字符串content 反序列化 成 Class类型的对象
写(可以把JSON字符串保存File、OutputStream等不同的介质中):
public void writeValue(File resultFile, Object value)
将 Objec转成 json字符串,并保存到 指定 File 内
public void writeValue(OutputStream out, Object value)
将 Objec转成 json字符串,并保存到 指定 OutputStream 内(使用 UTF8 编码)
public byte[] writeValueAsBytes(Object value)
将 Objec转成 json字符串,并把结果输出成 字节数组
public String writeValueAsString(Object value)
将 Objec转成 json字符串,并把结果输出成 字符串
4. Json 注解
@JsonIgnore 此注解用于属性上,作用是进行JSON操作时忽略该属性
@JsonFormat 此注解用于属性上,作用是把Date类型直接转化为想要的格式,如@JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")。
示例: @JsonFormat(pattern = "yyyy-MM-dd HH-mm-ss")
@JsonProperty 此注解用于属性上,作用是把该属性的名称序列化为另外一个名称
示例: @JsonProperty("AliasName")
5. Bean对象 => Json 字符串 (Json 序列化)
// TODO 用来转换的 Bean
case class UserBean(@BeanProperty name: String
, @BeanProperty age: Int
, @BeanProperty birthday: Date
, @BeanProperty email: String)
// TODO Bean对象 => Json 字符串 (Json 序列化)
object Bean2Json extends App {
val user: UserBean = UserBean("张飞", 21, new Date(), "hao123@163.com")
val mapper: ObjectMapper = new ObjectMapper()
// user 对象 转 json字符串
val beanJson: String = mapper.writeValueAsString(user)
println(beanJson)
// {"name":"张飞","age":21,"birthday":1660115099317,"email":"hao123@163.com"}
// scala 集合 转 json字符串
val list: Array[UserBean] = Array(
UserBean("刘备", 21, new Date(), "hao123@163.com"),
UserBean("关羽", 22, new Date(), "hao456@163.com"),
UserBean("张飞", 23, new Date(), "hao789@163.com")
)
private val listJson: String = mapper.writeValueAsString(list)
println(listJson)
// [{"name":"刘备","age":21,"birthday":1660115099712,"email":"hao123@163.com"},{"name":"关羽","age":22,"birthday":1660115099712,"email":"hao456@163.com"},{"name":"张飞","age":23,"birthday":1660115099712,"email":"hao789@163.com"}]
}
6. Json 字符串 => Bean对象 (Json 反序列化)
// TODO 由于 利用反射 对json串反序列化,所有必须有 空参构造 + get、set方法
class UserBean1() {
@BeanProperty var name: String = _
@BeanProperty var age: Int = _
@BeanProperty var birthday: Date = _
@BeanProperty var email: String = _
override def toString = s"UserBean1($name, $age, $birthday, $email)"
}
// TODO Json 字符串 => Bean对象 (Json 反序列化)
object Json2Bean extends App {
val jsonBean: String =
"""
|{"name":"张飞","age":21,"birthday":1660115099317,"email":"hao123@163.com"}
""".stripMargin
val jsonArray: String =
"""
|[{"name":"刘备","age":21,"birthday":1660115099712,"email":"hao123@163.com"},{"name":"关羽","age":22,"birthday":1660115099712,"email":"hao456@163.com"},{"name":"张飞","age":23,"birthday":1660115099712,"email":"hao789@163.com"}]
""".stripMargin
val mapper: ObjectMapper = new ObjectMapper()
// json 转 bean 对象
private val bean: UserBean1 = mapper.readValue(jsonBean, classOf[UserBean1])
// json 数组 转 bean 对象数组
private val array: Array[UserBean1] = mapper.readValue(jsonArray, classOf[Array[UserBean1]])
array.foreach(println(_))
println(bean)
}
7. 使用注解
class UserBean2() {
@JsonIgnore //进行JSON操作时忽略该属性
@BeanProperty var name: String = _
@BeanProperty var age: Int = _
@JsonFormat(pattern = "yyyy-MM-dd") // 格式化日期属性
@BeanProperty var birthday: Date = _
@JsonProperty("mail_Alias")
@BeanProperty var email: String = _
override def toString = s"UserBean2($name, $age, $birthday, $email)"
}
// TODO 使用注解
object Bean2Json_Anno extends App {
val user: UserBean2 = new UserBean2()
user.setAge(21)
user.setName("张飞")
user.setBirthday(new Date())
user.setEmail("hao123@163.com")
val mapper: ObjectMapper = new ObjectMapper()
// user 对象 转 json字符串
val beanJson: String = mapper.writeValueAsString(user)
println(beanJson)
// {"age":21,"birthday":"2022-08-10","mail_Alias":"hao123@163.com"}
}
Original: https://www.cnblogs.com/bajiaotai/p/16573210.html
Author: 学而不思则罔！
Title: Jackson API_Scala中使用 Jackson API 进行JSON序列化和反序列化
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