使用Jackson来（De） - 将Scala案例类序列化 [英] Using Jackson to (De)-serialize a Scala Case Class

问题描述

我使用Jackson测试了Scala案例类的序列化。

I tested out the serialization of a Scala case class using Jackson.

DeserializeTest.java

    public static void main(String[] args) throws Exception { // being lazy to catch-all

        final ObjectMapper mapper          = new ObjectMapper();
        final ByteArrayOutputStream stream = new ByteArrayOutputStream();

        mapper.writeValue(stream, p.Foo.personInstance());

        System.out.println("result:" +  stream.toString());
    }
}

Foo.scala

object Foo {
  case class Person(name: String, age: Int, hobbies: Option[String])
  val personInstance = Person("foo", 555, Some("things"))
  val PERSON_JSON = """ { "name": "Foo", "age": 555 } """
}

当我运行上面的 main 的Java类，抛出异常：

When I ran the above main of the Java class, an exception was thrown:

[error] Exception in thread "main" org.codehaus.jackson.map.JsonMappingException: 
 No serializer found for class p.Foo$Person and no properties discovered 
 to create BeanSerializer (to avoid exception, 
 disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) )

我如何（de）-serial化Scala案例类？

How can I (de)-serialize Scala case classes?

推荐答案

Jackson希望你的类成为一个JavaBean，这意味着它希望这个类有一个getX（）和/或每个属性的setX（）。

Jackson is expecting your class to be a JavaBean, which means its expects the class to have a getX() and/or setX() for every property.

选项1

您可以创建JavaBean Scala中的类使用注释 BeanProperty 。

You can create JavaBean classes in Scala using the annotation BeanProperty.

示例

case class Person(
   @BeanProperty val name: String, 
   @BeanProperty val age: Int, 
   @BeanProperty val hobbies: Option[String]
)

在这种情况下，val将仅表示定义了一个getter。如果您想要用于反序列化的setter，则将属性定义为var。

In this case a val will mean only a getter is defined. If you want setters for deserialization you defined the properties as var.

选项2

虽然选项1可以工作，但如果你真的想使用Jackson，那么有一些包装器可以处理Scala类，比如 FasterXML的scala模块，这可能是一种更好的方法。我没有使用它，因为我刚刚使用内置的Json库来播放。

While option 1 will work, if you really want to use Jackson there are wrappers that allow it to deal with Scala classes like FasterXML's scala module which might be a better approach. I haven't used it as I've just been using the Json library built in to play.

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