如何使用json4s从json数组中解析和提取信息

I am currently trying to extract the information from a json array using json4s (scala).

我目前正在尝试使用json4s (scala)从json数组中提取信息。

An example data is as follows:

示例数据如下:

val json = """
  [
    {"name": "Foo", "emails": ["Foo@gmail.com", "foo2@gmail.com"]},
    {"name": "Bar", "emails": ["Bar@gmail.com", "bar@gmail.com"]}
  ]
"""

And my code is as follows:

我的代码如下:

case class User(name: String, emails: List[String])
case class UserList(users: List[User]) {
  override def toString(): String = {
    this.users.foldLeft("")((a, b) => a + b.toString)
  }
}

val obj = parse(json).extract[UserList]
printf("type: %s\n", obj.getClass)
printf("users: %s\n", obj.users.toString)

The output turns out to be:

输出结果为:

type: class UserList
users: List()

It seems that the data is not correctly retrieved. Is there any problem with my code?

似乎数据没有被正确地检索到。我的代码有问题吗?

UPDATE: It works according to the suggestion of @Kulu Limpa.

更新:根据@Kulu Limpa的建议工作。

1 个解决方案

#1

Your code is correct except that your JSON is simply an array, hence a List[User]. There are two ways to fix this, with a slightly different outcome:

您的代码是正确的，除了您的JSON只是一个数组，因此是一个列表[用户]。有两种方法可以解决这个问题，但结果略有不同:

Solution 1: Fix your json to

解决方案1:将json修改为

{"users": 
  [
    {"name": "Foo", "emails": ["Foo@gmail.com", "foo2@gmail.com"]},
    {"name": "Bar", "emails": ["Bar@gmail.com", "bar@gmail.com"]}
  ]
}

Solution2: Change the type parameter of extract to

解决方案2:将提取的类型参数更改为

val obj = parse(json).extract[List[User]]

#1