scala 如何使用json4s从json数组中解析和提取信息
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How to parse and extract information from json array using json4s
提问by yxjiang
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": ["[email protected]", "[email protected]"]},
{"name": "Bar", "emails": ["[email protected]", "[email protected]"]}
]
"""
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:
结果是：
type: class UserList
users: List()
It seems that the data is not correctly retrieved. Is there any problem with my code?
似乎未正确检索数据。我的代码有问题吗？
UPDATE: It works according to the suggestion of @Kulu Limpa.
更新：它根据@Kulu Limpa 的建议工作。
回答by Kulu Limpa
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，只是您的 JSON 只是一个数组，因此List[User]. 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：将您的 json 修复为
{"users":
[
{"name": "Foo", "emails": ["[email protected]", "[email protected]"]},
{"name": "Bar", "emails": ["[email protected]", "[email protected]"]}
]
}
Solution2: Change the type parameter of extract to
解决方案2：将extract的类型参数改为
val obj = parse(json).extract[List[User]]
