Scala中使用 Jackson API 进行JSON序列化和反序列化

<dependency>

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

    <artifactId>jackson-databind</artifactId>

    <version>2.7.4</version>

</dependency>

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

    功能:

        ObjectMapper 提供了 读写Json的功能

    读:

        public <T> T readValue(String content, Class<T> valueType)

            将 字符串content 反序列化 成 Class<T>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

    @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")

// 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(), "[email protected]")

  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":"[email protected]"}

  // scala 集合 转 json字符串

  val list: Array[UserBean] = Array(

    UserBean("刘备", 21, new Date(), "[email protected]"),

    UserBean("关羽", 22, new Date(), "[email protected]"),

    UserBean("张飞", 23, new Date(), "[email protected]")

  )

  private val listJson: String = mapper.writeValueAsString(list)

  println(listJson)

  // [{"name":"刘备","age":21,"birthday":1660115099712,"email":"[email protected]"},{"name":"关羽","age":22,"birthday":1660115099712,"email":"[email protected]"},{"name":"张飞","age":23,"birthday":1660115099712,"email":"[email protected]"}]

}

// 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":"[email protected]"}

    """.stripMargin

  val jsonArray: String =

    """

      |[{"name":"刘备","age":21,"birthday":1660115099712,"email":"[email protected]"},{"name":"关羽","age":22,"birthday":1660115099712,"email":"[email protected]"},{"name":"张飞","age":23,"birthday":1660115099712,"email":"[email protected]"}]

    """.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)

}

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("[email protected]")

  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":"[email protected]"}

}